Effect of Phosphorus on Operation and Characteristics of MBR

Abstract

The impact of phosphate-phosphorus loading on the biological characteristics and operational performance of a pilot-scale, aerobic membrane bioreactor (MBR) system was investigated. The system was operated to steady state under conditions of limited and excess phosphorus. The microbial population in the MBR was not effected substantially under either phosphorus condition and was highly effective in the oxidation and nitrification of a municipal strength, high protein, synthetic wastewater. Overall metabolic activity and some specific enzymes, particularly phosphotases, decreased significantly in the presence of excess phosphorus. Although more phosphorus was utilized by the microbial population when the feed phosphorus concentration was increased, degradation of the soluble organic compounds did not change significantly. After the increase of phosphorus in the bioreactor, the organic content of the effluent increased and stabilized at higher levels. Phosphorus spiking experiments showed that phosphorus adsorbed to the particulate phase of the sludge and caused an immediate increase in the concentration of organic compounds in the effluent. Excess phosphorus released organic matter of a size smaller than 0.1 μm into the soluble phase of the bioreactor, resulting in the deterioration of the permeate. It was concluded that phosphorus is an important factor in the operation of an MBR, and excess amounts or shock loads reduce the effectiveness of the system.