Study On Microbial Degrdation Of Garlic Wastewater Based On MBBR

Garlic processing wastewater contains garlic polysaccharides,sulfur-containing proteins and sulfur ether compounds,which are difficult to degrade,and the concentration of pollutants is high,causing serious pollution to the air and water environment.Using physical or chemical treatment,the effluent quality cannot meet the standard.Not only can the contaminants not be completely removed by conventional biological treatment,but the high concentration of garlic processing wastewater will greatly limit the growth and reproduction of microorganisms.To this end,a moving bed biofilm reactor（MBBR）is used to enhance the biological treatment effect,combined with the back-end Anaerobic/Oxic（A/O）process to treat garlic processing wastewater.In this paper,membrane bioreactors（MBR）are inoculated with activated sludge for domestication and cultivation.The chemical oxygen demand（COD）removal rate was 96%on average and the ammonia nitrogen（abbreviated NH₃-N）removal rate was 85%on average with a flow rate of 3 L/h,a hydraulic retention time（HRT）of 24 h,a temperature of 30℃and an organic load of 6～7 g COD/（m³·d）.From the analysis of the effluent quality,the activated sludge in MBR can basically remove most of the organic matter in garlic processing wastewater,and the sludge morphology is good,and the concentration of activated sludge has also increased compared with that before inoculation.It indicates that the microorganisms in MBR can already adapt to the environment with garlic processing wastewater as the only carbon source.The microorganisms in the activated sludge before and after incubation were isolated and identified,and one strain CAS1 was isolated from the activated sludge before inoculation and identified as Arthrobacter sp..Three dominant strains WPG1,WPG2 and WPG3 were isolated from the activated sludge after the culture was completed.16S r RNA identified WPG1 as Alcaligenes sp.,WPG2 as Acinetobacter sp.and WPG3 as Achromobacter sp..The three strains were compounded by isolating after the completion of activated sludge culture.The results showed that WPG1+WPG2+WPG3（1:1:1）had the best effect on COD and polysaccharide degradation.Response surface methodology was used to study the effects of the complex strains WPG1+WPG2+WPG3（1:1:1）on the degradation of garlic processing wastewater under three different conditions.p H（5,7,9）,inoculum（1%,5%,10%）and oscillation intensity（120,150,180 r/min）.The results of response surface fitting showed that the best degradation effect was obtained at p H 8,inoculum level of 8.5%and oscillation intensity of 180 r/min.The theoretical COD removal rate was 66.7%and the polysaccharide removal rate was 86.6%under the optimal conditions.The test results showed that the COD removal rate was 74.8%and the polysaccharide removal rate was88.2%under the optimal conditions.Under the optimal conditions,the degradation test was conducted for garlic wastewater with different COD concentrations using mixed bacterial flora,and the results showed that the COD degradation effect of mixed bacterial flora in the range of 5000～15000 mg/L was in accordance with the primary kinetic model.The screened dominant strains and activated sludge are mixed and put into the MBBR for membrane hanging culture.Due to the dominant bacteria and activated sludge can adapt to the low flow rate of garlic processing wastewater,the membrane hanging is fast and the biofilm can be formed quickly.The average removal rate of COD in the MBBR process is78%,the removal rate of NH₃-N is 88%,the removal rate of total nitrogen（TN）is 60%,and the removal rate of Total phosphorus（TP）is 95%,which is not enough to completely remove contaminants from water.Therefore,the treatment effect of combining tertiary A/O and primary A/O at the back end was investigated respectively,and the effluent quality was analyzed.The first-level A/O is sufficient to further degrade the effluent of MBBR and discharge up to standard.When the influent flow rate was 170 L/h,the HRT was 24 h,and the organic load was about 35.90 g COD/（m²·d）,the overall COD removal rate of MBBR-A/O was 98%,the removal rate of NH₃-N was 98%,the removal rate of TN was 96%,and the removal rate of TP was 95%.