Preparation Of Starch/Polyvinyl Alcohol Slow Release Carbon Source And Research On Denitrification Application

At present,the secondary effluent of urban sewage plants is mostly low C/N sewage,which limits the denitrification efficiency,and the deep denitrification process requires an additional carbon source.Traditional organic carbon sources,such as ethanol,glucose,acetate,methanol and other liquid carbon sources,often appear excessive or insufficient,leading to the increase of DOC in wastewater or the accumulation of nitrite.To avoid these risks,solid organic carbon sources are considered to be a better alternative to denitrification.In order to improve the denitrification performance and service life of the traditional starch/PVA solid carbon source,a new type of sustained-release carbon source was prepared by using the method of interfacial polymerization and coating the traditional starch/PVA surface with an organic porous thin film as a safety layer?PA layer?.In this paper,the optimum material ratio of sustained-release carbon source,the release law of carbon source and the operation characteristics of denitrification process were investigated,and the microbial community structure in denitrification process system was analyzed by high-throughput sequencing technology.The specific research results are as follows:The microstructure of the carbon source was characterized by SEM,ATR-FTIR and XPS spectra.SEM observation showed that after interfacial polymerization on SP carbon source,the surface of CSP carbon source showed a typical"peak-valley"structure of polyamide layer with relatively smooth surface.The characteristic peaks of polyamides at¹609 cm^-11 and¹498 cm^-1can be attributed to the N-H deformation vibration of aryl amides and the amide II band?N-H planar bending and N-C tensile vibration in the-CO-NH-group?in the ATR-FTIR spectral analysis,indicating that the PA layer was successfully formed on the surface of the SP carbon source.The characteristic peaks of CSP carbon source were analyzed by XPS,which also indicated that PA layer was successfully formed on the surface of carbon source.The results showed that with the increase of starch content in SP carbon source,the concentration of DOC in water also increased.For CSP carbon source,a similar trend of DOC concentration was observed.The denitrification performance of the prepared sustained-release carbon source material was tested and analyzed.The results showed that the DOC concentrations of CSP₁ and CSP₂ were 30 mg/L and 40mg/L,respectively,which was less than half of that of the SP carbon source and consistent with the static carbon release results.CSP₃ is less structurally complete than CSP₁ and CSP₂,which are also relatively easily hydrolyzed by hydrolyzed bacteria.The study of carbon source dynamics of CSP₂ showed that there was a highly linear correlation between nitrate and time,and the correlation coefficient R²=0.97,indicating that the denitrification process was a zero-order reaction.In the continuous denitrification experiments,the reactor for water quantity,water quality of the water has a certain ability to adapt,when HRT is 4 h temperature is 25?,the reactor?water DOC to an average of 20 mg/L.In addition,ammonia nitrogen was detected in both reactors throughout the continuous experiment,indicating a possible nitrate disassimilation and reduction to ammonium?DNRA?process.Proteobacteria?Proteobacteria?and Bacteroidetes?Bacteroidetes?are the main phyla in the microbial community on the surface biofilms of SP₂ and CSP₂ carbon sources,accounting for about 94%?reactor I?and 93%?reactor II?.Firmicutes?reactor I,mean 6.1%;Reactor II,mean6.0%?.At the genus level,a total of 221 genera were detected in both groups of samples,and overall,the microbial community is very different from the denitrification systems of classical and other types of biodegradable polymers?BDP?using liquid carbon sources.This study is novel in the preparation of sustained-release carbon source materials.The new sustained-release carbon source has good denitrification performance and reasonable denitrification cost.At the same time,the internal law of denitrification performance of the new carbon source material was analyzed from the microbiological level.The research results have certain application value and guiding significance for improving the technical level of denitrification of secondary effluent in urban sewage plant.