Olive Mills Wastewater Effect on Domestic Wastewater Treatment Plants: Gaza Strip Case Study

Olive Mills Wastewater Effect on Domestic Wastewater Treatment Plants: Gaza Strip Case Study | 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 Olive Mills Wastewater Effect on Domestic Wastewater Treatment Plants: Gaza Strip Case Study Ahmed Al Manama, Izziddin AlShawa, Ahmed Albahnasavi This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4574549/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 17 Dec, 2024 Read the published version in Environmental Monitoring and Assessment → Version 1 posted 4 You are reading this latest preprint version Abstract The improper disposal of olive mill wastewater (OMW) poses a substantial environmental challenge for wastewater treatment plants (WWTPs) in the Gaza Strip. This study examines the impact of OMW on WWTPs facilities. Samples were collected from both olive mills and WWTPs across the Gaza Strip and analyzed for key biological wastewater parameters: Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), phenols, oil and grease, and Total Suspended Solids (TSS). The findings reveal that the olive oil production process generates significant quantities of pollutants, including 3374.76 tons of COD, 797.55 tons of BOD 5 , 1.33 tons of phenol, 184.42 tons of oil and grease, and 1204.99 tons of TSS. During the olive harvesting season, there was a notable increase in influent pollutant levels. The Gaza Central WWTP recorded the highest levels, with BOD at 1382 mg/L, COD at 3040 mg/L, and TSS at 1810 mg/L. This spike is attributed to the high concentration of olive mills in the area. Conversely, the North Gaza WWTP, which serves a region with fewer olive mills, reported lower pollutant values: BOD at 760 mg/L and TSS at 933 mg/L. By the end of December, influent pollutant levels returned to normal domestic sewage ranges, indicating that the impact of OMW is temporary and closely associated with the olive harvesting season and related activities. Olive mils wastewater Gaza Strip WWTPs Organic load Activated sludge Figures Figure 1 Figure 2 Figure 3 Figure 4 1 Introduction Olive mills are considered a significant source of environmental pollution in all olive oil-producing countries, where the oil extraction processes need a significant amount of water and generate a massive quantity of waste streams in a short time from October to January in olive oil extraction season (Zema et al., 2019 ). Olive oil extraction generates two types of by-product waste streams. a liquid stream called Olive mill wastewater (OMW), locally known as Zeebar, and a solid residue known as Jeft (Khatib et al., 2009 ). OMW is characterized by an extremely high degree of organic pollution (up to 300 g/l of COD) and a low degree of biodegradability due to the acidity, high content of polyphenols (up to 80 g/L), and high toxicity against the whole natural ecosystem including, microorganisms, soil, plants and animals. (Beccari et al., 1999 ; Domingues et al., 2018 ; Gernjak et al., 2004 ). In terms of pollution effect, 1 m 3 of OMW is equivalent to 100–200 m 3 of domestic wastewater (Tsagaraki et al., 2007 ). The generated untreated OMW is usually released in the sea, aquatic surface reservoirs, soil and public wastewater networks. This uncontrolled and inadequate disposal into water bodies inhibits of auto-purification processes, as well as phytotoxic impacts on aquatic fauna and ecological equilibria (Dhaouadi & Marrot, 2010 ; Ochando-Pulido et al., 2017 ), also depletes the dissolved oxygen producing malodorous gases due to the decomposition of organic compounds (Saez et al., 1992 ). Moreover, the disposal of the OMW to the sea and rivers can have negative impacts on their respective colors, which change to dark black due to the presence of a high amount of polyphenol. (McNamara et al., 2008 ). Moreover, direct disposal of the OMW can alter soil quality such as the decrease in pH, the reduction of the nitrate, and phytotoxicity (Peikert et al., 2017 ). Furthermore. OMW affects the growth of trees, plants, and terrestrial grasses. (Koparal & Bakır, 2006 ). In addition to, changing the air-water balance of the soil, the oil content may also reduce the infiltration rate (Abu-Rumman, 2016 ). Discharging OMW to open evaporation ponds in huge quantity requires large areas and increase the natural fermentation which causes emissions, insect proliferation, and bad odors (Jarboui et al., 2010 ; Roig et al., 2006 ; Souilem et al., 2017 ). In terms of OMW treatment, conventional physicochemical processes and common biological treatments such as those based on active sludge do not provide a high effectiveness for the typical OMW effluent characteristics (Ochando-Pulido et al., 2017 ). These typical physicochemical characteristics mainly the acidic pH, lack of alkalinity and nitrogen, high salinity and above all its lipidic fractions and phenolic compounds, in addition to the long chain organic fatty acids, make this wastewater potentially toxic substrate and not suitable for anaerobic treatment. To overcome these problems several synthetic nutrients, chemical additions and pretreatments (chemical and biochemical) have been reported to enable OMW anaerobic digestion. (Dareioti et al., 2009 ; Martinez-Garcia et al., 2009 ; Sampaio et al., 2011 ). To prevent failures related to the biological treatment applied in aerobic and anaerobic wastewater treatment plants, different regulations were implemented in Mediterranean countries to control the discharging of wastewater through municipal sewers(Fleyfel et al., 2022 ). There is no mutual EU law for safe OMW disposal, which leads countries to put their limits and regulations of discharge (Esteves et al., 2019 ; Fleyfel et al., 2022 ; Koutsos et al., 2018 ). In Italy, the adopted typical solution for disposing of the OMW is applying it on the soil. The Italian law in force (L. 574/1996) allows discharge of a maximum of 50 m 3 /ha/year when OMW comes from a traditional mill and 80 m 3 /ha/year when OMW comes from a continuous mill. In doing so, agronomic reports to the responsible municipality have to be submitted at least 30 days before spreading. Surface runoff is to be avoided. However, in case of environmental risk municipalities are entitled to adjust the legal thresholds. The spreading of OMW is prohibited when affects human health and drinking water resources. In Spain, they are using evaporation ponds and spreading on agricultural land as a disposal option, olive mill owners need authorization for evaporation ponds and spreading. Decree (4/2011) sets a discharge limit of 50 m3/ha/year. Surface runoff, leaching and damage to the water table are to be avoided and spreading is prohibited at less than 500 m from urban areas, 100 m from public water protection areas and 100 m from shorelines. In Greece, based on Decree (1650/1986) for the protection of the environment olive mill owners need to provide an environmental impact assessment study of their own business Prosodol & Life (2012). Greece's legislation prohibits the application of untreated OMW on water bodies and soils but does not formulate final limits for OMW on a national level. In some provinces in Greece, it is not prohibited to discharge OMW into the aquatic environment without treatment. In Jordan, the majority of mills dispose their OMW without any pre-treatment due to lack of knowledge, complexity, and costs of treatment or transport to a landfill site (Bawab et al., 2018 ). Around 80% of mills dispose the OMW in cesspools, 15% in drying beds and around 5% use other methods. The connection with the sewage system is prohibited since the mill's wastewater characteristics were not in compliance with the corresponding local specifications (Khdair et al., 2017 ). Until now, no special regulation and standard for OMW disposal has been imposed in Palestine. The olive oil mills usually discharge their liquid wastes in one of these ways: sewerage networks, cesspools, or water streams and valleys. Due to the high loads of toxic organic compounds in OMW, the improper discharge of it disrupts the biological activities in domestic wastewater plants. Lately, the local ministries have started to set up standards for the safe disposal of the OMW and prevent the direct discharge of the OMW to the wastewater networks. This study offers a novel examination of the environmental impact of olive mill wastewater (OMW) on wastewater treatment plants (WWTPs) in the Gaza Strip. By providing precise measurements of pollutants such as Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), phenols, oil and grease, and Total Suspended Solids (TSS) generated by olive oil production, the research highlights the significant burden these pollutants place on WWTPs. The focus on the Gaza Strip, a region with unique environmental challenges, adds to the study's specificity and relevance. A key aspect of the research is the analysis of seasonal variations, showing a notable increase in pollutant levels during the olive harvesting season. The objective of this study was to assess the impact of discharging OMW into the central wastewater treatment plants (WWTPs) in the Gaza Strip. This sudy aimed to evaluate the potential consequences of incorporating OMW into the existing wastewater treatment processes. To achieve this, samples were collected from both the olive mills industry and the wastewater treatment plants, and these samples were subsequently analyzed and characterized. In addition, the OMW quantities were estimated by measuring the produced quantities from OMW due to pressing one ton of olive for each type of mill technique and thereafter multiplied by the total amounts from pressed olives in all mills in Gaza Strip. By conducting this characterization, a comprehensive understanding of the nature and composition of the OMW as well as the functioning of the WWTPs was gained. Subsequently, the effects of incorporating OMW into the WWTPs' operations were evaluated. This assessment aimed to determine how the presence of OMW influenced the influents of the wastewater treatment plants. By conducting this study, the understanding of the potential drawbacks of discharging OMW directly into central wastewater treatment plants in Gaza Strip. This information could contribute to understanding the feasibility and potential environmental impact of such a practice, which would aid in the development of effective strategies for wastewater management in the Gaza Strip. 2. MATERIALS AND METHOD 2.1 Study area Recently, Olive oil production has become a significant agroindustry in Gaza Strip as a result of an increase in olive area cultivation. According to the Ministry of Agriculture (MOA), 46,000 dunums are cultivated with olives which consist of around 52% from the horticulture crops in Gaza Strip. In addition, the number of olive mills increased from 23 olive mills in 2013 to 39 olive mills in 2022 (MOA, 2022 ). The olive oil extraction process is a seasonal activity only carried out during the olive harvest season. The average harvest season period is approximately 60–90 days between October and December. Olive oil in Gaza Strip is extracted mainly according to two types of mills; traditional mills (Classical pressing) and 3-phase mills (Centrifuging). Eight of the functioning olive mills in Gaza Strip are traditional and the rest are continuous (three-phase centrifuge decanter). While there is no one from the 2-phase olive mill type. MOA classified the season of 2022 from the heavily harvested olive season years ago. The average estimated production rate in 2022 was one ton per dunum. Usually, 80–85% of the olive yearly production is used in oil pressing and the rest for the pickles. The safe disposal of the OMW concerns the local authorities in the Gaza Strip, especially with the current disposal demeanor for the OMW without any proper treatment mainly to the public wastewater networks or to the environment in some cases. In 2022, the WWTPs recorded high contents from the organic pollutants in the influents that exceeded the design loads of the plants during the oil pressing season and the treatment was affected even a failure case for the treatment processes was recorded in the Gaza Central Treatment Plant. 