Abstract
Although simultaneous P-removal and nitrate reduction has been observed in laboratory studies as well as full-scale plants, there are contradictory reports on the ability of PAO I to efficiently use nitrate as electron acceptor. Such discrepancy could be due to other microbial groups performing partial denitrification from nitrate to nitrite. The denitrification capacities of two different cultures, a highly enriched PAO I and a PAO I-GAO cultures were assessed through batch activity tests conducted before and after acclimatization to nitrate. Negligible anoxic phosphate uptake coupled with a reduction of nitrate was observed in the highly enriched PAO I culture. On the opposite, the PAO I-GAO culture showed a higher anoxic phosphate uptake activity. Both cultures exhibited good anoxic phosphate uptake activity with nitrite (8.7 ± 0.3 and 9.6 ± 1.8 mgPO4-P/gVSS.h in the PAO I and PAO I-GAO cultures, respectively). These findings suggest that other microbial populations, such as GAOs, were responsible to reduce nitrate to nitrite in this EBPR system, and that PAO I used the nitrite generated for anoxic phosphate uptake. Moreover, the simultaneous denitrification and phosphate removal process using nitrite as electron acceptor may be a more sustainable process as can: i) reduce the carbon consumption, ii) reduce oxygen demand of WWTP, and iii) due to a lower growth yield contribute to a lower sludge production.
Highlights
Phosphate is a key nutrient to remove from wastewater streams to avoid eutrophication of water bodies (Yeoman et al, 1988)
Candidatus Accumulibacter phosphatis are one of the main polyphosphate accumulating organisms (PAOs) performing the biological removal of phosphate in wastewater treatment plants (WWTP) (Hesselmann et al, 1999)
PAOs proliferate in WWTP's by recirculating the activated sludge mixed liquor through anaerobic and aerobic/anoxic conditions, and directing the influent rich in volatile fatty acids (VFAs) to the anaerobic tank (Barnard, 1975)
Summary
Phosphate is a key nutrient to remove from wastewater streams to avoid eutrophication of water bodies (Yeoman et al, 1988). One of the ways to remove phosphate is biologically, through the use of polyphosphate accumulating organisms (PAOs) in wastewater treatment plants (WWTP). PAOs are able to store volatile fatty acids (VFAs) as polyhydroxyalkanoates (PHAs), generating the required reduction equivalents (NADH2) by converting glycogen to PHA. This fermentation pathway generates some energy in the form of ATP, the remainder of the energy needed is supplied by polyphosphate consumption. Under aerobic or anoxic conditions, PAOs oxidize stored PHA to generate energy which is used to replenish polyphosphate and glycogen, to grow, and for maintenance purposes (Smolders et al, 1994a, 1994b; Kuba et al, 1996). PAOs proliferate in WWTP's by recirculating the activated sludge mixed liquor through anaerobic and aerobic/anoxic conditions, and directing the influent rich in VFAs to the anaerobic tank (Barnard, 1975)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
