Study On Treating Isophthalonitrile Wastewater By Microorganism Immobilization Technology And Immobilized Reactor

Isophthalonitrile(IPN) used in this study is a key pesticide intermediate of chlorothalonil. The effluent emitted from IPN production is one kind of high-concentration of cyanophenyl, acid amide and ammonia with complicated water quality such as poor biodegradability characteristics. Under the use of immobilized microbial technology, it is possible to reduce the loss of microorganisms in the reactor, and enhance the system's ability to resist changes in water quality and toxic shocks. The choice of carrier is the key factor of immobilized biological technology.On the basis of building high efficiently microorganism with immobilizeation technology was used to deal with the IPN wastewater. The coupling microorganism is consisted of 4 single strains which were in effect in dealing with the IPN wastewater. After comparing the degradation effect of these two immobilization methods:adsorption method and embedding method, used the better one to carry out in a immobilized aerated filter (IBAF) which was used to treat wastewater containing high concentration of IPN.Two immobilization methods, adsorption with ceramic as the carrier, embedding with Sodium Alginate(SA) and Polyvinyl Alcohol -Sodium Alginate(PVA-SA) as the carrier, the research is conducted into the degradation effects, physical stability, and ammonium-nitrogen removal capabilities. Results showed that IPN biodegradation by adsorption method had the better effect. The IPN degradation rate kept stable and the removal rate was over 95.5% in 5 hours. In addition, the PVA-SA gel was the most stable and efficient in embedding carriers.The results demonstrated that the maximum concentration of IPN biodegraded by BAF with ceramic support was 190mg/L in the hydraulic retention time of 24 hours. In ensuring the removal rate of 90%, and the stability of the effluent water's quality, the highest concentration of IPN wastewater is 160mg/L in the HRT of 10 hours. Compared the treatment effect of activated sludge biological filter with glucose as co-substrate, the maximal tolerable concentration was 55mg/L under which the removal rate was near 60%.The contrastive analysis showed that the biodegradability of BAF with immobilized bacteria was significantly better than the activated sludge biological filter.The nitrification in the IBAF began to play a role in process of time while the ammonia nitrogen removal rate is low in the biofilm formation stage. The ammonia nitrogen removal rate had been enormous increases in the process of the influent IPN concentration increased from 100mg/L to 190mg/L. During the period of shortening of HRT, filter ability of nitrification weakened. The average removal rate of ammonia nitrogen is 58±9.78% in the stable HRT of 10 hours. Investigation on the directional distribution of nitrobacteria and carbonize heterotrophic bacteria in the immobilized BAF. Results showed that the main growth sector of the former was underneath the filter while the latter was in the upper part of the filter.As the concentration of IPN was increasing, the actingarea of nitrobacteria was moving up while the carbonize hererotrophic was moving down.