2.2 Sampling and field measurements procedures The study was started with the selection of twelve olive mills using different oil extraction techniques (traditional and continuous) for environmental auditing and analyzing their chemical polluting characteristics. Measurements of water used in the processing of one ton of olives and the quantities of OMW generated by each extraction process were recorded. Samples of mill effluents were taken in triplicates for chemical analysis from each mill. The laboratory tests for both effluents; OMW and washing water were carried out, which included BOD 5 , COD, phenols, Oil& Grease and TSS, according to the Standard Methods for the Examination of Water and Wastewater (APHA, 2017 ). The results were used to estimate the pollution loads per ton of olives processed and consequently for the total pollution loads in season 2022 in the Gaza Strip. 3 Results and Discussion 3.1 Water Consumption by the olive oil industry Olive oil production processes need quantities of water that vary and depend upon many factors such as olive cleanness, olive maturation, harvesting time, irrigation periodically, mill owners' behavior and pressing techniques. Part of the water is used in olive washing where the olive is contaminated with dust and soil. The average water quantity measured based on the field survey for washing processes was 0.39 m 3 / ton and ranges between 0.27 and 0.48 m 3 / ton. Washing water consumption rates go along with what is used in Mediterranean countries which is (0.30–0.50) m 3 / ton of olives processed. Noticing that the 3-phase mills consumed the same amount of water used by traditional technology as a result of process requirements. In addition to that, water is used in another stage, mainly in the 3-phase type mills. It assists in the transferring of the olive paste from the malaxer to the decanter. The average rate was measured by recording the rate of added water (L/hr) for many olive quantities and the time for adding process. The value varied between 0.40 and 0.450 m 3 / ton. While minor quantities were added to the malaxation process in the traditional mills in the case of dry olives. According to the MOA, ( 2022 ), the average estimated production rate was one ton per dunum in 2022, which means that around 46,000 tons of olive were produced. Around 38,000 tons were pressed in Gaza Olive Mills and disturbed as 92% in the 3-phase olive mills, while the remained in the traditional mills. By multiplying the average water consumption rate with the quantities of the pressed olive for the two types of mills, the average water consumption in this season reached 29678 m 3 . 3.2 OMW audit results According to the field measurements that were conducted in the audited olive mills, OMW generating rates per pressing one ton from different types of olives and for the two types of mills were quantified. The results showed that the average OMW generation rate for traditional mills was 0.50 m 3 / ton. Compared with the traditional mills, the 3-phase mills produced higher OMW rates with an average of 1,065 m 3 / ton. This difference was due to the added water in the 3-phase processes. Accordingly, and based on the MOA pressed olive data, the total amount of OMW generated in the 2022 season was calculated as 37,232 CM and 1,672 CM for the 3-phase and traditional mills respectively. 3.3 Olive Oil production results The work also included the records for the oil production rate for various types of olive in the audited mills. It is noticed that the 3-phase mills produced olive oil rates more than the traditional mills. The average olive oil production rate was 167.1 kg/ton, and 159.6 kg/ton for the 3-phase and traditional mills respectively. MOA classified the season 2022 as a good harvesting season. By considering the MOA data for season 2022, the total olive oil production was estimated at 6,327 tons. 3.4 Main pollutants results Table 1 shows the average lab results for the key parameters to identify the characteristics of the OMW and the washing water that was collected from the audited mills: Table 1 Average lab results for the key parameters for the OMW and the washing water Lab Test Unit OMW - Traditional OMW - 3-phase Washing Water BOD 5 mg/l 42,500 19,639 1,535 COD mg/l 128,760 86,467 4,117 TSS mg/l 46,933 30,617 1,983 Oil and Grease mg/l 3,730 3,316 4,005 Total Phenol mg/l 55 29.52 12.2 It is noticed that the effluents from traditional mills generated higher pollution loads compared with the 3-phase mills in all parameters. This variation is due to the dilution of the OMW resulting from adding water in the mixing processes in 3-phase mills. Moreover, the COD/BOD 5 ratios were 3.03 and 4.40 for the traditional and 3- phases, respectively. This indicates the complexity of the biological degradation of the OMW. Direct discharge for the OMW without any proper treatment to the public wastewater networks affects the treatment in the WWTP. This case was recorded in recent years and concurrently with the operation of the new treatment plants in Gaza Strip that depend on the aerobic treatment process (Activated sludge). 3.5 Pollution load estimation Firstly, a pollution estimation due to pressing one ton of olive was done based on the source of pollution. As mentioned above, the average OMW quantity generated based on the mills type was 550 L/ton and 1065 L/ton for traditional and 3-phase mills, respectively. The washing water consumption in both mill types was 390 L/ton. These rates are multiplied by the lab results parameters listed in Table 1 to calculate the pollution loads per pressing one ton from olive as shown in Table 2 . Table 2 The pollution loads per pressing one ton from olive. Item Unit OMW - Traditional OMW − 3-phase Washing Water OMW Quantity [L/ton] 550 1,065 390 BOD5 [Kg/t] 23.4 20.9 0.59 COD [Kg/t] 70.8 92.1 1.6 TSS [Kg/t] 25.8 32.6 0.77 Oil and Grease [Kg/t] 2.1 3.5 1.56 Total Phenol [Kg/t] 0.03 0.031 0.005 The results showed that the pollutant in terms of BOD 5 is higher in the traditional mill's type, while the other parameters recorded higher values in the 3-phase mill's type. While the washing water has minor quantities of pollutants as shown. To estimate the total pollution loads due to olive oil production in Gaza Strip, the quantities of the olive pressed in the two mills types are multiplied by the average of pollutants per ton which is calculated in Table 2 . The total OMW pollution loads from Gaza strip is presented in Table 3 . Table 3 Gaza Strip: OMW total pollution loads in season 2022. Item Unit OMW - Traditional OMW − 3-phase Washing Water Total Olive Qty (ton) 3040 34,960 38,000 38,000 BOD 5 (ton) 71.06 703.74 22.75 797.55 COD (ton) 215.29 3098.46 61.01 3374.76 TSS (ton) 78.47 1097.13 29.39 1204.99 Oil and Grease (ton) 6.24 118.83 59.35 184.42 Total Phenol (ton) 0.09 1.06 0.18 1.33 It is noticed that olive oil production generates high pollutant quantities. These pollutants include 797.55 tons of BOD 5 , 3374.76 tons of COD, 1204.99 tons of TSS, 184.42 tons of oil& grease and 1.33 tons of phenol. These loads will be additional pollutants on the WWTPs in Gaza Strip. 3.6 Effect of OMW on the WWTP influents characteristics Around 85% of olive mills in Gaza Strip are connected to public sewage networks. Subsequently, the influents characteristics were affected and an increase in the pollutants was recorded in treatment plants with values beyond the design. This will affect the treatment efficiency in these plants. Five wastewater treatment plants for domestic sewage treatment are operating in Gaza Strip, three eastern regional plants with high-quality techniques with aeration processes: North Gaza WWTP & Central Gaza WWTP (Activated Sludge), and Khan Younis WWTP (Oxidation Ditches). These plants will replace the intermediate and moderate-quality plants which are Gaza WWTP and Rafah WWTP(Al Manama & Al-Najar, 2023 ). Figure 1 shows the wastewater treatment plants and the olive mills with wastewater disposal methods in Gaza Strip: The 2022 olive season commenced in the middle of October and lasted approximately till the end of November. Semi-daily measurements were conducted by the operators of these plants and reported to the Water and Environment Quality Authority (WEQA, 2022 ). The following charts show the main influents characteristics parameters BOD, COD, and TSS in the regional plants from 01/10/2022 to 31/12/20222. In the Khan Younis area, 11 olive mills directly release their wastewater into the sewer network, which eventually flows into the Khan Younis wastewater treatment plant. As shown in Fig. 2 , the highest recorded levels of COD, BOD, and TSS concentration in the wastewater were 2200 mg/L, 680 mg/L, and 1825 mg/L, respectively. These concentrations are indicative of a significant organic load for activated sludge systems. The OMW exhibited high levels of COD, BOD, and TSS. COD is a measurement of the amount of oxygen required to chemically oxidize organic compounds present in the wastewater. In this case, the maximum recorded COD level was 2200 mg/L, indicating a substantial concentration of organic substances that need to be treated. BOD, on the other side, is a measure of the oxygen consumed by microorganisms during the decomposition of organic matter in water. With a maximum BOD level of 680 mg/L, the wastewater contains a considerable amount of biodegradable organic material. In addition, the TSS concentration in the wastewater, reaching a maximum value of 1825 mg/L, indicates the presence of suspended solid particles that contribute to the overall organic load. These high concentrations of COD, BOD, and TSS pose a challenge for the activated sludge systems used in the wastewater treatment plant. Activated sludge systems rely on microorganisms to break down organic matter, but the presence of such a strong organic load can potentially overwhelm the system and affect its performance. In the Middle and Gaza Governorates, 17 olive mills directly release their wastewater into the sewer network, which ultimately flows into the Gaza Central WWTP. As shown in Fig. 3 , The highest recorded levels of COD, BOD, and TSS concentration in the wastewater were 3040 mg/L, 1382 mg/L, and 1810 mg/L, respectively. These concentrations were beyond the design values for this domestic WWTP which are 1300 mg/L, 600 mg/L, and 650 mg/L, for COD, BOD and TSS respectively. Comparing this data to the previous paragraph, it is evident that the olive mill wastewater in the Middle and Gaza areas exhibits higher levels of organic pollutants compared to the Khan Younis area. The maximum COD concentration of 3040 mg/L is significantly higher than the 2200 mg/L recorded in the