Assessment of potential risks of heavy metals from wastewater treatment plants of Srinagar city, Kashmir

Globally an enormous amount of sewage and sludge is being generated which has turned out to be a major environmental threat due to the associated risks arising from heavy metals. In this context the present study aimed to assess the concentration of heavy metals in sewage and sludge from wastewater treatment plants located around Dal Lake of Srinagar city. Aluminum, iron, zinc, lead, copper, mercury, arsenic, cadmium and chromium were determined using atomic absorption spectrophotometer. Certain key physico-chemical characteristics of sewage in raw and effluent were also evaluated. Health risk assessment using non-carcinogenic and carcinogenic risk revealed suitability of sludge in agriculture which till now remain a neglected resource in the city. Principal component analysis showed that the maximum variability in the data was reflected from sludge samples, whereas correlation among physico-chemical parameters and heavy metals revealed influence of ionic properties of wastewater on heavy metal distribution. While concentration of heavy metals was within the discharge standards, physico-chemical parameters like total suspended solids, ammonia, biochemical oxygen demand and total phosphorus were exceeding the standards meant for effluent disposal. This is one of the unique situations wherein the waste water from the entire city is discharged into Dal Lake without subjecting to advanced treatment. Since the lake is directly linked with supply chain of food and water, continuous discharge of heavy metals have the potential to build up toxicity and cause harm to the lake biota and public health thereof.