Experimental Study On Intermittent Biochemical Treatment Of Domestic Sewage By Underwater Aeration

The characteristics of domestic sewage produced in the small town are listed as follows,low C/N ratio,rapid changes in water quality and water quantit y,scattered distribution.Serious water pollution in most of the vast rural areas and lacking of funds to build the actual situation of sewage stations are the current phenomenon.Based on these features,it is of great practical significance to explore a kind of high efficiency nitrogen and carbon removal,high load,economical and energy saving sewage treatment process.Regarding campus sewage as the object of the study,the self-developed and time-controlled mechanical intermittent reactor(invention patent,application number:201710651869.6)is used.In the initial stage,the basic parameters were determined by the experiments which were run in the fresh water;In the later stage,the experimental parameters were optimized under the condition of 1.5,2.0,2.5kgCOD/(m~3·d)volumetric load with intermittent influent and intermittent aeration.The experiment explores the better test conditions and analyzes the performance of the sludge reduction.The test period lasted for 131 days,and the following conclusions are drawn:(1)According to the clean water test,a better basic operating parameters of the test is determined under the present reactor conditions:water submerged depth 5cm in the top of the air intake cylinder,speed is 700~1000r/min,inlet cylinder diameter is30mm,impeller diameter is 10cm,Impeller underwater submerged depth of 35cm.Which provides the reference for subsequent experiments and practical engineering applications.(2)The author looked for the optimum operating conditions in 1.5,2.0 and2.5kgCOD/(m~3·d).The water could all meet the discharge requirements of 50,5 and15mg/L in the final effluent.Considering the effect of treatment and the load,2.0kgCOD/(m~3·d)is thought to be the best optimum operating condition.The removal rates of COD,ammonia nitrogen and total nitrogen are 87.1%,96.2%and 81.9%respectively.The operating parameters are listed as follows:HRT was 2.8h;sludge reflux ratio was 30%;dissolved oxygen in the two aeration areas was 1.8mg/L,0.7mg/L respectively;the number of daily cycles was 12;the influent time was 30min.The aeration time is 70 min and 60 min in the two areas respectively,the rest is the precipitation time.And the inflow of water is about one-third of the total amount of water.(3)The author performed a comparative test with changing different waterway thickness of the impeller under the optimum conditions of 2.5kgCOD/(m~3·d)load.The experimental conditions are proved and the results show that stirring aeration capacity is the strongest,and the sewage treatment is the best in the thickness of 5mm waterway.The best removal rate of COD,ammonia nitrogen and total nitrogen are86.1%,95.7%and 83.6%respectively.(4)Under the volume load,the sludge reduction rate of the reactor are 75%,79%and 80%respectively.The reduction effect was better than the traditional activated sludge method.(5)Compared with the test running parameters and pollutants removal effect between Zhao Yapeng and the author’s,the characteristics of this reactor are listed as follows:noise reduction,homogenization,mass transfer and efficient oxygen dissolution.The reactor is proved that it owe more other features,such as high efficiency,capacity reduction,energy saving and economy.Besides,the process could depend on the promoting function of flow to drain off water.The reactor showed high automatic performance.This experiment,which puts forward an efficient and stable treatment for the treatment of domestic sewage in small towns,provides an important refere nce value for the practical engineering treatment of domestic sewage.