Khan Younis area. Similarly, the maximum BOD concentration of 1382 mg/L exceeds the 680 mg/L recorded in Khan Younis. These higher levels of COD and BOD signify greater amounts of organic compounds present in the wastewater, indicating a stronger organic load. Additionally, the TSS concentration in the central Gaza WWTP, reaching a maximum value of 1810 mg/L, is lower compared to the 1825 mg/L recorded in the Khan Younis WWTP. This suggests that there are fewer suspended solid particles in the wastewater from the Middle and Gaza Governates, potentially indicating differences in the industrial processes or characteristics of the OMW in these regions. The higher levels of COD and BOD in the Gaza Central WWTP present a more significant challenge for activated sludge systems used in the wastewater treatment plant. The increased organic load can potentially strain the system's capacity to effectively treat the wastewater, leading to decreased treatment efficiency and potential environmental consequences if not managed appropriately. In contrast, the North Gaza WWTP, which serves the North Gaza area with only three olive mills, recorded lower pollutant values, with 760 mg/L for BOD and 933 mg/L for TSS. It is also noteworthy that the influent values returned to normal ranges of domestic sewage by the end of December. This indicates that the increased pollutant levels during the olive harvesting season were temporary and linked to the activities associated with olive mills. The pollutant levels subsequently decreased, suggesting that the wastewater composition reverted to typical domestic sewage characteristics once the olive harvesting season concluded. To summarize, Figs. 2 , 3 and 4 indicate a noticeable increase in influent pollutants during the olive harvesting season. They demonstrate an observed increase in influent pollutants during the olive harvesting season. The Gaza Central WWTP, with a higher concentration of olive mills in its served area, experienced the highest pollutant values. In contrast, the North Gaza WWTP, serving a region with fewer olive mills, recorded lower pollutant values. The influent pollutant levels returned to normal domestic sewage ranges by the end of December, indicating a temporary impact associated with the olive harvesting season. 3.7 OMW treatment As can be understood from its synthesis, OMW has a two-sided nature. It is a waste and strong pollutant that should be treated and at the same time a possible resource of valuable components that should be recovered (Hamimed & Kthiri, 2022 ; Tsagaraki et al., 2007 ). Several stand-alone and integrated processes for the treatment of OMW have already been developed at a pilot scale or in olive mills, but unfortunately, have not yet led to completely satisfactory results (Aggoun et al., 2016 ; Zahi et al., 2022 ). Basically, treatment options can be categorized into 3 different types of treatment However, often combinations of all of these options are applied. Accordingly, treatments can be categorized as follows: Physical treatment: Thermal (Natural or Vacuum Evaporation), Electrolysis, Membrane process. Chemical treatment: Coagulation-flocculation, Oxidation Process (Chlorine, Ozone, UV, Hydrogen peroxide, Fenton advanced oxidation, Ozonation, Photocatalysis). Biological treatment: Aerobic, Anaerobic, Oxidation treatment. The valorization processes of OMW are based on the remodeling of the vision of OMW from environmental hazards to valuable raw materials, thus contributing to a circular economy. (Land application (fertilizer), Adsorption into resins). 4 Conclusions The improper disposal of olive mill wastewater (OMW) poses a significant environmental challenge for wastewater treatment plants (WWTPs) in the Gaza Strip. This study examined the impact of OMW on WWTPs in the region by analyzing wastewater samples collected from olive mills and presenting the main influents pollutants indicators for the WWTPs in the Gaza Strip. Specifically, the study focused on changes in COD, BOD, and TSS. The findings revealed that olive oil production generates substantial quantities of pollutants, including 797.55 tons of BOD, 3374.76 tons of COD, 1204.99 tons of TSS, 184.42 tons of oil and grease, and 1.33 tons of phenol. These pollutants place an additional burden on the wastewater treatment plants in the Gaza Strip. During the olive harvesting season, a significant increase in influent pollutants was observed in the Gaza Strip, particularly at the Gaza Central WWTP, which recorded the highest levels of BOD (1382 mg/L), COD (3040 mg/L), and TSS (1810 mg/L). This rise was attributed to the concentration of olive mills in that specific region. In contrast, the North Gaza WWTP, serving an area with fewer olive mills, reported lower pollutant values, with BOD at 760 mg/L and TSS at 933 mg/L. By the end of December, influent pollutant levels had returned to the normal range for domestic sewage, indicating a temporary impact associated with the olive harvesting season and the activities related to olive mills. Declarations Acknowledgment The authors acknowledge the ministry of agriculture -Palestine- and the Water& Environment Quality Authority (WEQA) for providing some valuable data and information related to the study. Author contribution Ahmed Al Manama: Methodology, Experiment conducting, Writing-Original draft . Izziddin AlShawa: Methodology, Experiment conducting, Writing-Original draft, Ahmed Albahnasavi: Methodology, Editing. Funding Financial support from International Committee of the Red Cross (ICRC) and the Water& Environment Quality Authority (WEQA) . Data availability The authors confirm that the data supporting the findings of this study are available within the article . Ethics approval: All authors have read, understood, and have complied as applicable with the statement on “Ethical responsibilities of Authors” as found in the Instructions for Authors . Consent for publication: All authors gave their consent for publication in the journal . Competing interests: The authors declare no competing interests. References Abu-Rumman, G. (2016). Effect of olive mill solid waste on soil physical properties. International Journal of Soil Science , 11 (3), 94–101. https://doi.org/10.3923/ijss.2016.94.101 Aggoun, M., Arhab, R., Cornu, A., Portelli, J., Barkat, M., & Graulet, B. (2016). Olive mill wastewater microconstituents composition according to olive variety and extraction process. Food Chemistry , 209 , 72–80. https://doi.org/10.1016/j.foodchem.2016.04.034 Al Manama, A., & Al-Najar, H. (2023). The Effect of Seawater Desalination for Domestic Purposes on The Reuse of Treated Effluents in Gaza Strip. Israa University Journal for Applied Science , 6 (2), 169–183. https://doi.org/10.52865/otst4140 APHA. (2017). Standard methods for the examination of water and wastewater. American Public Health Association (APHA) . Bawab, A. Al, Ghannam, N., Abu-Mallouh, S., Bozeya, A., Abu-Zurayk, R. A., Al-Ajlouni, Y. A., Alshawawreh, F., Odeh, F., & Abu-Dalo, M. A. (2018). Olive mill wastewater treatment in Jordan: A Review. IOP Conference Series: Materials Science and Engineering , 305 (1). https://doi.org/10.1088/1757-899X/305/1/012002 Beccari, M., Majone, M., Riccardi, C., Savarese, F., & Torrisi, L. (1999). Integrated treatment of olive oil mill effluents: Effect of chemical and physical pretreatment on anaerobic treatability. Water Science and Technology , 40 (1), 347–355. https://doi.org/10.1016/S0273-1223(99)00383-2 Dareioti, M. A., Dokianakis, S. N., Stamatelatou, K., Zafiri, C., & Kornaros, M. (2009). Biogas production from anaerobic co-digestion of agroindustrial wastewaters under mesophilic conditions in a two-stage process. Desalination , 248 (1–3), 891–906. https://doi.org/10.1016/j.desal.2008.10.010 Dhaouadi, H., & Marrot, B. (2010). Olive mill wastewater treatment in a membrane bioreactor: Process stability and fouling aspects. Environmental Technology , 31 (7), 761–770. https://doi.org/10.1080/09593331003636621 Domingues, E., Gomes, J., Quina, M. J., Quinta-Ferreira, R. M., & Martins, R. C. (2018). Detoxification of olive mill wastewaters by fenton’s process. In Catalysts (Vol. 8, Issue 12). MDPI. https://doi.org/10.3390/catal8120662 Esteves, B. M., Rodrigues, C. S. D., Maldonado-Hódar, F. J., & Madeira, L. M. (2019). Treatment of high-strength olive mill wastewater by combined Fenton-like oxidation and coagulation/flocculation. Journal of Environmental Chemical Engineering , 7 (4). https://doi.org/10.1016/j.jece.2019.103252 Fleyfel, L. M., Leitner, N. K. V., Deborde, M., Matta, J., & El Najjar, N. H. (2022). Olive oil liquid wastes–Characteristics and treatments: A literature review. In Process Safety and Environmental Protection (Vol. 168, pp. 1031–1048). Institution of Chemical Engineers. https://doi.org/10.1016/j.psep.2022.10.035 Gernjak, W., Maldonado, M. L., Malato, S., Cáceres, J., Krutzler, T., Glaser, A., & Bauer, R. (2004). Pilot-plant treatment of olive mill wastewater (OMW) by solar TiO 2 photocatalysis and solar photo-Fenton. Solar Energy , 77 (5), 567–572. https://doi.org/10.1016/j.solener.2004.03.030 Hamimed, S., & Kthiri, A. (2022). Potential valorization of polyphenols from olive mill wastewater on sheep rumen function. International Journal of Environmental Science and Technology . https://doi.org/10.1007/s13762-022-04120-z Jarboui, R., Chtourou, M., Azri, C., Gharsallah, N., & Ammar, E. (2010). Time-dependent evolution of olive mill wastewater sludge organic and inorganic components and resident microbiota in multi-pond evaporation system. Bioresource Technology , 101 (15), 5749–5758. https://doi.org/10.1016/J.BIORTECH.2010.02.069 Khatib, A., Aqra, F., Yaghi, N., Basheer, S., Sabbah, I., Al-Hayek, B., & Mosa, M. (2009). ENVIRONMENTAL POLLUTl0N RESULTING FROM OLIVE OIL PRODUCTION IN PALESTINE. SOUTHERN BRAZILIAN JOURNAL OF CHEMISTRY , 17 (17), 7–20. https://doi.org/10.48141/sbjchem.v17.n17.209.9_2009.pdf Khdair, A., Abu-Rumman, G., & Khdair, A. I. (2017). Evaluation of Environmental Pollution from Olive Mill Wastewater EVALUATION OF THE ENVIRONMENTAL POLLUTION FROM OLIVE MILLS WASTEWATER . https://www.researchgate.net/publication/338914192 Koparal, A., & Bakır, U. (2006). Electrocoagulation of olive mill wastewaters¨U wastewaters¨ wastewaters¨U. Separation and Purification Technology , 52 , 136–141. https://doi.org/10.1016/j.seppur.2006.03.029¨U Koutsos, T. M., Chatzistathis, T., & Balampekou, E. I. (2018). A new framework proposal, towards a common EU agricultural policy, with the best sustainable practices for the re-use of olive mill wastewater. In Science of the Total Environment (Vols. 622–623, pp. 942–953). Elsevier B.V. https://doi.org/10.1016/j.scitotenv.2017.12.073 Martinez-Garcia, G., Johnson, A. C., Bachmann, R. T., Williams, C. J., Burgoyne, A., & Edyvean, R. G. J. (2009). Anaerobic treatment of olive mill wastewater and piggery effluents fermented with Candida tropicalis. Journal of Hazardous Materials , 164 (2–3), 1398–1405. https://doi.org/10.1016/J.JHAZMAT.2008.09.055 McNamara, C. J., Anastasiou, C. C., O’Flaherty, V., & Mitchell, R. (2008). Bioremediation of olive mill wastewater. In International Biodeterioration and Biodegradation (Vol. 61, Issue 2, pp. 127–134). https://doi.org/10.1016/j.ibiod.2007.11.003 MOA. (2022). Annual Report - Ministry of Agriculture (MOA), Gaza, Palestine . Ochando-Pulido, J. M., Pimentel-Moral, S., Verardo, V., & Martinez-Ferez, A. (2017). A focus on advanced physico-chemical