| Biogas slurry produced from swine manure by anaerobic fermentation has the characteristics of a large quantity in volume,pollutant and nutrients co-exist in nature.It will take a series of ecosystem problems such as water eutrophication,air pollution if it not gets reasonable disposal methods.Therefore,in view of the current situation of the treatment and utilization of biogas slurry produced from swine manure in China and technical requirements for its high value utilization,in this study,the biogas slurry of swine manure was used as the object,and the magnetic coagulation and ceramic membrane and nanofiltration membrane combined process was used to treat it,in order to provide a new thought for the high value utilization and water reuse of biogas slurry.Optimized the process parameters of magnetic coagualtion treatment of swine manure biogas slurry,and revealed the magnetic coagulation mechanism.This result shown that the favorable process parameter for magnetic coagulation were as follow:the dosage of PAC,PAM,magnetic seed were 5 g·L-1,120 mg·L-1,3 g·L-1 respectively,and the rotation speed was 250 rpm.Under this optimum condition,the residue concentration of turbidity,chemical oxygen demand,total phosphorous,phosphate and ammonia nitrogen were 610 NTU,6050 mg·L-1,26.28 mg·L-1,14.52 mg·L-1 and 2382 mg·L-1,correspondingly,and the removal rate were 83.78%,57.59%,86.59%,74.79%and 31.59%individually,which is benefit to shorten sedimentation time and reduction the subsequent process treatment load effectively.Compared with conventional coagulation,magnetic coagulation increases floc specific gravity,shorten the solid-liquid separation time,and improves sedimentation performance and coagulation effect.Magnetic coagulation and ceramic membrane and nanofiltration membrane combination process can realize the concentration and enrichment of nitrogen and phosphorus and water reuse in swine manure biogas slurry.The combined process of treating swine manure biogas slurry showed that the turbidity,chemical oxygen demand,total phosphorous,phosphate and ammonia nitrogen concentration of the nanofiltration membrane produced water were 0.2 NTU,351±22.59 mg·L-1,0.1±0.02 mg·L-1,0.07±0.01 mg·L-1 and 631±108.53 mg·L-1,and the removal rate were 99.99%,97.53%,99.94%,99.87%,81.85%,correspondingly,so to a certain degree,achieve water reuse in some area.Under the concentrate factor of three,the contents of the concentrate liquid of COD,NH4+-N,TP,PO43--P were 4190 mg·L-1,1794mg·L-1,9.3 mg·L-1 and 5.5 mg·L-1,respectively.Concentration polarization was the main factor to result from the membrane flux attenuation rapidly in the double membrane system operation process.The fouling of tubular ceramic membrane is the mainly caused by organic substances,which is mainly caused by concentration polarization phenomenon;the membrane pollutants are unevenly distributed in the tube,the pollutants are mainly concentrated at the inlet of the tube,and the deposits are mainly Tyrosine-like and tryptophan-like proteins.In-line coagulation of polyaluminum chloride(PAC)can improve the initial membrane flux and inhibition the reduction of membrane flux,which is owing to competition adsorption effect both large-scale floc and pollutant to the membrane,which is benefit to form a loose membrane fouling layer,and avoid to dense gel layer were formed effectively. |
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