Study On Atificial Strengthening Water-dropping Aeration Contact Oxidation Dealing With The Water Quality Of Inland Rivers

With the rapid development of economy and significantly increased urbanization, water environment pollution and water shortage are increasingly severe, especially the inland rivers pollution.The formation of inland river pollution lies in two aspects.One is the metastasis of upstream pollutants,another is the not thorough of rainfall-sewage separation.The pollution not only does harm to downstream water,but also affects the city appearance even normal residents.Therefore,how to improve the water quality of inland rivers has raised a universal attention among experts and scholars and plays a key role in the improvement of life quality of urban inhabitation.Baoding Fu River is located at the upstream of Baiyangdian. The water quality of Fu River has a direct affect on Baiyangdian. Detections showed that,the water pollution mainly embodies at blacking and stink, eutrophication,low dissolved oxygen and the contents of COD,NH4+-N or turbidity are far exceed the fifth-class water quality standard.But there is sill some self-purification capacity,which meets the demand of inland rivers.This paper takes Fu Rive as the research object,put forward and confirms a process called artificial strengthening water-dropping contact oxidation to improve the inland rivers quality .During the experiment,the emphasis was put on whether the artificial strengthening water-dorpping contact oxidation can meet the demand of contact oxidation.Meanwhile,the remove rates of COD,NH4+-N and turbidity under low temperature were also investigated.The experiment contains two parts,one is water-dropping reaeration experiment ,which investigated the influence of water-dropping height,temperature, water-dropping region depth and water-dropping flow .Meanwhile,we also have a sorting for them.Another is artificial strengthening water-dropping aeration contact oxidation dealing with inland rivers experiment,which investigated the starting effect of system.The emphasis was put on hydraulic retention time, temperature and dissolved oxygen.Water-dropping reaeration experiment shows,the effect of water-dropping aeration will be affected by height,flow,temperature and depth.The sorting is, from big to small, water-dropping height,flow,depth and temperature.Through the experiment,we can preliminary make sure that the economic water-dropping height is 0.6 meter;the best water-dropping flow is 1.0 m3/h,but the final flow still depends on the residence time of the system;the most suitable temperature is between 15℃and 18℃,but temperature has little effect on water-dropping aeration ,which we can neglect;the more shallow the water-dropping region is,the better effect of the water-dropping aeration.According to the characteristics of Fu River channel,we know that,the water depth is less than 20 centimeter mostly,only a small part is at about 50 centimeter.Thus,the experiment will take the 50 centimeter depth as the most adverse condition.When the dissolved oxygen can not meet the demand,we have to do the supplement by artificial oxygenation.The system adopts two-segment biofilm culturing starting under no artificial condition and low temperature.The start-up period is about 35 days.After the success of start-up,the remove rates of COD,NH4+-N and turbidity can respectively reach to 72%,5%,81%.At the first stage of biofilm culturing,though high DO value,but for low oxygen utilization coefficient and DO mass transfer efficiency or biofilm,the phenomenons of biofilm aging exfoliated and effluent turbidity did not happen.The activity of microorganism is low when temperature is cold.So, two-segment biofilm culturing starting adopts long residence time,24h for the first stage,4h for stuffiness solarization and12h for the second stage,which supply plenty time for growth and reproduction of the microorganism. Two-segment biofilm culturing starting has the advantages of no additional carbon source,no reflux,easy operation process and enegy-saving,which can achieve the success in a relatively short time.When adopting atificial strengthening water-dropping aeration contact oxidation dealing with the water quality of inland rivers,low water temperature has little effect on the remove rates of COD and turbidity but much on NH4+-N.When the temperature is under 5℃, ammonifying bacteria and nitrifying bacteria will stop their life activity ,but the removal of NH4+-N still exists with a not obvious effect.Meanwhile, relatively large fluctuation of influent quality will lead to a instability of organic loading and the scour of aeration bubble will make the biofilm exfoliated.All these factors above will bring adverse effect to the growth of initial microorganism.After stable operation and 4℃~15℃water temperature ,the removal rates of COD,NH4+-N and turbidity respectively are 66%~82%,4%~37%,81%~92%.Some detection datas showed that,when the water temperature is under 5℃,the remove rate of COD is blow 20% while none for NH4+-N and 70% for turbidity.When the water temperature ranges from 16℃to 25℃,the remove rates are 80%~87%,48%~68%,93%~96% respectively.When 26℃~32℃,the rates are 84%~87%,67%~70%,93%~96%.The system has a better effect in spring,summer and early autumn compared with early spring,late fall and winter.The system will be affected by water quality fluctuation,water temperature change and unstable DO value and the remove rates of COD,NH4+-N and turbidity also have a big fluctuation.Through the experiment,the paper got the best conditions of the system:2h for HRT, 26℃~32℃for water temperature, 2~3mg/L DO value for the first-order contact oxidation and less than 0.5mg/L DO value for the second-order contact oxidation.The result shows, artificial strengthening water-dropping aeration contact oxidation dealing with the water quality of inland rivers has the advantages of feasible process route, reliable econemy, stable operation and better effect.In spring,summer and autumn,the effect can meet the demand of inflow water quality in Baiyangdian ,especially for the sensitive NH4+-N.