The Variation Of Dissolved Organic Matter Characteristics In Secondary Effluent Of Fermentation Pharmaceutical Wastewater During Advanced Treatment

Fermentation pharmaceutical wastewater belongs to one of the refractory industrial wastewaters.After physical and chemical pretreatment and biological treatment facilities,the secondary effluent of fermentation pharmaceutical wastewater still has high content of dissolved soluble organic matter（DOM）.Owing to the extensive molecular heterogeneity and polydispersity,the DOM in secondary effluent of pharmaceutical wastewater is the key limiting factor of wastewater advanced treatment and reuse.In this study,the secondary effluents from five kinds of fermentation pharmaceutical wastewater including amino acids,cephalosporin antibiotics,mixed antibiotics,vitamins and abamectin were collected,and the characteristics of DOM in effluents were analyzed.Furthermore,coagulation and ozone oxidation coupled with reverse osmosis membrane separation were used to advanced treat DOM in secondary effluent of antibiotic wastewater,the removal efficiency and characteristics of DOM such as the content,molecular weight distribution,hydrophobicity,fluorescent characteristic and molecular composition were analyzed.The research contributes to the optimization of advanced treatment for fermentation pharmaceutical wastewater.The main results are as follows:（1）The characteristics of DOM in secondary effluent from five fermented pharmaceutical wastewaters.High salinity,color and organic matter concentration were observed in the wastewater,the content of chemical oxygen demand（CODcr）and total organic carbon（TOC）were 156.9～736.3 mg·L^-1 and 48.6～232.2 mg·L^-1,and humic acids and protein were the mainly organic matters.The DOM in secondary effluent was mainly composed of hydrophobic components.The molecular weight（MW）of DOM was widely distributed in the range of 210～17000 Da.By FTIR analysis,it was found that DOM contains benzene rings structure,aromatic hydrocarbon compounds and functional groups such as-OH and-COOH.Three humic-like substance（C1,C3 and C4）and one protein-like substance（C2）were found by EEM-PARAFAC analysis.By FT-ICR-MS analysis,DOM in effluent of mixed antibiotics wastewater mainly composed of CHON compounds,such as lignin and unsaturated carbonaceous organic materials,which were difficult to remove.（2）The removal efficiency and characteristics of DOM in secondary effluent of antibiotic pharmaceutical wastewater during PAC coagulation.The operating variables,including initial p H,dosage of PAC was optimized for pretreatment DOM in effluent by coagulation process.The results showed that,under the optimum condition(250 mg·L^-1 PAC,p H=7～8,30 minutes),the highest removal of DOC,UV₂₅₄,color were 13.05%,23.65%,12.66%,63.6%,respectively.Coagulation could remove 50.33%of macromolecules organic matter（MW>10 k Da）and 21.56%of hydrophobic neutral component,the removal of components with MW<1k Da was2.26%.Three humic-like（C1,C3,C4）and one protein-like（C2）components of DOM in secondary effluent were determined by EEM-PARAFAC analysis,the highest removal of humic acid fraction（C1）by coagulation was 46.22%.Coagulation might have preferentially reacted with the humic-like hydrophobic fraction rather than protein-like fraction.The results of FT-ICR-MS analysis showed that coagulation had a poor ability to remove lignin compounds.As a deep treatment process,coagulation can partly remove hydrophobic and macromolecules component and have poor ability to remove chromaticity,so it cannot meet the requirements of standard discharge.（3）The removal efficiency and characteristics of DOM in secondary effluent of pharmaceutical wastewater during ozone oxidation.The optimal dosage of ozone was22.90 mg·L^-1·min^-1,the removal of chroma,humic acid and protein were 85%,57.8%and 26.8%,respectively.The removal of DOC was low,it was found that ozone can only partially mineralize organic matter,and react with benzene ring and aromatic hydrocarbon structure organics of DOM.At a low ozone dosage of 11.03mg·L^-1·min^-1,the oxidation of hydrophobic components with ozone reaction decreased as HOA>HON>HOB,and the HOA component firstly reacted with ozone and was transformed to HIS by oxidation.The 3-component fluorescence model was observed by EEM-PARAFAC analysis,the maximum fluorescence intensity(F_max)removal rate of all 3 components（C1～C3）was more than 60%.By FT-ICR-MS analysis,ozone had a strong oxidation capacity for lignin,aromatic hydrocarbons and unsaturated hydrocarbons.As a deep treatment process,ozone oxidation had a good decolorization effect,which can significantly change the chemical structure and molecular composition of DOM.However,it had a low mineralization rate of organic matter,which cannot meet the requirements of standard discharge.（4）DOM removal in secondary effluent from antibiotic wastewater treated by different pretreatment combined RO process.Antibiotic wastewater effluent was filtered by RO membrane,the permeate flux increased with the increase of pressure.After coagulation,ozonation and ultrafiltration pretreatment,the membrane flux decreased by 40.89%,37.23%and 33.67%,respectively.Pretreatment is helpful to improve the water quality of the feed liquid,ultrafiltration and ozone are effective as pretreatment methods.After ozone pretreatment at different filtration times,the removal rate of UV₂₅₄ and DOC in the RO effluent reached more than 99%,the results of MW distribution of DOM in different pretreatment effluent and RO membrane effluent showed that the ability of ultrafiltration pretreatment to retain organics was greater than ozone peroxidation,the organic macromolecules were removed effectively by RO separation,the remaining MW were almost below 100 Da.