Study On The Technology Of Treating High Strength Emulsified Oily Wastewater

Emulsified oily wastewater, which is functional in cooling,lubricating and washing, is widely used in metal material proce ssingand machining industry and the wastewater which is produced duringthe machining process is the one of O/W in high density. The massiveuse of the cutting fluid and washing agent in the machining industrydetermines the fact that the machine oil, sur factants, soluble organiccompounds and solid suspended matter will be in the majority of thewaste water, though which will not be large in quantity, COD and oilwill be high in index. Therefore, the discharge of the emulsified oilywastewater without any treatment will seriously pollute the water itgoes into.Due to the beamed absorption by the emulsifier moleculesdwelling on the interface between the water and the oil, a solidinterfacial film will be formed and at the same time the efficientdouble charge layers will be greatly thickened, in other words, boththe width and the gradient of potential distribution of the doublecharge layers will be enlarged. Thus, those oil droplets, which aremeasured by micron, are evenly distributed in the water and a re hardto separate. All these contribute that emulsified oil can survive in thewater in a stable way and is difficult to be cleaned out. For this reason,in order to destroy the stability of the emulsified oil, the interfacialabsorption film must be demulsified in prior to separate the oil and the water. Therefore, demulsification is critical in the process oftreating emulsified oily wastewater.After demulsification, the surfactants and soluble organiccompounds in the majority will be left in the wastewater, which arenon-biodegradable. And generally those which are hard todecomposable by microorganism are correspondently stable inchemical property, and thus difficult to mineralize by commonoxidizing agents. This calls for a chemical oxidizing agent whichsuffices the oxidizing ability. Meanwhile, the Advanced OxidationTechnologies featuring hydroxyl radicals can answer the call.The research target of the thesis is the self -made emulsified oilywastewater in which the emulsified oil procured percen ts 5. Theresearch focuses on the conditions under which the waster water istreated by demulsification using flocculant, and the feasibility of thefurther treatment, which adopting the technology of electrolysis andbiochemical treatment, of the waste water after the processes ofdemulsification and flocculation.After changing the doses of the flocculants of PAC PFS PASPAM and self-made flocculant, the temperature of demulsification,and the pH of the emulsified oily wastewater, their affects on thedemulsification are analyzed, the effects of the five flocculants arecompared, and the demulsification mechanism as well as itscharacteristics of the polymeric flocculants are also included in thisresearch. As the research shows, when PFS at 10 g/L is us ed asflocculant, the temperature of demulsification is 65 , and the pH of the emulsified oily wastewater is 8, the remov al rate of COD andturbid degree achieves 93 and 99 respectively.By conducting the contrastive experiments on the waste waterafter demulsification and flocculation, namely through biochemicaltreatment on one hand and on the other the electrolysis andbiochemical treatment, it is learned that those organic compounds inthe waste water which are non-biodegradable can be greatly changedin molecular structure and into degradable compounds by aerobeafter electrolysis in the electrobath consisting of the graphite as thecathode and the electrode of Ti/PbO2 as the anode. Then, thebiodegradability of the waste water can be improved a grea t deal bybenefiting the degradation of the aerobe.It is already known that the treatment of the industrial emulsifiedoily wastewater produced by an engine factory during the machiningprocess using the technology of demulsification flocculationelectrolysis biological contact oxidation is feasible. As the resultshows, after the treatment the COD which is originally more than100,000 mg/L in the egress water can be reduced to 670~690 mg/L.