Coating Process Phosphorus Wastewater Characteristics And Pollution Control Research

Painting is a very importent infact thing in surface treatment. TP concentration is very high, but COD and BOD are relatively low of the phosphatizing wastewater from painting surface pretreatment. Eutrophication becomes serious environmental problem these days, and the major factor is phosphate for eutrophication. Therefore, we consider it even more important to remove phosphate from wastewater for entrophication control. Painting surface pretreatment process is the key factor to practice cleaner production for painting, due to the fact that it yield most of the pollutant, and it consumes most of the energy, most of the fresh water.Phosphatizing wastewater with zinc from refrigerator painting process was studied about character and pollution control. Some pollution treatment methods about phosphate and zinc removal by chemical precipitation method, reducing COD were also discussed in this thesis. It was mainly studied the effect of phosphate and zinc removal under different reagents, different add-on quality, different pH and so on. It's the first time that cleaner production was used in painting surface pre-treatment process. It can improve economic benefit applying cleaner production, reducing discharged pollutant and phosphatizing reagents in painting surface pre-treatment process.It discussed the theory of precipitation and its influential factor, the best pH range on theory, while treating phosphatizing wastewater with Fe²⁺, Fe³⁺ and Ca²⁺ as precipitator.The results indicated that pH shouldn't exceed 3.95 with Fe²⁺, pH shouldn't exceed 3.20 with Fe³⁺. And higher pH will be better while using Ca²⁺ to remove PO₄^3-. To remove zinc from wastewater, for the pH, 8.0-10 will be better.The TP of wastewater with an inlet concentration of 9.63mg/L⁹.68mg/L, some phosphate can be removed by centrifugation, but it has little purpose, only 10.07% of the TP removed, with 3000r/min, after 8min.In this experiment, we made Fe²⁺, Fe²⁺, Ca²⁺ as precipitator, PAM as coagulation, regulated pH of wastewater by adding H₂SO₄, NaOH or Ca(OH)₂, studied the change of TP and COD before and after precipitation. It was indicated that Fe²⁺, Fe²⁺, Ca²⁺ had a good effect to phosphate removal and COD removal of phosphatizing wastewater with zinc. When inlet TP is 11.97mg/L, added 0.25kg Fe₂(SO₄)₃ per one ton wastewater, 0.005 kg PAM per one ton wastewater, then outlet TP was 0.44mg/L. When inlet TP is 12.44mg/L, if we added 0.2kg...