Development of Low Energy Aeration System For Enhanced Biological Phosphorus Removal (EBPR)

In a world that is witnessing an everlasting growth and accelerating increase in its population, an increase in the amount of wastewater produced is inevitable. In order to recycle this wastewater back to the environment, all nutrients should be removed. Unfortunately, removing the nutrients from wastewater is expensive due to the oxygen and chemicals requirement. Phosphorus removal is an important part of wastewater treatment process; Enhanced Biological Phosphorus Removal (EBPR) is one of the main processes responsible for phosphorus removal in wastewater treatment plants. EBPR consist of two major phases: anaerobic phase and aerobic phase. Aeration costs in the aerobic phase are relatively high in EBPR system. Finding a new approach for decreasing the amount of aeration needed for EBPR systems recently has grown in importance. Most of the research done on EBPR process was focusing on continued aeration, the effect of intermittent aeration is not widely researched. Thus, this research aims to overcome the previously mentioned challenges towards achieving stable EBPR process through different optimization techniques. To achieve this goal, a new aeration strategy has been developed to stepwise decrease the dissolved oxygen (DO) to reach very low DO conditions for EBPR. The new strategy depends on using intermittent aeration as a method of providing DO to the system. The SBR was operated over the span of 140 days under very low DO concentrations ranged from 0.5-1.0 mg/L, and achieved stable nutrients removal with removal efficiencies of: phosphorus removal efficiency (99%), ammonia removal efficiency (99%), COD removal Efficiency (100%).
In addition, the effect of acetate to propionate ratio as a carbon source for EBPR systems under low DO concentrations have been studied, to investigate the effect of carbon source on the competition between Glycogen Accumulating Organism (GAO) and Polyphosphate Accumulating Organism (PAO) in EBPR systems. Propionate was found to be the best carbon source for EBPR process, after different compositions of COD were used as a carbon source for the EBPR process. The combination of low DO concentrations and propionate as a carbon source has been found to be a successful approach in controlling the competition between GAO and PAO in EBPR systems.