EVALUATION OF AERATED LAGOON FOR THE TREATMENT OF DOMESTIC WASTEWATER IN LAHORE AND ITS COMPARISON WITH WASTEWATER STABILIZATION PONDS

A study was carried out to evaluate the efficiency of aerated lagoon for the treatment of domestic wastewater of Lahore. For the purpose, a bench scale model of aerated lagoon (AL) comprising of an aeration tank and secondary clarifier was used. The model was operated continuously for 65 days at different aeration time i.e. 7, 5, 3, 2 days and finally at 1 day. Settled domestic wastewater was used as influent to the aerated lagoon. Biochemical oxygen demand (BOD), chemical oxygen demand (COD) and total suspended solids (TSS) were measured for influent and effluent to evaluate the efficiency of aerated lagoon. The results of the study demonstrated that National Environmental Quality Standards (NEQS) were met even at an aeration time of 1 day. Overall BOD removal rate constant (K) had a mean value of 1.23 per day. It was also revealed that 60 % of the total BOD was in particulate form and 40% in the dissolved/soluble form. A comparison of AL was made with wastewater stabilization ponds (WSP) using results of previous studies on WSP. The comparison revealed that for comparable effluent characteristic, per capita land area requirement for AL (detention time = 2 days) is approximately 11% of WSP, while the cost of AL is 149% of the cost of WSP. Since sufficient land area for construction of WSP is not available near Lahore, therefore, aerated lagoons have been recommended as most suited option for the treatment of domestic wastewater of Lahore