Study On The Pretreatment Of High Concentration Emulsion Wastewater By Coagulation-Fenton Oxidation

At present,the emulsion waste liquid is listed in the national hazardous waste list,which requires the corresponding hazardous waste disposal.The cost of hazardous waste disposal by the relevant units often amounts to thousands of yuan per ton,which cannot be borne by the machining enterprises for a long time.Therefore,it is necessary to find an economical way to make the wastewater discharge reach the standard after the enterprise’s own treatment.If the biological method is used to directly treat the high concentration emulsion wastewater,the biological method has higher requirements on the quality of the inlet water,and the problems such as large organic load and easy poisoning of microorganisms will occur,so it must be pretreated.Coagulation demulsification is a commonly used treatment method.However,due to the characteristics of high concentration emulsion wastewater such as poor biodegradability,high concentration of organic matter and difficulty in degradation,the wastewater after conventional coagulation treatment cannot meet the requirements of organic matter degradation efficiency and subsequent biodegradability.Therefore,in this study,coagulation-Fenton oxidation was used to treat high concentration emulsion wastewater.In the coagulation pretreatment experiment,the dilution ratio of the wastewater was first studied,and the optimal condition was determined for the treatment of the emulsion wastewater with the dilution of 2 times.Then the inorganic coagulants were screened and optimized by Polymeric Aluminum Ferric Chloride（PAFC）,Poly Aluminum Chloride（PAC）and Polymeric ferric sulfate（PFS）.Finally,the inorganic coagulant PAFC was used after experimental research and comparative analysis.In coagulation optimization experiments,taking inorganic coagulants Polymeric Aluminum Ferric Chloride（PAFC）iron and organic high polymer flocculant polyacrylamide（PAM）combination of 2 times diluted emulsion wastewater treatment,it is concluded that the optimum technological conditions for coagulation experiment:adjust wastewater pH=9,PAFC dosing quantity is 4.5g/L,PAM dosing quantity is 37.5mg/L,precipitation time 30 minutes,at this time the highest removal rate of COD and turbidity,84.22%、94.68%respectively.After coagulation and demulsification,the COD value of emulsion wastewater was reduced to 2840mg/L,and the turbidity was reduced to 58NTU.Fenton oxidation advanced treatment of demulsified wastewater can improve its biodegradability and further reduce its organic content.Firstly,through the exploration of preliminary experimental conditions,the influencing factors and levels of the orthogonal experiment were simplified.The results of preliminary experiments are as follows:it is beneficial to remove organic matter by adjusting pH to be alkaline and settling down after reaction.Agitation has little effect on the reaction.Secondly,through the orthogonal experiment was adopted to determine the initial optimal range of the main influencing factors,and then the single factor experimental conditions are analyzed on the basis of this range,finally the optimum process conditions of Fenton oxidation experiment is:adjust the initial pH=3,H₂O₂dosing quantity of 10m L/L,Fe SO₄·7H₂O dosing quantity is 3.0g/L,1h reaction time,adjust pH to 9 after reaction,30 minutes precipitation time.at this time,the COD removal rate reached 67.54%.Combined coagulation and Fenton oxidation to pretreat high concentration emulsion wastewater,the total COD removal rate can reach 94.87%,the effluent COD concentration can eventually be reduced to 922mg/L.This provides a guarantee for subsequent biochemical treatment up to the national level 3 emission standard.At the same time,the process design is also carried out,and the feasibility of applying the process in the actual project is explored.The pretreatment cost of each ton of high concentration emulsion wastewater is 113.75yuan,and this process has obvious advantages over direct external treatment in operation cost.