Denitrification And Dephosphorization Technology In Fluidized Bed With Struvite Crystallization Method

Phosphorus is a kind of non-renewable irreplacable limited mineral resources.China's irrational exploitation and utilization of phosphorus resources is increasing the crisis of China's phosphorus resources,and its associated water eutrophication problems are also increasingly prominent.In the natural and social cycle of phosphorus,the recovery of nitrogen and phosphorus in high concentration wastewater is the responsibility of water pollution control.On the one hand,it can effectively control the large amount of phosphorus into the natural water body,which may cause eutrophication.On the other hand,may utilize phosphorus resources to ease the crisis.Struvite(Magnesium phosphate precipitation method,abbreviated as MAP method)as a environmentally friendly new technology in the field of water treatment at home and abroad,has been widely used in the past 20 years,is getting maturing,in response to the world's phosphorus resource shortage and water nitrogen and phosphorus pollution background.However,the domestic research on the struvite method is mainly staying in the laboratory scale,and reactors for pilot and productive tests are rarely used,while the struvite reactor is the only way to industrialize struvite technology,a lot of research have been studied in foreign countries,efficient reactors used in production are also developed.Aiming at the problem of hysteresis reactor research in China,the results of task group are inherited,use Alkaline Magnesium Carbonate as the best Magnesium source,P recovery as the main target,continue to explore the the optimum reaction conditions for the removal of nitrogen and phosphorus with struvite,optimize the test scheme and strengthen the nitrogen and phosphorus recovery efficiency of the fluidized bed reactor to give the operating parameters for the pilot test of the fluidized bed.The main contents and main conclusions are as follows:(1)The results of orthogonal test showed that the reaction conditions were: pH = 8,Mg: N: P = 1.6: 1.25: 1,N initial concentration 200 mg / L,The results of the BBD-RSM combination test showed that the pH value was 8.16,Mg: N: P = 1.71: 1.2: 1,the model was in good agreement with the orthogonal design,the difference between the model predictive value and the actual verification value is only 0.92%;(2)Control the pH = 8,stirring time 90 min,stirring speed 120 r / min,n(Mg): n(N)= 1.3,the effect of the organic matter in the digestion solution(N = 73.03 mg / L,P = 136.06 mg / L)on the recovery of nitrogen and phosphorus is as follows: When N(N): n(P)is high,the inhibitory effect is lower,and there is no obvious effect on the lower ones.The organic matter can be effectively removed during the crystallization reaction.(3)The integrated fluidized bed reactor is used to induce nucleation on enhanced nitrogen and phosphorus removal test,do not adjust the pH,HRT = 10 min,screening out 1 ~ 2mm ceramsite as the best induced nuclei,with cheap,efficient,high efficiency,P,N recovery rates were as high as 97.5%,80%,corresponding to an increase of 3%,10%,effective dosage of 0.77 g / L water,the market price is 0.8 ? / kg;(4)The results of scanning electron microscopy(SEM)show that the fluidized bed produces a large amount of struvite crystals and some by-products during operation,and verifies that the production of struvite in the upper and middle areas is higher than that of the bottom,but the particle size is smaller after the crystallization of struvite crystals can form larger particles.