Increasing municipal wastewater BNR by using the preferred carbon source derived from kitchen wastewater to enhance phosphorus uptake and short-cut nitrification-denitrification

A new method for increasing municipal wastewater biological nutrient removal (BNR) by using kitchen wastewater-derived carbon source to simultaneously enhance phosphorus uptake and short-cut nitrification–denitrification was reported. Firstly, laboratory tests were conducted to maximize the volatile fatty acids (VFA) production with the greatest propionic/acetic acid ratio (i.e., the preferred carbon source) from kitchen wastewater. Compared with the un-controlled pH fermentation, alkaline fermentation increased the yield of VFA and the ratio of propionic/acetic acid by 63.6% and 140.5%, respectively. Then, the alkaline fermentation liquid was used as the additional carbon source of municipal wastewater BNR in lab-scale reactors, and the results showed that it achieved much greater nitrogen and phosphorus removal than the un-fermented kitchen wastewater. Finally, the full-scale works with alkaline fermentation of kitchen wastewater and the application of the fermentation liquid to improve municipal wastewater BNR were operated. The long-term experiments indicated that the alkaline fermentation liquid had a VFA content of 66.3% (COD based), VFA yield of 0.63, and ratio of propionic/acetic acid of 0.86/1, and the supplement of alkaline fermentation liquid to municipal wastewater caused higher total nitrogen and total phosphorus removal than acetic acid (78.2% versus 69.6%, and 95.2% against 88.4%). Further mechanism investigation indicated that the presence of propionic and humic acids significantly increased phosphorus uptake, denitrifying phosphorus removal, and short-cut nitrification and denitrification in the BNR experiments, which was the main reason for alkaline fermentation liquid showing greater total nitrogen and phosphorus removal abilities than traditional carbon source.