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

BACKGROUNDNutrient 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.

RESULTSIn 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 (22.391.08 mgN g(-1)VSS h(-1) and 3.41 +/- 1.71mgP g(-1)VSS h(-1) when SFL was added compared with 7.80 +/- 1.23mgN g(-1)VSS h(-1) and 1.09 +/- 0.12mgP g(-1)VSS 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. (c) 2014 Society of Chemical Industry