Hybrid Constructed Wetlands for Tertiary Treatment of Poultry Slaughter Wastewater to Meet Quality Standards of Discharge and Reuse: A Full-Scale Case Study in Vietnam

Hybrid Constructed Wetlands for Tertiary Treatment of Poultry Slaughter Wastewater to Meet Quality Standards of Discharge and Reuse: A Full-Scale Case Study in Vietnam | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Hybrid Constructed Wetlands for Tertiary Treatment of Poultry Slaughter Wastewater to Meet Quality Standards of Discharge and Reuse: A Full-Scale Case Study in Vietnam Hung Viet Dang, Huy Quoc Lam, Linh My Nguyen This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4923724/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 01 Feb, 2025 Read the published version in Environmental Monitoring and Assessment → Version 1 posted 4 You are reading this latest preprint version Abstract The construction and operation of a small-scale hybrid constructed wetland (HCW) system for tertiary wastewater treatment was presented. The HCW system includes a vertical sub-surface flow CW (VFCW), a horizontal sub-surface flow CW (HFCW) and a free water surface flow CW (FWSCW) operated in series had a total area of 150 m2. It received 7.5 m3/day of secondary effluent wastewater from the existing treatment system of a poultry slaughter enterprise at the production capacity of 500 ducks per day in an on-site experiment of 12 months. The results showed that the removal efficiencies of biological oxygen demand (BOD5), chemical oxygen demand (COD), total suspended solids (TSS), ammonia nitrogen (NH4+-N), nitrate nitrogen (NO3--N), total nitrogen (TN), orthophosphate (PO43--P), total phosphorus (TP), Escherichia coli (E. coli) and total coliforms (T. coli) reached average values of 76.2, 78.7, 77.1, 83.9, 86.3, 84.9, 72.3, 73.9, 98.9 and 96.4%, respectively, while the effluent concentrations of the study system complied with the most difficult limits not only for discharge into the receiving water source but also for reusing wastewater to water plants. The function made by various configurations such as a VFCW, a HFCW and a FWSCW placed sequentially in the HCW system proved crucial to treat wastewater and make it reusable. Hybrid constructed wetlands Poultry slaughter wastewater Tertiary treatment Discharge Reuse Figures Figure 1 Figure 2 Figure 3 Highlights - The HCW system achieved a good removal of BOD 5 , COD, TSS, NH 4 + - N, NO 3 - - N, TN, PO 4 3- - P, TP, E. coli and T. coli with a total wetland area demand of 20 m 2 /m 3 . - Tertiary effluent concentrations, especially E. coli parameter reached the highest limits for both discharge and reclamation in Vietnam. - The VFCW removed the majority of pollutants, whereas the succeeding HFCW and FWSCW as a polishing step. - The HCW system is an approriate advanced technology to treat wastewater and make it reusable. 1. Introduction Small and medium-sized enterprises often have technical and economic limitations in treating domestic and production wastewater to meet environmental requirements for discharge. The wastewater treatment systems including primary and secondary treatment stages that these businesses are operating always only achieve low discharge limits as Column B of Vietnamese technical regulation on industrial wastewater, QCVN 40:2011/BTNMT (MONRE, 2011) and occasionally some nutrient parameters, i.e., NH 4 + - N, TN and TP exceed the limits (Nguyen Thi Phuong Thao et al., 2022; Nga Tran Thi Viet et al., 2023). In addition to treating wastewater to follow discharge regulations, Law on Environmental Protection 2020 in Vietnam encourages companies to reuse wastewater after treatment if they ensure the quality standards of reused wastewater, especially obeying the microbiological requirements. Wastewater reuse is the process of converting domestic and/or industrial wastewater into water that can be reused for a variety of purposes. It is also called, water reuse, water recycling or water reclamation. In fact, reused wastewater has been used a lot in agricultural irrigation because this is one of the sectors with the highest water demand (Xi Nan et al., 2020). Therefore, seeking suitable tertiary technologies for wastewater discharge and reclamation which are technically feasible, economically viable and environment friendly for connection to existing wastewater treatment systems has been mentioned. Constructed wetlands (CWs) are often preferably considered interesting options because of ease of construction and installation, low investment and maintenance cost, and high removal efficiency with no secondary pollution (A.I. Stefanakis et al., 2019). CWs are artificial systems that operate under natural conditions which can treat many types of wastewater including domestic and production wastewater to satisfy above requirements (Vymazal, 2005; Comino et al., 2011; Saeed et al., 2012; Stefanakis, 2018). They apply various technological designs, using natural wetland processes, associated with wetland hydrology, soils, microbes and plants for contaminants removal (Vymazal, 2007). Depending on the flow layout, CWs are generally categorized into two major groups: free water surface flow and sub-surface flow. Furthermore, sub-surface flow CWs are categorized into horizontal and vertical sub-surface flow CWs (Vymazal, 2005; Divyesh Parde et al., 2021). They have been successfully applied in almost all the world's countries over the last decades (Vymazal, J., 2011; Dong Qing Zhang et al., 2014). Several studies were completed showing the effectiveness of CWs in wastewater treatment at different stages known as primary, secondary and tertiary (Cristina Ávila et al., 2014; F. Licciardello et al., 2018). It has been widely agreed that the reasonable application of configuration and the appropriate selection of vegetations are essential to attain high treatment efficiency in CWs (Brix, 1997; Divyesh Parde et al., 2021). Each type of CWs has different advantages and disadvantages regardless of the stage of treatment. Therefore, much attention has been paid to increase their conveniences and decrease their limitations. One of the new trends in wetland-based wastewater treatment is the combination of various CW types into one system called “hybrid” CW (HCW) system in order to establish physicochemical and microbiological conditions which would allow for the synergy of pollutant removal mechanisms to occur simultaneously (Cristina Ávila et al., 2014; Shama Sehar et al., 2015; Amir Gholipour et al., 2021). However, CW research works and their applications under tropical climate condition like Southwestern Vietnam with the air temperature from 20 to 30 0 C, the annual rainfall from 1,200 to 1,800 mm and the air humidity above 80% have been still limited. Furthermore, there is a lack of information and reporting on CW construction and operation for on-site advanced treatment and reuse of wastewater for crops such as poultry slaughter wastewater (Dong Qing Zhang et al., 2014; F. Licciardello et al., 2018; Rita P. Shingare et al., 2019; Jan Vymazal et al., 2021). This paper describes the construction and operation details of a small-scale HCW system consisting of a vertical sub-surface flow CW (VFCW), a horizontal sub-surface flow CW (HFCW) and a free water surface flow CW (FWSCW) operated in series for tertiary wastewater treatment of an poultry slaughter enterprise in Southwestern Vietnam and presents the results of an on-site experiment of 12 months. The main objective of the experiment study were to verify whether the effluent quality of advanced wastewater treatment under the specific tropical climate complied with the limits not only for discharge into the receiving water source but also for reusing wastewater to water plants. Moreover, the role of each CW configuration and its appropriate site selection in the HCW system were also discussed. 2. Materials and methods 2.1. Research location The HCW system was built to treat the secondary effluent wastewater from the existing treatment system of a poultry slaughter enterprise at the production capacity of 500 ducks per day at Long Phung Commune, Can Giuoc District, Long An Province, Vietnam (10◦32 11.7 N, 106◦39 50.4 E). The location is approximately from 2 to 3 m above sea level. The total land area of the enterprise is 2,718 m 2 . The climate of the area is tropical monsoon, so there are two seasons. They are known as the rainy and dry seasons. The rainy season lasts from May to October and the dry season lasts from November to April next year. The weather is warm all year round. From June 2021 to May 2022, the temperature was from 24.1 to 29.8 0 C and the yearly temperature was 26.7 0 C. The average rainfall and humidity were 1,576 mm and 84.8%, respectively. It is shown that the climate conditions of the region were favorable for the development and survival of animals, plants and microorganisms in the treatment system and the pollutant removal possibility was not much affected at different times of the year. 2.2. Experimental system The existing poultry slaughter wastewater treatment system consisted of a primary treatment stage (a dissolved air flotation (DAF) system) and a secondary treatment stage (an upflow anaerobic sludge blanket (UASB) reactor together with an activated sludge system followed). Its capacity was 10.0 m 3 /day of wastewater. For the experiment, about 7.5 m 3 /day of unchlorinated secondary effluent wastewater from this system was pumped into the HCW system. The study system included a VFCW, a HFCW and a FWSCW sequentially placed at decreasing levels (0.2 m) to enable natural flow of wastewater under gravity. An effluent collection tank (ET) was used to collect and store tertiary effluent wastewater from the HCW system. A schematic representation of the overall treatment process is shown in Fig. 1 . Two sub-surface flow CWs (VFCW and HFCW) with the size of each as 10.0 m (length) x 5.0 m (width) had the total area of ​​100 m 2 . The depth of these two CWs was 1.3 m. Waterproof liner was used on the sides and bottom of each with the bottom slope from 1 to 2%. They contained two porous media layers. The bottom well-washed coarse gravel layer was 300 mm in depth (20–40 mm in diameter, about 40% in porosity). The top well-washed fine gravel layer was 700 mm in depth (2–5 mm in diameter, about 35% in porosity). Water level in these two CWs were kept below the fine gravel surface about 50–100 mm and monitored by measurements taken from observation pipes placed in different parts of each. A freeboard of 300 mm was maintained. In the VFCW, five distribution pipes Ø27 mm on the fine gravel surface with 8 holes Ø10 mm every 1.0 m distance were arranged to distribute the effluent wastewater from the existing system uniformly across the entire surface. Three collection pipes Ø42 mm at the bottom of this wetland with 15 holes Ø12 mm every 0.6 m distance enclosed by coarse gravel were arranged to transfer wastewater from the VFCW to the HFCW. The HFCW had an inlet zone and an outlet zone with 1 m in length of each, which were filled of stone (40–80 mmm in diameter) to facilitate the flow. In the inlet zone, two distribution pipe Ø60 mm on the top of the stone layer along the upstream width side with 28 holes Ø12 mm every 0.1 m distance was arranged to distribute the effluent wastewater from the VFCW fully through the horizontal section of the HFCW. In the outlet zone, three collection pipes Ø42 mm at the bottom of the stone layer along the downstream width side with 14 holes Ø12 mm every 0.2 m distance were arranged to transfer wastewater from the HFCW to the FWSCW. The FWSCW had a surface area of 50 m 2 with 10.0 m (length), 5.0 m (width). Waterproof liner was also used on the sides and bottom with the bottom slope from 1 to 2%. It contained two media layers. The bottom well-washed gravel layer was 500 mm in depth. The top soil layer was 100 mm in depth. Water level in this wetland was kept over the top soil layer about 100 mm and a freeboard of 300 mm is maintained. The pipes at input and output were 60 mm in diameter. The flow path through this wetland was assumed to be horizontal. Wastewater flowed from the HCW to the ET under gravity naturally. Flow rate of wastewater among different CWs was regulated by valves. The usable capacity of the ET was 5.0 m 3 with 5.0 m in length, 1.5 m in width, and 2.2 m in depth. Effluent wastewater from the experimental system was pumped out for discharge or reuse (two submersible pumps, one pump running and one pump standby, 1/4 Hp, maximum flow rate 1.0 m 3 /h). 