processes for olive mill wastewater treatment. In Separation and Purification Technology (Vol. 179, pp. 161–174). Elsevier B.V. https://doi.org/10.1016/j.seppur.2017.02.004 Peikert, B., Schaumann, G. E., Bibus, D., Fischer, J., Braun, U., & Brunkhardt, J. (2017). Effects of olive oil mill wastewater on chemical, microbiological, and physical properties of soil incubated under four different climatic conditions. Biology and Fertility of Soils , 53 (1), 89–102. https://doi.org/10.1007/s00374-016-1157-x Roig, A., Cayuela, M. L., & Sánchez-Monedero, M. A. (2006). An overview on olive mill wastes and their valorisation methods. Waste Management , 26 (9), 960–969. https://doi.org/10.1016/J.WASMAN.2005.07.024 Saez, L., Perez, J., & Martinez, J. (1992). Low molecular weight phenolics attenuation during simulated treatment of wastewaters from olive oil mills in evaporation ponds. Water Research , 26 (9), 1261–1266. https://doi.org/10.1016/0043-1354(92)90187-9 Sampaio, M. A., Gonçalves, M. R., & Marques, I. P. (2011). Anaerobic digestion challenge of raw olive mill wastewater. Bioresource Technology , 102 (23), 10810–10818. https://doi.org/10.1016/j.biortech.2011.09.001 Souilem, S., El-Abbassi, A., Kiai, H., Hafidi, A., Sayadi, S., & Galanakis, C. M. (2017). Olive oil production sector: Environmental effects and sustainability challenges. In Olive Mill Waste: Recent Advances for Sustainable Management (pp. 1–28). Elsevier Inc. https://doi.org/10.1016/B978-0-12-805314-0.00001-7 Tsagaraki, E., Lazarides, H. N., & Petrotos, K. B. (2007). Olive mill wastewater treatment. In Utilization of By-Products and Treatment of Waste in the Food Industry (pp. 133–157). Springer US. https://doi.org/10.1007/978-0-387-35766-9_8 WEQA. (2022). Wastewater Treatment Plant Records, Water & Environment Quality Authority , Gaza, Palestine . Zahi, M. R., Zam, W., & El Hattab, M. (2022). State of knowledge on chemical, biological and nutritional properties of olive mill wastewater. In Food Chemistry (Vol. 381). Elsevier Ltd. https://doi.org/10.1016/j.foodchem.2022.132238 Zema, D. A., Esteban Lucas-Borja, M., Andiloro, S., Tamburino, V., & Zimbone, S. M. (2019). Short-term effects of olive mill wastewater application on the hydrological and physico-chemical properties of a loamy soil. Agricultural Water Management , 221 , 312–321. https://doi.org/10.1016/j.agwat.2019.04.011 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 17 Dec, 2024 Read the published version in Environmental Monitoring and Assessment → Version 1 posted Editorial decision: Revision requested 22 Jul, 2024 Editor assigned by journal 18 Jul, 2024 Submission checks completed at journal 18 Jul, 2024 First submitted to journal 13 Jun, 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. 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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-4574549","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":330449427,"identity":"9a3071e1-47e3-4416-8ffe-56fdfaf8bc57","order_by":0,"name":"Ahmed Al Manama","email":"","orcid":"","institution":"Water and Environment Quality Authority","correspondingAuthor":false,"prefix":"","firstName":"Ahmed","middleName":"Al","lastName":"Manama","suffix":""},{"id":330449428,"identity":"31f2bed4-29b3-42cf-9ef9-63151d62ce2f","order_by":1,"name":"Izziddin AlShawa","email":"","orcid":"","institution":"Ministry of Agriculture","correspondingAuthor":false,"prefix":"","firstName":"Izziddin","middleName":"","lastName":"AlShawa","suffix":""},{"id":330449429,"identity":"fd778d53-1f5b-49f0-a0ee-faeae0c1d99d","order_by":2,"name":"Ahmed Albahnasavi","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABFklEQVRIiWNgGAWjYDACCSDmYbBIADNAbH4QmVBAUIsEQotkA0iLAQlaGAwOgEncOvhndyc+eFMjkcc/u/fgxx81h2WMz69O/PDAgEGeX+wAdkvunN1sOOeYRLHEnXPJ0jzHDvOY3Xi7WQLoMMOZsxOwW3Mjd5s0D5tEYsONHANpBrbbQC1nN4C0JBjcxq5F/kbu9t88/yQS59/IMf75499tHuMZZzf/wKfFAGgLM2+bROKGGzlmErxtt3kM+Hu34bXF8EbuZsm5fRLFhkAt1rx9/3kkbvBus0gwkMDpF7kbuRs/vPlmkycHdNjNH9/S7Pn7z26++aPCRp5fGof3MYEEWKUEAVUogP8AKapHwSgYBaNgBAAAnJtkfmZEs4wAAAAASUVORK5CYII=","orcid":"","institution":"Gebze Technical University","correspondingAuthor":true,"prefix":"","firstName":"Ahmed","middleName":"","lastName":"Albahnasavi","suffix":""}],"badges":[],"createdAt":"2024-06-13 08:14:20","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4574549/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4574549/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s10661-024-13553-7","type":"published","date":"2024-12-17T15:57:37+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":62658766,"identity":"5908255b-6371-4ce7-b9c6-226301c37f03","added_by":"auto","created_at":"2024-08-17 02:19:00","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1685971,"visible":true,"origin":"","legend":"\u003cp\u003eWastewater treatment plants and Olive mills in Gaza Strip.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-4574549/v1/8434b4660441ce91f5089d31.png"},{"id":62658764,"identity":"a154c2ae-affa-45a5-a348-dc691d477c98","added_by":"auto","created_at":"2024-08-17 02:19:00","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":143858,"visible":true,"origin":"","legend":"\u003cp\u003eInfluent pollutants characteristics for Khan Younis WWTP.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-4574549/v1/da922b96acbfbfe4c50c6dfa.png"},{"id":62658765,"identity":"8d741c93-e3a0-4af8-8c56-dc6b3384d40b","added_by":"auto","created_at":"2024-08-17 02:19:00","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":167052,"visible":true,"origin":"","legend":"\u003cp\u003eInfluent pollutants characteristics for Gaza Central WWTP.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-4574549/v1/ae0437f8dc0557d02eed3ec3.png"},{"id":62658767,"identity":"3bee8925-92fe-4f32-be4e-47a36ded236a","added_by":"auto","created_at":"2024-08-17 02:19:00","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":160638,"visible":true,"origin":"","legend":"\u003cp\u003eInfluent pollutants characteristics for North Gaza WWTP.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-4574549/v1/aad6bf09137961dc31f25f64.png"},{"id":72201865,"identity":"ad1f20c5-bc8a-4491-a271-78afb42e752f","added_by":"auto","created_at":"2024-12-23 16:11:23","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2613629,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4574549/v1/8de21eb3-93b8-4d3f-ba7e-3bb296624558.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Olive Mills Wastewater Effect on Domestic Wastewater Treatment Plants: Gaza Strip Case Study","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eOlive mills are considered a significant source of environmental pollution in all olive oil-producing countries, where the oil extraction processes need a significant amount of water and generate a massive quantity of waste streams in a short time from October to January in olive oil extraction season (Zema et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Olive oil extraction generates two types of by-product waste streams. a liquid stream called Olive mill wastewater (OMW), locally known as Zeebar, and a solid residue known as Jeft (Khatib et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2009\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eOMW is characterized by an extremely high degree of organic pollution (up to 300 g/l of COD) and a low degree of biodegradability due to the acidity, high content of polyphenols (up to 80 g/L), and high toxicity against the whole natural ecosystem including, microorganisms, soil, plants and animals. (Beccari et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Domingues et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Gernjak et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). In terms of pollution effect, 1 m\u003csup\u003e3\u003c/sup\u003e of OMW is equivalent to 100\u0026ndash;200 m\u003csup\u003e3\u003c/sup\u003e of domestic wastewater (Tsagaraki et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2007\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe generated untreated OMW is usually released in the sea, aquatic surface reservoirs, soil and public wastewater networks. This uncontrolled and inadequate disposal into water bodies inhibits of auto-purification processes, as well as phytotoxic impacts on aquatic fauna and ecological equilibria (Dhaouadi \u0026amp; Marrot, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Ochando-Pulido et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), also depletes the dissolved oxygen producing malodorous gases due to the decomposition of organic compounds (Saez et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e1992\u003c/span\u003e). Moreover, the disposal of the OMW to the sea and rivers can have negative impacts on their respective colors, which change to dark black due to the presence of a high amount of polyphenol. (McNamara et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). Moreover, direct disposal of the OMW can alter soil quality such as the decrease in pH, the reduction of the nitrate, and phytotoxicity (Peikert et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Furthermore. OMW affects the growth of trees, plants, and terrestrial grasses. (Koparal \u0026amp; Bakır, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). In addition to, changing the air-water balance of the soil, the oil content may also reduce the infiltration rate (Abu-Rumman, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eDischarging OMW to open evaporation ponds in huge quantity requires large areas and increase the natural fermentation which causes emissions, insect proliferation, and bad odors (Jarboui et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Roig et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Souilem et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). In terms of OMW treatment, conventional physicochemical processes and common biological treatments such as those based on active sludge do not provide a high effectiveness for the typical OMW effluent characteristics (Ochando-Pulido et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). These typical physicochemical characteristics mainly the acidic pH, lack of alkalinity and nitrogen, high salinity and above all its lipidic fractions and phenolic compounds, in addition to the long chain organic fatty acids, make this wastewater potentially toxic substrate and not suitable for anaerobic treatment. To overcome these problems several synthetic nutrients, chemical additions and pretreatments (chemical and biochemical) have been reported to enable OMW anaerobic digestion. (Dareioti et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Martinez-Garcia et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Sampaio et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2011\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTo prevent failures related to the biological treatment applied in aerobic and anaerobic wastewater treatment plants, different regulations were implemented in Mediterranean countries to control the discharging of wastewater through municipal sewers(Fleyfel et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). There is no mutual EU law for safe OMW disposal, which leads countries to put their limits and regulations of discharge (Esteves et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Fleyfel et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Koutsos et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). In