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 (Φ25 × 12, Φ25 × 4, Φ15 × 15, and Φ10 × 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 Φ15 × 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 Φ15 × 15 poly-carrier was compared with the other three carriers, while the genes of the Φ15 × 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 Φ15 × 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 effluent as possible reclaimed water, thus providing a good showcase of N-rich reverse osmosis concentrate purification in practical application.
Highlights
The water crisis caused by water pollution and water shortage has directly affected the sustainable development of the global economy and society [1]
The reactors were inoculated by activated sludge, which was collected from the anoxic tank of Beijing Xiao Jia He Wastewater Treatment Plant (WWTP)
At the beginning of operation, the removal rate of NO3 - –N in moving bed biofilm reactor (MBBR) varied with the influent fluctuation and the MBBRs were unstable
Summary
The water crisis caused by water pollution and water shortage has directly affected the sustainable development of the global economy and society [1]. Due to the lack of water resources, some water-deficient areas have used the effluent of wastewater treatment plants (WWTP) as a water source to produce high-quality reclaimed water [2]. One of the techniques to treat WWTP effluent is the low-pressure reverse osmosis membrane. It would produce a certain amount of reverse osmosis concentrate during the treatment process. Preliminary study showed that this type of reverse osmosis concentrate is different from conventional reverse osmosis concentrated water [3] and has the characteristics of high total nitrogen (TN) concentration and salinity, high NO3 –- N/TN ratio, low C/N as well as poor biodegradability. Nitrogen (N) is one of the main elements of water eutrophication
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