Experimental Study On The Treatment Of The Stretch Oil Wastewater From Mechanical Processing Of Aluminum Products

The stretch oil wastewater from mechanical processing of aluminum products has characteristics of poor biodegradability,chemical stability,complex structure,high concentration,hard degradation of organic matter,particularly for the stretch oil emulsion of high stability,which is separated difficultly.The problem of domestic and foreign treatment method are as follows:(1)The COD removal efficiency of Acid precipitation,Coagulation,Salting out,Air flotation is low,which only reaches30%~60%,and the removal effect for small molecules of dissolved oil is poor;(2)The Membrane separation method is usually used in the treatment of low concentration oily wastewater.Because the membrane is difficult to be cleaned,and which has characteristics of non-corrosion resisting,high investments and cost,regeneration of adsorption medium;(3)Fenton oxidation method has strict requirements on the reaction conditions and the dosage,and the cost is high.The research of the stretch oil wastewater of aluminium products has become the key of research direction in the field of environmental protection.In this paper,the wastewater of stretch oil from an aluminum processing plant in Qingdao was used as the research and process object.The characteristics of the wastewater are high thickness of the suspended substance and organics(the concentration of COD is more than 40000mg/L),complex composition,a large amount of oil.The reagent type,dosage,pH and reaction time of Acid precipitation demulsification,Coagulation demulsification,Acid precipitation + Coagulation,Acid precipitation + Fenton oxidation were studied,the process parameters were screened and optimized,the wastewater after demulsificationis was treated by biochemical methods,the change of effluent water COD concentration was studied.The analysis of the experiment results showed that the better treatment method was Coagulation + Biochemical method.The optimum process parameters were as follows: when pH was 8.5,the dosage of PFS was 1.5g/L,the dosage of CPAM was15mg/L,the stirring time was 30 min,the concentration of COD was reduced from46564mg/L to 1249mg/L.The wastewater treated by Coagulation was mixed withactivated sludge,when the concentration of activated sludge was 5000mg/L,the aeration was 1.5 L/min,the concentration of COD was reduced from 1249mg/L to150mg/L after 2 days of successive aeration,and the removal rate was 98.5%.