Improving Performance of Water Treatment on Oxidation Ditch Using Modification of Reactor Hydrodynamic

Urban wastewater treatment in Indonesia is limited, due to its high investment cost. To date, there are only 11 big cities that have centralized domestic wastewater treatment plant, such as in Jakarta, Tangerang, Bandung, Medan, Yogyakarta and Surakarta. There is also city sludge faecal treatment plant, like in Surabaya, Jakarta, Yogyakarta and Semarang. All the treatment process in these treatment plants is based on biological process, which are oxidation ditch (Tangerang and Surabaya), stabilization pond (Bandung) and extended aeration (Jakarta and Yogyakarta). Mostly, the biological treatment on the plants are malfunctioning, some of them because of operational capacity which cannot fulfill the design capacity. Yet, the effort of optimization only focuses on biological process aspect, while the hydraulic and physical aspects have a great influence to treatment performance. Research on modification of hydraulic aspect, both experimentally and by using computer simulation to improve treatment performance is needed.