Design And Practice Of A Two-piece Canmaking Wastewater Plant

Wastewater from two-piece-can production has the characteristics of high oil, large acidity, poor biodegradability and containing F-, increasing the difficulty of wastewater pretreatment. It has been a problem urgent to be solved to design a set of wastewater treatment technology with low operation cost and high treatment efficiency. Emulsified wastewater and washing wastewater are produced from a two-piece-can manufacturing enterprise. The major pollutants are CODCr, F-, oil, SO42-, PO43- and so on. The washing wastewater has poor biodegradability and large acidity. The emulsified wastewater has high oil and poor mobility. In this paper, a set of two-piece-can production wastewater system is designed for wastewater pretreatment according to the practical requirement, such as process selection, engineering design, construction, equipment installation.According to the wastewater quality analysis and comparative analysis of existing wastewater pretreatment technology, the pretreatment process of emulsified wastewater and washing wastewater from two-piece-can production is put forward. The acidification deemulsification and high efficiency oil-water separator were adopted to pretreat emulsified wastewater. The optimum pH obtained through tests in acidification deemulsification is 2. The oil elimination-neutralization-precipitation integrated reactor, containing two-stage pH adjustment system, was adopted to remove complex pollutants and floating oil beads by the addition of flocculants. The pH value is adjusted from 4 to 5 by CaCO3 filter in the first stage pH adjustment system. F- and SO42- are removed by precipitation when reacted with Ca2+. The surface of CaCO3 filter won't covered by precipitation as the CaCO3 filter uses upflow filter. The pH value is adjusted to 7 to 9 by sodium hydroxide solution in the second stage pH adjustment system. And then the polymer flocculants are added to strengthen the sedimentation effect, accelerating the separation of mud and water and the removal of fine particles.The detailed technical proposal, processing design, estimation of project investment and benefit analysis had been carried out, and the wastewater treatment was planted.The experimental results of wastewater from two-piece-can production show that the removal rate of CODCr, F-, oil, SO42- and PO43- was over 50%,88%.91.5%,94% and 38%, respectively. The effluent quality can achieve the third class criteria specified in the demand of Integrated Wastewater Discharge Standard (GB8978-1996), and the cost of the pretreatment is 2.59 Yuan/m3. The treatment processing is reasonable and effective for the pretreatment of two-piece-can production wastewater, and can be applied as a model project.