Abstract
Candidatus Accumulibacter phosphatis is in general presented as the dominant organism responsible for the biological removal of phosphorus in activated sludge wastewater treatment plants. Lab-scale enhanced biological phosphorus removal (EBPR) studies, usually use acetate as carbon source. However, the complexity of the carbon sources present in wastewater could allow other potential poly-phosphate accumulating organism (PAOs), such as putative fermentative PAOs (e.g., Tetrasphaera), to proliferate in coexistence or competition with Ca. Accumulibacter. This research assessed the effects of lactate on microbial selection and process performance of an EBPR lab-scale study. The addition of lactate resulted in the coexistence of Ca. Accumulibacter and Tetrasphaera in a single EBPR reactor. An increase in anaerobic glycogen consumption from 1.17 to 2.96 C-mol/L and anaerobic PHV formation from 0.44 to 0.87 PHV/PHA C-mol/C-mol corresponded to the increase in the influent lactate concentration. The dominant metabolism shifted from a polyphosphate-accumulating metabolism (PAM) to a glycogen accumulating metabolism (GAM) without EBPR activity. However, despite the GAM, traditional glycogen accumulating organisms (GAOs; Candidatus Competibacter phosphatis and Defluvicoccus) were not detected. Instead, the 16s RNA amplicon analysis showed that the genera Tetrasphaera was the dominant organism, while a quantification based on FISH-biovolume indicated that Ca. Accumulibacter remained the dominant organism, indicating certain discrepancies between these microbial analytical methods. Despite the discrepancies between these microbial analytical methods, neither Ca. Accumulibacter nor Tetrasphaera performed biological phosphorus removal by utilizing lactate as carbon source.
Highlights
Enhanced biological phosphorus removal (EBPR) or chemical phosphorus removal process or a combination of both processes aims to minimize the proliferation of cyanobacteria and algae in receiving surface water bodies by minimizing the phosphate load to these surface waters (Yeoman et al, 1988)
Previous research has suggested that Candidatus Accumulibacter phosphatis (PAOs which anaerobically store volatile fatty acids (VFAs)), Tetrasphaera and most recently Thiothrix caldifontis can be potential organisms responsible for the biological removal of phosphorus in wastewater treatment plants (Hesselmann et al, 1999; Nguyen et al, 2011; Rubio-Rincón et al, 2017b)
The EBPR was inoculated with activated sludge from the Harnaschpolder EBPR wastewater treatment plant (Den Horn, The Netherlands)
Summary
Enhanced biological phosphorus removal (EBPR) or chemical phosphorus removal process or a combination of both processes aims to minimize the proliferation of cyanobacteria and algae in receiving surface water bodies by minimizing the phosphate load to these surface waters (Yeoman et al, 1988). EBPR is carried out by poly-phosphate accumulating organisms (PAOs) capable of storing phosphorus beyond their growth requirements. PAOs proliferate in activated sludge wastewater treatment plants (WWTP) by recirculating the sludge through anaerobic and anoxic/oxic conditions while directing the influent rich in volatile fatty acids (VFAs) to the anaerobic stage (Barnard, 1975). Previous research has suggested that Candidatus Accumulibacter phosphatis (PAOs which anaerobically store VFAs), Tetrasphaera (able to ferment different carbon sources) and most recently Thiothrix caldifontis (mixotrophic PAOs capable to use sulfide as energy source) can be potential organisms responsible for the biological removal of phosphorus in wastewater treatment plants (Hesselmann et al, 1999; Nguyen et al, 2011; Rubio-Rincón et al, 2017b). Accumulibacter phosphatis has been associated with a good EBPR in WWTP with different configurations located worldwide (Kong et al, 2002; Zilles et al, 2002; Saunders et al, 2003; He et al, 2005; Wong et al, 2005; López-Vázquez et al, 2008)
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