UPGRADING OF FACULTATIVE PONDS TO TREAT A TOXIC ORGANIC WASTE-WATER

This study investigated the efficiency and performance of attached-growth waste stabilization ponds (AGWSP) treating a high-strength phenolic wastewater, The experiments employed 4 laboratory-scale pond units installed with an artificial attached-growth media. A control pond unit without attached-growth media (or WSP) was run in parallel for data comparison. The experimental results revealed that the AGWSP units could remove about 99, 50, 45 and 28% of phenol when operated at influent phenol concentrations of 500, 1000, 1500 and 2000 mg/l (corresponding to organic loading rates (OLR) of 180, 360, 540 and 720 kg COD/(ha.day), respectively); these removal efficiencies were consistently higher than those observed in the WSP unit. The influent phenol concentrations of 1000-2000 mg/l resulted in some toxic effects and over loading to the pond system, causing the phenol removal efficiencies to decrease. The amount of phenol loss from the pond water through volatilization was found to be approximately 10%. A relationship between phenol removal rates (excluding volatilization) and phenol dosages to the AGWSP was developed. The superior performance of the AGWSP over the WSP appeared to be due to the biofilm biomass growing on the attached-growth media surface, resulting in increased potential biomass in the pond water.