2.3. Wetland plants Selection of macrophytes was made on the requirement that they were found growing naturally in this area and tolerant enough for contaminants and saturated soil conditions. (Shama Sehar et al., 2015; Fernando García-´Avila et al., 2023). The VFCW and HFCW were planted with Phragmites australis (common reed) with the density of 12–14 plants/m 2 . The FWSCW was planted with Typha angustifolia L. (Typhaceae) with the density of 6–8 plants/m 2 . They are capable of growing up to 1.5–3.0 m and are generally branched with leaf sheaths overlapping. Young shoots were collected from nearby natural wetland sites and transplanted on the top layers of the HCW system. 2.4. System performance Before going into the official experiment, the HCW system was kept soaked with fresh water for 2 weeks in order to acquire saturated growth of plants and associated microbial community in the rhizosphere, soil and gravel layer. The study system was run to adapt the secondary effluent wastewater from the existing system with an initial flow rate of 0.75 m 3 /day. After 4 weeks, the plants grew well with the height over 0.8 m. Then, flow rate was increased gradually until it reached an average value of 7.5 m 3 /day (15% increase each week). This was the survey flow rate of the study system to evaluate removal efficiencies. For the VFCW, HFCW and FWSCW, the hydraulic residence times (HRTs) were 2.4, 2.4 and 1.8 days, respectively (Recep Çakir et al., 2015; Raja Zubair Zahoor Qadiri et al., 2021). The total area of the HCW system was 150 m 2 and the area required for wetland treatment was 20 m 2 /m 3 . The hydraulic loading rates (HLRs) of the VFCW, HFCW and FWSCW were the same as 0.15 m/d. 2.5. Wastewater quality monitoring – statistical analyses The experiment system started from March 2021 to May 2022. The adaptation period for the HCW system lasted 3 months. Once stabilized, sampling and analyzing wastewater was carried out once a week. Wastewater samples were taken at the four different points of the whole study system, i.e., HCW input, VFCW output, HFCW output and FWSCW output. After sampling, the physical-chemical parameters of wastewater such as temperature, pH, dissolved oxygen (DO) and total dissolved solids (TDS) were measured onsite by portable Toledo meters. Then samples were properly stored in a cool box, sent to the Laboratory of Research Institute for Aquaculture No. 2 - Ho Chi Minh City and analyzed immediately for total suspended solids (TSS), biological oxygen demand (BOD 5 ), chemical oxygen demand (COD), ammonia nitrogen (NH 4 + -N), nitrate nitrogen (NO 3 − -N), total nitrogen (TN), orthophosphate (PO 4 3− -P), total phosphorus (TP), Escherichia coli (E. coli), total coliforms (T. coli) according to Vietnamese technical regulation together with American Public Health Association (APHA) Standard Methods (APHA, 2012). Harvesting was carried out after 6 months (end of December 2021) and 12 months (end of May 2022) from the end of adaptation period, because it was assumed that the HCW system was in a steady state based on observations of plant growth height variation and start of inflorescence formation. The plants growth before and after harvesting was recorded. At each time of harvesting, plants were cut approximately 10 cm above the gravel or water surface to prevent flooding and supply regeneration of the remaining shoots. Biomass samples were weighed onsite for fresh weight. Then, they were dried to fixed weight for 72 hours at 70 0 C, re-weighed for dry weight and ground for nutrient analysis at the Laboratory (Jeroen J.M et al., 2020). All analyses were repeated three times and the measurements were based on average values. Obtained results were subjected to statistical analysis and t-test was used to determine significant differences between the mean values of pollutant concentrations at the various treatment units and between the mean values of pollutant removals at the first and second harvests. 95% confidence interval (p < 0.05) was considered as minimum value for statistical significance. Absolute removal for each constituent at one intermediate stage or unit of the study system was calculated based on its concentrations at the input and output of the stage or unit. Relative removal for each pollutant at one intermediate stage or unit of the system was calculated based on its concentrations at the input of the system and the output of the stage or unit, and subtracting the removal in the previous stages or units. Cumulative removal for each constituent at one intermediate stage or unit of the system was calculated based on its concentrations at the input of the system and the output of the stage or unit. 3. Results And Discussion National technical regulation on industrial wastewater of Vietnam, QCVN 40:2011/BTNMT (MONRE, 2011) at Column A is used as the limits for discharge into the receiving water source. National technical regulation on livestock wastewater used for crops of Vietnam, QCVN 01-195:2022/BNNPTNT (MARD, 2022) at Class I, II, III, IV is used as the limits of pH and E. coli for reusing wastewater to water plants. The regulation has not the limits of organic matter and suspended solids for wastewater reuse but Law on Environmental Protection 2020 in Vietnam allows the application of similar standards of developed industrial countries. In this case, Regulation (EU) 2020/741 of the European Parliament and of the Council of 25 May 2020 on minimum requirements for water reuse (EU, 2020) at Class B is used as the limits of BOD 5 and TSS. The variations in physical, chemical, and microbiological parameters at the four different points of the whole study system in comparison with these limits were presented in Table 1 . Table 1 Average (Mean), standard deviation (SD), minimum (Min) and maximum (Max) values of physicochemical parameters and bacteriological concentrations at HCW input (In), VFCW output (VF), HFCW output (HF) and FWSCW output (FWS) in comparision with Limits for discharge into the receiving water source (Discharge) and Limits for reusing wastewater to water plants (Reusing). Parameter (n = 52) Unit In VF HF FWS Discharge (MONRE, 2011) Reusing (MARD, 2022) pH Mean ± SD Min - Max - 7.04 ± 0.28 6.75–7.53 7.22 ± 0.18 6.99–7.41 7.28 ± 0.14 7.12–7.47 7.33 ± 0.12 7.21–7.42 6.0–9.0 5.5–9.0 DO Mean ± SD Min - Max mg/L 2.56 ± 0.37 2.12–3.14 2.10 ± 0.45 1.66–2.63 1.53 ± 0.33 1.17–1.96 1.63 ± 0.39 1.24–2.08 - - TDS Mean ± SD Min - Max mg/L 272 ± 46 214–326 245 ± 42 199–301 234 ± 39 187–284 227 ± 32 182–276 - - TSS Mean ± SD Min - Max mg/L 35 ± 13 20–53 12 ± 8 10–27 10 ± 6 7–20 8 ± 5 6–18 50 35 (EU, 2020) BOD 5 Mean ± SD Min - Max mg/L 21 ± 12 14–33 10 ± 5 6–16 7 ± 4 5–13 5 ± 3 4–11 30 25 (EU, 2020) COD Mean ± SD Min - Max mg/L 47 ± 23 27–69 23 ± 12 14–39 14 ± 8 10–26 10 ± 4 8–18 75 - NH 4 + - N Mean ± SD Min - Max mg/L 9.3 ± 3.6 7.1–15.4 4.7 ± 1.6 2.8–7.0 3.0 ± 0.9 2.2–4.3 1.5 ± 0.5 1.0–2.4 5 - NO 3 − - N Mean ± SD Min - Max mg/L 20.5 ± 7.7 15.8–32.5 12.5 ± 5.4 7.2–19.6 5.2 ± 3.1 3.5–9.8 2.8 ± 1.7 1.6–5.5 - - TN Mean ± SD Min - Max mg/L 33.8 ± 9.3 20.1–45.6 18.4 ± 6.5 13.9–28.7 9.7 ± 3.6 5.1–13.9 5.1 ± 2.2 2.9–8.4 20 - PO 4 3− - P Mean ± SD Min - Max mg/L 5.8 ± 2.4 3.2–9.7 4.4 ± 1.6 2.7–6.3 3.0 ± 1.1 1.6–4.2 1.6 ± 0.5 1.0–2.7 - - TP Mean ± SD Min - Max mg/L 6.9 ± 2.9 4.4–10.6 4.8 ± 1.6 3.1–5.7 3.2 ± 1.2 2.0–4.5 1.8 ± 0.6 1.3–2.9 4 - E. coli Mean ± SD Min - Max CFU/ 100mL 4.65 ± 1.28 2.94–6.37 (x10 3 ) 0.48 ± 0.21 0.19–0.73 (x10 3 ) 0.24 ± 0.07 0.12–0.36 (x10 3 ) 0.05 ± 0.03 0.02–0.09 (x10 3 ) - Class I* ≤ 0.2x10 3 Class II ≤ 1.0x10 3 Class III ≤ 5.0x10 3 Class IV > 5.0x10 3 T. coli Mean ± SD Min - Max MPN/ 100mL 22.3 ± 5.8 16.8 − 30.5 (x10 3 ) 4.6 ± 1.6 3.1–6.8 (x10 3 ) 1.4 ± 0.5 1.0–2.3 (x10 3 ) 0.8 ± 0.2 0.5–1.3 (x10 3 ) 3.0x10 3 - *National technical regulation on livestock wastewater used for crops of Vietnam, QCVN 01-195:2022/BNNPTNT (MARD, 2022) has Class I: All types of plants; Class II: All types of plants except annual vegetables and medicinal plants; Class III: All types of plants except plants used as food for humans and animals; and Class IV: Not used for crops. 3.1. Changes of parameters and effluent of the system Because pH values of secondary effluent wastewater were in the neutral range, the mean pH values at four points of the HCW system were 7.04, 7.22, 7.28 and 7.33 (Table 1 ). It tended to increase as it went from the VFCW to the HFCW to the FWSCW through pollutant removal metabolic pathways (Amir Gholipour et al., 2021). The mean DO concentrations from the input to the output of the HCW system were 2.56, 2.10, 1.53 and 1.63 mg/L (Table 1 ). The higher value at the input compared with the lower value at the output was reasonable because the wastewater flowing into the HCW system had been artificially aerated before while the wastewater flowing out of the HCW system was only naturally aerated afterward. Variation of mean DO concentrations in these three CWs reflected the different presence of the main oxygen supply pathways which may be atmospheric reoxygenation and plant oxygen release (Jingying Zhang et al., 2023). Each type of CWs has its distinct source of oxygen and VFCW provides the best oxygen supply because of the basis of the wastewater flow type favorable for air dissolution (Sohair I.Abou-Elela et al., 2013; Amir Gholipour et al., 2021). The mean concentrations of TDS and TSS gradually decreased from 272 and 35 mg/L at the input of the HCW system to 245 and 12 mg/L at the output of the VFCW to 234 and 10 mg/L at the output of the HFCW to 227 and 8 mg/L at the output of FWSCW, respectively (Table 1 ). When wastewater passed through the HCW system, there was no notable removal of TDS but TSS was greatly removed with mean removal efficiency of 77.1% (Fig. 3 ), thus highlighting the importance of macrophytes in removal of suspended solids (Georgios D. Gikas et al., 2012; Cristina Ávila et al., 2014). Contaminants such as suspended solids can be settled and filtered within CWs, including the blocking effect of macrophyte roots and the gravitational interception of solid objects between coarse and fine gravel particles (Brix, 1997; Divyesh Parde et al., 2021). The maximum TSS effluent concentrations of the HCW system were much lower than the Vietnamese regulation limits of 50 mg/L for discharge into the receiving water source and 35 mg/L for reusing wastewater to water plants. Significant reduction in BOD 5 or COD was observed in the HCW system with mean tertiary effluent concentrations of 5 and 10 mg/L, respectively (Table 1 ). The maximum tertiary effluent concentrations of BOD 5 and COD were fully below the Vietnamese regulation limits of 30 and 75 mg/L, respectively for discharge as well as 25 mg/L in BOD 5 for reusing. The mean concentrations of NH 4 + - N, NO 3 − - N, TN, PO 4 3− P and TP of secondary effluent wastewater were 9.3, 20.5, 33.8, 5.8 and 6.9 mg/L, respectively, which decreased along the HCW system with mean effluent concentrations of 4.7, 12.5, 18.4, 4.4 and 4.8 mg/L at the VFCW; 3.0, 5.2, 9.7, 3.0 and 3.2 mg/L at the HFCW; 1.5 mg/L, 2.8, 5.1, 1.6 and 1.8 mg/L at the FWSCW, respectively (Table 1 ). In CW systems, the nitrogen removal mechanisms are accomplished by biological processes such as ammonification, nitrification, denitrification, plant uptake, biomass assimilation, dissimilatory nitrate reduction and physicochemical routes such as ammonia volatilization, adsorption, ion exchange (Brix, 1997; Vymazal, 2007). The removal of phosphorus in CW systems involves a number of biological processes including plant uptake, biomass assimilation, biological storage in microorganisms, e.g., polyphosphate accumulating organism (PAO) and physicochemical pathways such as precipitation, adsorption (Brix, 1997; Vymazal, 2007). The maximum NH 4 + - N, TN and TP tertiary effluent concentrations were less than the Vietnamese regulation limits of 5, 20 and 4 mg/L, respectively for discharge while there were no limits of them for reusing. The mean concentrations of E. coli and T. coli in the effluent wastewater of the HCW system were 0.05x10 3 CFU/100mL and 0.8x10 3 MPN/100mL, respectively (Table 1 ). These bacteriological values reached the Vietnamese regulation limits of 0.2x10 3 CFU/100mL for reusing (Class I) and 3.0x10 3 MPN/100mL for discharge (Column A). 