Coal Pyrolysis Wastewater Research Articles

Synergistic degradation on aromatic cyclic organics of coal pyrolysis wastewater by lignite activated coke-active sludge process

In current study, the degradation of aromatic cyclic organics (ACOs) of coal pyrolysis wastewater (CPW) by lignite activated coke-active sludge (LAC-AS) process was investigated through the insight into synergistic effect of LAC and microbial community. As a contrast, the study on single AS process revealed that high phenols (>200 mg·L−1) exerted irreversible toxicity by eliminating biomass. Meanwhile, quinoline and naphthalene exhibited joint inhibition with phenols on bio-community. Absence of functional genus and insufficient interspecific cooperation caused interrupted biological reaction, leading to degenerated ecosystem and vicious circle. However, LAC-AS performed synergistic degradation of ACOs, leading to developed ecosystems and benign substance metabolisms. Specifically, LAC alleviated toxicity on suspended AS by ACOs adsorption, and the facultative bacteria enriched by LAC exerted synergistic degradation in biochemical processes. Firstly, the bacteria on biofilm facilitated direct interspecies electron transfer for ring-cleavage reaction, and electroactive bacteria (Cloacibacterium, Hydrogenophaga and Stenotrophomonas) were critical for the process. Secondly, suspended AS further degraded ring-cleavage products, achieving the interspecific cooperation with biofilm. The synergistic nitrogen metabolism by different paths also contributed to the benign metabolic circulation.

Selective adsorption and bioavailability relevance of the cyclic organics in anaerobic pretreated coal pyrolysis wastewater by lignite activated coke

This study originally investigated the selective adsorption of cyclic organics in APCPW by LAC, corresponding to the change of the bioavailability. As a product from low rank coal, LAC showed more oxygen (O)-containing groups and mesoporous structure than PAC. Adsorption mechanisms were analyzed by equilibrium isotherms and kinetics models combined with physicochemical properties of adsorbent and adsorbates. The results indicated that selectivity of LAC was dominated by chemical interaction and its mesoporous, and was enhanced by hydrophobicity of adsorbates. In addition, PAC and LAC were applied for the treatment of APCPW. Compared with PAC, LAC adsorption exhibited superior removal efficiency of Tph, TOC and TN at 85.90%, 91.15% and 51.64%, respectively. Furthermore, preferential adsorption of biotoxic and bioresistant cyclic organics by LAC was further proved by GC–MS analysis, resulting in increased bioavailability of APCPW. Specifically, LAC exerted sustained detoxication capacity until 86.50% reduction of TU by D. magna evaluation, and lowered toxicity rank (TU = 4.51, classIII) to T. pyriformis than that after PAC adsorption (TU > 10, ClassIV). Meanwhile, biodegradability was also improved by 9.17% after LAC adsorption. Lastly, LAC would exhibit great economic benefits as an alternative for PAC in subsequent process after anaerobic pretreatment.