Peter BurnsSPRING 2004AbstractIntroductionObjectivesOffValueResults and DiscussionTABLE 4 – Influent and Effluent Phosphorus Concentrations for Standard and EBPR SystemsConclusionReferencesINVESTIGATION OF BIOLOGICALPHOSPHORUS REMOVAL IN A SEQUENCINGBATCH REACTORRESEARCH FOR CEE 453: LABORATORY RESEARCH IN ENVIRONMENTAL ENGINEERINGPeter BurnsAlex MikszewskiBrett BoveeSPRING 2004AbstractEnhanced Biological Phosphorus Removal (EBPR) is a biological alternative to the more commonplace chemical phosphorus treatment methods. Research is ongoing to maximize EBPR removal efficiencies and make the treatment system a viable alternative.This experiment attempted to construct a functional EBPR wastewater plant in a laboratory setting to test phosphorus removal efficiency and compare it to large-scale systems. A small, software controlled treatment plant was constructed and operated for several weeks. Results showed a definite improvement in phosphorus removal, which was comparable to published values. The EBPR in this experiment attained a 70% removal rate. It is possible to improve removal efficiency by increasing microbial selection time and creating a favorable environment for phosphorus assimilating organisms, and such improvements are left for further study.IntroductionThe need for increased phosphorus removal from municipal and industrial wastewater is becoming more and more pertinent. Phosphorus is most often the limiting nutrient for algal growth in freshwater bodies. The over-fertilization of freshwater with phosphorus is known as eutrophication, which causes the unnatural stimulus of algae and weeds in water. The respiration and decomposition of algae in eutrophic waters depletes dissolved oxygen, causing “extinction zones” where no aquatic animals can survive (Lind, 1998). In order to protect freshwater bodies from destruction, efficient phosphorusremoval techniques must be developed and implemented. In January 2001, the United States Environmental Protection Agency (EPA) published new recommendations for water quality nutrient criteria. The EPA threshold effluent phosphorus concentrations range from 0.0076 mg/L to as low as 0.010 mg/L depending on the sensitivity of the region (Lesjean 2003). As typical secondary effluent without phosphorus removal has total phosphorus concentrations ranging from 2.5 to 6 mg/L, advanced treatment is essential to comply with EPA recommendations (PA DEP, 2004).A long used technique for phosphorus removal is chemical precipitation through addition of a precipitant like ferric chloride. Chemical removal processes typically get high removal efficiencies and are easily implemented. However, chemical additives are very expensive and can cause severe contamination of sewage sludges (WERF, 2003). As a result, more current wastewater engineering research is exploring the potential of enhanced biological phosphorus removal (EBPR) processes. EBPR treatment plants select for specific phosphorus accumulation organisms (PAOs) that efficiently uptake freephosphorus in the wastewater (WERF, 2003). An initial anaerobic stage allows the PAOsto adhere to organic matter, releasing cellular phosphorus through expenditure of energy. Upon aeration, the cells accumulate large amounts phosphorus for use as a substrate for energy production and storage (Weber-Shirk, 2004). EBPR processes are still mysteriousin that the specific PAOs are as of now unidentifiable. Some publications single out Acineotobacter or Microlunatus phosphovorus as the predominant PAOs, but the subject is still up to debate (Cloete, 2003). The main problem with current EBPR use is that the required, ultra high removal efficiencies are not guaranteed. PAOs compete with gram negative G bacteria and other organisms, and thus can have population limits.Furthermore, exact conditions conducive to PAO growth are not conclusively known (WERF, 2003). The environmental and financial benefits associated with use of EBPR techniques over chemical precipitation merit their continued research and improvement.ObjectivesThe primary objective of this experiment was to create a functional EBPR batch-sequencing reactor. This was accomplished in two stages. First an activated sludge batchsequencing reactor was constructed with stages for aeration, BOD removal, and denitrification. The reactor was run continuously for three weeks prior to the beginning of stage two. In stage two, the reactor’s phosphorus removal was enhanced via the addition of an hour-long anaerobic stage immediately following the input of the waste. It was expected that the plant, before the addition of the initial anaerobic stage, would remove a small, but measurable, amount of phosphorus. Furthermore it was expected that a much more significant amount of phosphorus would be removed under the EBPR operating mode. It was difficult to foresee how scaling down both the size of the plant and the time frame of microbial activity would affect the phosphorus removal. However, based on published data, it was expected that the amount of phosphorus removed by the standard process would be around 15% and that of the EBPR would be less than 70%.MethodsTo test the efficiency of Enhanced Biological Phosphorus Removal (EBPR), a model was constructed to simulate the flows and processes of a real world wastewater treatment plant. The model consisted of a 5 L plastic tank with various inflow and outflow pipes. Inflows included concentrated waste solution and distilled water, which were pumped into the plant by a peristaltic pump at a rate of 178 mL/min. Outflow consisted of clarified effluent, which was drained out by gravity. The plant was mixed with a magnetic stirrer and aerated by pressurized airflow dispersed through an aeration stone. The airflow rate was determined by the procedures outlined in Weber-Shirk (2004). Dissolved oxygen was continuously measured with a dissolved oxygen probe suspended in the plant. The plant was operated as a batch reactor, treating and draining a single volume of wastewater at a time. Treatment consisted of several discrete operational stages, listed in Table 1. The parameter values used in defining these stages are found in Table 2. Process Controller software was used to define and manage these stages (Weber-Shirk, 2004). Once programmed and tested, the software was in complete control of the plant operation. Daily checks were done to ensure that the plant was functioning