Nutrient Removal and ORP Monitoring in the Intermittent Aeration System with Continuous Inflow

Abstract

Intermittent aeration system with continuous inflow (IASWCI) was fed with synthetic wastewater to clarify the possibility of simultaneous removal of nitrogen, phosphorus, and organic substances by modifying operational schedule. This system was composed of aerobic, anoxic, anaerobic, aerobic, settle and decant phases in a single tank. Synthetic wastewater was flown continuously into the pre-react zone. Anaerobic phase was provided for the phosphorus release without mixing and aerating. The laboratory scale system was operated 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, chemical oxygen demand (COD) removal efficiencies were greater than 90%. The average 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, and ORP and measured P uptake in the second aerobic phase. In this case, ORP appears to be related to measured P release and P uptake, as is indicated by the good fit of the linear regression equation. It can be used to good advantage at the operational level to give plant operators a real time indication of P release and uptake condition in this process.