Effects Of Coking Wastewater And Its Toxic Substances On Microfauna Community Of Activated Sludge

Coking wastewater is a kind of typical industrial wastewater, which contains various high toxic organic compounds, but the activated sludge process using for coking wastewater treatment often faces the problem that COD, NH4+-N or total cyanide is difficult to reach the effluent standard, actually. Owing to it's importance of microfauna in the micro-ecological system of activated sludge, this study focused on the micro-ecological level of activated sludge, explore the effects of coking wastewater and its toxic substances on the microfauna community of activated sludge to reveal their toxic effect, in order to provide a biological basis for improving effect of the coking wastewater treatment. In present research, we confirmed the basic characteristics and change rule of the microfauna community structure in treatment of coking wastewater by activated sludge process, via investigating the microfauna community of activated sludge in a full-scale coking wastewater treatment plant. Meanwhile, we discussed the relationship between the microfauna community of activated sludge and performance of the activated sludge for coking wastewater treatment; The continuous load impact test of coking wastewater to the activated sludge system verified that the substantial effects of coking wastewater on structure and species biodiversity of the microfauna community of activated sludge; In addition, we further analysed the acute toxic effect of the typical PHs toxic substances in coking wastewater on the microfauna community and common species of activated sludge, and the sustainably ecological effects of coking wastewater on structure, species biodiversity and stability of the microfauna community by doing the 24 h acute toxicity test and continuous load impact test of 3 kinds of typical phenolic substances(PHs)(including phenol, o-Cresol, m-Cresol) in coking wastewater to the microfauna community of activated sludge. The main research conclusions are as follows:1. Dominant groups of microfauna community in the activated sludge system using for coking wastewater treatment were sessile ciliates and crawl ciliates, and Vorticella sp. contains the most species, but its species and quantity were relative lower compared to the conventional sewage treatment of activated sludge. what's more, Vorticella microstoma was the absolute dominant species, and the community structure was changeable and unstable.2. The relationship between microfauna community and performance of the activated sludge for coking wastewater treatment was complex. For instance, the correlations among the most species of microfauna community and effluent quality or operational parameters were not significant, besides the classic SBI as activated sludge evaluation method was failure in the evaluation of the activated sludge for coking wastewater.3. The results of factor analysis showed that nitrification efficiency, microorganism, operational parameters, etc. were the important influence factors associated with the activated sludge system using for coking wastewater treatment, and some microfauna species(genus) had interrelations, eg. a similar "cooperative" relationship existed between Epistylis sp. and Podophrya sp., while a similar "competition" relationship existed between Aspidisca costata and Aspidisca lynceus.4. Coking wastewater had a significant impact on the microfauna community structure of activated sludge, and had different effects on the same group or different groups with different loads of coking wastewater. It may promote the growth of some groups of the microfauna community, while restrain other groups.5. Relative abundance(namely structure) of microfauna community in the activated sludge system dynamically changed with the time variation; Coking wastewater also had an impact on the dynamic change of structure of the microfauna community of activated sludge, and it had significant difference on the community structure at different loads of coking wastewater; Toxicity of coking wastewater reduced species richness and evenness of the microfauna community of activated sludge, while increased the species dominance, thereby reducing the level of species biodiversity, and the larger loads of coking wastewater the more obvious the decreasing of species diversity level of the microfauna community of activated sludge.6. The acute toxicity test results showed that there was an obvious "dose-effect" relationship between the concentrations of 3 kinds of PHs and abundance of the microfauna community or some species of them. i.e., the toxic effect to the microfauna community and some microfauna species of activated sludge enhanced significantly with the increasing of the PHs concentrations. Some microfauna of the activated sludge changed their form by encysting to adapt to bad living environment under the toxicity action of PHs, and different concentrations of PHs toxic substances had different degree influence on forms of microfauna. Under the long-term action of the high PHs concentrations, this kind of survival mechanism became invalid, gradually.7. Different PHs substances had different effects on the microfauna community structure of activated sludge, and the high concentrations of PHs had a significant impact on the community structure. PHs substances had a significant inhibitory effect on some groups of the microfauna community, and others opposite.8. High concentrations of the PHs would significantly reduce the level of species biodiversity of the microfauna community of activated sludge in long term effects, and there were the different degrees influence to species biodiversity and different types of stability index of the microfauna community of activated sludge for different PHs. For instance, high concentrations of phenol promoted the species stability of the microfauna community, while o-cresol and m-cresol reduced it, but all of them significantly reduced the stability of community diversity.