North Carolina Agricultural and Technical State University

The biological removal of phosphorus from simulated wastewater using miniature bioreactors

The objective of this study was to utilize miniature bioreactors in a laboratory-scale setting to biologically deplete excessive amounts of phosphorus (P). P occurring in wastewater is usually found in the form of phosphate (PO4). The potential for phosphate-removing bacteria (PRB) to overload significant levels of PO4 under aerobic/anaerobic conditions was observed and evaluated. Wastewater was simulated by adding four different PO4 concentrations of 20, 30, 38, and 45 mg-L-1 to deionized water, and it was retained in 100 mL bioreactors. Ten grams of a sludge enriched with PRB was added to a batch of bioreactors containing the four PO4 concentrations, and 15 mL of the simulated wastewater was extracted from the bioreactors over four different time periods of 3, 6, 9, and 13 days. After a series of filtrations, the mixed liquor solution remaining from each wastewater specimen was analyzed with Flow Injection Analysis (FIA) for total PO4 concentrations. Likewise, a second batch of bioreactors containing a sludge that was autoclaved to eliminate PRB was utilized with the same methodology to compare the differences. The measured concentrations of the bioreactors containing the sludge enriched with PRB showed an uptake and release of PO4. As PO4 was biochemically cycled in the batch containing the PRB, a pH decrease was observed in correspondence to the periods of uptake and release. The bioreactors containing the autoclaved sludge with no active PRB, showed sustained high levels of PO4 throughout the entire 13-day sequence.

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