| With the increase in the living standards of the people,the amount of domestic waste has increased,so that the amount of waste compression leachate produced during garbage transfer and compression increases.The high concentration organic and nitrogen-containing contaminants contained therein have a great threat to the water ecological environment.Based on the above background,this study selected a garbage transfer station pressure filter as a target water sample.Electrocoagulation-ozone flotation was used as both pretreatment and advanced treatment process,and anoxic-aerobic（A/O）MBR system was used as secondary biological treatment process.We constructed a waste compression leachate purification system with the handling capacity of 1.5m3/d,and studied the purification effect of the system on pollutants and draw the following conclusions:（1）The optimal operating conditions of electrocoagulation-ozone flotation pretreatment process are ozone dose of 60 g/h,current intensity of 60 A,influent flow of100L/h;the optimal operating conditions of MBR system are as follows.For A tank,HRT is 4d,and DO is less than 0.5 mg/L.For O tank,HRT is 8d,and nitrification liquid reflux ratio is 200%～250%,and MLSS is less than 20400mg/L,and DO is 3.7 mg/L～5.2 mg/L;The optimal operating conditions for advanced treatment are ozone dose of 20 g/h and current intensity of 20A.Under the optimal operating conditions,90d continuous test results show that the removal efficiency of COD,TN,NH3-N and TP by pretreatment is37%,9%,18%and 35%,and the B/C increases from less than 0.4 to 0.6,indicating that the biodegradability of the waste compression leachate has been improved.AO-MBR combined electrocoagulation-ozone flotation advanced treatment process corresponded to the removal efficiency of 95%,94%,92%,91%respectively.The effluent of the system is stable to meet the A-level requirements of the Water Quality Standard for Wastewater Discharge into Urban Sewer（GB/T 31962-2015）.（2）The change of dissolved organic matter（DOM）in each treatment stage was studied by three-dimensional fluorescence method.It is found that the organic composition of the filtrate is complex,including easily biodegradable tyrosine,tryptophan proteins and non-biodegradable humic acids.After pretreatment,the fluorescence intensity of humic acid decreased and the biodegradable organic compounds such as tryptophan and tyrosine increased,indicating that pretreatment improved the biodegradability of the pressure filtrate.The content of proteins in MBR effluent is weak,indicating that it is absorbed by microorganisms,while there are still humic acids that are difficult to biodegrade;the fluorescence intensity of refractory DOM such as humic acid is obviously weakened after deep treatment,indicating that advanced treatment can effectively remove refractory organics,which is consistent with the change of COD concentration in the degradation process.（3）Using Illumina Miseq sequencing technology,the following conclusions were obtained,with the increase of operation time,the diversity of microorganism species in anoxic pool is increasing and Proteobacteria、Bacteroidetes and Chloroflexi were the dominant bacteria at the phylum level;The diversity of microbial species in aerobic tank increased first and then decreased,the dominant bacteria were Proteobacteria、Chloroflex、Patesicibacteria and Firmicutes at the phylum level.（4）The treatment cost of waste compression leachate by electrocoagulation-ozone flotation-MBR combined system is 137yuan/t,which is only 46%of the local market price,indicating that this process has wide popularization and application value for waste compression leachate purification.The above studies show that the system has process feasibility,operation stability and cost economy for the purification of municipal solid waste filtrate,and it suggests that this treatment system has a wide application and market value.Based on the above research,the system has the process feasibility,operation stability and cost economy for the treatment of waste filter pressing liquid in transfer station,which can provide theoretical support and reference for the treatment of waste compression leachate in engineering scale. |