Italy, the adopted typical solution for disposing of the OMW is applying it on the soil. The Italian law in force (L. 574/1996) allows discharge of a maximum of 50 m\u003csup\u003e3\u003c/sup\u003e /ha/year when OMW comes from a traditional mill and 80 m\u003csup\u003e3\u003c/sup\u003e/ha/year when OMW comes from a continuous mill. In doing so, agronomic reports to the responsible municipality have to be submitted at least 30 days before spreading. Surface runoff is to be avoided. However, in case of environmental risk municipalities are entitled to adjust the legal thresholds. The spreading of OMW is prohibited when affects human health and drinking water resources. In Spain, they are using evaporation ponds and spreading on agricultural land as a disposal option, olive mill owners need authorization for evaporation ponds and spreading. Decree (4/2011) sets a discharge limit of 50 m3/ha/year. Surface runoff, leaching and damage to the water table are to be avoided and spreading is prohibited at less than 500 m from urban areas, 100 m from public water protection areas and 100 m from shorelines. In Greece, based on Decree (1650/1986) for the protection of the environment olive mill owners need to provide an environmental impact assessment study of their own business Prosodol \u0026amp; Life (2012). Greece's legislation prohibits the application of untreated OMW on water bodies and soils but does not formulate final limits for OMW on a national level. In some provinces in Greece, it is not prohibited to discharge OMW into the aquatic environment without treatment. In Jordan, the majority of mills dispose their OMW without any pre-treatment due to lack of knowledge, complexity, and costs of treatment or transport to a landfill site (Bawab et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Around 80% of mills dispose the OMW in cesspools, 15% in drying beds and around 5% use other methods. The connection with the sewage system is prohibited since the mill's wastewater characteristics were not in compliance with the corresponding local specifications (Khdair et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eUntil now, no special regulation and standard for OMW disposal has been imposed in Palestine. The olive oil mills usually discharge their liquid wastes in one of these ways: sewerage networks, cesspools, or water streams and valleys. Due to the high loads of toxic organic compounds in OMW, the improper discharge of it disrupts the biological activities in domestic wastewater plants. Lately, the local ministries have started to set up standards for the safe disposal of the OMW and prevent the direct discharge of the OMW to the wastewater networks.\u003c/p\u003e \u003cp\u003eThis study offers a novel examination of the environmental impact of olive mill wastewater (OMW) on wastewater treatment plants (WWTPs) in the Gaza Strip. By providing precise measurements of pollutants such as Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), phenols, oil and grease, and Total Suspended Solids (TSS) generated by olive oil production, the research highlights the significant burden these pollutants place on WWTPs. The focus on the Gaza Strip, a region with unique environmental challenges, adds to the study's specificity and relevance. A key aspect of the research is the analysis of seasonal variations, showing a notable increase in pollutant levels during the olive harvesting season. The objective of this study was to assess the impact of discharging OMW into the central wastewater treatment plants (WWTPs) in the Gaza Strip. This sudy aimed to evaluate the potential consequences of incorporating OMW into the existing wastewater treatment processes. To achieve this, samples were collected from both the olive mills industry and the wastewater treatment plants, and these samples were subsequently analyzed and characterized. In addition, the OMW quantities were estimated by measuring the produced quantities from OMW due to pressing one ton of olive for each type of mill technique and thereafter multiplied by the total amounts from pressed olives in all mills in Gaza Strip. By conducting this characterization, a comprehensive understanding of the nature and composition of the OMW as well as the functioning of the WWTPs was gained. Subsequently, the effects of incorporating OMW into the WWTPs' operations were evaluated. This assessment aimed to determine how the presence of OMW influenced the influents of the wastewater treatment plants. By conducting this study, the understanding of the potential drawbacks of discharging OMW directly into central wastewater treatment plants in Gaza Strip. This information could contribute to understanding the feasibility and potential environmental impact of such a practice, which would aid in the development of effective strategies for wastewater management in the Gaza Strip.\u003c/p\u003e"},{"header":"2. MATERIALS AND METHOD","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Study area\u003c/h2\u003e \u003cp\u003eRecently, Olive oil production has become a significant agroindustry in Gaza Strip as a result of an increase in olive area cultivation. According to the Ministry of Agriculture (MOA), 46,000 dunums are cultivated with olives which consist of around 52% from the horticulture crops in Gaza Strip. In addition, the number of olive mills increased from 23 olive mills in 2013 to 39 olive mills in 2022 (MOA, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe olive oil extraction process is a seasonal activity only carried out during the olive harvest season. The average harvest season period is approximately 60\u0026ndash;90 days between October and December. Olive oil in Gaza Strip is extracted mainly according to two types of mills; traditional mills (Classical pressing) and 3-phase mills (Centrifuging). Eight of the functioning olive mills in Gaza Strip are traditional and the rest are continuous (three-phase centrifuge decanter). While there is no one from the 2-phase olive mill type. MOA classified the season of 2022 from the heavily harvested olive season years ago. The average estimated production rate in 2022 was one ton per dunum. Usually, 80\u0026ndash;85% of the olive yearly production is used in oil pressing and the rest for the pickles.\u003c/p\u003e \u003cp\u003eThe safe disposal of the OMW concerns the local authorities in the Gaza Strip, especially with the current disposal demeanor for the OMW without any proper treatment mainly to the public wastewater networks or to the environment in some cases. In 2022, the WWTPs recorded high contents from the organic pollutants in the influents that exceeded the design loads of the plants during the oil pressing season and the treatment was affected even a failure case for the treatment processes was recorded in the Gaza Central Treatment Plant.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Sampling and field measurements procedures\u003c/h2\u003e \u003cp\u003eThe study was started with the selection of twelve olive mills using different oil extraction techniques (traditional and continuous) for environmental auditing and analyzing their chemical polluting characteristics. Measurements of water used in the processing of one ton of olives and the quantities of OMW generated by each extraction process were recorded. Samples of mill effluents were taken in triplicates for chemical analysis from each mill. The laboratory tests for both effluents; OMW and washing water were carried out, which included BOD\u003csub\u003e5\u003c/sub\u003e, COD, phenols, Oil\u0026amp; Grease and TSS, according to the Standard Methods for the Examination of Water and Wastewater (APHA, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). The results were used to estimate the pollution loads per ton of olives processed and consequently for the total pollution loads in season 2022 in the Gaza Strip.\u003c/p\u003e \u003c/div\u003e"},{"header":"3 Results and Discussion","content":"\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Water Consumption by the olive oil industry\u003c/h2\u003e \u003cp\u003eOlive oil production processes need quantities of water that vary and depend upon many factors such as olive cleanness, olive maturation, harvesting time, irrigation periodically, mill owners' behavior and pressing techniques. Part of the water is used in olive washing where the olive is contaminated with dust and soil. The average water quantity measured based on the field survey for washing processes was 0.39 m\u003csup\u003e3\u003c/sup\u003e/ ton and ranges between 0.27 and 0.48 m\u003csup\u003e3\u003c/sup\u003e/ ton. Washing water consumption rates go along with what is used in Mediterranean countries which is (0.30\u0026ndash;0.50) m\u003csup\u003e3\u003c/sup\u003e/ ton of olives processed. Noticing that the 3-phase mills consumed the same amount of water used by traditional technology as a result of process requirements. In addition to that, water is used in another stage, mainly in the 3-phase type mills. It assists in the transferring of the olive paste from the malaxer to the decanter. The average rate was measured by recording the rate of added water (L/hr) for many olive quantities and the time for adding process. The value varied between 0.40 and 0.450 m\u003csup\u003e3\u003c/sup\u003e/ ton. While minor quantities were added to the malaxation process in the traditional mills in the case of dry olives.\u003c/p\u003e \u003cp\u003eAccording to the MOA, (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), the average estimated production rate was one ton per dunum in 2022, which means that around 46,000 tons of olive were produced. Around 38,000 tons were pressed in Gaza Olive Mills and disturbed as 92% in the 3-phase olive mills, while the remained in the traditional mills. By multiplying the average water consumption rate with the quantities of the pressed olive for the two types of mills, the average water consumption in this season reached \u003cb\u003e29678 m\u003c/b\u003e\u003csup\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.2 OMW audit results\u003c/h2\u003e \u003cp\u003eAccording to the field measurements that were conducted in the audited olive mills, OMW generating rates per pressing one ton from different types of olives and for the two types of mills were quantified. The results showed that the average OMW generation rate for traditional mills was 0.50 m\u003csup\u003e3\u003c/sup\u003e/ ton. Compared with the traditional mills, the 3-phase mills produced higher OMW rates with an average of \u003cb\u003e1,065\u003c/b\u003e m\u003csup\u003e3\u003c/sup\u003e/ ton. This difference was due to the added water in the 3-phase processes. Accordingly, and based on the MOA pressed olive data, the total amount of OMW generated in the 2022 season was calculated as 37,232 CM and 1,672 CM for the 3-phase and traditional mills respectively.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Olive Oil production results\u003c/h2\u003e \u003cp\u003eThe work also included the records for the oil production rate for various types of olive in the audited mills. It is noticed that the 3-phase mills produced olive oil rates more than the traditional mills. The average olive oil production rate was 167.1 kg/ton, and 159.6 kg/ton for the 3-phase and traditional mills respectively. MOA classified the season 2022 as a good harvesting season. By considering the MOA data for season 2022, the total olive oil production was estimated at 6,327 tons.