Simultaneous removal of COD and nitrogen using a novel carbon-membrane aerated biofilm reactor

A membrane aerated biofilm reactor is a promising technology for wastewater treatment. In this study, a carbon-membrane aerated biofilm reactor （CMABR） has been developed, to remove carbon organics and nitrogen simultaneously from one reactor. The results showed that CMABR has a high chemical oxygen demand （COD） and nitrogen removal efficiency, as it is operated with a hydraulic retention time （HRT） of 20 h, and it also showed a perfect performance, even if the HRT was shortened to 12 h. In this period, the removal efficiencies of COD, ammonia nitrogen （NH4^＋-N）, and total nitrogen （TN） reached 86%, 94%, and 84%, respectively. However, the removal efficiencies of NH4^＋-N and TN declined rapidly as the HRT was shortened to 8 h. This is because of the excessive growth of biomass on the nonwoven fiber and very high organic loading rate. The fluorescence in situ hybridization （FISH） analysis indicated that the ammonia oxidizing bacteria （AOB） were mainly distributed in the inner layer of the biofilm. The coexistence of AOB and eubacteria in one biofilm can enhance the simultaneous removal of COD and nitrogen.

Removal of veterinary antibiotics from anaerobically digested swine wastewater using an intermittently aerated sequencing batch reactor

A lab-scale intermittently aerated sequencing batch reactor（IASBR）was applied to treat anaerobically digested swine wastewater（ADSW）to explore the removal characteristics of veterinary antibiotics.The removal rates of 11 veterinary antibiotics in the reactor were investigated under different chemical organic demand（COD）volumetric loadings,solid retention times（SRT）and ratios of COD to total nitrogen（TN）or COD/TN.Both sludge sorption and biodegradation were found to be the major contributors to the removal of veterinary antibiotics.Mass balance analysis revealed that greater than 60%of antibiotics in the influent were biodegraded in the IASBR,whereas averagely 24%were adsorbed by sludge under the condition that sludge sorption gradually reached its equilibrium.Results showed that the removal of antibiotics was greatly influenced by chemical oxygen demand（COD）volumetric loadings,which could achieve up to 85.1%±1.4%at 0.17±0.041 kg COD/m-3/day,while dropped to 75.9%±1.3%and 49.3%±12.1%when COD volumetric loading increased to 0.65±0.032 and1.07±0.073 kg COD/m-3/day,respectively.Tetracyclines,the dominant antibiotics in ADSW,were removed by 87.9%in total at the lowest COD loading,of which 30.4%were contributed by sludge sorption and 57.5%by biodegradation,respectively.In contrast,sulfonamides were removed about 96.2%,almost by biodegradation.Long SRT seemed to have little obvious impact on antibiotics removal,while a shorter SRT of 30–40 day could reduce the accumulated amount of antibiotics and the balanced antibiotics sorption capacity of sludge.Influent COD/TN ratio was found not a key impact factor for veterinary antibiotics removal in this work.

Comparative study on microbial community in intermittently aerated sequencing batch reactors （SBR） and a traditional SBR treating digested piggery wastewater

A traditional sequencing batch reactor （SBR） and two intermittently aerated sequencing batch reactors （IASBRs） were parallelly operated for treating digested piggery wastewater. Their microbial communities were analyzed, and the nitrogen removal performance was compared during the long term run. IASBRs demonstrated higher removal rates of total nitrogen （TN） and ammonium nitrogen （NH4＋ -N） than the SBR, and also demonstrated higher resistance against TN shock load. It was found that the more switch times between aerobic/anoxic in an IASBR, the higher the removal rates of TN and NH4＋ N. All the reactors were predominated by Thauera, Nitrosomonas and Nitrobacter, which were considered to be species of denitrifiers, ammonium oxidizing bacteria （AOB） and nitrite oxidizing bacteria （NOB）, respectively. However, the abundance and diversity was of great difference. Compared with SBR, IASBRs achieved higher abundance of denitrification related bacteria. IASBR 1# with four aerobic/anoxic switch times was detected with 25.63% of Thauera, higher than that in IASBR 2# with two aerobic/anoxic switch times （l 1.57% of Thauera）, and much higher than that in the SBR （only 6.19% of Thauera）. IASBR 2# had the highest percentage of AOB, while 1ASBR 1# had the lowest percentage. The denitrifiers abundance was significantly positive correlated with the TN removal rate. However, the NH4＋ N removal rate showed no significant correlation with the AOB abundance, but might relate to the AOB activity which was influenced by the average free ammonium （FA） concentration. Nitrobacter was the only NOB genus detectable in all reactors, and were less than 0.03%.