Anaerobic ponds treatment of starch wastewater: case study in Thailand

Anaerobic ponds are particularly effective in treating high-strength wastewater containing biodegradable solids as they achieve the dual purpose of particulate settlement and organic removal. Performance of an anaerobic pond system for treatment of starch wastewater containing high organic carbon, biodegradable starch particulate matter and cyanide was assessed under tropical climate conditions. Approximately 5000 m3/d of wastewater from starch industry was treated in a series of anaerobic ponds with a total area of 7.39 ha followed by facultative ponds with an area of 29.11 ha. Overall COD and TSS removal of over 90% and CN removal of 51% was observed. Active biomass obtained from the anaerobic ponds sediments and bulk liquid layer exhibited specific methanogenic activity of 20.7 and 11.3 ml CH4/g VSS d, respectively. The cyanide degradability of sludge at initial cyanide concentration of 10 and 20 mg/l were determined to be 0.43 and 0.84 mg CN−/g VSS d, respectively. A separate settling column experiment with starch wastewater revealed that a settling time of approximately 120 min is sufficient to remove 90–95% of the influent TSS.