Experimental Study On The Treatment Of Simulated Rural Domestic Sewage By The Compound Cascade Circulating Water Drop Aeration Baffle Reactor

Rural domestic sewage treatment is a prominent shortcoming of the current rural human settlement environment improvement.The key to solving this problem lies in how to choose a treatment process that meets the actual rural economic and social development.Therefore,it is imperative to study sewage treatment processes that are adapted to local conditions,high efficiency,low consumption,long-term operation,and simple operation.Based on the change characteristics of rural domestic sewage and from the perspective of energy saving and consumption reduction,this study proposes a composite stepped cyclic water drop aeration and baffle reactor.Its main feature is:sewage is circulated in a biological pond with fillers arranged like a step With baffled flow,the device will have water drop aeration and oxygenation due to the existence of the height difference,and the treated effluent will be discharged from the combined sedimentation tank.Through in-depth research on the oxygenation performance and treatment effect of the reactor,the results show that:（1）The drop height,drop flow rate and water distribution method can affect the oxygenation effect of the reactor from different angles.When the falling water flow rate and water distribution method are constant,changing the falling water height only changes the position of the water surface of the lower-level plunge pool intercepting the water curtain of the upper-level plunge pool.As the height of the water drop increases from 20cm to 50cm,the K_La first increases sharply and then slightly decreases or remains unchanged.At this time,the area of the water curtain and the width of the bottom edge of the water curtain control the oxygenation effect of the water drop;when the height of the water drop When the water distribution method is constant,as the water drop flow rate increases from 0.6m³/h to 2.0m³/h,K_La first increases and then decreases.At this time,the water curtain area and the water curtain thickness control the effect of water drop and oxygenation;When the drop height and the drop flow rate are constant,the water distribution method affects the contact form between the water curtain and the air.Regardless of the size of the falling water flow,the effluent of the flat weir always shrinks to the center to form a continuous arc surface water curtain;the effluent of the triangular weir is divided into linear shapes when the falling water flow is small;the water effluent of the trapezoidal weir is when the falling water flow is small It is divided into two layers.Among the three water distribution methods,the water curtain of the flat weir changes uniformly and steadily,and the water flow energy is concentrated,which has a certain impact force and is beneficial to the mixing of sewage in the reactor.Therefore,the flat weir is selected as the outlet weir of the drop pool.Through analysis,the relevant parameters of the cascade circulating water drop aeration reactor are preliminarily determined,that is,the drop height H=40cm,1.0m³/h≤water drop flow Q≤1.6m³/h.In this case,the oxygenation capacity of the reactor is 0.0166～0.0261kg O₂/（h·m）.（2）At the beginning of the reactor trial operation,the DO and ORP in the system were measured to be about 5.3mg/L and 185mv respectively.Because the system is in an oxidizing environment,the effective removal of nitrogen and phosphorus cannot be achieved.The average removal rate of COD,NH4+-N,TN and TP by the reactor is86%,53.23%,20.65%,18.21%.At the same time,during the operation,it was also found that the mixing of each plunge pool was uneven,and there was a phenomenon of sludge siltation at the bottom corner,which indirectly reduced the effective volume of the reactor and made the removal efficiency of pollutants inefficient.（3）In order to solve the above-mentioned two major system problems,the research has adopted two major measures to transform the original reactor.One is to fix a35×15cm plexiglass baffle under the water surface of theⅠ,Ⅱ,Ⅲ,andⅣdrop pools for guiding.Flow,transform the four drop tanks of the reactor into a baffled form,and the second is to add suspended fillers in the system.The research after the improvement of the reactor shows that the folded flow eliminates the dead zone in the plunge pool,and the activated sludge forms a dynamic suspension layer in the second,third,and fourth grids of the plunge pool,which increases the sludge concentration in the area on the one hand.,The pollutants are trapped in the suspended sludge layer;on the other hand,the sludge concentration in the suspended sludge layer is higher,and the oxygen consumption rate is higher,which can effectively reduce the DO concentration.The MLSS and DO of the sludge suspension layer are measured respectively.It is 3300～3800mg/L and 1.1～3.6mg/L.After adding the filler and filming,the biomass of the system is greatly increased,which can accelerate the consumption of DO and significantly reduce the DO and ORP in the reactor.The optimal filler dosing method for the reactor is fromⅠtoⅣ.The proportions of filler dosing in the plunge pool are:20%,10%,20%,and 10%.Under this condition,adjust the circulating flow rate to 1.0m3/h,and measure the distribution of DO as:0.12～2.26mg/L,0.22～2.55mg/L,0～3.13mg/L,0.08～3.32mg/L,0.1～2.63mg/L,the average concentration of COD,NH₄⁺-N,TN,TP in the reactor effluent is 35.2mg/L,2.95mg/L,13.94mg/L and 0.95mg/L.The above results indicate that the reactor has successfully constructed a system with alternating aerobic,anoxic and anaerobic environments through the integration of circulating water aeration,baffled flow and biofilm technology,so that organic matter,nitrogen and phosphorus can be stable and efficient.Remove.（4）Through the orthogonal experiment of key influencing factors,the operating condition parameter range of the reactor during stable operation is optimized,namely F/M is about 0.15,HRT is 12h,SRT is 25d,and the effluent COD,NH₄⁺-N,TN,TP The average removal rates are 92.12%,98.06%,66.07%,85.58%,and all four indicators can meet the Class 1 A standard of the Pollutant Discharge Standards for Urban Wastewater Treatment Plants.The impact load experiment for 3 consecutive days shows that the composite cascade circulating water drop aeration and baffle reactor has high impact resistance and is suitable for the treatment of rural domestic sewage.