| The feasibility of enhanced biological phosphorus removal (EBPR) in high strength wastewater was evaluated. Unlike domestic wastewater, industrial wastewater, especially from dairy, contains a high concentration level of organic substances. Because polyphosphate-accumulating organisms (PAOs) are believed to play an important role in EBPR process, it was necessary to investigate the performance of PAOs under high organic loading conditions. Due to the difficulty of obtaining a pure culture of PAOs, activated sludge was enriched with PAOs by culturing in normal steady state condition. Batch reactor tests demonstrated that EBPR was deteriorated when a considerable amount of substrate was available during aerobic conditions. Compared to full-scale activated sludge, PAO-enriched sludge showed better EBPR efficiency and produced a higher fraction of poly-hydroxylvalerate (PHV) in poly-hydroxylalkanoates (PHAs) accumulation. In an anaerobic-aerobic sequencing batch reactor (A/O SBR), after normal steady condition was established to enrich PAOs, the initial acetate concentration increased steadily. Although the initial COD level fluctuated throughout the experiment, the nutrients balance in the feed solution was kept constant at COD: nitrogen (N): phosphorus (P) = 100:5:8. When the initial acetate level increased to 300 mg-COD/L, the system showed unstable EBPR performance because the metabolic balance of PAOs was disturbed, indicating a polyphosphate limited condition. When the initial acetate level increased to 500 and 1,000 mg-COD/L, the EBPR system shifted to a glycogen-limited system.; Since the flow rate is highly dynamic in full-scale wastewater treatment, the microbial adaptability under organic loading fluctuation was evaluated in another A/O SBR. When the initial acetate increased smoothly, the system did not suffer perturbation and performed stable EBPR. During high organic loading fluctuation, the system showed unstable EBPR and microorganisms could not adapt themselves for over a month. However, when a normal steady condition was provided, the system recovered within two days. During low organic loading fluctuation, a large amount of PHB was utilized than newly formed, leading to a considerable loss in biomass. |
