Treatment of pesticide contaminated surface water for production of potable water by a coagulation-adsorption-nanofiltration approach

The surface water bodies have become very much susceptible to pollution by pesticides due to their increased application in agriculture. The production of potable water from pesticide contaminated lake and river water was investigated by a coagulation-adsorption-nanofiltration approach. Isoproturon (IPU) was selected as a target pesticide and spiked in distilled water and then in surface water. Coagulation was done before adsorption and coagulant dosage was selected on the basis of turbidity removal. Various adsorbents such as powdered activated charcoal (PAC), bentonite, chitosan were tried at different dosages to evaluate their efficiency in IPU removal. The effect of initial pesticide concentration was studied on percent removal of pesticide when treated with selected adsorbent at a particular dosage. The values of adsorption capacity calculated from Langmuir and Freundlich equations were 104.21 mg/g and 69.4 mg/g respectively indicating favorable adsorption of IPU on powdered activated charcoal surface. After optimizing the coagulation and adsorption protocol, nanofiltration (NF) was performed on pretreated water in a test cell in dead end mode. The NF permeate was analyzed for pH, turbidity, TDS, COD, TOC, conductivity, hardness, and colony count. Reverse osmosis (RO) was done after NF if required. The quality of NF/RO permeate was found comparable to the standards of drinking water.