Nutrient removal and ORP monitoring in the intermittent aeration system with continuous inflow

Intermittent aeration system with continuous inflow (IASWCI) was fed with s ynthetic wastewater to clarify the possibility of simultaneous removal of n itrogen, phosphorus, and organic substances by modifying operational schedu le. This system was composed of aerobic, anoxic, anaerobic, aerobic, settle and decant phases in a single tank. Synthetic wastewater was flown continu ously into the pre-react zone. Anaerobic phase was provided for the phospho rus release without mixing and aerating. The laboratory scale system was op erated for four months. phosphorus release from the sludge was measured in the anaerobic condition after denitrification. The following luxury uptake of phosphorus was observed the second aerobic phase. During 4 months, chemi cal oxygen demand (COD) removal efficiencies were greater than 90%. The ave rage COD effluent was approximately 17 mgl(-1). The effluent had, average, during phosphorus concentration less than 0.5 mgl(-1), and ammonia nitrogen concentration lower than 3 mgl(-1). A correlation exists between oxidation -reduction potential (ORP) and observed P release in the anaerobic phase, a nd ORP and measured P uptake in the second aerobic,ic phase. In this case, ORP appears to be related to measured P release and P uptake, as is indicat ed by the good fit of the linear regression equation. It can he used to goo d advantage at the operational level to give plant operators a real time in dication of P release and uptake condition in this process.