Old Landfill Leachate and Municipal Wastewater Co-Treatment by Sequencing Batch Reactor Combined with Coagulation–Flocculation Using Novel Flocculant

Abstract

The use of novel flocculants in combination with a sequencing batch reactor (SBR) for the treatment of landfill leachate and municipal wastewater has been shown to be an effective method for reducing polluted effluents. Co-treatment of landfill leachate with a mixture of municipal wastewater was performed at 5%, 10%, 15% and 20% in SBR and effluent was treated by coagulation–flocculation. SBR with 6 d hydraulic retention time (HRT) and 30 d solids retention time (SRT) removed 58 to 70% COD, 86 to 93% ammonia, 76 to 83% nitrate and 69 to 95% phosphate. Coagulation–flocculation with different dosages of alum and ferric chloride with polyacrylamide grafted gum ghatti (GGI-g-PAM) as a novel flocculant was used for chemical oxygen demand (COD), turbidity, total suspended solids (TSS) and color removal. Maximum COD removal was at 20% leachate, which was 74% with alum at 2800 mg/L and 77% with ferric chloride at 470 mg/L. Alum and ferric chloride with GGI-g-PAM flocculant removed 96% and 82% of turbidity and 80% and 82% TSS, respectively. At 20% leachate, combined treatment with SBR and coagulation–flocculation resulted in the total removal of 89% COD, 83% ammonia, 82% nitrate 98% turbidity and 93% TSS with alum. The combined treatment with ferric chloride resulted in a removal of 90% COD, 86% ammonia, 83% nitrate, 98% turbidity and 94% TSS. Except for nitrate combined treatment with both the coagulants at 20% landfill leachate to municipal wastewater ratio removed COD, ammonia, phosphate and TSS to a level that met international standards for discharges to inland surface water. As such, the use of new flocculants with SBR can help reduce water pollution from landfill leachate and municipal wastewater. In addition to coagulation–flocculation, other physico–chemical processes can also be studied as post-treatment options for the co-treatment of wastewater mixture.