Nutrient removal via nitrite from reject water and polyhydroxyalkanoate (PHA) storage during nitrifying conditions

Abstract

BACKGROUND Nutrient removal via nitrite was investigated in a sequencing batch reactor (SBR) treating reject water produced from the anaerobic digestion of sewage sludge and the subsequent dewatering process. The polyhydroxyalkanoate (PHA) storage capacity of the biomass obtained under nitrifying (nitritation) and non‐nitrifying aerobic conditions was investigated in batch reactors for biomass taken from the SBR. RESULTS In situ activity tests showed that the nitritation rate was not affected by the type of external organic carbon source that was added (i.e. propionic acid ‐ HPr and sludge fermentation liquid ‐ SFL). In contrast, the specific nitrite uptake rate (sNUR) and the specific phosphate uptake rate (sPUR) via nitrite were much higher when SFL was applied compared with HPr (22.39 ± 1.08 mgN g−1VSS h−1 and 3.41 ± 1.71mgP g−1VSS h−1 when SFL was added compared with 7.80 ± 1.23mgN g−1VSS h−1 and 1.09 ± 0.12mgP g−1VSS h−1 when HPr was added). The majority of phosphorus removal was attributed to the normal growth of biomass rather than the activity of phosphorus accumulating organisms (PAOs). The PHA yield was 0.65–0.67 C‐mmol PHA/C‐mmol short chain fatty acid (SCFA) when nitrification was inhibited, and 0.60–0.63 C‐mmol PHA/C‐mmol SCFA when nitritation also occurred. CONCLUSION The PHA yield was not adversely affected under nitrifying conditions, demonstrating that nitritation can be integrated with the production of PHA. © 2014 Society of Chemical Industry

Smart Approaches to Food Waste Final Disposal

“…Other interesting examples of the “biorefinery approach” are ongoing studies [17] on the anaerobic digestion of separate collected diapers, from which it is possible to recover a volatile fatty acid (VFA) stream usable for PHA production. Other authors have shown that it is possible to accumulate PHAs in sequencing batches (SBR), treating anaerobic digestion supernatants and recovering VFAs from alkaline fermentation with simultaneous nutrient removal [18,19]. The recovery of VFAs has been of great interest recently thanks to their value as chemical building blocks, and food waste fermentation is the most productive substrate giving the best yields [20].…”

Opportunities and challenges in sustainable treatment and resource reuse of sewage sludge: A review

“…However, being aerobic, these processes are energy intensive (1 kg PHA production requires ~39 MJ), when the aerobic accumulation step is used [137]. WWT has been using streams with high VFAs resulting from fermentation of solids to produce enhanced biomass along with high PHA accumulation [135,143,144], which has been reported as unnecessary [140]. Therefore, the conversion of highly concentrated VFA-media into only polymers seems to be a good choice rather than biomass and polymers.…”

Application of dissolved oxygen (DO) level control for polyhydroxyalkanoate (PHA) accumulation with concurrent nitrification in surplus municipal activated sludge

“…Nitrification should not impact PHA yield under aerobic conditions [32], but alkalinity consumption could increase the variation of pH when dosing acidic fermented substrates. However, denitrification is an alkalinity producing process, which mitigates the lowering of pH caused by nitrification in the mixed liquor when the two processes occur simultaneously.…”