Advanced C, N and P removal performance and mechanism of municipal wastewater in lab-scale denitrifying filter for generating biogenic manganese oxides

Abstract

In order to cost-effectively remove carbon (C), nitrogen (N) and phosphorus (P) from secondary effluent (SE), a lab-scale denitrifying filter (DF) for generating biogenic manganese oxides (BMOs) was constructed, and its influent was the mixture of real SE and secondary influent (SI). When NH₄⁺-N in the influent rose to around 3.2 mg/L with the improvement of the SI ratio, the effluent COD, filtered total nitrogen (TN) and phosphorus (TP) were 7.80, 0.63 and 0.014 mg/L with the corresponding removal rate (CRR) of 84.72 %, 97.17 % and 95.15 %, respectively. The refractory organics were oxidized and hydrolyzed to biodegradable organics, providing carbon source, and the residual organics were hardly further removed, owing to their extremely poor biodegradability. N was synergistically removed by denitrification coupled with partial-denitrification anammox (PDA), which was confirmed by the fact that the contribution rate of PDA to TN removal was 30.43 % and removing 1 mg TN actually consumed 2.02 mg COD. P was mainly removed by reacting with Mn²⁺ from the influent or BMOs reduction to form chemical precipitation (Mn₃(PO₄)₂). The presence of the main functional bacteria (manganese oxidizing bacteria (MnOB), anammox, denitrifying and hydrolytic bacteria) and the main functional genes further explained the efficient C, N and P removal and clarified the advanced C, N and P removal mechanism. This novel technique removed C, N and P with extremely high efficiency, extremely low operational cost and no secondary pollution.