[Characteristic of Benzo[a]pyrene Anaerobic Degradation by Phenol Co-substrate and Microbial Communities from Two Types of Sludge].

Benzo[a]pyrene (BaP) is a typical representative of PAHs in coking wastewater and priority-controlled pollutants in the coking industry; its response characteristics with microorganisms and the methods to promote its degradation are worth studying. On the other hand, because the inoculated sludge for the adjustment and operation of newly-constructed coking wastewater treatment plants comes from municipal sludge or other coking plants, currently, the study of the microbial properties of different sludges', sludge availability, and the conditions that influence these properties are lacking. On account of the above perspectives, an experiment to study and compare the durability of municipal sludge and coking sludge, and their ability to degrade BaP was carried out. An anaerobic reactor was selected for the experiment and anaerobic-activated sludges were collected from a coking wastewater processing unit and a municipal wastewater plant. Then, 10 mg·L-1 of BaP alone and BaP with phenol as a co-metabolic carbon source was added to the coking and municipal sludge samples, respectively, for comparison experiments to study the microbial degradation of BaP and its dynamics. Moreover, high-throughput sequencing technology was also used to analyze the changes in the microbial community structure before and after the degradation experiment. The results showed that:① Both sludges were capable of degrading BaP, but municipal sludge showed a higher degradation efficiency than coking sludge; ② Adding phenol as co-substrate promoted the biodegradation of BaP in both sludges. When BaP was the sole carbon source, the half-life of BaP in the two sludges was 155.41 d and 116.3 d respectively. After the addition of phenol, the half-life was reduced to 81.25 d and 38.44 d, respectively; ③ According to the analysis of the microbial community structure, the community composition in both sludges changed markedly. Moreover, the microbial community in the municipal sludge showed a more evident change than that of the coking sludge. In the coking sludge, the dominant bacteria community changed a little after acclimation, most of the observed bacteria were previously reported common PAH-degrading strains. In contrast, the dominant bacteria community in the municipal sludge varied greatly after acclimation, and the most abundant bacteria were not common PAH-degrading strains. In addition, some frequently reported PAHs-degrading bacteria such as Bacillus sp., Pseudomonas, Achromobacter, and Sphingomonas sp., were identified in both the sludges and were present in high abundance. The results indicated that municipal sludge utilized BaP more actively than coking sludge; this phenomenon can be explained by the fact that municipal sludge contained a higher diversity of microbes that were involved in the degradation of BaP. Furthermore, the presence of phenol promoted the degradation of PAHs like BaP. Therefore, we proposed that the PAHs in coking sludge discharge might be reduced by the addition phenol and municipal wastewater.

[Behavior and Degradation of Polycyclic Aromatic Hydrocarbons (PAHs) in Coking Wastewater of A/O2 and A/O/H/O Processes].

Polycyclic aromatic hydrocarbons (PAHs) are typical organic pollutants found in coking wastewater, and their behavior and reduction can be affected by different treatment processes. Based on these considerations, this study investigated the behaviors of PAHs in coking wastewater under A/O2 and A/O/H/O treatment processes, respectively. In order to evaluate variations in PAH removal under two different treatment processes, samples were taken from different treatment units for quantification of PAHs using gas chromatography-mass spectrometry. Results showed that PAHs were barely degraded in anaerobic tanks of either treatment process and accumulated much higher concentrations than in aerobic and hydrolytic tanks. While low molecular weight PAHs (LMW PAHs) in aqueous phase from anaerobic tanks were degraded effectively in aerobic tanks, high molecular weight PAHs (HMW PAHs) mostly accumulated in the sludge phase; these potentially pose a higher environmental risk and therefore need to be treated separately. Moreover, the A/O/H/O process showed higher degradation of PAHs bioavailability and higher removal effectiveness for PAHs with four or more benzene rings than the A/O2 process; this is attributed to the hydrolytic tank's ability to promote hydrolysis of macromolecular organic compounds and therefore improve biodegradability of PAHs. Comprehensive results from the study indicated that the A/O/H/O process is more advantageous for degradation of PAHs than the A/O2 process.