The Research Of Chemical Precipitation And Coagulation-air Floatation Process To Dispose Pickling And Parkerising Sewage

The wire rope is so widely used in modern industry. But it can produce plenty of sewage in the process of wire rope production. The sewage of wire rope factory is formed in the process of wire rope production by pickling, phosphorising, washing and electroplating. It includes ammonia nitrogen, oil, lead ions, zinc ions, iron ions, phosphate, sulfate ions and other contaminants. It can cause serious environment pollution because of complex compositions, heavy concentration and high toxicity of sewage. The paper shows that I adopt coagulation-air flotation process to the sewage of a wire rope factory for experimental research and practical engineering application. At the same time I perform a theoretical analysis for the air floating process.This paper adopts chemical precipitation process to remove phosphate ions and heavy metal of sewage preliminarily at first. Then This paper adopts coagulation-air flotation process to remove surplus heavy metal and other contaminants of sewage further. This paper chooses a variety of inorganic flocculants to coagulate in my experiment. It shows that different flocculants will create different effects to the sewage by using exclusively in the result. The effect of PAFC is best than others’ in dispose of sewage. It shows that the effect of inorganic-organic flocculants is better than single flocculant’s by comparing PAFC using exclusively with PAFC-organic flocculants combined using in dispose of sewage. It can improve water purification effect and reduce drug consumption in proper ratio.The experiment certificates that the best conditions include that PH is 9, n(PO43-):n(Ca2+) is 1.0:1.3, reaction period is 30 min and setting period is 30 min by chemical precipitation process to remove most pollution of sewage of the wire rope factory. The removal rates for Zn2+, Pb2+ and phosphate ions of sewage are up to 99.0%, 95.3% and 99.6% respectively in the best setting conditions. According to coagulation air floatation experiments by the prototype, I identify that the removal rates for Zn2+, Pb2+ and phosphate ions and COD are respectively to be up to 83.3%、85.1%、85,.2%、77.0% when PAFC, PAM, PH and air pressure are respectively to be 20mg/L, 3mg/L, 7.5 and 1.2Mpa under coagulation air floatation system.The experimental technological process and operating parameters are applied to the actual sewage treatment of a wire rope factory by running continuously. It shows that the sewage treatment effect of the wire rope factory is good under the technological process. Design flow, phosphorus concentration of inflow, concentration of Pb2+, concentration of Zn2+, COD and HRT are respectively to be 40m3/d, 228mg/L, 40mg/L, 285mg/L, 230mg/L and 8h. The average concentration of pollutants in the water as follows: concentration of phosphate ions, concentration of Pb2+, concentration of Zn2+ and COD are respectively to be 0.4mg/L, 0.6mg/L, 0.5mg/L and 25mg/L under the treatment process through continuous steady operation. The concentration of phosphate ions and COD can both reach requirement of direct discharge in the Liaoning province class a of integrated wastewater discharge standard(DB 21/1627-2008). The concentration of Pb2+ and concentration of Zn2+ can also reach requirement of first level discharge in the integrated wastewater discharge standard(GB 8978-1996). The cost of sewage treatment is 2.49 RMB per ton.The floating pressure and reflux ratio make a great effect to the absorption efficiency of air floating pond on the theoretical analysis. The concentration of air in the air floating pond is 22.0L/m3 and the number of micro air bubble per unit volume sewage is 9.89×1014entries/m3 when air floating pressure is 0.6MPa,. reflux ratio is 30%. I will do my best to improve reflux ratio to improve the absorption efficiency of air floating pond with engineering permission, The ascending velocity of air bubble 0.68mm/s on the best air floating conditions when the temperature is 20℃.