Comparative study of denitrifying-mbbrs with different polyethylene carriers for advanced nitrogen removal of real reverse osmosis concentrate

Abstract

Nitrogen (N) remains a great challenge in wastewater treatment while attempts to remove N has continuously been a research point for decades. In this study, the long-term performance of four identical-shape denitrification MBBRs (moving bed biofilm reactors) with four different configurations of cylindrical polyethylene as carriers (ɸ25 × 12, ɸ 25 × 4, ɸ 15 × 15, and ɸ 10 × 7 mm) for advanced N removal of real reverse osmosis concentrate was investigated in great detail. The N of the real concentrate can be effectively removed by denitrification MBBRs when the pH, temperature, hydraulic retention time (HRT), C/N ratio, and filling rate are 7.50–8.10, 24~26 °C, 12 hours, 6.6, and 50%, respectively. The results showed that the MBBR with the F15 ± 15 poly-carrier had the best removal efficiency on NO3 -–N (78.0 ± 15.8%), NO2 -–N (43.79 ± 9.30%), NH4 +–N (55.56 ± 22.28%), and TN (68.9 ± 12.4%). The highest biomass of 2.13 mg/g-carrier was in the ɸ 15 × 15 poly-carrier was compared with the other three carriers, while the genes of the ɸ 15 × 15 poly-carrier reactor were also the most abundant. Proteobacteria was the most abundant phylum in the system followed by Bacteroidetes and then Firmicutes. The entire experiment with various parameter examination supported that ɸ15 × 15 poly-carrier MBBR was a promising system for N removal in high strength concentrate. Despite the lab-scale trial, the successful treatment of high strength real reverse osmosis concentrate demonstrated the reality of the treated effuent as possible reclaimed water, thus providing a good showcase of N-rich reverse osmosis concentrate purification in practical application.