The advanced nutrient removal efficiency and microbial community of a pipeline biofilm system for tailwater transportation

To achieve advanced nutrient removal in wastewater treatment plants (WWTPs) with limited land and reuse wastewater in a low-cost way, a pilot-scale pipeline biofilm system integrating advanced simultaneous nitrogen and phosphorus removal with tailwater pressure transportation from WWTPs was proposed in this research. Results indicated that with the wall-attached polyurethane foams, the system was established after 7 days of starting operation and the enriched biomass reached 12.79 kg/m(3). Simultaneous high-efficiency purification and high velocity (0.7 m/s) delivery of tailwater were realized. Furthermore, the removal efficiency was significantly affected by COD/TN and flow velocity. Under the optimal condition, the removal efficiencies of COD, NH4+-N, NO3--N, TN and PO43--P were 85.97 +/- 4.53 %, 78.63 +/- 4.00 %, 98.17 +/- 1.19 %, 94.99 +/- 0.90 % and 82.52 +/- 5.45 %, respectively. TN removal rate per unit area biocarrier was 32.17 x 10(-3) mg/(L h m(2)) and PO43--P removal rate was 1.24 x 10(-3) mg/(L h m(2)). High-throughput sequencing validated that heterotrophic nitrification aerobic denitrification bacteria (Acinetobacter), denitrifying polyphosphate accumulating organisms (Dechloromonas) and denitrifying bacteria (Hydrogenophaga, Cloacibacterium and Clostridium) synergistically contributed to pollutants removal. This study provided a new strategy for advanced nutrient removal and sewage reuse.