Research And Application Of Flocculant In Oily Wastewater Treatment

The current situation of water resources in our country is not optimistic, and the pollution of oily sewage has attracted people's attention gradually. According to the actual requirements of the oil slick oily sewage difficult to deal with the problems and issues, this paper prepared flocculating agent to deal with oily wastewater of the ship, and on this basis, design and research of new type of sewage treatment equipment, to meet the effluent oil removal rate reached more than 90%, the COD removal rate reached more than 75% of the surface, no oil and impurities of the project requirements. The research of this paper is mainly from the following two aspects.The research of this paper is mainly focused on the two aspects. The first is the preparation and performance of the flocculant. The main component of the flocculant is the polymeric aluminum ferric chloride and inorganic weighting material. Therefore, we mainly studied the synthesis of polymeric aluminum ferric chloride in the experiment. The reaction temperature, reaction time, aluminum iron ratio, alkalinity and compounding ratio were considered when preparating the flocculant, these flocculant samples were then used for the oily wastewater flocculation experiment. After the flocculation reaction, we studied the sewage and flocs, the effluent water quality, and also COD removal rate. Finally,we got the optimum preparation parameters of the flocculant as follows: the reaction temperature was 90 oC, reaction time was 2h, the ratio of reactant aluminum chloride and ferric chloride aluminum iron was 9:1, the best basicity was 2, aging time was 24 h, the ratio of polymerization aluminum chloride iron and inorganic weighting material compound was 10:6. The performance of the flocculant was studied by using in the simulated oily wastewater treating experiment. The main factrs of reagent dosage, sewage temperature and p H value were tested, we got the following conclusion: the optimal dosage of flocculant was 300 mg/L, the oil and COD removal rate remained stable when synthetic reagents was in 0~40 oC, there is no need to adjust the p H value of wastewater as the flocculation effect well when p H was in 6~8. Under these conditions, the biggest oil removal rate was 96.7% by using the homemade flocculation, and the cod removal rate was 82.3%. We applied our homemade flocculation, polymerization aluminum chloride(commercially available), and polymeric aluminum ferric chloride(commercially available) on the following for actual sewage, two cabinet sewage(No.I, II) and two sewage tanks(No.II, III), only the homemade flocculation coud settele all the oil and coagulation, and the COD removal rate were than other two kinds of flocculants.The second research focused on the instrument design of treating oily wastewater. Based on the acctual oily wastewater treatment environment and the characteristics of the homemade flocculation(large proportion and easy to sink), we designed a simple device for the amplification experiment of oily wastewater. We researched the problems of low oil slick settlement, reagent to participate fully in the reaction, as well as the water outlet design. On the basis of a large number of experiments, we designed the new oily sewage treatment equipment, it is divided into three parts: the sewage storage reaction unit, sewage recycle mixing unit and dosing unit. The main equipment of the sewage storage reaction unit is the flocculation reaction tank, the sewage enters the reaction tank, and then returns to the reaction tank for flocculation and sedimentation. After working for a period of time, the treated sewage can be discharged out of the tank through the drain port. The circulation unit is mainly composed by mixed sewage floating oil collector, circulating pump and pipeline mixer. There is a fux grooves in collector' surface, it can effective collect the surface oil. The sewage will get into the pipeline mixer by a circulating pump, and mixed flocculants and the outlet is discharged into a flocculation reaction pool. The main device of the dosing unit is a metering pump and reagent box, the usage of flocculants could be calculated by the records of metering pump dosing time. The water outlet was designed as a rotating spray structure, there are four spouts toward different directions respectively, which is help to decrease the oil floating on the surface. The optimal processing parameters of the equipment were the following: when processing one ton of oily sewage, the best dosage was 840 g, the optimal running time is 20~30 min, the effluent quality oil and COD removal rate reached 96% and 81% respectively.