| There are high concentrations of nitrogenous heterocyclic compounds(NHCs)and polycyclic aromatic hydrocarbons(PAHs)in coking wastewater.NHCs such as quinoline and indole have serious carcinogenic and mutagenic effects,which have a negative impact on environmental quality and human health.Therefore,it is of great significance to study the degradation of NHCs in coking wastewater.Therefore,in this paper,banana peel,cabbage leaf and corncob are selected as fermentation substrates to prepare garbage enzymes,which are used as co-metabolic substrates to degrade quinoline and indole by bioaugmentation technology,in order to improve the degradation performance of quinoline and indole and realize the simultaneous removal of total nitrogen.In this study,banana peel,cabbage leaf and corncob were broken and fermented at different temperatures(25 ℃,35 ℃,45 ℃,55 ℃)according to brown sugar: substrate: water ratio of 1:3:10.Through the comparison of their fermentation products,the garbage enzymes suitable for co-metabolic substrate were selected.The acid production was studied in the fermentation process.Four organic acids were detected: citric acid,lactic acid,acetic acid and tartaric acid.At 25 ℃ and 35 ℃,lactic acid and acetic acid are the main components,and the total amount is about 12 g/L at 35 ℃;At 45 and 55 ℃,the citric acid content increased,but the acid production decreased.Because lactic acid and acetic acid can be used as high-quality carbon sources,three garbage enzymes at 35 ℃ were finally selected for follow-up experimental research.By using three garbage enzymes fermented at 35 ℃ as co-metabolic substrates to degrade quinoline and indole in simulated NHCs wastewater,the feasibility of using them as cometabolic substrates was analyzed,and the effects of microorganisms contained in garbage enzymes and p H on degradation performance were investigated.The results showed that:(1)banana peel,cabbage leaf and corncob were suitable co-metabolic substrates for the biodegradation of quinoline and indole in coking wastewater.(2)Non sterilized garbage enzymes are more suitable as co-metabolic substrates for the degradation of quinoline and indole.Low p H of garbage enzymes will inhibit the growth of strains,and it is more suitable for the growth of strains after adjusting p H.after adjusting p H,the degradation effect of quinoline by garbage enzymes in Chinese cabbage leaves is the best,and the removal rate is48%.Therefore,it will be used as a co-metabolic substrate for subsequent research to further strengthen the degradation effect of quinoline.Strain P-1 was added to biologically strengthen the degradation of quinoline,and the degradation effect of quinoline and indole was further improved by preparing mixed strain FP-1 and optimizing the dosage of garbage enzymes.The degradation of quinoline and indole was identified by GC-MS.The results showed that:(1)the addition of strain P-1 enhanced the degradation of quinoline,not only achieved the purpose of degrading quinoline,but also increased the degradation rate of indole.In addition,the addition of strain P-1 also promoted the denitrification performance of F-1,and the ammonia nitrogen concentration remained below 10 mg / L at the end of the reaction.(2)The degradation performance of mixed strain FP-1 was better,and the concentrations of ammonia nitrogen,total nitrogen and TOC were lower than those of single inoculation;It also showed a good degradation effect on quinoline and indole,which made the degradation rate of indole faster and further shortened the degradation cycle of indole.From the effect of nitrogen and carbon removal,when the dosage is 4ml,the removal rate of ammonia nitrogen and total nitrogen is better,and the TOC concentration is relatively low.Therefore,when 4 ml garbage enzyme is added,it is more suitable to degrade quinoline and indole as a co-metabolic substrate.(3)The main intermediate products of quinoline degradation are 2(1H)-quinolinone,2,8-dihydroxyquinoline,8-hydroxycoumarin and 2,3-dihydroxybenzoic acid,which are typical degradation pathways of8-hydroxycoumarin;The main intermediate products of indole degradation are 2-indolone,indigo,o-aminobenzoic acid and benzoate,which are typical ways of indigo degradation.Finally,high-throughput sequencing was used to analyze the microbial community of strains F-1,P-1,FP-1 and the simulated wastewater degraded for 48 h.Compared with FP-1,the simulated wastewater degraded for 48 h has higher microbial community diversity and abundance.The dominant genera of F-1,P-1 and FP-1 were Comamonas,Pseudomonas and Rhodococcus,accounting for 30.95%,69.07% and 94.25% respectively.In the simulated wastewater,Proteobacteria accounts for the highest proportion at the phylum level,at the class level,the main dominant bacteria are γ-Gammaproteobacteria;at the genus level,Pseudomonas is its dominant genus. |