3.2. Efficiencies at the various CWs of the system The pollutant loading rates to the whole wetland system were 10.5 g BOD 5 /m 2 .day, 23.5 g COD/m 2 .day, 17.5 g TSS/m 2 .day, 4.6 g NH 4 + - N/m 2 .day, 10.2 g NO 3 − - N/m 2 .day, 16.9 g TN/m 2 .day, 2.9 g PO 4 3− - P/m 2 .day and 3.4 g TP/m 2 .day. The mean concentrations of E. coli and T. coli in the influent wastewater of the HCW system were 4.65x10 3 CFU/100mL and 22.3x10 3 MPN/100mL. The average removal efficiencies of the HCW system were 76.2% for BOD 5 , 78.7% for COD, 77.1% for TSS, 83.9% for NH 4 + - N, 86.3% for NO 3 − - N, 84.9% for TN, 72.3% for PO 4 3− - P, 73.9% for TP, 98.9% for E.coli and 96.4% for T. coli (Fig. 3 ). The performance of the HCW system were similar or even better than the tertiary constructed wetland in a previous study, where mean concentrations of BOD 5 , COD and TSS were reduced by about 70%, 80% and 90%, respectively and output concentration of E.coli was 0,04x10 3 CFU/100 mL (S.Ç. Ayaz, 2008). For the VFCW, HFCW and FWSCW, the average mass removal rates were 5.5, 1.5 and 1.0 g BOD 5 /m 2 .day; 12.0, 4.5 and 2.0 g COD/m 2 .day; 11.5, 1.0 and 1.0 g TSS/m 2 .day whereas mean relative removal efficiencies were 52.4, 14.3 and 9.5% for BOD 5 ; 51.1, 19.1 and 8.5% for COD; 65.7, 5.7 and 5.7% for TSS, respectively (Fig. 3 ). The CW where most relative removal efficiencies of organic matter and suspended solids occurred was the VFCW. The CW with the lower relative removal efficiencies of organic matter and suspended solids was the FWSCW. The VFCW placed in front of the HFCW and FWSCW removed more than half of organic matter and suspended solids mass removal rates of the whole HCW system. Generally, as most of the published studies indicate, the majority of pollutants is mainly removed in the first CW rather than the later CWs of the hybrid CW systems (Cristina Ávila et al., 2014; Shama Sehar et al., 2015). This is completely reasonable because the degradation of pollutants requires aerobic conditions and VFCW is naturally aerated better than HFCW and FWSCW. The HFCW and FWSCW showed a similar performance as a polishing step of the HCW system. Although secondary effluent concentrations of BOD 5 , COD and TSS were lower than the Vietnamese regulation limits for discharge, the fact that the maximum tertiary effluent concentrations of them always complied with the Vietnamese regulation limits for reuse also demonstrated that the HFCW and FWSCW had done a good job of supporting and completing the VFCW and were a necessary addition in the treatment train. Futhermore, having many various CW configurations delays wastewater passage through the combined system which in turn increases the retention time and as a consequence, the removal efficiencies of pollutants. The average mass removal rates in the VFCW, HFCW and FWSCW were 2.3, 0.8 and 0.7 g NH 4 + - N/m 2 .day; 4.0, 3.6 and 1.2 g NO 3 − - N/m 2 .day; 7.7, 4.3 and 2.3 g TN/m 2 .day; 0.7, 0.7 and 0.7 g PO 4 3− - P/m 2 .day; 1.0, 0.8 and 0.7 g TP/m 2 .day, respectively, whereas mean relative removal efficiencies were 49.5, 18.3 and 16.1% for NH 4 + - N; 39.0, 35.6 and 11.7% for NO 3 − - N; 45.6, 25.7 and 13.6% for TN; 24.1, 24.1 and 24.1% for PO 4 3− - P; 30.4, 23.2 and 20.3% for TP, respectively (Fig. 3 ). Relative removal efficiencie of NH 4 + - N decreased from the VFCW to the HFCW and vice versa, removal efficiency of NO 3 − - N increased from the VFCW to the HFCW. The design of VFCW typically provides a nitrified effluent due to the strong aerobic conditions and HFCW design generally promotes the development of anoxic conditions that favour denitrification process (Brix, 1997; Vymazal, 2007). That is why HFCW is often used after VFCW in order to provide denitrification process for the nitrified effluent of VFCW (Shama Sehar et al., 2015; Amir Gholipour et al., 2021). The lowest removal efficiencies of NH 4 + - N, NO 3 − - N, TN, PO 4 3− - P and TP were at the FWSCW. The results indicated that operation of the VFCW, HFCW and FWSCW placed in series would be more efficient in terms of nitrogen and phosphorus removal compared with operating them individually or in parallel (Georgios D. Gikas et al., 2012; Sohair I.Abou-Elela et al., 2013; Raja Zubair Zahoor Qadiri et al., 2021). Removal of phosphorus tends not to be as high as nitrogen removal in CW systems and typical amounts of phosphorus removal are in the range of 40 to 60%. However, when operated with the input loading rates of 2.9 g PO 4 3− - P/m 2 .day and 3.4 g TP/m 2 .day, the HCW system had treatment efficiencies of 72.3% for PO 4 3− - P and 73.9% for TP (Fig. 3 ). The diversity of hydrological processes, flow directions, macrophytes growth and microorganisms presence is very important to treatment efficiency of CW systems. Most likely, utilization of several different CW types into one system provides a more effective synergy of pollutant removal mechanisms, which encourages the system to remove more of nutrients from wastewater. To the VFCW, HFCW and FWSCW, the average removal efficiencies were 89.6, 5.2 and 4.1% for E. coli; 79.4, 14.3 and 2.7% for T. coli, respectively. This result was in accordance with Cristina Ávila et al., 2014 as, they found overall removal rate of E. Coli up to 99.99% for a full-scale hybrid CW system for domestic wastewater treatment and reuse in small communities. The HCW system showed more reduction concentration of E. coli and T. coli as compared to previously reported studies in individual CW systems with only one or two types (Sohair I.Abou-Elela et al., 2013; Amir Gholipour et al., 2021). HLR and corresponding HRT are considered the major operational control factors in CW systems as they can provide sufficient contact between contaminants, rhizosphere of plants and attached microorganisms, thus decrease concentration of E. coli and T. coli in wastewater (Recep Çakir et al., 2015; Shama Sehar et al., 2015). In general, effective removal of pathogens from wastewater using CW systems requires low HLR, and subsequently long HRT. Owing to the HLR of 0.15 m/day and the HRT of 6.6 days, the slow moving wastewater in the VFCW, HFCW and FWSCW configurations enabled pathogens to settle out and thus the HCW system was capable to removing high percentages of E. coli and T. coli. The function made by various CW configurations in series proved crucial to achieve a treated wastewater quality appropriate for its discharge and reusing. 3.3. Reuse potential of the treated wastewaters Effluent wastewater of the study system were evaluated in terms of potential for reusing wastewater to water plants. Generally, the main parameters that need to be met for wastewater reuse are pH, TDS, TSS, BOD 5 , COD, heavy metals, trace organic contaminants and pathogenic microorganisms of helminthes, protozoans, fungi, bacteria, and viruses (A. Ghermandi et al., 2007). To poultry slaughter wastewater, the parameters mentioned in the standard for effluent reuse are pH, TSS, BOD 5 and E. coli (EU, 2020; MARD, 2022). For advanced wetland-based wastewater treatment, effluent concentration of E. coli is difficult to reach the limit for wastewater reuse without disinfection (Selma Ç. Ayaz et al., 2015). Based on National technical regulation on livestock wastewater used for crops of Vietnam, QCVN 01-195:2022/BNNPTNT (MARD, 2022), the limits of E. coli are 0.2x10 3 CFU/100 mL for Class I and 1.0x10 3 CFU/100 mL for Class II. In this experiment, secondary effluent parameters had basically satisfied their limits for reusing wastewater to water plants except for microbiological parameter, E. coli. To the VFCW, HFCW and FWSCW, effluent concentrations of E. coli were 4.65x10 3 , 0.48x10 3 and 0.05x10 3 CFU/100 mL, respectively. This showed that effluent concentrations of E. coli gradually decreases along the HCW system and only reached the limit for Class I at the final step, FWSCW. The system had to use all its capabilities to reach the most difficult limits on wastewater reuse in Vietnam. On the other hand, each CW in the system contributed to E. coli treatment and strongly affected the reuse level of the effluent wastewater. The HCW system provided an effluent quality that allowed for its reuse in watering plants and lawns on business premises. The total investment cost for this tertiary treatment system was only a small part compared to the existing secondary treatment system while operating and maintaining the system only required a non-specialized staff right at the enterprise. It can be easily seen that CW technology can be easily implemented everywhere, depending on local conditions. CW system in advanced treatment for wastewater reuse also aims to sustainably use resources and environment for sustainable development. 3.4. Plant uptake and biomass production Macrophyte growth in three CWs of the HCW system requires a defined program for harvesting and controlling of the biomasses produced. Phragmites australis and Typha angustifolia L. grew so relatively quickly that they needed to be harvested and assessing every 180 days to avoid dead plant matter pollution in the effluent wastewater. Observing the plant growth showed that the root systems of Phragmites australis and Typha angustifolia L. strongly expanded with average length 40–60 cm while sticking entirely to the soil and gravel layers in the system. Trunk diameter of them was from 1.26 to 2.03 cm. Phragmites australis and Typha angustifolia L. survived and developed well in the system with growth height of 39 and 32 cm/plant.month, respectively. Average height and dry weight of Phragmites australis reached 248 cm and 1.43 kg/m 2 for the two harvests in the VFCW and 225 cm and 1.37 kg/m 2 for the two harvests in the HFCW, respectively (Raja Zubair Zahoor Qadiri et al., 2021). Phragmites australis grew well in both the VFCW and HFCW and did not change significantly between the first and second harvests (Sohair I.Abou-Elela et al., 2013). Height and biomass production of Phragmites australis in the VFCW were slightly more than these in the HFCW. In the FWSCW, Typha angustifolia L. had 18 to 20 leaves/plant with average height and dry weight of 216 cm and 0.33 kg/m 2 for the two harvests, respectively (Jeroen J.M et al., 2020). Plant harvesting showed that Typha angustifolia L. grew during the rainy season months almost similarly to during the dry season months. In a simple way, the nitrogen and phosphorus uptake in the VFCW, HFCW and FWSCW was 7.7, 4.3 and 2.3 gN/m 2 , respectively and 1.0, 0.8 and 0.7 gP/m 2 , respectively. Phragmites australis can be used as livestock feed and young stem of Typha angustifolia L. can be used as green vegetables for human meals. 4. Conclusions The secondary effluent from a poultry slaughter wastewater treatment system was successfully treated at tertiary stage by the HCW system consisting of a VFCW, a HFCW and a FWSCW placed in series. The removal efficiencies of BOD 5 , COD, TSS, NH 4 + - N, NO 3 - - N, TN, PO 4 3- - P, TP, E. coli and T. coli reached average values of 76.2, 78.7, 77.1, 83.9, 86.3, 84.9, 72.3, 73.9, 98.9 and 96.4%, respectively, while the effluent concentrations of the system complied with the limits not only for discharge into the receiving water source (Column A) but also for reusing wastewater to water plants (Class I) in Vietnam. The HCW system provided a more effective synergy of pollutant removal mechanisms to thoroughly treat wastewater. The three-step CW system had advantages over single CW systems such that removal of organic matter, suspended solids, nitrogen and phosphorus as well as pathogens were mainly achieved in the VFCW, whereas the succeeding HFCW and FWSCW played the role as a polishing step of the HCW system. Phragmites australis grew well in both the VFCW and HFCW and Typha angustifolia L. was also good selection for the FWSCW. With a total wetland area demand of 20 m 2 /m 3 , the HCW system was considered to be approriate for small and medium-sized enterprises in advanced wastewater treatment for discharge and reclamation. Declarations Acknowledgement The authors would like to greatly acknowledge the support of time and facilities from University of Technology, Vietnam National University – Ho Chi Minh City, Vietnam and Ho Chi Minh City University of Technology and Education, Ho Chi Minh City, Vietnam for this study. Conflict of Interest The authors declare that they have no conflict of interest. Data Availability The authors declare that the data supporting the findings of this study are available within this published article. Authors Contributions Hung Viet Dang: Supervision, Writing - original draft, reviewing and Editing; Huy Quoc Lam: Data curation, Formal analysis; Linh My Nguyen: Methodology ,Conceptualization, Writing - reviewing and Editing. 