Induction of anammox and partial denitrification activities of pig manure effluents Available to Purchase

Piggery wastewater typically contains high levels of ammonium, and discharge of the wastewater into the environment without adequate treatment could cause algal blooms and negatively impact the ecosystem. The integration of anaerobic ammonium oxidation (anammox) and partial denitrification (PD) has been proposed as an alternative method to remove ammonium. Therefore, enrichment cultures of anammox bacteria and partial denitrifying bacteria (PDB) are desired to attain efficient and stable ammonium removal. In this study, the activity induction of anammox bacteria and PDB were investigated in separate lab-scale batch cultures using pig manure effluents as the inoculum and synthetic wastewater as the substrate. The synthetic wastewater used for the activity induction of anammox bacteria contained NO₂⁻and NH₄⁺ as the main substrates, and the variation in the molar ratios of NO₂⁻/ NH₄⁺ was monitored and analyzed for their correlations with the anammox activity. The synthetic wastewater used for the activity induction of PDB contained acetate, NO₃^-, and NH₄⁺ as the main substrates, and the variations in the molar ratios of C/N were monitored and analyzed for their correlations with the PDB activity. For the experiments on the anammox, the highest specific anammox activity and nitrogen removal rate were estimated to be 14.97 mg/g volatile suspended solids (VSS) d and 19.58 mg/L d, respectively, at a NO₂⁻/ NH₄⁺ molar ratio of 1.57. However, the anammox activity was inhibited when the NO₂⁻/ NH₄⁺ molar ratio reached 2.15. For the experiments on the PD, the COD had decreased from day 0 to day 4, causing the variations of the COD to NO₃⁻-N (C/N) through the culture period; i.e., 3.05, 1.70, 1.09, 0.60, and 0.66 on day 0, 1, 2, 3, and 4, respectively, whereas in theory, 1.14 g COD is required to denitrify 1 g of NO₃⁻-N (C/N=2) to NO₂⁻-N. The specific rates of nitrate consumption of 3.32 mg/g VSS d and nitrite production of 10.06 mg/g VSS d, the nitrogen removal efficiency of 94.69%, and the nitrate reduction efficiency of 51.20% were achieved at a C/N ratio of 0.66. The results demonstrated that the ratio of NO₂⁻/ NH₄⁺ was a crucial parameter that strongly influenced the anammox activity, whereas the C/N ratios had relatively small effects on the PD activity.