Screening Of Indigenous Bacteria And Research On The Remediation Effect Of Black-Odorous Water In Combination With Biological Stimulant

The black-odorous river is the environmental problem that the public reacts the most strongly,and it also a prominent water environment problem in China.As a low-cost,high-efficiency,and environmentally friendly restoration method,the microbial remediation has been developed and gradually applied to river management.Taking the black-odorous river sediments（River Renjing,Shenyang）and simulated black-odorous water as experimental objects,the indigenous bacterial were isolated and screened from the black and odorous sediment,which can efficiently degrade pollutants.Under intermittent aeration condition,the restoration effect of indigenous bacteria combined with bio-stimulant on black-odorous water was explored.Firstly,the indigenous bacteria a and N1 were obtained from the sediment of black-odorous river（River Renjing,Shenyang）by routine isolation and screening of bacteria,which have the COD_Cr and NH₄⁺-N degradation ability in black-odorous water.Combined with morphological observation and 16S r DNA gene sequence analysis,strain a was identified as Bacillus toyonensis,and strain N1 was identified as Bacillus aryabhattai.The single-test experiments were used to optimize cultivation conditions.The optimal culture conditions of strain a were p H 7.0,equipment the liquid volume was 25%,temperature was 32°C;the optimal culture conditions of strain N1 were p H 7.5,equipment the liquid volume was 25%,temperature was 35°C.Furthermore,the growth curve of strains were measured to determine the optimal inoculation point.The optimal inoculation point of strain a and N1 were cultured for 12 h and 16 h,respectively.Then,the COD_Cr and NH₄⁺-N degradation performance of strain a and N1 in black-odorous water was further studied,respectively.Experimental results show that:the degradation effect of strain a on organic matter is better than other domestically reported strains.When the initial COD_Cr of black-odorous water is 86.2 mg/L,the degradation rate of organic matter can reach 64.75%.Under the same experimental conditions,COD_Cr removal rate is higher when the initial bacterial concentration of strain a is 1%（volume fraction）,and increasing initial concentration of bacteria resulted in increasing of COD_Cr removal rate and then decreasing.Strain a has a high utilization rate of small molecular weight organic matter such as glucose and methanol,which can reach more than 65%.In the initial NH₄⁺-N 33.7 mg/L water sample,the degradation rate of NH₄⁺-N by N1 can reach 56.21%.Under the same experimental conditions,when the initial bacterial concentration of strain N1 is 0.5%and 1%,NH₄⁺-N removal rate reaches more than 55%,and the removal rate of NH₄⁺-N increased first and then decreased with increasing initial concentration.When the carbon source is organic acids such as sodium acetate and sodium citrate,it is more beneficial to the degradation of NH₄⁺-N by strain N1.Last,strain a and strain N1 were compounded into composite native bacteria according to the inoculum amount of 1%and 0.5%,and the removal effects of different dosages of composite bacteria and bio-stimulant on pollutants were explored and the optimal dosage was determined.The optimal dosage of composite bacteria and bio-stimulant is 3%and 3 g/L,respectively.Taking the black-odorous river sediments（River Renjing,Shenyang）and simulated black-odorous water as experimental objects,a 25-day restoration experiment of composite indigenous bacteria combined with bio-stimulant was carried out.At the end of the experiment,in the overlying water,COD_Cr dropped from 95 mg/L to below 30 mg/L,NH₄⁺-N concentration dropped from 27 mg/L to below 1.5 mg/L,all meeting the surface water classⅣstandard.TP concentration dropped from 1.2 mg/L to below 0.4 mg/L,meeting the surface water class V standard.During the experiment period,the microbial DHA in the sediment was basically higher than the control group.Compared with A0＿1,both at phylum level and genus level,the relative abundance of bacteria and genera related to organic matter degradation,denitrification and sulfur oxidation in the A0＿2 all increased.It indicated that the dominant bacteria with the function of pollutant degradation were clustered in the A0＿2.While the pollutants were effectively degraded,the microbial diversity of the sediment was also improved.The microbial community composition of sediment succeeded in a direction that was conducive to pollutant degradation.