MODELING MICROBIAL CONSORTIA BASED AEROBIC EBPR

Abstract

Phosphorus is often the limiting nutrient in most of the freshwater systems. Depending upon the tocatioii of the plant and the potential impacts on receiving wastewaters, the treatment plant effluent discharging limits range from 0.10 to 2.0 mg/I of phosphorus. Chemical treatments using coagulants such as alum and iron salts were used in 1970s but the success of Full Scale Plant for Biological Phosphorus Removal in early 1980s encouraged utilization of biological methods for Phosphorus removal from Wastewater. A20 (Anaerobic, Anoxic and Aerobic sequence) systems are designed and operated worldwide to remove phosphorus biologically, a process known as EBPR (Enhanced Biological Phosphorus Removal). It implements the presence of anaerobic tank (NO2 and 02 are absent) before the use of aeration tank. Under these prevailing conditions, heterotrophic bacterias known as Polyphosphate- Accumulating Organisms (PAOs) are enriched in bacterial community in the activated sludge. 'I'hesc PAOs accumulates huge masses of polyphosphates within their cells and phosphorus removal takes place. I lowever, recent studies indicate that phosphorus can be removed using PAO culture in activated Sludge process also. Such a study utilizing activated sludge process for Biological Phosphorus Removal has been carried out at this institute. A Laboratory Scale Aerobic Cubical Reactor having 35 1. capacity was used in the study to perform BPR using microbial consortia for around 300 days at different phosphorus concentrations of 1.4, 10, 20, 30 and 40 mg/I for the COD concentration of 500 mg/I and again at 3, 10,20,30 and 40mg/I for the COD concentration of 1000 mg/I. The results showed inhibitory effects at higher phosphorus loading on the reactor. Modeling the Activated Sludge processes is one of the most important aspect of design and operation of WWTPs (Waste Water treatment Plants). Various Activated sludge models i.e. ASM I. ASM 2, ASM2d. ASM 3 and TUI)P models have been developed as modeling tools for Activated Sludge Process but only ASM 3 deals with the inhibitory aspects of Substrate Utilization Rate. Various Kinetic Parameters such as k, Kd ,Y and K were determined using Monod Kinetics and the results were expressed as functions of limiting substrate concentration to model aerobic * biological phosphorus removal (ACBPR). These equations were used in the ASIM (Activated Sludge Simulation Program) Software. The results obtained compared well with of the reactor.