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Supplementary Files GraphicalAbstract.png Cite Share Download PDF Status: Published Journal Publication published 01 Feb, 2025 Read the published version in Environmental Monitoring and Assessment → Version 1 posted Editorial decision: Revision requested 23 Aug, 2024 Editor assigned by journal 22 Aug, 2024 Submission checks completed at journal 22 Aug, 2024 First submitted to journal 16 Aug, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4923724","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":344392926,"identity":"8e22d5b5-8d72-40d5-81a9-9995eac48d59","order_by":0,"name":"Hung Viet Dang","email":"","orcid":"","institution":"University of Technology, Vietnam National University","correspondingAuthor":false,"prefix":"","firstName":"Hung","middleName":"Viet","lastName":"Dang","suffix":""},{"id":344392927,"identity":"0bb06b89-d868-470b-956c-299dab9d6f8b","order_by":1,"name":"Huy Quoc Lam","email":"","orcid":"","institution":"Can Tho University","correspondingAuthor":false,"prefix":"","firstName":"Huy","middleName":"Quoc","lastName":"Lam","suffix":""},{"id":344392928,"identity":"d66ae2ee-5cf4-48b7-8163-651a75a805af","order_by":2,"name":"Linh My Nguyen","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAwklEQVRIiWNgGAWjYBACPmYGNiBlkwATYGwgpIUNoiUtAaaaCC1gxHCYFC3svMceF+acz+Ofdsb8wQcGG9kNB3jMHuB3GF+68cxtt4slbucYNs5gSDMGajE3wK+Fx0yad9vtxA3SOYbNPAyHEzccYEuTIELLOYiWPwz/idZyAKKFgQHIOMB8jBgtyYkzbqcVzuwxSDaeeZiAFn7+MyAtdon9s5M3fPhRYSfbd7yxDa8WNAAKKmYS1I+CUTAKRsEowA4AZi9COayCzc8AAAAASUVORK5CYII=","orcid":"","institution":"Ho Chi Minh City University of Technology and Education","correspondingAuthor":true,"prefix":"","firstName":"Linh","middleName":"My","lastName":"Nguyen","suffix":""}],"badges":[],"createdAt":"2024-08-16 08:43:27","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4923724/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4923724/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s10661-025-13624-3","type":"published","date":"2025-02-01T15:57:13+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":66673960,"identity":"20ddba87-0d83-4e4a-b701-f36b2b123c72","added_by":"auto","created_at":"2024-10-15 10:55:39","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":61778,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic illustration of the HCW system\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-4923724/v1/00785815bba450e449225692.png"},{"id":66673963,"identity":"76bf1a73-eb39-4a5f-b7a9-290f99865b67","added_by":"auto","created_at":"2024-10-15 10:55:39","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":272921,"visible":true,"origin":"","legend":"\u003cp\u003eChanges in time of pH, DO, TDS, TSS, BOD\u003csub\u003e5\u003c/sub\u003e, COD, NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e- N, TN, PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3-\u003c/sup\u003e- P, TP, E. coli and T. coli during the operational period (Jan 2021 to Dec 2021) at In, VF, HF and FWS. Limits for discharge and reusing were shown as straight lines (wherever available).\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-4923724/v1/316f91b73713445e90f82dac.png"},{"id":66673962,"identity":"3290d390-96b0-4aff-bc83-bdab2797eb81","added_by":"auto","created_at":"2024-10-15 10:55:39","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":120177,"visible":true,"origin":"","legend":"\u003cp\u003eCumulative removal efficiencies (values shown inside the bars) and standard deviation (error lines) along the treatment system, i.e., VFCW, HFCW and FWSCW for BOD\u003csub\u003e5\u003c/sub\u003e, COD, NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e- N, TSS, NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e-\u003csub\u003e \u003c/sub\u003eN, TN, PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3-\u003c/sup\u003e- P, TP, E. coli and T. coli.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-4923724/v1/af63347d70d9fb329eb5666c.png"},{"id":75352080,"identity":"5eca54eb-0bf2-46dc-a015-1043fc88d06c","added_by":"auto","created_at":"2025-02-03 16:13:08","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1304879,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4923724/v1/4a297b99-6751-4ce5-b4e6-5b5fafe2d071.pdf"},{"id":66673961,"identity":"068d0f67-55bb-4df6-8418-535e0f364de3","added_by":"auto","created_at":"2024-10-15 10:55:39","extension":"png","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":117233,"visible":true,"origin":"","legend":"","description":"","filename":"GraphicalAbstract.png","url":"https://assets-eu.researchsquare.com/files/rs-4923724/v1/2319fae94a565135245b1236.png"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eHybrid Constructed Wetlands for Tertiary Treatment of Poultry Slaughter Wastewater to Meet Quality Standards of Discharge and Reuse: A Full-Scale Case Study in Vietnam\u003c/p\u003e","fulltext":[{"header":"Highlights","content":"\u003cp\u003e- The HCW system achieved a good removal of\u0026nbsp;BOD\u003csub\u003e5\u003c/sub\u003e, COD,\u0026nbsp;TSS,\u0026nbsp;NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e- N,\u0026nbsp;NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e-\u003csub\u003e\u0026nbsp;\u003c/sub\u003eN,\u0026nbsp;TN,\u0026nbsp;PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3-\u003c/sup\u003e- P, TP, E. coli and T. coli\u0026nbsp;with\u0026nbsp;a total wetland area demand of 20 m\u003csup\u003e2\u003c/sup\u003e/m\u003csup\u003e3\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003e- Tertiary effluent concentrations,\u0026nbsp;especially\u0026nbsp;E. coli parameter reached the highest limits for both discharge and reclamation in Vietnam.\u003c/p\u003e\n\u003cp\u003e- The VFCW removed the majority of pollutants, whereas the succeeding HFCW and FWSCW as a polishing step.\u003c/p\u003e\n\u003cp\u003e- The HCW system is an approriate advanced technology to treat wastewater and make it reusable.\u003c/p\u003e"},{"header":"1. Introduction","content":"\u003cp\u003eSmall and medium-sized enterprises often have technical and economic limitations in treating domestic and production wastewater to meet environmental requirements for discharge. The wastewater treatment systems including primary and secondary treatment stages that these businesses are operating always only achieve low discharge limits as Column B of Vietnamese technical regulation on industrial wastewater, QCVN 40:2011/BTNMT (MONRE, 2011) and occasionally some nutrient parameters, i.e., NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e- N, TN and TP exceed the limits (Nguyen Thi Phuong Thao et al., 2022; Nga Tran Thi Viet et al., 2023). In addition to treating wastewater to follow discharge regulations, Law on Environmental Protection 2020 in Vietnam encourages companies to reuse wastewater after treatment if they ensure the quality standards of reused wastewater, especially obeying the microbiological requirements. Wastewater reuse is the process of converting domestic and/or industrial wastewater into water that can be reused for a variety of purposes. It is also called, water reuse, water recycling or water reclamation. In fact, reused wastewater has been used a lot in agricultural irrigation because this is one of the sectors with the highest water demand (Xi Nan et al., 2020). Therefore, seeking suitable tertiary technologies for wastewater discharge and reclamation which are technically feasible, economically viable and environment friendly for connection to existing wastewater treatment systems has been mentioned. Constructed wetlands (CWs) are often preferably considered interesting options because of ease of construction and installation, low investment and maintenance cost, and high removal efficiency with no secondary pollution (A.I. Stefanakis et al., 2019).\u003c/p\u003e \u003cp\u003eCWs are artificial systems that operate under natural conditions which can treat many types of wastewater including domestic and production wastewater to satisfy above requirements (Vymazal, 2005; Comino et al., 2011; Saeed et al., 2012; Stefanakis, 2018). They apply various technological designs, using natural wetland processes, associated with wetland hydrology, soils, microbes and plants for contaminants removal (Vymazal, 2007). Depending on the flow layout, CWs are generally categorized into two major groups: free water surface flow and sub-surface flow. Furthermore, sub-surface flow CWs are categorized into horizontal and vertical sub-surface flow CWs (Vymazal, 2005; Divyesh Parde et al., 2021). They have been successfully applied in almost all the world's countries over the last decades (Vymazal, J., 2011; Dong Qing Zhang et al., 2014). Several studies were completed showing the effectiveness of CWs in wastewater treatment at different stages known as primary, secondary and tertiary (Cristina \u0026Aacute;vila et al., 2014; F. Licciardello et al., 2018). It has been widely agreed that the reasonable application of configuration and the appropriate selection of vegetations are essential to attain high treatment efficiency in CWs (Brix, 1997; Divyesh Parde et al., 2021). Each type of CWs has different advantages and disadvantages regardless of the stage of treatment. Therefore, much attention has been paid to increase their conveniences and decrease their limitations. One of the new trends in wetland-based wastewater treatment is the combination of various CW types into one system called \u0026ldquo;hybrid\u0026rdquo; CW (HCW) system in order to establish physicochemical and microbiological conditions which would allow for the synergy of pollutant removal mechanisms to occur simultaneously (Cristina \u0026Aacute;vila et al., 2014; Shama Sehar et al., 2015; Amir Gholipour et al., 2021). However, CW research works and their applications under tropical climate condition like Southwestern Vietnam with the air temperature from 20 to 30\u003csup\u003e0\u003c/sup\u003eC, the annual rainfall from 1,200 to 1,800 mm and the air humidity above 80% have been still limited. Furthermore, there is a lack of information and reporting on CW construction and operation for on-site advanced treatment and reuse of wastewater for crops such as poultry slaughter wastewater (Dong Qing Zhang et al., 2014; F. Licciardello et al., 2018; Rita P. Shingare et al., 2019; Jan Vymazal et al., 2021).\u003c/p\u003e \u003cp\u003eThis paper describes the construction and operation details of a small-scale HCW system consisting of a vertical sub-surface flow CW (VFCW), a horizontal sub-surface flow CW (HFCW) and a free water surface flow CW (FWSCW) operated in series for tertiary wastewater treatment of an poultry slaughter enterprise in Southwestern Vietnam and presents the results of an on-site experiment of 12 months. The main objective of the experiment study were to verify whether the effluent quality of advanced wastewater treatment under the specific tropical climate complied with the limits not only for discharge into the receiving water source but also for reusing wastewater to water plants. Moreover, the role of each CW configuration and its appropriate site selection in the HCW system were also discussed.