| Chemical fibre oil agent is one of the essential additives used in the spinning process and synthetic fiber manufacturing process. During the process of washing recovered oil product containers, a large number of emulsified oily wastewater with high concentration was produced. In order to reduce the difficulty of subsequent biological treatment and finally meet the discharge standard, the pretreatment technology is the key. In this study, according to the features of the wastewater such as high COD, two experiments were constructed to study emulsion demulsification method and demulsification effluent Fenton treatment, respectively. Firstly, the main factors controlling acid cracking and Fenton experiment were studied. Secondly, the process parameters of two pretreatment coupled process were optimized. Thirdly, the fate of pollutants component in the wastewater through the pretreatments was initially analyzed. Based on our findings, the pretreatment technology was applied to a emulsified wastewater treatment project (20m3/d) in a chemical fibre oil agent manufacturing plant. The main findings are as follows:1. Three ideal agents (H2SO4、HNO3and HCl) were tested to pretreat the oily emulsified wastewater, and we found that the treatment of H2SO4on demulsification was the best. The single factor experiments showed the optimum demulsification condition was obtained:the concentration of H2SO4is0.2%(v/v); the reaction temperature is equal or higher than60℃, the reaction time is equal or longer than60min, and the standing time is equal or longer than16h. After demulsification reaction, COD removal rate can reach more than90%. The data of GC/MS showed that main pollutants changed from oils (before demulsification) to organic chemicals (after demulsification).2. Fenton oxidation could significantly reduce COD of demulsification clear liquid and evidently improve its biodegradability. Under the condition of a fixed H2O2dosage (theoretical removal was5000mg/L), the best operational conditions for achieving the desired goal (i.e., BOD5/COD≥0.4) were:reaction temperature=50℃; n (H2O2):n (Fe2+)=10:1; initial pH=3; reaction time=2h. After Fenton oxidation with the conditions above, the demulsification clear liquid COD decreased by7440mg/L, BOD5/COD rose from0.21to0.41. The data of GC/MS showed the relative contents of organic acids and alcohols significantly increased while the relative content of long chain alkane, long chain alkene and aromatic was significantly reduced after Fenton oxidation.3. Acid cracking demulsification/Fenton/anaerobic/aerobic process was applied to wastewater treatment project. During the operation of the wastewater treatment works, the effect of acid cracking demulsification was susceptible to the quality of raw wastewater since its COD varied between24500mg/L-40200mg/L. The average COD removal of acid cracking demulsification unit could reach to90.1%. After Fenton oxidation, the average BOD5/COD of demulsification clear liquid increased by0.18. After regulating demulsification effluent with plant workshop wash and sewage, A/O Process was used to treat it. The results showed that COD decreased from1784±127mg/L to314±48mg/L and ammonia concentration decreased from48.7±0.6mg/L to5.1±1.2mg/L. The performance of the project indicated that the wastewater treatment process was stable and reliable. |
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