Application Research Of River Water Purification By Gravel Contact Oxidation Process

In this subject,a vertical flow multi-stage series-connected gravel contact oxidation reactor was designed,and the reactor pilot plant was built.The operation process of the reactor to strengthen the denitrification of micro-polluted water was studied,and the ecological dynamic model of system denitrification was established.The main findings are as follows:(1)The experimental design of the gravel contact oxidation reactor,the length,width,and height of the device are 12.0 ×2.0×1.5(m)respectively.There are 5 water distribution zones and 4 contact oxidation zones,Connect the water distribution area to the contact oxidation area and then to the water distribution area,and classify and number them sequentially.the design gravel packing height is 1 m,in which the gravel size of contact oxidation zone 1 and 4 is 40-50 mm,and the gravel size of contact oxidation zone 2 and 3 is 30-40 mm.During the reactor start-up,with the extension of the film hanging time,the removal rate of pollutants in the water gradually increased.The removal rates of ammonia nitrogen and COD in the late stage of film formation were about 85% and 60%,respectively.The mycelium of the nematode,with many creeping and attached protozoa and a small amount of micrometazoa,indicates that the biofilm structure has reached a stable state.(2)The effects of different operating parameters on the efficiency of the reactor are studied: Compare HRT at 7 h,5 h,4 h and 3 h respectively;The aeration conditions are I(only aeration in the oxidation zone 1),II(aeration in the oxidation zone 2 only),and III(aeration in the oxidation zone 1 and 2 at the same time);The water distribution methods are Ⅰ(water distribution zone 1,2 water intake,water intake ratio 7: 3),II(water distribution zone 1,2 water intake,water intake ratio 6: 4),Ⅲ(water distribution zone 1,3 water intake,water intake Water ratio 7:3),Ⅳ(water distribution zone 1,3 units,water inlet ratio 6:4),Under these conditions,the removal efficiency of the reactor effluent pollutants and the nitrogen distribution and removal effect along the way are comprehensively analyzed,and the best operating conditions in the stable operation stage are obtained as follows: HRT is 5 h,contact oxidation zone1 aeration,Water distribution zone 1 and 3 are fed with water at a ratio of6:4.Under this working condition,the removal rates of COD,ammonia nitrogen,TP,turbidity,TN,and nitrate nitrogen were 43.6%,80.5%,37.6%,49.2%,59.2%,and 42.8% of the effluent quality.(3)Operate stably under the better operating conditions obtained from the test,analyze the microbial distribution in the system under this condition,the high-throughput sequencing results of the flora showed that the diversity of bacteria in the biofilm at the front of the system and the enrichment of dominant bacteria were better than those in the biofilm at the back.The front end of the device mainly distributes Nitrospirales,Methylophilales,Rhodocyclales,Sphingobacteriales,etc.These bacteria are mainly aerobic heterotrophic bacteria,which can be used in raw water.Organic matter synthesizes its own substances and has the functions of nitrification and phosphorus removal;while the denitrification and phosphorus removal functions of Gemmobacter,Rhodobacter,Thiobacillusand,are behind the device The abundance of the end is high,and the reasonable distribution of various functional bacteria in the system realizes the high-efficiency degradation of organic matter in the raw water and the removal of nitrogen and phosphorus.(4)A conceptual model of nitrogen removal in the contact oxidation system between gravels was established and modeled with Vensim software.The model efficiency coefficients R of organic nitrogen,ammonia nitrogen,and nitrate nitrogen in the simulation system are verified.The winter coefficients are 51.5%,61.9%,and 66.3%,respectively;the summer coefficients are 56.3%,64.9%,and 70.1%,respectively.It can be seen that the overall efficiency coefficient of the model is not high,and the simulation effect in summer is better than that in winter.Since the low influent concentration will amplify the simulation error,and the external environment is time-varying,the established model is difficult to fit completely.In summary,the ecological dynamics model of the contact oxidation system between gravels established this time is more reasonable.The reactor adopts the water inlet method at both ends.By changing the direction of water inlet and outlet,the service life of the device can be prolonged and the number of backwashing can be reduced.In addition,the designed multi-stage series process,in addition to the quadruple device built in this experiment,can also adjust the number of reactors in series according to the water volume and pollution degree of the raw water to be treated,so as to broaden the scope of application and has a very broad application prospect.