Research On UASB-AO/MBR Combined Process For Treatment Of Compressed Liquid In Garbage Transfer Station

Since the implementation of garbage classification in Suzhou in 2020,the water quality of the garbage compression liquid in the garbage transfer station has changed slightly.The previous treatment methods may no longer apply to the current garbage compression liquid.Therefore,it is necessary to explore a new combined process for processing.Meet the urban municipal sewage discharge pipe standard to avoid its potential harm to water resources and human body.In this paper,the UASB-AO/MBR combined process is used to treat garbage compressed liquid,and the effect of its practical application is explored.The research results are as follows:（1）Water source site selection:In terms of water intake point selection,based on the principles of wide coverage,large coverage area,and representative sewage water quality,the service range of the water intake garbage transfer station should be balanced between urban and rural areas,and new and old urban areas should be combined,striving to achieve urbanization.All functional areas such as commercial areas,residential areas,industrial areas,and universities are fully covered.（2）Water quality analysis:Through the analysis of the sewage water quality,it is found that the COD of the water quality in various regions after the garbage classification has slightly decreased,while the TN and ammonia nitrogen have a tendency to increase.The Gusu District is particularly prominent.The highest COD concentration in the day before the garbage classification can reach 36580mg/L,The lowest is only 13600mg/L,the COD concentration after garbage classification is in the range of 10800mg/L-24350mg/L,while the TN concentration increases from an average of 1148mg/L to about 1371mg/L,and the ammonia nitrogen concentration is from 624mg/L before garbage classification increased to 774mg/L after garbage classification,and the compressed liquid water quality in summer is generally slightly worse than in winter in the same area,with large daily changes,poor water quality at14 o’clock every day,large fluctuations in water quality,and instability.（3）The main purpose of the experiment at this stage is to realize the start-up of the reactor and the sludge domestication through low-concentration organic wastewater,and by controlling the operating conditions,observing the operating effects of the reactor,and preliminarily determining the operating conditions of the UASB-AO/MBR combined process.The UASB-AO/MBR combined process is started.After the sludge is domesticated,a uniform experiment is carried out.During the operation,the HRT,DO and reflux ratio are changed,and the combined process operating conditions are determined by the difference of the effluent water quality.Experimental conclusion:when the hydraulic retention time is 12h,the external reflux ratio is 400%,and the dissolved oxygen in the water is 2-4mg/L,the effluent quality is the best.At this time,the effluent concentrations of COD,TN,TP and NH₃-N are28.4mg/L,37mg/L,2.3mg/L and 3.2mg/L,the average removal rate can reach 92.2%,64.1%,81.7%,93.8%.The effluent water quality is stable,and the water quality is not easy to fluctuate.COD,NH₃-N,and TP in the effluent can all achieve better treatment effects,but the removal rate of TN is low.As the experiment progresses,the removal rate of TN will be further reduced,so follow-up experiments need to explore how to effectively reduce TN content in the waste water of the garbage transfer station makes the effluent water quality up to the standard.Garbage compression liquid treatment effect:due to the low TN removal rate in the compression liquid treatment process,the secondary water quality analysis of the effluent showed that the C/N in the water reached 14 and the Kjeldahl nitrogen accounted for 95.9%of the total nitrogen.Therefore,there is no shortage of carbon sources in the effluent,and the theoretically biodegradable nitrogen can reach 95.8%.Therefore,it is believed that the low removal efficiency of TN is because carbon or nitrogen is not fully utilized.Therefore,it is optimized on the basis of the original combined process and uses the UASB-secondary AO/MBR process to treat the garbage compressed liquid.The results show that:HRT=12h,the external reflux ratio is 400%,and DO=2～4mg/L,the combined process Volume load is 1.8kg COD/（m³·t）,COD removal rate is about98%,TN removal rate is about 90%,ammonia nitrogen removal rate is about 90%,TP removal rate is about 81%,and there are more inorganic phosphorus in the water,which can be coagulated way to remove.（4）Qualcomm sequencing results showed that the diversity of microorganisms in the reactor was lower than before domestication,but the proportion of bacteria such as Proteobacteria,Chlorocurve,and Actinomycetes increased;the proportion of denitrifying bacteria increased from 4.18%to 17.88%,And some new dominant bacteria appeared in denitrifying bacteria after domestication,namely Planomicrobium and Planococcus,which accounted for 8.71%and 3.24%.In addition,some aerobic denitrifying bacteria（Hyphomyces,Bacillus）and autotrophic denitrifying bacteria（Nitrosomonas and Thiobacillus）have also appeared.This paper verifies the feasibility of the UASB-secondary AO/MBR combined process to treat the compressed waste liquid through experiments,and provides a reference method for the treatment of compressed waste liquid after waste classification.