High Efficient Anaerobic Biological Reactors Treating Chemical Synthesis-based Pharmaceutical Wastewater

In order to improve efficiencies and stabilities of biological processes treating chemical synthesis-based pharmaceutical wastewater, which contained large amounts of refractory, toxic and hazardous pollutants, three novel reactors of anaerobic baffled reactor(ABR), internal circulation anaerobic reactor (IC) , double circulation anaerobic reactor(DC) were utilized to treat the pharmaceutical wastewater. Furthermore, the biochemical reaction mechanisms and microbial properties were also analyzed.The key operation parameters on the performance of the ABR reactor were studied under ambient temperature (T=23-28℃) and low temperature (T=14℃) respectively. Within 23-28℃, the ABR reactor achieved about 70% COD removal efficiencies at hydraulic retention time (HRT) of 84 h and organic loading rate (OLR) of 2 kgCOD/m3·d. When increasing OLR to 3.6 kgCOD/m3·d, the COD removal efficiencies decreased to 65.1%. At 14℃, the COD removal efficiencies floated within 30-50%, while other operating conditions were maintained. Moreover, the acidification occurred during the operation of the ABR reactor, which resulted in instability of the system. These results showed that the performance of the ABR reactor was clearly needed to be improved.The performance of the IC reactor to treat pharmaceutical wastewater was also examined. The results indicated that the acclimation period lasted 23 days with high strength influent and high organic loading rate under mesophilic conditions. Granular sludge acclimation was achieved with COD removal efficiency of 70% and organic loading rate of 5 kgCOD/m3·d. When the HRT was 20 h under the stable operation condition, the COD removal efficiency of IC was stabilized at about 70% with optimal OLR of 8 kgCOD/m3·d. Compared with the ABR reactor, the HRT and OLR of IC reactor were 1/4 and 4 times of those of ABR reactor when achieving the same COD removal efficiencies. However, the organic loading rate and COD removal rate of IC reactor was still not high enough for treating pharmaceutical wastewater. The IC reactor happened acidification if the strong concentration influent was not diluted.A novel double circulation anaerobic (DC) reactor was designed for the treatment of pharmaceutical wastewater based on IC reactor. The experimental results showed that DC had the characteristics of quick start-up, running stability, and high volume loading rate. The COD removal of DC was up to 80% with OLR of 2.3-5.6 kgCOD/m3·d, HRT of 16h, when it was used to treat real synthesis-based pharmaceutical wastewater. When the DC reactor was used to treat mixed wastewater composed of real pharmaceutical wastewater and glucose simulated wastewater, COD removal rate could be stabilized at 80% with the volume loading rate increased from 5 to 30 kgCOD/m3·d. The COD removal efficiency decreased significantly when the volume loading rate rose to 44 kgCOD/m3·d. Although the wastewater COD/SO42- had a significant effect on COD removal efficiency of the DC reactor, while COD/SO42- value decreased from 10 to 3, COD removal decreased from 85% to 56.2%. DC reactor still had a good sulfate removal rate compared with the other anaerobic reactors; the sulfate removal rate of DC reactor was 50%-70% under stable operating conditions. Different reflux ratio of the DC reactor was evaluated to determine the optimal reflux ratio, which value was 6.The granular sludge morphology of DC and IC looked similar observed by SEM and the reactor construction had little effect on morphological changes. The distribution of microbial communities in different operation stages have been studied by means of PCR-DGGE analysis of genetic fingerprinting techniques. It was found that dominant population has experienced a significant dynamic succession process, especially for archaeal, and microbial climax community made up of specific populations was formed finally. The sequences indicated that total bacteria of Kluyvera sp, Lentisphaerae and the archaeal of Uncultured methanogenic archaeon, Methanoculleus, Methanosaeta concilii have maintained relatively stable dominance, while populations such as total bacteria of Aeromonas hydrophila, Acinetobacter and archaeal of Methanimicrococcus, Uncultured archaeon, Uncultured Methanosarcinales archaeon appeared transiently, the eventual predominant species with the succession of community evolved were Paenibacillus polymyxa, Myxococcales, Bacillus cereus and delta proteobacterium.