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Research location\u003c/h2\u003e \u003cp\u003eThe HCW system was built to treat the secondary effluent wastewater from the existing treatment system of a poultry slaughter enterprise at the production capacity of 500 ducks per day at Long Phung Commune, Can Giuoc District, Long An Province, Vietnam (10◦32 11.7 N, 106◦39 50.4 E). The location is approximately from 2 to 3 m above sea level. The total land area of the enterprise is 2,718 m\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. The climate of the area is tropical monsoon, so there are two seasons. They are known as the rainy and dry seasons. The rainy season lasts from May to October and the dry season lasts from November to April next year. The weather is warm all year round. From June 2021 to May 2022, the temperature was from 24.1 to 29.8\u003csup\u003e0\u003c/sup\u003eC and the yearly temperature was 26.7\u003csup\u003e0\u003c/sup\u003eC. The average rainfall and humidity were 1,576 mm and 84.8%, respectively. It is shown that the climate conditions of the region were favorable for the development and survival of animals, plants and microorganisms in the treatment system and the pollutant removal possibility was not much affected at different times of the year.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Experimental system\u003c/h2\u003e \u003cp\u003eThe existing poultry slaughter wastewater treatment system consisted of a primary treatment stage (a dissolved air flotation (DAF) system) and a secondary treatment stage (an upflow anaerobic sludge blanket (UASB) reactor together with an activated sludge system followed). Its capacity was 10.0 m\u003csup\u003e3\u003c/sup\u003e/day of wastewater. For the experiment, about 7.5 m\u003csup\u003e3\u003c/sup\u003e/day of unchlorinated secondary effluent wastewater from this system was pumped into the HCW system. The study system included a VFCW, a HFCW and a FWSCW sequentially placed at decreasing levels (0.2 m) to enable natural flow of wastewater under gravity. An effluent collection tank (ET) was used to collect and store tertiary effluent wastewater from the HCW system. A schematic representation of the overall treatment process is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTwo sub-surface flow CWs (VFCW and HFCW) with the size of each as 10.0 m (length) x 5.0 m (width) had the total area of ​​100 m\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. The depth of these two CWs was 1.3 m. Waterproof liner was used on the sides and bottom of each with the bottom slope from 1 to 2%. They contained two porous media layers. The bottom well-washed coarse gravel layer was 300 mm in depth (20\u0026ndash;40 mm in diameter, about 40% in porosity). The top well-washed fine gravel layer was 700 mm in depth (2\u0026ndash;5 mm in diameter, about 35% in porosity). Water level in these two CWs were kept below the fine gravel surface about 50\u0026ndash;100 mm and monitored by measurements taken from observation pipes placed in different parts of each. A freeboard of 300 mm was maintained.\u003c/p\u003e \u003cp\u003eIn the VFCW, five distribution pipes \u0026Oslash;27 mm on the fine gravel surface with 8 holes \u0026Oslash;10 mm every 1.0 m distance were arranged to distribute the effluent wastewater from the existing system uniformly across the entire surface. Three collection pipes \u0026Oslash;42 mm at the bottom of this wetland with 15 holes \u0026Oslash;12 mm every 0.6 m distance enclosed by coarse gravel were arranged to transfer wastewater from the VFCW to the HFCW. The HFCW had an inlet zone and an outlet zone with 1 m in length of each, which were filled of stone (40\u0026ndash;80 mmm in diameter) to facilitate the flow. In the inlet zone, two distribution pipe \u0026Oslash;60 mm on the top of the stone layer along the upstream width side with 28 holes \u0026Oslash;12 mm every 0.1 m distance was arranged to distribute the effluent wastewater from the VFCW fully through the horizontal section of the HFCW. In the outlet zone, three collection pipes \u0026Oslash;42 mm at the bottom of the stone layer along the downstream width side with 14 holes \u0026Oslash;12 mm every 0.2 m distance were arranged to transfer wastewater from the HFCW to the FWSCW.\u003c/p\u003e \u003cp\u003eThe FWSCW had a surface area of 50 m\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e with 10.0 m (length), 5.0 m (width). Waterproof liner was also used on the sides and bottom with the bottom slope from 1 to 2%. It contained two media layers. The bottom well-washed gravel layer was 500 mm in depth. The top soil layer was 100 mm in depth. Water level in this wetland was kept over the top soil layer about 100 mm and a freeboard of 300 mm is maintained. The pipes at input and output were 60 mm in diameter. The flow path through this wetland was assumed to be horizontal. Wastewater flowed from the HCW to the ET under gravity naturally. Flow rate of wastewater among different CWs was regulated by valves. The usable capacity of the ET was 5.0 m\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e with 5.0 m in length, 1.5 m in width, and 2.2 m in depth. Effluent wastewater from the experimental system was pumped out for discharge or reuse (two submersible pumps, one pump running and one pump standby, 1/4 Hp, maximum flow rate 1.0 m\u003csup\u003e3\u003c/sup\u003e/h).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Wetland plants\u003c/h2\u003e \u003cp\u003eSelection of macrophytes was made on the requirement that they were found growing naturally in this area and tolerant enough for contaminants and saturated soil conditions. (Shama Sehar et al., 2015; Fernando Garc\u0026iacute;a-\u0026acute;Avila et al., 2023). The VFCW and HFCW were planted with \u003cem\u003ePhragmites australis\u003c/em\u003e (common reed) with the density of 12\u0026ndash;14 plants/m\u003csup\u003e2\u003c/sup\u003e. The FWSCW was planted with \u003cem\u003eTypha angustifolia\u003c/em\u003e L. (Typhaceae) with the density of 6\u0026ndash;8 plants/m\u003csup\u003e2\u003c/sup\u003e. They are capable of growing up to 1.5\u0026ndash;3.0 m and are generally branched with leaf sheaths overlapping. Young shoots were collected from nearby natural wetland sites and transplanted on the top layers of the HCW system.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. System performance\u003c/h2\u003e \u003cp\u003eBefore going into the official experiment, the HCW system was kept soaked with fresh water for 2 weeks in order to acquire saturated growth of plants and associated microbial community in the rhizosphere, soil and gravel layer. The study system was run to adapt the secondary effluent wastewater from the existing system with an initial flow rate of 0.75 m\u003csup\u003e3\u003c/sup\u003e/day. After 4 weeks, the plants grew well with the height over 0.8 m. Then, flow rate was increased gradually until it reached an average value of 7.5 m\u003csup\u003e3\u003c/sup\u003e/day (15% increase each week). This was the survey flow rate of the study system to evaluate removal efficiencies. For the VFCW, HFCW and FWSCW, the hydraulic residence times (HRTs) were 2.4, 2.4 and 1.8 days, respectively (Recep \u0026Ccedil;akir et al., 2015; Raja Zubair Zahoor Qadiri et al., 2021). The total area of the HCW system was 150 m\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e and the area required for wetland treatment was 20 m\u003csup\u003e2\u003c/sup\u003e/m\u003csup\u003e3\u003c/sup\u003e. The hydraulic loading rates (HLRs) of the VFCW, HFCW and FWSCW were the same as 0.15 m/d.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5. Wastewater quality monitoring \u0026ndash; statistical analyses\u003c/h2\u003e \u003cp\u003eThe experiment system started from March 2021 to May 2022. The adaptation period for the HCW system lasted 3 months. Once stabilized, sampling and analyzing wastewater was carried out once a week. Wastewater samples were taken at the four different points of the whole study system, i.e., HCW input, VFCW output, HFCW output and FWSCW output. After sampling, the physical-chemical parameters of wastewater such as temperature, pH, dissolved oxygen (DO) and total dissolved solids (TDS) were measured onsite by portable Toledo meters. Then samples were properly stored in a cool box, sent to the Laboratory of Research Institute for Aquaculture No. 2 - Ho Chi Minh City and analyzed immediately for total suspended solids (TSS), biological oxygen demand (BOD\u003csub\u003e5\u003c/sub\u003e), chemical oxygen demand (COD), ammonia nitrogen (NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e-N), nitrate nitrogen (NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e-N), total nitrogen (TN), orthophosphate (PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e-P), total phosphorus (TP), \u003cem\u003eEscherichia coli\u003c/em\u003e (E. coli), total coliforms (T. coli) according to Vietnamese technical regulation together with American Public Health Association (APHA) Standard Methods (APHA, 2012). Harvesting was carried out after 6 months (end of December 2021) and 12 months (end of May 2022) from the end of adaptation period, because it was assumed that the HCW system was in a steady state based on observations of plant growth height variation and start of inflorescence formation. The plants growth before and after harvesting was recorded. At each time of harvesting, plants were cut approximately 10 cm above the gravel or water surface to prevent flooding and supply regeneration of the remaining shoots. Biomass samples were weighed onsite for fresh weight. Then, they were dried to fixed weight for 72 hours at 70\u003csup\u003e0\u003c/sup\u003eC, re-weighed for dry weight and ground for nutrient analysis at the Laboratory (Jeroen J.M et al., 2020).\u003c/p\u003e \u003cp\u003eAll analyses were repeated three times and the measurements were based on average values. Obtained results were subjected to statistical analysis and t-test was used to determine significant differences between the mean values of pollutant concentrations at the various treatment units and between the mean values of pollutant removals at the first and second harvests. 95% confidence interval (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) was considered as minimum value for statistical significance. Absolute removal for each constituent at one intermediate stage or unit of the study system was calculated based on its concentrations at the input and output of the stage or unit. Relative removal for each pollutant at one intermediate stage or unit of the system was calculated based on its concentrations at the input of the system and the output of the stage or unit, and subtracting the removal in the previous stages or units. Cumulative removal for each constituent at one intermediate stage or unit of the system was calculated based on its concentrations at the input of the system and the output of the stage or unit.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results And Discussion","content":"\u003cp\u003eNational technical regulation on industrial wastewater of Vietnam, QCVN 40:2011/BTNMT (MONRE, 2011) at Column A is used as the limits for discharge into the receiving water source. National technical regulation on livestock wastewater used for crops of Vietnam, QCVN 01-195:2022/BNNPTNT (MARD, 2022) at Class I, II, III, IV is used as the limits of pH and E. coli for reusing wastewater to water plants. The regulation has not the limits of organic matter and suspended solids for wastewater reuse but Law on Environmental Protection 2020 in Vietnam allows the application of similar standards of developed industrial countries. In this case, Regulation (EU) 2020/741 of the European Parliament and of the Council of 25 May 2020 on minimum requirements for water reuse (EU, 2020) at Class B is used as the limits of BOD\u003csub\u003e5\u003c/sub\u003e and TSS. The variations in physical, chemical, and microbiological parameters at the four different points of the whole study system in comparison with these limits were presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eAverage (Mean), standard deviation (SD), minimum (Min) and maximum (Max) values of physicochemical parameters and bacteriological concentrations at HCW input (In), VFCW output (VF), HFCW output (HF) and FWSCW output (FWS) in comparision with Limits for discharge into the receiving water source (Discharge) and Limits for reusing wastewater to water plants (Reusing).