| Due to the low ratio of the chemical oxygen demand（COD）to total nitrogen（TN）and poor biodegradability of digested piggery wastewater,the lack of a carbon source in subsequent biological treatment limits denitrification,resulting in the low denitrification efficiency.At the same time,the anaerobic digestion solution contains a large amount of nitrogen and phosphorus,which are nutrient elements.If nitrogen and phosphorus can be recovered,it will be a good pretreatment method for piggery wastewater for resource reuse,reduction of influent ammonia nitrogen in biological treatment,and improvement of COD/TN.At the same time,after the biological treatment of piggery wastewater has always had problems such as too high colority and high content of refractory organics matter.In this paper,the specific test contents of the systematic and integral treatment of piggery wastewater are as follows:In the first part,uses an ultrasonic pretreatment step to release phosphorus from the biogas slurry（including biogas residue）as a new phosphorus source of magnesium ammonium phosphate（MAP）and magnesium oxide desulfurization waste residue（MDWR）as a low-cost magnesium source of MAP.CO2 is removed by aeration stripping to increase the p H value of the system.To discuss the effect of sound energy density and ultrasonic time on the phosphorus release from piggery biogas slurry,and the effect of MDWR addition,initial p H value and aeration time on the recovery of nitrogen and phosphorus,and finally the structural characterization and composition of the recovered product were analyzed.In the second part,ultrasonication/alkali combined treatment of pig manure is used as the denitrification carbon source in the sewage treatment process.It mainly discussed the optimum preparation process of PMC,the effects of adding PMC on subsequent biological denitrification,and the effect of adding pig manure carbon source on microbial population change through high-throughput analysis.In the third part,the effluent after biological treatment is subjected to catalytic oxidation decolorization through ozone and pigsite biogas residue carbide.It mainly discussed the catalysts（biogas slurry carbides）,the addition of catalysts,the initial p H of the reaction and the reaction time of ozone to the chromaticity of the secondary biological treatment effluent and the degradation of organic compounds were discussed.And three-dimensional fluorescence spectroscopy and GC-MS technique were used to study the changes of organic composition in the effluent before and after catalytic ozonation.After the results of the three experiments and the analysis and discussion of the results,the following conclusions can be drawn:（1）In the study of ultrasonication,aeration/addition of Mg O desulfurization waste residue to pretreat piggery biogas slurry to recover nitrogen and phosphorus,the optimal process parameters of MAP were the MDWR addition amount of 0.8 g·L-1,p H=9.5,and aeration time of 2 h.Under the optimal parameters,the recovery percentage of PO43--P can reach 98.90%,the removal percentage of NH3-N can reach 66.84%,the content of NH3-N was reduced to 268.22 mg·L-1,and the recovery effect of nitrogen and phosphorus is obvious.The MAP recovery products were analyzed by scanning electron microscopy-energy dispersive spectroscopy（SEM-EDX）and X-ray diffraction（XRD）,which indicated that the recovered products were mainly magnesium ammonium phosphate.（2）In the study of the effects of pig manure as a traditional treatment of internal carbon sources on biological nitrogen removal,in the subsequent biological treatment with the addition of 1.78%PMC,the denitrification percentage reached 124.16%,which was87.07%higher than that without an added carbon source.The TN removal percentage was72.29%,which was 62.29%higher than that without an added carbon source and 36.74%higher than that with the added raw wastewater carbon（RWC）source.High-throughput sequencing revealed that the dominant microflora Thauera and Thermomonas,related to denitrification,increased from 1.13%and 0.55%to 6.19%and 4.69%,respectively,after the addition of PMC.The addition of PMC could significantly improve the denitrification of digested piggery wastewater in subsequent biological treatment,and the denitrification effect was obvious.（3）In the study of catalytic ozone oxidation biological effluent decolorization and refractory organic removal,when the catalyst was Mn O2/BRAC,the ozone dosage was22.50 mg·L-1,the catalyst dosage was 1.0 g·L-1,p H=9.0,and the ozone reaction time was20 min.The decoloration percentage of the filtrate after the reaction was 91.29%,the UV254removal percentage was 81.64%,the COD removal percentage was 61.07%.It is indicated that the Mn O2/BRAC catalytic ozone oxidation secondary biological treatment effluent colority and organic matter removal effect is particularly significant.The changes of organic compounds before and after treatment were analyzed by three-dimensional fluorescence spectra and GC-MS analysis.The macromolecular organic compounds before treatment mainly contained humic acids,and the volatile refractory organic compounds were mainly phenols,esters,alcohols and hydrocarbon organic compounds.After treatment,the removal effect of humic acid and volatile refractory organic compounds were particularly obvious.After the combined process of nitrogen and phosphorus recovery pretreatment,biological nitrogen removal and catalytic ozone deep treatment on the digested piggery wastewater,the COD,NH3-N,TP and TN of effluent all of which meet the emission standards of the“Fouling Standards for Pollutants in the Livestock Breeding Industry”（Second Consultation Draft）(150 mg·L-1 COD,40 mg·L-1 NH3-N,5 mg·L-1 TP,TN 70mg·L-1).At the same time,the study also clarified the main substances causing chroma and the components of volatile refractory organics in the piggery biological treatment effluent.The piggery wastewater can be disinfected and reused after deep treatment,which reduces the cost.This study provided scientific basis and guidance for the comprehensive treatment of piggery wastewater,which is beneficial to promote the development of livestock wastewater treatment technology. |
PDF Full Text Request