| Digested piggery wastewater(DPW) is characterized by high ammonium concentration while low carbon to nitrogen ratio(COD/TN), which is unable to meet the increasingly stringent emission standards with traditional biological treatment methods. An intermittent aeration sequencing batch reactor(IASBR) is developed on the base of the traditional SBR, and it has a distinct advantage on treating wastewater with high ammonia concentration but low COD/TN. In this study, both IASBR and traditional SBR were used for treating DPW. The pollutant removal performance was investigated and compared under different conditions(including switch times of intermittent aeration, influent COD/TN ratio and pollutant load). Microbial communities were also analyzed in order to explain the differences in pollutant removal between the two types of reactors. The results were as follows:1. Results under different COD/TN ratios and volumetric loadings showed that the more the number of intermittent aeration, the higher were the TN and ammonia nitrogen removal rates in the reactor, and the stronger resistance was the system to shock loading. When COD/TN was 3.0 and TN load was 0.38 kg/(m3·d), TN, ammonia and TOC removal rates reached as high as 92%, 99% and 92%, respectively in IASBR(4)(intermittent aeration of four times). The nitrification rate remained stable at 70%, significantly higher than the IASBR(2)(intermittent aeration of twice) and SBR.2. Influent and effluent Biogas slurry of three-dimensional fluorescence analysis showed that biogas slurry fluorescence peaks are mainly concentrated in the aromatic protein analogs in Zone I, II, and soluble by-products of microbial area in Zone IV. After treatment, the number of peak fluorescence increase, but the fluorescence intensity decreased, indicating that the organic molecules are broken down into small molecules, and IABR(4), IASBR(2) of the fluorescence intensity decreased more than SBR3. ORP and pH can well reflect running state change of the system, at low ammonia loading, IASBR(4), IASBR(2) appears pH "ammonia Valley", which Indicating completion of the oxidation of ammonia, but the SBR has not this phenomenon. Periodic FA concentration changes indicate that due to the IASBR(4) and IASBR(2) of ammonia oxidation rate faster, resulting FA concentration below the concentration inhibiting NOB in 100 min and 350 min, respectively. Low ammonia loading is not conducive to the realization of short-nitrification, increasing influent ammonia loading, is conducive to higher rates of nitrification. For SBR, because ammonia oxidation rate is slow, FA inhibition at a higher concentration, NOB is suppressed, SBR has always been able to obtain a higher rate of nitrification.4. Further optimization carbon addition method, based on IASBR(4), the result show that carbon utilization can be improved effectively, about 23% of the carbon added to the rear end of anoxic vote, compared to single mode, Saving 0.2 COD/TN. While batch tests show that long time hypoxia can inhibit the activity of NOB, the longer the time of hypoxia, the greater the inhibition, NOB need 15 min to restore its activity, when from anoxic environment into the aerobic environment.5. High-throughput sequencing show that dominant species is Proteobacteria, Bacteroidetes, Chloroflexi.etc, in three reactor. Related to nitrification and denitrification bacteria(Nitrosomonas, Thauera) accumulate preferably IASBR(4), IASBR(2) followed, SBR least. In addition, due to the different modes of aeration, IASBR(4) and IASBR(2) system could enrich more facultative anaerobes, the highest proportion of aerobic bacteria in SBR. Different models have different aeration microbial community structure, Alpha diversity analysis showed that, IASBR system species richness and complexity of the microbial community structure are better than traditional SBR.
|
PDF Full Text Request