Effect of ammonium nitrogen concentration on the ammonia-oxidizing bacteria community in a membrane bioreactor for the treatment of anaerobically digested swine wastewater

https://doi.org/10.1016/j.jbiosc.2014.02.017Get rights and content

A membrane bioreactor (MBR) was developed for the treatment of anaerobically digested swine wastewater and to investigate the effect of ammonium nitrogen concentration on biological nitrogen removal and ammonia-oxidizing bacteria (AOB) community structures. The MBR achieved a high NH4+-N removal efficiency of 0.08 kgNMLSS−1d−1 and removed 95% of the influent NH4+-N. The TN removal rate was highest of 82.62% at COD/TN and BOD5/TN ratios of 8.76 ± 0.30 and 3.02 ± 0.09, respectively. With the decrease in ammonium nitrogen concentrations, the diversity of the AOB community declined and showed a simple pattern of DGGE. However, the AOB population size remained high, with abundance of 107–109 copies mL−1. With the decrease of ammonium nitrogen concentrations, Nitrosomonas eutropha gradually disappeared, whereas Nitrosomonas sp. OZK11 showed constant adaptability to survive during each treatment stage. The selective effect of ammonium concentration on AOB species could be due to the affinity for NH4+-N. In this study, the changes of ammonium nitrogen concentrations in digested swine wastewater were found to have selective effects on the composition of AOB community, and biological nitrogen removal was improved by optimising the influencing parameters.

Section snippets

Experimental design and MBR operation strategy

The reactor was made of Plexiglas and had a working volume of 40 L (W 28 × L 46 × H 31 cm). The reactor was divided by a baffle into two parts: the biofilm zone (B zone) and the membrane zone (M zone) with volumes of 26.7 L and 13.3 L, respectively. A recycle ratio of 400% was maintained between the B and M zones. The B zone was filled with polyethylene carriers (diameter of 25 mm, height of 9 mm, porosity of 95%, specific surface area 500 of m2 m−3 and filling rate of 50%). The membrane module

Nitrogen removal in the MBR

The effluent nitrogen concentrations of MBR, including the NH4+-N, NO2-N and NO3-N concentrations, are shown in Table 2. The influent and effluent nitrogen concentrations are shown in Fig. 1A. With decreasing TN loading rates, the ammonium nitrogen removal efficiency in M-zone was 0.18, 0.08, 0.04 and 0.03 kgNkgMLSS−1d−1 for four stages respectively, and the effluent NH4+-N concentration decreased. Similar ammonium removal efficiency of 0.03–0.04 kg N kg MLSS−1 d−1 was reported by Deng et al.

Effect of ammonium nitrogen concentrations on AOB community

The AOB diversity declined as the influent ammonium nitrogen concentration decreased dramatically, with average values of Shannon–Weiner indices of 0.955, 0.967, 0.886 and 0.301 in B zone and 0.987, 0.971, 0.741 and 0.352 in M zone from stage I to IV, respectively, indicating that the ammonium nitrogen concentration could be a key factor in altering AOB community. As shown in Fig. 4, samples from stage I to II were positively influenced by the ammonium nitrogen concentration, whereas the

Acknowledgments

Funding was provided by Non-profit Research Foundation for Agriculture (201303091) and China Agriculture Research System (CARS-36).

References (33)

Cited by (54)

View all citing articles on Scopus
View full text