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;52)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnit\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIn\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eVF\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eHF\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eFWS\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eDischarge\u003c/p\u003e \u003cp\u003e(MONRE, 2011)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eReusing\u003c/p\u003e \u003cp\u003e(MARD, 2022)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH\u003c/p\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003cp\u003eMin - Max\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.04\u0026thinsp;\u0026plusmn;\u0026thinsp;0.28\u003c/p\u003e \u003cp\u003e6.75\u0026ndash;7.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.22\u0026thinsp;\u0026plusmn;\u0026thinsp;0.18\u003c/p\u003e \u003cp\u003e6.99\u0026ndash;7.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.28\u0026thinsp;\u0026plusmn;\u0026thinsp;0.14\u003c/p\u003e \u003cp\u003e7.12\u0026ndash;7.47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7.33\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12\u003c/p\u003e \u003cp\u003e7.21\u0026ndash;7.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e6.0\u0026ndash;9.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e5.5\u0026ndash;9.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDO\u003c/p\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003cp\u003eMin - Max\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emg/L\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.56\u0026thinsp;\u0026plusmn;\u0026thinsp;0.37\u003c/p\u003e \u003cp\u003e2.12\u0026ndash;3.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.10\u0026thinsp;\u0026plusmn;\u0026thinsp;0.45\u003c/p\u003e \u003cp\u003e1.66\u0026ndash;2.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.53\u0026thinsp;\u0026plusmn;\u0026thinsp;0.33\u003c/p\u003e \u003cp\u003e1.17\u0026ndash;1.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.63\u0026thinsp;\u0026plusmn;\u0026thinsp;0.39\u003c/p\u003e \u003cp\u003e1.24\u0026ndash;2.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTDS\u003c/p\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003cp\u003eMin - Max\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emg/L\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e272\u0026thinsp;\u0026plusmn;\u0026thinsp;46\u003c/p\u003e \u003cp\u003e214\u0026ndash;326\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e245\u0026thinsp;\u0026plusmn;\u0026thinsp;42\u003c/p\u003e \u003cp\u003e199\u0026ndash;301\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e234\u0026thinsp;\u0026plusmn;\u0026thinsp;39\u003c/p\u003e \u003cp\u003e187\u0026ndash;284\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e227\u0026thinsp;\u0026plusmn;\u0026thinsp;32\u003c/p\u003e \u003cp\u003e182\u0026ndash;276\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTSS\u003c/p\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003cp\u003eMin - Max\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emg/L\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e35\u0026thinsp;\u0026plusmn;\u0026thinsp;13\u003c/p\u003e \u003cp\u003e20\u0026ndash;53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e12\u0026thinsp;\u0026plusmn;\u0026thinsp;8\u003c/p\u003e \u003cp\u003e10\u0026ndash;27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10\u0026thinsp;\u0026plusmn;\u0026thinsp;6\u003c/p\u003e \u003cp\u003e7\u0026ndash;20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8\u0026thinsp;\u0026plusmn;\u0026thinsp;5\u003c/p\u003e \u003cp\u003e6\u0026ndash;18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e35\u003c/p\u003e \u003cp\u003e(EU, 2020)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBOD\u003csub\u003e5\u003c/sub\u003e\u003c/p\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003cp\u003eMin - Max\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emg/L\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e21\u0026thinsp;\u0026plusmn;\u0026thinsp;12\u003c/p\u003e \u003cp\u003e14\u0026ndash;33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10\u0026thinsp;\u0026plusmn;\u0026thinsp;5\u003c/p\u003e \u003cp\u003e6\u0026ndash;16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7\u0026thinsp;\u0026plusmn;\u0026thinsp;4\u003c/p\u003e \u003cp\u003e5\u0026ndash;13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5\u0026thinsp;\u0026plusmn;\u0026thinsp;3\u003c/p\u003e \u003cp\u003e4\u0026ndash;11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e25\u003c/p\u003e \u003cp\u003e(EU, 2020)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCOD\u003c/p\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003cp\u003eMin - Max\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emg/L\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e47\u0026thinsp;\u0026plusmn;\u0026thinsp;23\u003c/p\u003e \u003cp\u003e27\u0026ndash;69\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e23\u0026thinsp;\u0026plusmn;\u0026thinsp;12\u003c/p\u003e \u003cp\u003e14\u0026ndash;39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e14\u0026thinsp;\u0026plusmn;\u0026thinsp;8\u003c/p\u003e \u003cp\u003e10\u0026ndash;26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e10\u0026thinsp;\u0026plusmn;\u0026thinsp;4\u003c/p\u003e \u003cp\u003e8\u0026ndash;18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e- N\u003c/p\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003cp\u003eMin - Max\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emg/L\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.3\u0026thinsp;\u0026plusmn;\u0026thinsp;3.6\u003c/p\u003e \u003cp\u003e7.1\u0026ndash;15.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.7\u0026thinsp;\u0026plusmn;\u0026thinsp;1.6\u003c/p\u003e \u003cp\u003e2.8\u0026ndash;7.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.0\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9\u003c/p\u003e \u003cp\u003e2.2\u0026ndash;4.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5\u003c/p\u003e \u003cp\u003e1.0\u0026ndash;2.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e- N\u003c/p\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003cp\u003eMin - Max\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emg/L\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e20.5\u0026thinsp;\u0026plusmn;\u0026thinsp;7.7\u003c/p\u003e \u003cp\u003e15.8\u0026ndash;32.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e12.5\u0026thinsp;\u0026plusmn;\u0026thinsp;5.4\u003c/p\u003e \u003cp\u003e7.2\u0026ndash;19.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e5.2\u0026thinsp;\u0026plusmn;\u0026thinsp;3.1\u003c/p\u003e \u003cp\u003e3.5\u0026ndash;9.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.8\u0026thinsp;\u0026plusmn;\u0026thinsp;1.7\u003c/p\u003e \u003cp\u003e1.6\u0026ndash;5.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTN\u003c/p\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003cp\u003eMin - Max\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emg/L\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e33.8\u0026thinsp;\u0026plusmn;\u0026thinsp;9.3\u003c/p\u003e \u003cp\u003e20.1\u0026ndash;45.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e18.4\u0026thinsp;\u0026plusmn;\u0026thinsp;6.5\u003c/p\u003e \u003cp\u003e13.9\u0026ndash;28.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e9.7\u0026thinsp;\u0026plusmn;\u0026thinsp;3.6\u003c/p\u003e \u003cp\u003e5.1\u0026ndash;13.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.1\u0026thinsp;\u0026plusmn;\u0026thinsp;2.2\u003c/p\u003e \u003cp\u003e2.9\u0026ndash;8.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e- P\u003c/p\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003cp\u003eMin - Max\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emg/L\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.8\u0026thinsp;\u0026plusmn;\u0026thinsp;2.4\u003c/p\u003e \u003cp\u003e3.2\u0026ndash;9.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.4\u0026thinsp;\u0026plusmn;\u0026thinsp;1.6\u003c/p\u003e \u003cp\u003e2.7\u0026ndash;6.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.0\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1\u003c/p\u003e \u003cp\u003e1.6\u0026ndash;4.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5\u003c/p\u003e \u003cp\u003e1.0\u0026ndash;2.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTP\u003c/p\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003cp\u003eMin - Max\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emg/L\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.9\u0026thinsp;\u0026plusmn;\u0026thinsp;2.9\u003c/p\u003e \u003cp\u003e4.4\u0026ndash;10.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.8\u0026thinsp;\u0026plusmn;\u0026thinsp;1.6\u003c/p\u003e \u003cp\u003e3.1\u0026ndash;5.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.2\u0026thinsp;\u0026plusmn;\u0026thinsp;1.2\u003c/p\u003e \u003cp\u003e2.0\u0026ndash;4.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.8\u0026thinsp;\u0026plusmn;\u0026thinsp;0.6\u003c/p\u003e \u003cp\u003e1.3\u0026ndash;2.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eE. coli\u003c/p\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003cp\u003eMin - Max\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eCFU/\u003c/p\u003e \u003cp\u003e100mL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e4.65\u0026thinsp;\u0026plusmn;\u0026thinsp;1.28\u003c/p\u003e \u003cp\u003e2.94\u0026ndash;6.37\u003c/p\u003e \u003cp\u003e(x10\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e0.48\u0026thinsp;\u0026plusmn;\u0026thinsp;0.21\u003c/p\u003e \u003cp\u003e0.19\u0026ndash;0.73\u003c/p\u003e \u003cp\u003e(x10\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e0.24\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07\u003c/p\u003e \u003cp\u003e0.12\u0026ndash;0.36\u003c/p\u003e \u003cp\u003e(x10\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e0.05\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03\u003c/p\u003e \u003cp\u003e0.02\u0026ndash;0.09\u003c/p\u003e \u003cp\u003e(x10\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eClass I*\u003c/p\u003e \u003cp\u003e\u0026le;\u0026thinsp;0.2x10\u003csup\u003e3\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eClass II\u003c/p\u003e \u003cp\u003e\u0026le;\u0026thinsp;1.0x10\u003csup\u003e3\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eClass III\u003c/p\u003e \u003cp\u003e\u0026le;\u0026thinsp;5.0x10\u003csup\u003e3\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eClass IV\u003c/p\u003e \u003cp\u003e\u0026gt;\u0026thinsp;5.0x10\u003csup\u003e3\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eT. coli\u003c/p\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003cp\u003eMin - Max\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMPN/\u003c/p\u003e \u003cp\u003e100mL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22.3\u0026thinsp;\u0026plusmn;\u0026thinsp;5.8\u003c/p\u003e \u003cp\u003e16.8 \u0026minus;\u0026thinsp;30.5\u003c/p\u003e \u003cp\u003e(x10\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.6\u0026thinsp;\u0026plusmn;\u0026thinsp;1.6\u003c/p\u003e \u003cp\u003e3.1\u0026ndash;6.8\u003c/p\u003e \u003cp\u003e(x10\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.4\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5\u003c/p\u003e \u003cp\u003e1.0\u0026ndash;2.3\u003c/p\u003e \u003cp\u003e(x10\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.8\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e \u003cp\u003e0.5\u0026ndash;1.3\u003c/p\u003e \u003cp\u003e(x10\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3.0x10\u003csup\u003e3\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e*National technical regulation on livestock wastewater used for crops of Vietnam, QCVN 01-195:2022/BNNPTNT (MARD, 2022) has Class I: All types of plants; Class II: All types of plants except annual vegetables and medicinal plants; Class III: All types of plants except plants used as food for humans and animals; and Class IV: Not used for crops.