Exprement On The Treatment Of Domestic Sewage By Coagulation/Photovoltaic Power Biochemical Device

With the improvement of the living standard of rural residents in China,the discharge of domestic sewage in rural areas has increased rapidly,but the treatment of domestic sewage in rural areas is still at a low level,and a large amount of sewage drained off without effective treatment,leading to the worsening of the environment in rural areas.Aiming at the low efficiency and high operating cost of rural domestic sewage treatment,this paper establishes a domestic sewage treatment unit with coagulation/biological contact oxidation combined process as the main body,and uses photovoltaic power generation system to provide power for the unit,in order to provide technical support for rural domestic sewage treatment.In this paper,the removal effect of organic matter,nitrogen and phosphorus,suspended matter and the change rule of denitrifying bacteria and the number of nitrifying bacteria in the unit were investigated under different operating conditions,so as to determine the optimal operating condition of the unit and establish the mathematical model of the combined process to degrade pollutants.By analyzing the power consumption of the device and combining relevant research data,the relationship between sewage treatment amount and photovoltaic power generation system capacity(battery capacity,photovoltaic cell array area)is established.The photovoltaic power generation system is configured for the device and the power supply performance of the system is tested.The technical characteristics,economic and environmental benefits of the unit are analyzed in combination with the operation of the unit and the photovoltaic power generation system.The main conclusions of the experiment are as follows:(1)After 36 days of operation,COD removal rate and NH4'-N removal rate are stable to above 80%and above 60%respectively.Microscopic examination of the surface biofilm of packing materials shows that microorganisms such as amoeba,rotifer and nematode are observed,indicating that membrane hanging is basically completed.By examining the effect of different operating conditions on removal of organic matter,nitrogen and phosphorus,suspended matter,denitrifying bacteria and the number of nitrifying bacteria,the optimal operating conditions of the unit are obtained as follows:The mass ratio of compound coagulant HCA:PAC is 1:10,the dosage is 20 mg/L,the internal circulation ratio is 200%,the HRT of biological contact oxidation pool is 14.13 h,and the gas-water ratio is 15:1.At this time,the removal rates of COD,NH4+-N,TN,TP and SS are 89.78%,92.08%,58.53%,73.58%and 97.42%,respectively.The effluent concentration of other indexes all reached the first-level standard of The Discharge Standard of Water Pollutants for Rural Domestic Sewage Treatment Facilities(DB62/T 4014-2019)of Gansu Province.Combined with the actual test situation,a mathematical model for degradation of pollutants in the combined process is established,which can be used to predict the concentration of organic matter and total nitrogen in effluent.(2)Taking the test unit as an example,the power consumption of the unit is analyzed.Combined with relevant research data,a mathematical expression describing the relationship between the sewage treatment amount and the module capacity of the photovoltaic power generation system is established.The relationship between sewage treatment capacity Q and battery capacity C is:(?)The relationship between sewage treatment amount Q and photovoltaic cell array area S is:(?)Based on the basic parameters of batteries and photovoltaic panels and combined with the actual operation of the test device,the battery capacity C and photovoltaic array area S of the photovoltaic power generation system are designed.The designed battery bank is composed of four 12 V/100 A·h battery cells.The photovoltaic cell array consists of six photovoltaic panels with a single area of 0.9842 m2 and a single rated power of 130 W.The results of power supply performance investigation of photovoltaic power generation system show that:when the battery is discharged purely,the voltage decreases in a step-type,and the ambient temperature has a great influence on its discharge performance.Therefore,the battery should be maintained in a heat preservation manner when it is used in a low-temperature environment in winter.The photovoltaic power generation system provided sufficient power for the installation during the five-day operation period in March.The experimental results show that the photovoltaic power generation system is adopted to provide power for sewage treatment process,and the coagulation/biological contact oxidation combined process sewage treatment unit established has the advantages of stable effluent quality,small floor space,compact structure,convenient operation and maintenance,etc.Under the optimal operating conditions,the device has a good reduction effect on organic matter,nitrogen,phosphorus and suspended matter.Photovoltaic power generation system is used to provide power for the device,realizing the purpose of low cost operation of the device and providing technical support for rural domestic sewage treatment.