Research Of Domestic Sewage By A/O Biological Contact Oxidation Of Heat-treated Corn Cob Filler

The A/O biological contact oxidation process is a technology ideal for the treatment of rural domestic wastewater and has the benefits of simple operation and maintenance,a modest environmental impact,and significant adaptability.However,the issue of high consumption costs for the typically utilized biological filler in conventional biological contact oxidation still exists in rural regions,which drives up the process’s operating costs there.In order to achieve high efficiency and low consumption,save money,make management simple,and remove nitrogen and phosphorus,agricultural waste corn cob was used as the raw material in this study,and heat-treated corn cobs（HCC）were used as fillers to begin the operation of an integrated A/O biological contact oxidation reactor.The effects of various modification techniques on the physical characteristics,water immersion stability,and surface roughness of corn cobs were compared and analyzed.The comparison of the degree of charring,physical characteristics,and water immersion stability of corn cobs under various heating times and heating temperatures led to the optimization of the optimal thermal modification conditions.The HCC fillers were mounted to PVC filler supports and used as biological fillers in the aerobic tank of the integrated A/O biological contact oxidation reactor and the fillers were created under ideal modification circumstances.The campus wastewater of Lanzhou Jiaotong University was used to start the reactor with a continuous flow in order to simulate domestic wastewater from a rural area.Changes in the reactor’s ability to remove COD and NH₄⁺-N as well as its internal microbial phase were then examined,and the reactor’s membrane stabilization time had been determined.The ideal operating parameters of the reactor were optimized by examining the effects of various factors on pollutant removal efficiency at various influent flows,reflux ratios,aeration rates,and sludge ages after membrane stabilization.The reactor was affected by the epidemic and it went without inflow for 44days.After the starvation stage,the effects of pollutants removal in the reactor,changes in sludge characteristics,and the quantity of denitrogenated functional bacteria were all examined.High-throughput sequencing was used to compare and assess the microbial community structures in various areas of the aerobic zone and anoxic zone during the starving period and the stable period.By evaluating the pressure-bearing ability of the HCC packing and evaluating the apparent properties,the service life of the HCC packing in the reactor was explored.The following are the tests’principal findings:（1）HCC filler,manufactured at a temperature of 260～5°C for 50minutes,is excellent as a biological filler due to its rough surface structure,strong water immersion stability,pressure bearing capability of around 0.92～0.95Mpa,and porosity of about 52.03%.（2）On the 25th day of the membrane stabilization,a thick biofilm formed on the surface of the HCC filler.Upon microscopic inspection,the biofilm’s microbial population was discovered to be abundant and structurally sound.When the HCC filler surface was covered in a thick brown biofilm after 35days of operation and the rates of COD and NH₄⁺-N removal both exceeded 60%,the process was deemed to be finished.（3）The best operating parameters for the reactor are Q=200L/d,R=1,q=0.2m³/h,SRT=15d,under these conditions,the average removal rates of COD,TN,NH₄⁺-N,and TP can reach 90.1%,72.76%,89.57%,and 55.50%,respectively,and the average effluent concentration is 27.91mg/L,15.03mg/L,5.13mg/L,and 2.69.All of these indexes meet the secondary discharge standard in"Gansu Rural Domestic Wastewater Treatment Facility Water Pollutant Discharge Standard"（DB62/T 4014-2019）so the effuluent can be directly discharged into Class IV and V functional waters as stipulated in GB3838 or used for irrigation of woodland and grassland.Chemical phosphorus removal is only required to maximize the reactor’s phosphorus removal effect if it’s necessary to achieve the primary discharge criteria.（4）Suspended sludge MLSS dropped from 1829～1989mg/L in the steady stage to1402mg/L after starvation stage,but SVI increased from 41～57mg/g to 138mg/g.SVI increased from 37～51 m L/g to 155 m L/g at maximum,whereas suspended sludge MLSS in the aerobic tank reduced from 2620～2793mg/L at stable stage to 1985mg/L at minimum.The elimination effect of several contaminants had a good recovery after 25days.According to the results of the MPN method and high-throughput sequencing,the starvation stage in the reactor had an impact on the majority of heterotrophic bacteria as well as some nitrogen-removing functional bacteria.It also encouraged the relative abundance of"pyrogens decomposers"in the microbial community structure in each area of the reactor.（5）The pressure-bearing capacity of unmounted HCC packing is approximately 0.995MPa,while the pressure-bearing capacity of HCC packing after one year of use is only approximately 0.030MPa,which is approximately 97%lower than the pressure-bearing capacity in the stabilization period.However,the surface can still be attached with abundant microorganisms,and if no external force is applied,the HCC packing on the packing frame will essentially not fall off naturally and will not affect the normal However,it is thought fair to replace the HCC packing once every 12months in order to guarantee the reactor is using it effectively.The experimental study demonstrates that the use of HCC filler as a biological filler in the A/O biological contact oxidation reactor can guarantee that the reactor achieves a better removal effect of organic matter,nitrogen,phosphorus,and other pollutants under the best operating conditions,so that the effluent quality meets the secondary discharge standard in the"Gansu Rural Domestic Wastewater Treatment Facility Water Pollutant Discharge Standard"（DB62/T 4014-2019）,and can also ensure that the efflu It may be used to irrigate grassland and woods,or it may be released into Class IV and Class V functioning waters in accordance with GB3838.The goal of"treating waste with waste"in rural areas has been achieved by using corn cobs to treat domestic wastewater with high efficiency and low consumption.This method has also provided operational experience and technical support for the A/O biological contact oxidation process to treat rural domestic wastewater.