\u003c/p\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Changes of parameters and effluent of the system\u003c/h2\u003e \u003cp\u003eBecause pH values of secondary effluent wastewater were in the neutral range, the mean pH values at four points of the HCW system were 7.04, 7.22, 7.28 and 7.33 (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). It tended to increase as it went from the VFCW to the HFCW to the FWSCW through pollutant removal metabolic pathways (Amir Gholipour et al., 2021). The mean DO concentrations from the input to the output of the HCW system were 2.56, 2.10, 1.53 and 1.63 mg/L (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The higher value at the input compared with the lower value at the output was reasonable because the wastewater flowing into the HCW system had been artificially aerated before while the wastewater flowing out of the HCW system was only naturally aerated afterward. Variation of mean DO concentrations in these three CWs reflected the different presence of the main oxygen supply pathways which may be atmospheric reoxygenation and plant oxygen release (Jingying Zhang et al., 2023). Each type of CWs has its distinct source of oxygen and VFCW provides the best oxygen supply because of the basis of the wastewater flow type favorable for air dissolution (Sohair I.Abou-Elela et al., 2013; Amir Gholipour et al., 2021). The mean concentrations of TDS and TSS gradually decreased from 272 and 35 mg/L at the input of the HCW system to 245 and 12 mg/L at the output of the VFCW to 234 and 10 mg/L at the output of the HFCW to 227 and 8 mg/L at the output of FWSCW, respectively (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). When wastewater passed through the HCW system, there was no notable removal of TDS but TSS was greatly removed with mean removal efficiency of 77.1% (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), thus highlighting the importance of macrophytes in removal of suspended solids (Georgios D. Gikas et al., 2012; Cristina \u0026Aacute;vila et al., 2014). Contaminants such as suspended solids can be settled and filtered within CWs, including the blocking effect of macrophyte roots and the gravitational interception of solid objects between coarse and fine gravel particles (Brix, 1997; Divyesh Parde et al., 2021). The maximum TSS effluent concentrations of the HCW system were much lower than the Vietnamese regulation limits of 50 mg/L for discharge into the receiving water source and 35 mg/L for reusing wastewater to water plants.\u003c/p\u003e \u003cp\u003eSignificant reduction in BOD\u003csub\u003e5\u003c/sub\u003e or COD was observed in the HCW system with mean tertiary effluent concentrations of 5 and 10 mg/L, respectively (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The maximum tertiary effluent concentrations of BOD\u003csub\u003e5\u003c/sub\u003e and COD were fully below the Vietnamese regulation limits of 30 and 75 mg/L, respectively for discharge as well as 25 mg/L in BOD\u003csub\u003e5\u003c/sub\u003e for reusing. The mean concentrations of NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e- N, NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e- N, TN, PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003eP and TP of secondary effluent wastewater were 9.3, 20.5, 33.8, 5.8 and 6.9 mg/L, respectively, which decreased along the HCW system with mean effluent concentrations of 4.7, 12.5, 18.4, 4.4 and 4.8 mg/L at the VFCW; 3.0, 5.2, 9.7, 3.0 and 3.2 mg/L at the HFCW; 1.5 mg/L, 2.8, 5.1, 1.6 and 1.8 mg/L at the FWSCW, respectively (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). In CW systems, the nitrogen removal mechanisms are accomplished by biological processes such as ammonification, nitrification, denitrification, plant uptake, biomass assimilation, dissimilatory nitrate reduction and physicochemical routes such as ammonia volatilization, adsorption, ion exchange (Brix, 1997; Vymazal, 2007). The removal of phosphorus in CW systems involves a number of biological processes including plant uptake, biomass assimilation, biological storage in microorganisms, e.g., polyphosphate accumulating organism (PAO) and physicochemical pathways such as precipitation, adsorption (Brix, 1997; Vymazal, 2007). The maximum NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e- N, TN and TP tertiary effluent concentrations were less than the Vietnamese regulation limits of 5, 20 and 4 mg/L, respectively for discharge while there were no limits of them for reusing. The mean concentrations of E. coli and T. coli in the effluent wastewater of the HCW system were 0.05x10\u003csup\u003e3\u003c/sup\u003e CFU/100mL and 0.8x10\u003csup\u003e3\u003c/sup\u003e MPN/100mL, respectively (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). These bacteriological values reached the Vietnamese regulation limits of 0.2x10\u003csup\u003e3\u003c/sup\u003e CFU/100mL for reusing (Class I) and 3.0x10\u003csup\u003e3\u003c/sup\u003e MPN/100mL for discharge (Column A).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.2. Efficiencies at the various CWs of the system\u003c/h2\u003e \u003cp\u003eThe pollutant loading rates to the whole wetland system were 10.5 g BOD\u003csub\u003e5\u003c/sub\u003e/m\u003csup\u003e2\u003c/sup\u003e.day, 23.5 g COD/m\u003csup\u003e2\u003c/sup\u003e.day, 17.5 g TSS/m\u003csup\u003e2\u003c/sup\u003e.day, 4.6 g NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e- N/m\u003csup\u003e2\u003c/sup\u003e.day, 10.2 g NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e- N/m\u003csup\u003e2\u003c/sup\u003e.day, 16.9 g TN/m\u003csup\u003e2\u003c/sup\u003e.day, 2.9 g PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e- P/m\u003csup\u003e2\u003c/sup\u003e.day and 3.4 g TP/m\u003csup\u003e2\u003c/sup\u003e.day. The mean concentrations of E. coli and T. coli in the influent wastewater of the HCW system were 4.65x10\u003csup\u003e3\u003c/sup\u003e CFU/100mL and 22.3x10\u003csup\u003e3\u003c/sup\u003e MPN/100mL. The average removal efficiencies of the HCW system were 76.2% for BOD\u003csub\u003e5\u003c/sub\u003e, 78.7% for COD, 77.1% for TSS, 83.9% for NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e- N, 86.3% for NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e- N, 84.9% for TN, 72.3% for PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e- P, 73.9% for TP, 98.9% for E.coli and 96.4% for T. coli (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The performance of the HCW system were similar or even better than the tertiary constructed wetland in a previous study, where mean concentrations of BOD\u003csub\u003e5\u003c/sub\u003e, COD and TSS were reduced by about 70%, 80% and 90%, respectively and output concentration of E.coli was 0,04x10\u003csup\u003e3\u003c/sup\u003e CFU/100 mL (S.\u0026Ccedil;. Ayaz, 2008).\u003c/p\u003e \u003cp\u003eFor the VFCW, HFCW and FWSCW, the average mass removal rates were 5.5, 1.5 and 1.0 g BOD\u003csub\u003e5\u003c/sub\u003e/m\u003csup\u003e2\u003c/sup\u003e.day; 12.0, 4.5 and 2.0 g COD/m\u003csup\u003e2\u003c/sup\u003e.day; 11.5, 1.0 and 1.0 g TSS/m\u003csup\u003e2\u003c/sup\u003e.day whereas mean relative removal efficiencies were 52.4, 14.3 and 9.5% for BOD\u003csub\u003e5\u003c/sub\u003e; 51.1, 19.1 and 8.5% for COD; 65.7, 5.7 and 5.7% for TSS, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The CW where most relative removal efficiencies of organic matter and suspended solids occurred was the VFCW. The CW with the lower relative removal efficiencies of organic matter and suspended solids was the FWSCW. The VFCW placed in front of the HFCW and FWSCW removed more than half of organic matter and suspended solids mass removal rates of the whole HCW system. Generally, as most of the published studies indicate, the majority of pollutants is mainly removed in the first CW rather than the later CWs of the hybrid CW systems (Cristina \u0026Aacute;vila et al., 2014; Shama Sehar et al., 2015). This is completely reasonable because the degradation of pollutants requires aerobic conditions and VFCW is naturally aerated better than HFCW and FWSCW. The HFCW and FWSCW showed a similar performance as a polishing step of the HCW system. Although secondary effluent concentrations of BOD\u003csub\u003e5\u003c/sub\u003e, COD and TSS were lower than the Vietnamese regulation limits for discharge, the fact that the maximum tertiary effluent concentrations of them always complied with the Vietnamese regulation limits for reuse also demonstrated that the HFCW and FWSCW had done a good job of supporting and completing the VFCW and were a necessary addition in the treatment train. Futhermore, having many various CW configurations delays wastewater passage through the combined system which in turn increases the retention time and as a consequence, the removal efficiencies of pollutants.\u003c/p\u003e \u003cp\u003eThe average mass removal rates in the VFCW, HFCW and FWSCW were 2.3, 0.8 and 0.7 g NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e- N/m\u003csup\u003e2\u003c/sup\u003e.day; 4.0, 3.6 and 1.2 g NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e- N/m\u003csup\u003e2\u003c/sup\u003e.day; 7.7, 4.3 and 2.3 g TN/m\u003csup\u003e2\u003c/sup\u003e.day; 0.7, 0.7 and 0.7 g PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e- P/m\u003csup\u003e2\u003c/sup\u003e.day; 1.0, 0.8 and 0.7 g TP/m\u003csup\u003e2\u003c/sup\u003e.day, respectively, whereas mean relative removal efficiencies were 49.5, 18.3 and 16.1% for NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e- N; 39.0, 35.6 and 11.7% for NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e- N; 45.6, 25.7 and 13.6% for TN; 24.1, 24.1 and 24.1% for PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e- P; 30.4, 23.2 and 20.3% for TP, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Relative removal efficiencie of NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e- N decreased from the VFCW to the HFCW and vice versa, removal efficiency of NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e- N increased from the VFCW to the HFCW. The design of VFCW typically provides a nitrified effluent due to the strong aerobic conditions and HFCW design generally promotes the development of anoxic conditions that favour denitrification process (Brix, 1997; Vymazal, 2007). That is why HFCW is often used after VFCW in order to provide denitrification process for the nitrified effluent of VFCW (Shama Sehar et al., 2015; Amir Gholipour et al., 2021). The lowest removal efficiencies of NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e- N, NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e- N, TN, PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e- P and TP were at the FWSCW. The results indicated that operation of the VFCW, HFCW and FWSCW placed in series would be more efficient in terms of nitrogen and phosphorus removal compared with operating them individually or in parallel (Georgios D. Gikas et al., 2012; Sohair I.Abou-Elela et al., 2013; Raja Zubair Zahoor Qadiri et al., 2021). Removal of phosphorus tends not to be as high as nitrogen removal in CW systems and typical amounts of phosphorus removal are in the range of 40 to 60%. However, when operated with the input loading rates of 2.9 g PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e- P/m\u003csup\u003e2\u003c/sup\u003e.day and 3.4 g TP/m\u003csup\u003e2\u003c/sup\u003e.day, the HCW system had treatment efficiencies of 72.3% for PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e- P and 73.9% for TP (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The diversity of hydrological processes, flow directions, macrophytes growth and microorganisms presence is very important to treatment efficiency of CW systems. Most likely, utilization of several different CW types into one system provides a more effective synergy of pollutant removal mechanisms, which encourages the system to remove more of nutrients from wastewater.\u003c/p\u003e \u003cp\u003eTo the VFCW, HFCW and FWSCW, the average removal efficiencies were 89.6, 5.2 and 4.1% for E. coli; 79.4, 14.3 and 2.7% for T. coli, respectively. This result was in accordance with Cristina \u0026Aacute;vila et al., 2014 as, they found overall removal rate of E. Coli up to 99.99% for a full-scale hybrid CW system for domestic wastewater treatment and reuse in small communities. The HCW system showed more reduction concentration of E. coli and T. coli as compared to previously reported studies in individual CW systems with only one or two types (Sohair I.Abou-Elela et al., 2013; Amir Gholipour et al., 2021). HLR and corresponding HRT are considered the major operational control factors in CW systems as they can provide sufficient contact between contaminants, rhizosphere of plants and attached microorganisms, thus decrease concentration of E. coli and T. coli in wastewater (Recep \u0026Ccedil;akir et al., 2015; Shama Sehar et al., 2015). In general, effective removal of pathogens from wastewater using CW systems requires low HLR, and subsequently long HRT. Owing to the HLR of 0.15 m/day and the HRT of 6.6 days, the slow moving wastewater in the VFCW, HFCW and FWSCW configurations enabled pathogens to settle out and thus the HCW system was capable to removing high percentages of E. coli and T. coli. The function made by various CW configurations in series proved crucial to achieve a treated wastewater quality appropriate for its discharge and reusing.