Co-pretreatment of Municipal Wastewater and Landfill Leachate by Chemical Coagulation Using Ferric Chloride and Aluminum Sulfate

Assessing efficiency and economic viability in treating leachates emanating from the municipal landfill site at Gazipur, India

The leachates emanating from the landfills are high in organic loads and thus become potential sources of contamination for both surface and groundwater. As the landfill ages, the nature of leachate changes from acidic to alkaline. The change in pH level affects the chemical oxygen demand (COD)/biochemical oxygen demand (BOD) ratio and when it is less than 0.63, chemical treatments are more effective over the biological treatment methods such as upflow anaerobic sludge blankets (UASB). The existing literature suggests coagulation-flocculation and advanced oxidation process (Fenton) as effective methods for treating wastewater but no comparison of the two are available. Thus, the present study attempts to identify the most efficient coagulants out of ferric chloride (FeCl₃), ferrous sulphate (FeSO₄) and alum [Al₂(SO₄)₃]. Ferric chloride leading to 99% colour removal, 98% COD removal, 99% decrease in total organic carbon, 94.3% removal in NH₃-N and 91.4% removal in total Kjeldahl nitrogen is observed to be the most efficient coagulant and surprisingly, proves to be even better than Fenton. To understand the field applicability of the two treatment procedures, coagulation with FeCl₃ and Fenton are compared with the UASB method which is currently employed at Gazipur landfill site, Delhi. With lesser operational cost than UASB, both FeCl₃ and Fenton perform better on cost-efficiency scale. Switching from in-suit UASB method to the FeCl₃ method of treatment may result in decreasing the operational cost by 71.9% and to conventional Fenton may result in decreasing the operational cost by 76.8%.