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/m3. 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 × 10-3 mg/(L h m2) and PO43--P removal rate was 1.24 × 10-3 mg/(L h m2). 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.