Environmental compatibility assessment of sewage treatment plants in Himachal Pradesh

Abstract Sewage treatment plants (STPs), since their introduction in the 19th century have been considered as a boon for helping manage the domestic waste which can cause a menace if left unattended. STPs have evolved towards efficiency in their functioning with time. But, with the increasing demand of these basic service delivery assets, some of their ill effects have started hovering over the environment. The increase in the incoming sewage as compared to the limited capacity of the plant, inadequate functioning of the plants, unskilled manpower, etc. are some of the reasons causing impacts on the environment. Keeping this in mind, the present study was conducted with the objective to study the impacts of STPs on the environmental quality of the state. Quality of soil and water near these plants was evaluated. In soils, pH, electrical conductivity, organic matter and toxic elements (Arsenic, cadmium, chromium, copper, nickel, lead and zinc) were estimated which ranged from 5.33–6.12, 0.373–0.617 dS m− 1, 0.51–1.33%, 6.49–12.16 mg kg− 1, 1.15–3.05 mg kg− 1, 71.04–87.60 mg kg− 1, 103.5–287.5 mg kg− 1, 14.76–38.68 mg kg− 1, 47.55–94.90 mg kg− 1 and 168.3- 316.6 mg kg− 1, respectively. In water parameters including pH, electrical conductivity, biochemical oxygen demand and heavy metals (cadmium, chromium, copper, iron and zinc) were studied which ranged from 7.25–7.75, 0.26–0.36 dS m− 1, 4.56–6.33 mg l− 1, 0.001–0.005 mg l− 1, 0.025–0.040 mg l− 1, 0.97–2.22 mg l− 1, 0.19–0.32 mg l− 1 and 2.63–4.42 mg l− 1, respectively. Parameters including organic matter, cadmium, copper and zinc in soil and biochemical oxygen demand, chromium, copper and iron in water were above their permissible limits. This indicated that STPs have started to degrade the environmental quality by adding toxic metals to their surroundings creating a need to keep a check on these plants.