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.3. Reuse potential of the treated wastewaters\u003c/h2\u003e \u003cp\u003eEffluent wastewater of the study system were evaluated in terms of potential for reusing wastewater to water plants. Generally, the main parameters that need to be met for wastewater reuse are pH, TDS, TSS, BOD\u003csub\u003e5\u003c/sub\u003e, COD, heavy metals, trace organic contaminants and pathogenic microorganisms of helminthes, protozoans, fungi, bacteria, and viruses (A. Ghermandi et al., 2007). To poultry slaughter wastewater, the parameters mentioned in the standard for effluent reuse are pH, TSS, BOD\u003csub\u003e5\u003c/sub\u003e and E. coli (EU, 2020; MARD, 2022). For advanced wetland-based wastewater treatment, effluent concentration of E. coli is difficult to reach the limit for wastewater reuse without disinfection (Selma \u0026Ccedil;. Ayaz et al., 2015). Based on National technical regulation on livestock wastewater used for crops of Vietnam, QCVN 01-195:2022/BNNPTNT (MARD, 2022), the limits of E. coli are 0.2x10\u003csup\u003e3\u003c/sup\u003e CFU/100 mL for Class I and 1.0x10\u003csup\u003e3\u003c/sup\u003e CFU/100 mL for Class II. In this experiment, secondary effluent parameters had basically satisfied their limits for reusing wastewater to water plants except for microbiological parameter, E. coli. To the VFCW, HFCW and FWSCW, effluent concentrations of E. coli were 4.65x10\u003csup\u003e3\u003c/sup\u003e, 0.48x10\u003csup\u003e3\u003c/sup\u003e and 0.05x10\u003csup\u003e3\u003c/sup\u003e CFU/100 mL, respectively. This showed that effluent concentrations of E. coli gradually decreases along the HCW system and only reached the limit for Class I at the final step, FWSCW. The system had to use all its capabilities to reach the most difficult limits on wastewater reuse in Vietnam. On the other hand, each CW in the system contributed to E. coli treatment and strongly affected the reuse level of the effluent wastewater. The HCW system provided an effluent quality that allowed for its reuse in watering plants and lawns on business premises. The total investment cost for this tertiary treatment system was only a small part compared to the existing secondary treatment system while operating and maintaining the system only required a non-specialized staff right at the enterprise. It can be easily seen that CW technology can be easily implemented everywhere, depending on local conditions. CW system in advanced treatment for wastewater reuse also aims to sustainably use resources and environment for sustainable development.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.4. Plant uptake and biomass production\u003c/h2\u003e \u003cp\u003eMacrophyte growth in three CWs of the HCW system requires a defined program for harvesting and controlling of the biomasses produced. \u003cem\u003ePhragmites australis\u003c/em\u003e and \u003cem\u003eTypha angustifolia\u003c/em\u003e L. grew so relatively quickly that they needed to be harvested and assessing every 180 days to avoid dead plant matter pollution in the effluent wastewater. Observing the plant growth showed that the root systems of \u003cem\u003ePhragmites australis\u003c/em\u003e and \u003cem\u003eTypha angustifolia\u003c/em\u003e L. strongly expanded with average length 40\u0026ndash;60 cm while sticking entirely to the soil and gravel layers in the system. Trunk diameter of them was from 1.26 to 2.03 cm. \u003cem\u003ePhragmites australis\u003c/em\u003e and \u003cem\u003eTypha angustifolia\u003c/em\u003e L. survived and developed well in the system with growth height of 39 and 32 cm/plant.month, respectively. Average height and dry weight of \u003cem\u003ePhragmites australis\u003c/em\u003e reached 248 cm and 1.43 kg/m\u003csup\u003e2\u003c/sup\u003e for the two harvests in the VFCW and 225 cm and 1.37 kg/m\u003csup\u003e2\u003c/sup\u003e for the two harvests in the HFCW, respectively (Raja Zubair Zahoor Qadiri et al., 2021). \u003cem\u003ePhragmites australis\u003c/em\u003e grew well in both the VFCW and HFCW and did not change significantly between the first and second harvests (Sohair I.Abou-Elela et al., 2013). Height and biomass production of \u003cem\u003ePhragmites australis\u003c/em\u003e in the VFCW were slightly more than these in the HFCW. In the FWSCW, \u003cem\u003eTypha angustifolia\u003c/em\u003e L. had 18 to 20 leaves/plant with average height and dry weight of 216 cm and 0.33 kg/m\u003csup\u003e2\u003c/sup\u003e for the two harvests, respectively (Jeroen J.M et al., 2020). Plant harvesting showed that \u003cem\u003eTypha angustifolia\u003c/em\u003e L. grew during the rainy season months almost similarly to during the dry season months. In a simple way, the nitrogen and phosphorus uptake in the VFCW, HFCW and FWSCW was 7.7, 4.3 and 2.3 gN/m\u003csup\u003e2\u003c/sup\u003e, respectively and 1.0, 0.8 and 0.7 gP/m\u003csup\u003e2\u003c/sup\u003e, respectively. \u003cem\u003ePhragmites australis\u003c/em\u003e can be used as livestock feed and young stem of \u003cem\u003eTypha angustifolia\u003c/em\u003e L. can be used as green vegetables for human meals.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe secondary effluent from a poultry slaughter wastewater treatment system was successfully treated at tertiary stage by the HCW system consisting of a VFCW, a HFCW and a FWSCW placed in series. The removal efficiencies of BOD\u003csub\u003e5\u003c/sub\u003e, COD, TSS, NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e- N, NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e- N, TN, PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3-\u003c/sup\u003e- P, TP, E. coli and T. coli reached average values of 76.2, 78.7, 77.1, 83.9, 86.3, 84.9, 72.3, 73.9, 98.9 and 96.4%, respectively, while the effluent concentrations of the system complied with the limits not only for discharge into the receiving water source (Column A) but also for reusing wastewater to water plants (Class I) in Vietnam. The HCW system provided a more effective synergy of pollutant removal mechanisms to thoroughly treat wastewater. The three-step CW system had advantages over single CW systems such that removal of organic matter, suspended solids, nitrogen and phosphorus as well as pathogens were mainly achieved in the VFCW, whereas the succeeding HFCW and FWSCW played the role as a polishing step of the HCW system. \u003cem\u003ePhragmites australis\u003c/em\u003e grew well in both the VFCW and HFCW and \u003cem\u003eTypha angustifolia\u003c/em\u003e L. was also good selection for the FWSCW. With a total wetland area demand of 20 m\u003csup\u003e2\u003c/sup\u003e/m\u003csup\u003e3\u003c/sup\u003e, the HCW system was considered to be approriate for small and medium-sized enterprises in advanced wastewater treatment for discharge and reclamation.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors would like to greatly acknowledge the support of time and facilities from University of Technology, Vietnam National University – Ho Chi Minh City, Vietnam and Ho Chi Minh City University of Technology and Education, Ho Chi Minh City, Vietnam for this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;The authors declare that the data supporting the findings of this study are available within this published article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eHung Viet Dang: Supervision, Writing - original draft, reviewing and Editing; Huy Quoc Lam: Data curation, Formal analysis; \u0026nbsp;Linh My Nguyen: Methodology ,Conceptualization, Writing - reviewing and Editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent of human participants\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study did not involve human participants, and therefore, no consent was required.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding Declaration\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was funded by Hi-Tech BK Environmental Company Limited, Ho Chi Minh City, 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https://doi.org/10.1016/j.ecoleng.2013.10.010\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"environmental-monitoring-and-assessment","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"emas","sideBox":"Learn more about [Environmental Monitoring and Assessment](http://link.springer.com/journal/10661)","snPcode":"10661","submissionUrl":"https://submission.nature.com/new-submission/10661/3","title":"Environmental Monitoring and 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The HCW system includes a vertical sub-surface flow CW (VFCW), a horizontal sub-surface flow CW (HFCW) and a free water surface flow CW (FWSCW) operated in series had a total area of 150 m2. It received 7.5 m3/day of secondary effluent wastewater from the existing treatment system of a poultry slaughter enterprise at the production capacity of 500 ducks per day in an on-site experiment of 12 months. The results showed that the removal efficiencies of biological oxygen demand (BOD5), chemical oxygen demand (COD), total suspended solids (TSS), ammonia nitrogen (NH4+-N), nitrate nitrogen (NO3--N), total nitrogen (TN), orthophosphate (PO43--P), total phosphorus (TP), Escherichia coli (E. coli) and total coliforms (T. coli) reached average values of 76.2, 78.7, 77.1, 83.9, 86.3, 84.9, 72.3, 73.9, 98.9 and 96.4%, respectively, while the effluent concentrations of the study system complied with the most difficult limits not only for discharge into the receiving water source but also for reusing wastewater to water plants. The function made by various configurations such as a VFCW, a HFCW and a FWSCW placed sequentially in the HCW system proved crucial to treat wastewater and make it reusable.","manuscriptTitle":"Hybrid Constructed Wetlands for Tertiary Treatment of Poultry Slaughter Wastewater to Meet Quality Standards of Discharge and Reuse: A Full-Scale Case Study in Vietnam","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-10-15 10:55:34","doi":"10.21203/rs.3.rs-4923724/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-08-24T00:49:38+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-08-22T09:52:52+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-08-22T09:51:22+00:00","index":"","fulltext":""},{"type":"submitted","content":"Environmental Monitoring and Assessment","date":"2024-08-16T08:42:06+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"environmental-monitoring-and-assessment","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"emas","sideBox":"Learn more about [Environmental Monitoring and Assessment](http://link.springer.com/journal/10661)","snPcode":"10661","submissionUrl":"https://submission.nature.com/new-submission/10661/3","title":"Environmental Monitoring and Assessment","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"9c6b0b35-6854-4b81-92a6-7481e8abaaea","owner":[],"postedDate":"October 15th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-02-03T16:10:36+00:00","versionOfRecord":{"articleIdentity":"rs-4923724","link":"https://doi.org/10.1007/s10661-025-13624-3","journal":{"identity":"environmental-monitoring-and-assessment","isVorOnly":false,"title":"Environmental Monitoring and Assessment"},"publishedOn":"2025-02-01 15:57:13","publishedOnDateReadable":"February 1st, 2025"},"versionCreatedAt":"2024-10-15 10:55:34","video":"","vorDoi":"10.1007/s10661-025-13624-3","vorDoiUrl":"https://doi.org/10.1007/s10661-025-13624-3","workflowStages":[]},"version":"v1","identity":"rs-4923724","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4923724","identity":"rs-4923724","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}