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Main pollutants results\u003c/h2\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows the average lab results for the key parameters to identify the characteristics of the OMW and the washing water that was collected from the audited mills:\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 lab results for the key parameters for the OMW and the washing water\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\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=\"char\" char=\".\" 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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLab Test\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\u003eOMW - Traditional\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eOMW - 3-phase\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eWashing Water\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eBOD\u003c/b\u003e\u003csub\u003e\u003cb\u003e5\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emg/l\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e42,500\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e19,639\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1,535\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCOD\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emg/l\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e128,760\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e86,467\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4,117\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTSS\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emg/l\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e46,933\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e30,617\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1,983\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eOil and Grease\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emg/l\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3,730\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3,316\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4,005\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTotal Phenol\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emg/l\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e29.52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e12.2\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\u003eIt is noticed that the effluents from traditional mills generated higher pollution loads compared with the 3-phase mills in all parameters. This variation is due to the dilution of the OMW resulting from adding water in the mixing processes in 3-phase mills. Moreover, the COD/BOD\u003csub\u003e5\u003c/sub\u003e ratios were 3.03 and 4.40 for the traditional and 3- phases, respectively. This indicates the complexity of the biological degradation of the OMW. Direct discharge for the OMW without any proper treatment to the public wastewater networks affects the treatment in the WWTP. This case was recorded in recent years and concurrently with the operation of the new treatment plants in Gaza Strip that depend on the aerobic treatment process (Activated sludge).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Pollution load estimation\u003c/h2\u003e \u003cp\u003eFirstly, a pollution estimation due to pressing one ton of olive was done based on the source of pollution. As mentioned above, the average OMW quantity generated based on the mills type was 550 L/ton and 1065 L/ton for traditional and 3-phase mills, respectively. The washing water consumption in both mill types was 390 L/ton. These rates are multiplied by the lab results parameters listed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e to calculate the pollution loads per pressing one ton from olive as shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe pollution loads per pressing one ton from olive.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eItem\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\u003eOMW - Traditional\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eOMW \u0026minus;\u0026thinsp;3-phase\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eWashing Water\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eOMW Quantity\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e[L/ton]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e550\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1,065\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e390\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eBOD5\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e[Kg/t]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e23.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e20.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.59\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCOD\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e[Kg/t]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e70.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e92.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTSS\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e[Kg/t]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e25.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e32.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.77\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eOil and Grease\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e[Kg/t]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.56\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTotal Phenol\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e[Kg/t]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.031\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.005\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\u003eThe results showed that the pollutant in terms of BOD\u003csub\u003e5\u003c/sub\u003e is higher in the traditional mill's type, while the other parameters recorded higher values in the 3-phase mill's type. While the washing water has minor quantities of pollutants as shown.\u003c/p\u003e \u003cp\u003eTo estimate the total pollution loads due to olive oil production in Gaza Strip, the quantities of the olive pressed in the two mills types are multiplied by the average of pollutants per ton which is calculated in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The total OMW pollution loads from Gaza strip is presented in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eGaza Strip: OMW total pollution loads in season 2022.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eItem\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\u003eOMW - Traditional\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eOMW \u0026minus;\u0026thinsp;3-phase\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eWashing Water\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eOlive Qty\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e(ton)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3040\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e34,960\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e38,000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e38,000\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eBOD\u003c/b\u003e\u003csub\u003e\u003cb\u003e5\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e(ton)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e71.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e703.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e22.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e797.55\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCOD\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e(ton)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e215.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3098.46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e61.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3374.76\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTSS\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e(ton)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e78.47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1097.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e29.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1204.99\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eOil and Grease\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e(ton)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e118.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e59.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e184.42\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTotal Phenol\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e(ton)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.33\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\u003eIt is noticed that olive oil production generates high pollutant quantities. These pollutants include 797.55 tons of BOD\u003csub\u003e5\u003c/sub\u003e, 3374.76 tons of COD, 1204.99 tons of TSS, 184.42 tons of oil\u0026amp; grease and 1.33 tons of phenol. These loads will be additional pollutants on the WWTPs in Gaza Strip.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.6 Effect of OMW on the WWTP influents characteristics\u003c/h2\u003e \u003cp\u003eAround 85% of olive mills in Gaza Strip are connected to public sewage networks. Subsequently, the influents characteristics were affected and an increase in the pollutants was recorded in treatment plants with values beyond the design. This will affect the treatment efficiency in these plants. Five wastewater treatment plants for domestic sewage treatment are operating in Gaza Strip, three eastern regional plants with high-quality techniques with aeration processes: North Gaza WWTP \u0026amp; Central Gaza WWTP (Activated Sludge), and Khan Younis WWTP (Oxidation Ditches). These plants will replace the intermediate and moderate-quality plants which are Gaza WWTP and Rafah WWTP(Al Manama \u0026amp; Al-Najar, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows the wastewater treatment plants and the olive mills with wastewater disposal methods in Gaza Strip:\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe 2022 olive season commenced in the middle of October and lasted approximately till the end of November. Semi-daily measurements were conducted by the operators of these plants and reported to the Water and Environment Quality Authority (WEQA, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The following charts show the main influents characteristics parameters BOD, COD, and TSS in the regional plants from 01/10/2022 to 31/12/20222.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn the Khan Younis area, 11 olive mills directly release their wastewater into the sewer network, which eventually flows into the Khan Younis wastewater treatment plant. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the highest recorded levels of COD, BOD, and TSS concentration in the wastewater were 2200 mg/L, 680 mg/L, and 1825 mg/L, respectively. These concentrations are indicative of a significant organic load for activated sludge systems. The OMW exhibited high levels of COD, BOD, and TSS. COD is a measurement of the amount of oxygen required to chemically oxidize organic compounds present in the wastewater. In this case, the maximum recorded COD level was 2200 mg/L, indicating a substantial concentration of organic substances that need to be treated. BOD, on the other side, is a measure of the oxygen consumed by microorganisms during the decomposition of organic matter in water. With a maximum BOD level of 680 mg/L, the wastewater contains a considerable amount of biodegradable organic material. In addition, the TSS concentration in the wastewater, reaching a maximum value of 1825 mg/L, indicates the presence of suspended solid particles that contribute to the overall organic load. These high concentrations of COD, BOD, and TSS pose a challenge for the activated sludge systems used in the wastewater treatment plant. Activated sludge systems rely on microorganisms to break down organic matter, but the presence of such a strong organic load can potentially overwhelm the system and affect its performance.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn the Middle and Gaza Governorates, 17 olive mills directly release their wastewater into the sewer network, which ultimately flows into the Gaza Central WWTP. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, The highest recorded levels of COD, BOD, and TSS concentration in the wastewater were 3040 mg/L, 1382 mg/L, and 1810 mg/L, respectively. These concentrations were beyond the design values for this domestic WWTP which are 1300 mg/L, 600 mg/L, and 650 mg/L, for COD, BOD and TSS respectively. Comparing this data to the previous paragraph, it is evident that the olive mill wastewater in the Middle and Gaza areas exhibits higher levels of organic pollutants compared to the Khan Younis area. The maximum COD concentration of 3040 mg/L is significantly higher than the 2200 mg/L recorded in the Khan Younis area. Similarly, the maximum BOD concentration of 1382 mg/L exceeds the 680 mg/L recorded in Khan Younis. These higher levels of COD and BOD signify greater amounts of organic compounds present in the wastewater, indicating a stronger organic load. Additionally, the TSS concentration in the central Gaza WWTP, reaching a maximum value of 1810 mg/L, is lower compared to the 1825 mg/L recorded in the Khan Younis WWTP. This suggests that there are fewer suspended solid particles in the wastewater from the Middle and Gaza Governates, potentially indicating differences in the industrial processes or characteristics of the OMW in these regions. The higher levels of COD and BOD in the Gaza Central WWTP present a more significant challenge for activated sludge systems used in the wastewater treatment plant. The increased organic load can potentially strain the system's capacity to effectively treat the wastewater, leading to decreased treatment efficiency and potential environmental consequences if not managed appropriately.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn contrast, the North Gaza WWTP, which serves the North Gaza area with only three olive mills, recorded lower pollutant values, with 760 mg/L for BOD and 933 mg/L for TSS. It is also noteworthy that the influent values returned to normal ranges of domestic sewage by the end of December. This indicates that the increased pollutant levels during the olive harvesting season were temporary and linked to the activities associated with olive mills. The pollutant levels subsequently decreased, suggesting that the wastewater composition reverted to typical domestic sewage characteristics once the olive harvesting season concluded.\u003c/p\u003e \u003cp\u003eTo summarize, Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e and \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e indicate a noticeable increase in influent pollutants during the olive harvesting season. They demonstrate an observed increase in influent pollutants during the olive harvesting season. The Gaza Central WWTP, with a higher concentration of olive mills in its served area, experienced the highest pollutant values. In contrast, the North Gaza WWTP, serving a region with fewer olive mills, recorded lower pollutant values. The influent pollutant levels returned to normal domestic sewage ranges by the end of December, indicating a temporary impact associated with the olive harvesting season.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.7 OMW treatment\u003c/h2\u003e \u003cp\u003eAs can be understood from its synthesis, OMW has a two-sided nature. It is a waste and strong pollutant that should be treated and at the same time a possible resource of valuable components that should be recovered (Hamimed \u0026amp; Kthiri, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Tsagaraki et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). Several stand-alone and integrated processes for the treatment of OMW have already been developed at a pilot scale or in olive mills, but unfortunately, have not yet led to completely satisfactory results (Aggoun et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Zahi et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Basically, treatment options can be categorized into 3 different types of treatment However, often combinations of all of these options are applied. Accordingly, treatments can be categorized as follows:\u003c/p\u003e \u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003ePhysical treatment: Thermal (Natural or Vacuum Evaporation), Electrolysis, Membrane process.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eChemical treatment: Coagulation-flocculation, Oxidation Process (Chlorine, Ozone, UV, Hydrogen peroxide, Fenton advanced oxidation, Ozonation, Photocatalysis).\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eBiological treatment: Aerobic, Anaerobic, Oxidation treatment.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e \u003cp\u003eThe valorization processes of OMW are based on the remodeling of the vision of OMW from environmental hazards to valuable raw materials, thus contributing to a circular economy. (Land application (fertilizer), Adsorption into resins).\u003c/p\u003e \u003c/div\u003e"},{"header":"4 Conclusions","content":"\u003cp\u003eThe improper disposal of olive mill wastewater (OMW) poses a significant environmental challenge for wastewater treatment plants (WWTPs) in the Gaza Strip. This study examined the impact of OMW on WWTPs in the region by analyzing wastewater samples collected from olive mills and presenting the main influents pollutants indicators for the WWTPs in the Gaza Strip. Specifically, the study focused on changes in COD, BOD, and TSS. The findings revealed that olive oil production generates substantial quantities of pollutants, including 797.55 tons of BOD, 3374.76 tons of COD, 1204.99 tons of TSS, 184.42 tons of oil and grease, and 1.33 tons of phenol. These pollutants place an additional burden on the wastewater treatment plants in the Gaza Strip. During the olive harvesting season, a significant increase in influent pollutants was observed in the Gaza Strip, particularly at the Gaza Central WWTP, which recorded the highest levels of BOD (1382 mg/L), COD (3040 mg/L), and TSS (1810 mg/L). This rise was attributed to the concentration of olive mills in that specific region. In contrast, the North Gaza WWTP, serving an area with fewer olive mills, reported lower pollutant values, with BOD at 760 mg/L and TSS at 933 mg/L. By the end of December, influent pollutant levels had returned to the normal range for domestic sewage, indicating a temporary impact associated with the olive harvesting season and the activities related to olive mills.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgment\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors acknowledge the ministry of agriculture -Palestine- and the Water\u0026amp; Environment Quality Authority (WEQA) for providing some valuable data and information related to the study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;Ahmed Al Manama: Methodology, Experiment conducting, Writing-Original draft\u003cspan dir=\"RTL\"\u003e.\u003c/span\u003e Izziddin AlShawa: Methodology, Experiment conducting, Writing-Original draft, Ahmed Albahnasavi: Methodology, Editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFinancial support from International Committee of the Red Cross (ICRC) and the Water\u0026amp; Environment Quality Authority (WEQA)\u003cspan dir=\"RTL\"\u003e.\u003c/span\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;The authors confirm that the data supporting the findings of this study are available within the article\u003cspan dir=\"RTL\"\u003e.\u003c/span\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval:\u0026nbsp;\u003c/strong\u003e All authors have read, understood, and have complied as applicable with the statement on \u0026ldquo;Ethical responsibilities of Authors\u0026rdquo; as found in the Instructions for Authors\u003cspan dir=\"RTL\"\u003e.\u003c/span\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication:\u003c/strong\u003e All authors gave their consent for publication in the journal\u003cspan dir=\"RTL\"\u003e.\u003c/span\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests:\u003c/strong\u003e The authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eAbu-Rumman, G. (2016). Effect of olive mill solid waste on soil physical properties. \u003cem\u003eInternational Journal of Soil Science\u003c/em\u003e, \u003cem\u003e11\u003c/em\u003e(3), 94\u0026ndash;101. https://doi.org/10.3923/ijss.2016.94.101\u003c/li\u003e\n \u003cli\u003eAggoun, M., Arhab, R., Cornu, A., Portelli, J., Barkat, M., \u0026amp; Graulet, B. (2016). Olive mill wastewater microconstituents composition according to olive variety and extraction process. \u003cem\u003eFood Chemistry\u003c/em\u003e, \u003cem\u003e209\u003c/em\u003e, 72\u0026ndash;80. https://doi.org/10.1016/j.foodchem.2016.04.034\u003c/li\u003e\n \u003cli\u003eAl Manama, A., \u0026amp; Al-Najar, H. (2023). The Effect of Seawater Desalination for Domestic Purposes on The Reuse of Treated Effluents in Gaza Strip. \u003cem\u003eIsraa University Journal for Applied Science\u003c/em\u003e, \u003cem\u003e6\u003c/em\u003e(2), 169\u0026ndash;183. https://doi.org/10.52865/otst4140\u003c/li\u003e\n \u003cli\u003eAPHA. (2017). Standard methods for the examination of water and wastewater. \u003cem\u003eAmerican Public Health Association (APHA)\u003c/em\u003e.