The Integrated Process Of Biological Material Filtration And Membrane Concentration For Anaerobic Digestion Effluent That Based On Recycle And Reuse

The biogas project as an ecology engineering,it can produce green energy from the waste,but it can also produce a great amount of biogas residue and anaerobic digestion effluent(ADE).The ADE as a kind of waste,its treatment and utilization method is various,but the promotion and application is very few.In order to improve the utilization of waste and reduce the secondary pollution in ADE treatment process.This paper used the ADE(pig)as research object,studied the effect of biological material on ADE filtration by the way of orthogonal test,and then optimized the combination of the pretreatment process of ADE.Secondly,we conducted the esearch and optimization of filter material geometry parameters for the purpose of enhancing the service life and hydraulic load of filter material.Then we verified the membrane filtration concentration effect of ADE after the pretreatment.Finally,we determined the best conditions for filter material composting,and studied the application effect of membrane concentrate and composting products in soilless cultivation substrate and evaluate its biological effect.On the base of the whole study,we build an integrated process of biological material filtration and membrane concentratio for ADE that based on filter material composting.The results indicated that:(1)The highest COD removal rate of the ADE was 87%,the highest removal rate of suspended matter was up to 97%,the coarse corn stalks showed the best treatment efficiency,1 m3 of filter materials can handle 2.78 m3 of ADE.The result of orthogonal analysis showed that the type and size of the filter material had a great impact on the ADE filtration.(2)After the series filtration of coarse corn stalks,fine corn stalks and fine-grained walnut shell,the turbidity of ADE was reduced by 95%,the removal rate of suspended solids reached to 86%,but the COD removal rate was only 41%.The treatment capacity of the coarse corn stalks in the first filter could be increased by 55%.The nutrient in the ADE had various degrees of loss after the three-stage filtration,but the content of potassium increased.As to the heavy metals it also showed a certain removal effect.(3)After the optimization of the geometric parameters of the filter loading,the pretreatment parameters of the ADE was:first filter coarse cornstalk,loading density 0.094g/cm3,secondary filter fine cornstalk,loading density 0.099g/cm3,third filter corn cob(grain diameter 0.9mm),loading density 0.33g/cm3,the diameter and height radio of the filter material was 27:8(diameter 30cm),water flow 5L/h.For high and low pollution concentration of ADE,the average removal rate of COD was 64%,the average removal rate of suspended solids was 89%.(4)After the membrane concentration by the ultrafiltration membrane and nanofiltration membrane,the suspended solids in the ADE was completely removed,the volume enrichment factor was 11,the sum of nitrogen,phosphorus and potassium in the concentrate was 6.36g/L on average,the maximum concentration multiple of all nutrient was 9.07,however,the COD and ammonium nitrogen concentration in the permeate was a little high.(5)The optimization results of the composting conditions for the material composting showed that,each compost treatment could heat up normally,the highest temperature could reach to 64.7?,The longest duration of the high temperature period was 5d.The analysis of compost maturity,gas emissions and microbial changes indicated that,the optimum moisture content was 60%and the suitable C/N ratio was 24 for the filter materials compost.(6)The concentrate and compost products from the ADE treatment process showed a certain advantage in the cucumber plug seedlings,instead 50%of the vermiculite by filter material compost,it could meet the growth needs of cucumber seedlings without fertilization,it could increase the number of leaves,fresh weight above the ground,shoot dry weight and some other indicators of the cucumber seedlings.(7)After the re-combination of biological material filtration and membrane concentration,supposing the processing capacity was 200t/d,the system need 2.5t of cornstraw and 1.4t of corncobs per day approximately,it can produced 18.2 tons of concentrate and 4 tons of compost.The new system can reduce the cost of ADE treatment process by 11%.