\u003c/li\u003e\n \u003cli\u003eBawab, A. Al, Ghannam, N., Abu-Mallouh, S., Bozeya, A., Abu-Zurayk, R. A., Al-Ajlouni, Y. A., Alshawawreh, F., Odeh, F., \u0026amp; Abu-Dalo, M. A. (2018). Olive mill wastewater treatment in Jordan: A Review. \u003cem\u003eIOP Conference Series: Materials Science and Engineering\u003c/em\u003e, \u003cem\u003e305\u003c/em\u003e(1). https://doi.org/10.1088/1757-899X/305/1/012002\u003c/li\u003e\n \u003cli\u003eBeccari, M., Majone, M., Riccardi, C., Savarese, F., \u0026amp; Torrisi, L. (1999). Integrated treatment of olive oil mill effluents: Effect of chemical and physical pretreatment on anaerobic treatability. \u003cem\u003eWater Science and Technology\u003c/em\u003e, \u003cem\u003e40\u003c/em\u003e(1), 347\u0026ndash;355. https://doi.org/10.1016/S0273-1223(99)00383-2\u003c/li\u003e\n \u003cli\u003eDareioti, M. A., Dokianakis, S. N., Stamatelatou, K., Zafiri, C., \u0026amp; Kornaros, M. (2009). Biogas production from anaerobic co-digestion of agroindustrial wastewaters under mesophilic conditions in a two-stage process. \u003cem\u003eDesalination\u003c/em\u003e, \u003cem\u003e248\u003c/em\u003e(1\u0026ndash;3), 891\u0026ndash;906. https://doi.org/10.1016/j.desal.2008.10.010\u003c/li\u003e\n \u003cli\u003eDhaouadi, H., \u0026amp; Marrot, B. (2010). Olive mill wastewater treatment in a membrane bioreactor: Process stability and fouling aspects. \u003cem\u003eEnvironmental Technology\u003c/em\u003e, \u003cem\u003e31\u003c/em\u003e(7), 761\u0026ndash;770. https://doi.org/10.1080/09593331003636621\u003c/li\u003e\n \u003cli\u003eDomingues, E., Gomes, J., Quina, M. J., Quinta-Ferreira, R. M., \u0026amp; Martins, R. C. (2018). Detoxification of olive mill wastewaters by fenton\u0026rsquo;s process. In \u003cem\u003eCatalysts\u003c/em\u003e (Vol. 8, Issue 12). MDPI. https://doi.org/10.3390/catal8120662\u003c/li\u003e\n \u003cli\u003eEsteves, B. M., Rodrigues, C. S. D., Maldonado-H\u0026oacute;dar, F. J., \u0026amp; Madeira, L. M. (2019). Treatment of high-strength olive mill wastewater by combined Fenton-like oxidation and coagulation/flocculation. \u003cem\u003eJournal of Environmental Chemical Engineering\u003c/em\u003e, \u003cem\u003e7\u003c/em\u003e(4). https://doi.org/10.1016/j.jece.2019.103252\u003c/li\u003e\n \u003cli\u003eFleyfel, L. M., Leitner, N. K. V., Deborde, M., Matta, J., \u0026amp; El Najjar, N. H. (2022). Olive oil liquid wastes\u0026ndash;Characteristics and treatments: A literature review. In \u003cem\u003eProcess Safety and Environmental Protection\u003c/em\u003e (Vol. 168, pp. 1031\u0026ndash;1048). Institution of Chemical Engineers. https://doi.org/10.1016/j.psep.2022.10.035\u003c/li\u003e\n \u003cli\u003eGernjak, W., Maldonado, M. L., Malato, S., C\u0026aacute;ceres, J., Krutzler, T., Glaser, A., \u0026amp; Bauer, R. (2004). Pilot-plant treatment of olive mill wastewater (OMW) by solar TiO 2 photocatalysis and solar photo-Fenton. \u003cem\u003eSolar Energy\u003c/em\u003e, \u003cem\u003e77\u003c/em\u003e(5), 567\u0026ndash;572. https://doi.org/10.1016/j.solener.2004.03.030\u003c/li\u003e\n \u003cli\u003eHamimed, S., \u0026amp; Kthiri, A. (2022). Potential valorization of polyphenols from olive mill wastewater on sheep rumen function. \u003cem\u003eInternational Journal of Environmental Science and Technology\u003c/em\u003e. https://doi.org/10.1007/s13762-022-04120-z\u003c/li\u003e\n \u003cli\u003eJarboui, R., Chtourou, M., Azri, C., Gharsallah, N., \u0026amp; Ammar, E. (2010). Time-dependent evolution of olive mill wastewater sludge organic and inorganic components and resident microbiota in multi-pond evaporation system. \u003cem\u003eBioresource Technology\u003c/em\u003e, \u003cem\u003e101\u003c/em\u003e(15), 5749\u0026ndash;5758. https://doi.org/10.1016/J.BIORTECH.2010.02.069\u003c/li\u003e\n \u003cli\u003eKhatib, A., Aqra, F., Yaghi, N., Basheer, S., Sabbah, I., Al-Hayek, B., \u0026amp; Mosa, M. (2009). ENVIRONMENTAL POLLUTl0N RESULTING FROM OLIVE OIL PRODUCTION IN PALESTINE. \u003cem\u003eSOUTHERN BRAZILIAN JOURNAL OF CHEMISTRY\u003c/em\u003e, \u003cem\u003e17\u003c/em\u003e(17), 7\u0026ndash;20. https://doi.org/10.48141/sbjchem.v17.n17.209.9_2009.pdf\u003c/li\u003e\n \u003cli\u003eKhdair, A., Abu-Rumman, G., \u0026amp; Khdair, A. I. (2017). \u003cem\u003eEvaluation of Environmental Pollution from Olive Mill Wastewater EVALUATION OF THE ENVIRONMENTAL POLLUTION FROM OLIVE MILLS WASTEWATER\u003c/em\u003e. https://www.researchgate.net/publication/338914192\u003c/li\u003e\n \u003cli\u003eKoparal, A., \u0026amp; Bakır, U. (2006). Electrocoagulation of olive mill wastewaters\u0026uml;U wastewaters\u0026uml; wastewaters\u0026uml;U. \u003cem\u003eSeparation and Purification Technology\u003c/em\u003e, \u003cem\u003e52\u003c/em\u003e, 136\u0026ndash;141. https://doi.org/10.1016/j.seppur.2006.03.029\u0026uml;U\u003c/li\u003e\n \u003cli\u003eKoutsos, T. M., Chatzistathis, T., \u0026amp; Balampekou, E. I. (2018). A new framework proposal, towards a common EU agricultural policy, with the best sustainable practices for the re-use of olive mill wastewater. In \u003cem\u003eScience of the Total Environment\u003c/em\u003e (Vols. 622\u0026ndash;623, pp. 942\u0026ndash;953). Elsevier B.V. https://doi.org/10.1016/j.scitotenv.2017.12.073\u003c/li\u003e\n \u003cli\u003eMartinez-Garcia, G., Johnson, A. C., Bachmann, R. T., Williams, C. J., Burgoyne, A., \u0026amp; Edyvean, R. G. J. (2009). Anaerobic treatment of olive mill wastewater and piggery effluents fermented with Candida tropicalis. \u003cem\u003eJournal of Hazardous Materials\u003c/em\u003e, \u003cem\u003e164\u003c/em\u003e(2\u0026ndash;3), 1398\u0026ndash;1405. https://doi.org/10.1016/J.JHAZMAT.2008.09.055\u003c/li\u003e\n \u003cli\u003eMcNamara, C. J., Anastasiou, C. C., O\u0026rsquo;Flaherty, V., \u0026amp; Mitchell, R. (2008). Bioremediation of olive mill wastewater. In \u003cem\u003eInternational Biodeterioration and Biodegradation\u003c/em\u003e (Vol. 61, Issue 2, pp. 127\u0026ndash;134). https://doi.org/10.1016/j.ibiod.2007.11.003\u003c/li\u003e\n \u003cli\u003eMOA. (2022). \u003cem\u003eAnnual Report - Ministry of Agriculture (MOA), Gaza, Palestine\u003c/em\u003e.\u003c/li\u003e\n \u003cli\u003eOchando-Pulido, J. M., Pimentel-Moral, S., Verardo, V., \u0026amp; Martinez-Ferez, A. (2017). A focus on advanced physico-chemical processes for olive mill wastewater treatment. In \u003cem\u003eSeparation and Purification Technology\u003c/em\u003e (Vol. 179, pp. 161\u0026ndash;174). Elsevier B.V. https://doi.org/10.1016/j.seppur.2017.02.004\u003c/li\u003e\n \u003cli\u003ePeikert, B., Schaumann, G. E., Bibus, D., Fischer, J., Braun, U., \u0026amp; Brunkhardt, J. (2017). Effects of olive oil mill wastewater on chemical, microbiological, and physical properties of soil incubated under four different climatic conditions. \u003cem\u003eBiology and Fertility of Soils\u003c/em\u003e, \u003cem\u003e53\u003c/em\u003e(1), 89\u0026ndash;102. https://doi.org/10.1007/s00374-016-1157-x\u003c/li\u003e\n \u003cli\u003eRoig, A., Cayuela, M. L., \u0026amp; S\u0026aacute;nchez-Monedero, M. A. (2006). An overview on olive mill wastes and their valorisation methods. \u003cem\u003eWaste Management\u003c/em\u003e, \u003cem\u003e26\u003c/em\u003e(9), 960\u0026ndash;969. https://doi.org/10.1016/J.WASMAN.2005.07.024\u003c/li\u003e\n \u003cli\u003eSaez, L., Perez, J., \u0026amp; Martinez, J. (1992). Low molecular weight phenolics attenuation during simulated treatment of wastewaters from olive oil mills in evaporation ponds. \u003cem\u003eWater Research\u003c/em\u003e, \u003cem\u003e26\u003c/em\u003e(9), 1261\u0026ndash;1266. https://doi.org/10.1016/0043-1354(92)90187-9\u003c/li\u003e\n \u003cli\u003eSampaio, M. A., Gon\u0026ccedil;alves, M. R., \u0026amp; Marques, I. P. (2011). Anaerobic digestion challenge of raw olive mill wastewater. \u003cem\u003eBioresource Technology\u003c/em\u003e, \u003cem\u003e102\u003c/em\u003e(23), 10810\u0026ndash;10818. https://doi.org/10.1016/j.biortech.2011.09.001\u003c/li\u003e\n \u003cli\u003eSouilem, S., El-Abbassi, A., Kiai, H., Hafidi, A., Sayadi, S., \u0026amp; Galanakis, C. M. (2017). Olive oil production sector: Environmental effects and sustainability challenges. In \u003cem\u003eOlive Mill Waste: Recent Advances for Sustainable Management\u003c/em\u003e (pp. 1\u0026ndash;28). Elsevier Inc. https://doi.org/10.1016/B978-0-12-805314-0.00001-7\u003c/li\u003e\n \u003cli\u003eTsagaraki, E., Lazarides, H. N., \u0026amp; Petrotos, K. B. (2007). Olive mill wastewater treatment. In \u003cem\u003eUtilization of By-Products and Treatment of Waste in the Food Industry\u003c/em\u003e (pp. 133\u0026ndash;157). Springer US. https://doi.org/10.1007/978-0-387-35766-9_8\u003c/li\u003e\n \u003cli\u003eWEQA. (2022). \u003cem\u003eWastewater Treatment Plant Records, Water \u0026amp; Environment Quality Authority , Gaza, Palestine\u0026nbsp;\u003c/em\u003e.\u003c/li\u003e\n \u003cli\u003eZahi, M. R., Zam, W., \u0026amp; El Hattab, M. (2022). State of knowledge on chemical, biological and nutritional properties of olive mill wastewater. In \u003cem\u003eFood Chemistry\u003c/em\u003e (Vol. 381). Elsevier Ltd. https://doi.org/10.1016/j.foodchem.2022.132238\u003c/li\u003e\n \u003cli\u003eZema, D. A., Esteban Lucas-Borja, M., Andiloro, S., Tamburino, V., \u0026amp; Zimbone, S. M. (2019). Short-term effects of olive mill wastewater application on the hydrological and physico-chemical properties of a loamy soil. \u003cem\u003eAgricultural Water Management\u003c/em\u003e, \u003cem\u003e221\u003c/em\u003e, 312\u0026ndash;321. https://doi.org/10.1016/j.agwat.2019.04.011\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 Assessment","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Olive mils wastewater, Gaza Strip WWTPs, Organic load, Activated sludge","lastPublishedDoi":"10.21203/rs.3.rs-4574549/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4574549/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe improper disposal of olive mill wastewater (OMW) poses a substantial environmental challenge for wastewater treatment plants (WWTPs) in the Gaza Strip. This study examines the impact of OMW on WWTPs facilities. Samples were collected from both olive mills and WWTPs across the Gaza Strip and analyzed for key biological wastewater parameters: Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), phenols, oil and grease, and Total Suspended Solids (TSS). The findings reveal that the olive oil production process generates significant quantities of pollutants, including 3374.76 tons of COD, 797.55 tons of BOD\u003csub\u003e5\u003c/sub\u003e, 1.33 tons of phenol, 184.42 tons of oil and grease, and 1204.99 tons of TSS. During the olive harvesting season, there was a notable increase in influent pollutant levels. The Gaza Central WWTP recorded the highest levels, with BOD at 1382 mg/L, COD at 3040 mg/L, and TSS at 1810 mg/L. This spike is attributed to the high concentration of olive mills in the area. Conversely, the North Gaza WWTP, which serves a region with fewer olive mills, reported lower pollutant values: BOD at 760 mg/L and TSS at 933 mg/L. By the end of December, influent pollutant levels returned to normal domestic sewage ranges, indicating that the impact of OMW is temporary and closely associated with the olive harvesting season and related activities.\u003c/p\u003e","manuscriptTitle":"Olive Mills Wastewater Effect on Domestic Wastewater Treatment Plants: Gaza Strip Case Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-08-17 02:18:55","doi":"10.21203/rs.3.rs-4574549/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-07-23T02:07:02+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-07-18T20:24:46+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-07-18T20:24:19+00:00","index":"","fulltext":""},{"type":"submitted","content":"Environmental Monitoring and Assessment","date":"2024-06-13T08:12:31+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":"2af5b463-0c63-40ca-8310-629155331a0e","owner":[],"postedDate":"August 17th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-12-23T16:02:38+00:00","versionOfRecord":{"articleIdentity":"rs-4574549","link":"https://doi.org/10.1007/s10661-024-13553-7","journal":{"identity":"environmental-monitoring-and-assessment","isVorOnly":false,"title":"Environmental Monitoring and Assessment"},"publishedOn":"2024-12-17 15:57:37","publishedOnDateReadable":"December 17th, 2024"},"versionCreatedAt":"2024-08-17 02:18:55","video":"","vorDoi":"10.1007/s10661-024-13553-7","vorDoiUrl":"https://doi.org/10.1007/s10661-024-13553-7","workflowStages":[]},"version":"v1","identity":"rs-4574549","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4574549","identity":"rs-4574549","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}