Environmental protection: engineering example of electroplating wastewater advanced treatment based

Environmental protection: engineering example of electroplating wastewater advanced treatment based on resin adsorption

by:Ocpuritech     2021-03-28
Environmental: electroplating treatment of wastewater engineering resin adsorption based on the article of Example: electroplating wastewater complex components, various additives which the main pollutants and heavy metal ions in the electroplating process, is a typical compound pollution. The heavy metals and organic pollutants in electroplating wastewater have changed their existing form in the aqueous solution through a series of physical and chemical effects, and also put forward greater challenges to the conventional water treatment process; composite pollutants make the existence of heavy metals in the environment more Complexity increases the difficulty of governance and brings great risks to human health and ecological safety. GB21900-2008 has higher requirements for emission standards in sensitive areas. For example, the mass concentration and COD emission standards for nickel, copper and zinc in the Taihu Lake Basin are 0.1, 0.3, 1.0 mg/L and 50 mg/L, respectively. The United States EPA833-B-94-002 total wastewater toxicity control recommended limit requirements, the chronic toxicity is less than 1TUc, and the acute toxicity is less than 0.3TUa. Facing increasingly stringent environmental standards, Jiangsu, Zhejiang, and Guangdong have gradually increased their environmental protection requirements and began to adopt the Table 3 standards of GB21900-2008. The development of high-efficiency and low-cost advanced treatment technology is not only a new problem in the field of environmental engineering, but also an important national demand for solving the problem of electroplating wastewater pollution. Treatment technologies such as membrane separation, biotechnology, adsorption and ion exchange are widely used in the research of advanced treatment of electroplating wastewater. Among them, the ion exchange technology has stable effluent quality and is especially suitable for the treatment of low-content wastewater. 1. Wastewater source and treatment process An electroplating company in Jiangsu mainly processes gold plating, silver plating, nickel plating, copper plating, chrome white and painting, etc. The daily average total waste water is about 300t/d. Electroplating wastewater is mainly cyanide-containing, chromium-containing, and acid-alkali comprehensive wastewater. After these three components are pretreated, they enter the adjustment tank for mixing, coagulation and sedimentation, and then discharge. The process flow is shown in Figure 1. It is difficult to achieve effective reduction of toxic pollutants in the original treatment facility after cyanide breaking, chromium removal, coagulation precipitation and other conventional treatments. Various complexing agents, stabilizers and brighteners in the actual electroplating wastewater form stable complexes with heavy metals. As a result, the metals in the effluent from the conventional treatment are extremely unstable, and the various indicators of the effluent are far from reaching the standard in Table 3 of GB21900-2008. The company is located in a relatively sensitive area of u200bu200bthe city. According to the requirements of environmental protection work, in order to ensure that it does not cause serious impact on the surrounding water environment, the electroplating wastewater of this project must meet the GB21900-2008 Table 3 standard and the GB3838-2002 Class III water standard. . The original treatment facilities and the standards to be implemented are shown in Table 1. Based on the characteristics of the electroplating wastewater of the company, the integrated process centered on the full-mixed magnetic ion exchange technology and the new chelating resin separation technology has been studied to form an integrated process with low sludge production and high economic and technical feasibility. Resin adsorption is the core of 'biological contact oxidation + magnetic resin + chelating resin' electroplating wastewater toxic pollutants in-depth control technology, in order to achieve comprehensive toxicity reduction. 2. The biological contact oxidation tank of the main structure is the biological contact oxidation technology, which fills the tank with fillers and supplements the dissolved oxygen in the water by aeration, so that microorganisms can stably adhere to the fillers. It is an activated sludge and biological filter. A method of combining. The designed treatment capacity is 300m3/d, the residence time is 7.2h, and the volume flow of the inlet water is controlled to be maintained at 12m3/h during operation, and the air volume is adjusted to make the aeration effect uniform. After 2 months of cultivation, the growth of activated sludge was good, and the filming was good. At present, it is still operating stably, the effluent COD is basically maintained at 50-60mg/L, and the removal rate is maintained at 40%-50%. 3. Magnetic resin adsorption tank. The magnetic resin is added with a series of iron oxides such as Fe2O3 or Fe3O4 during the synthesis process. The addition of magnets increases the density of the resin and is easy to separate from water. At the same time, its particle size is that of ordinary resin. 1/4~1/6, so its dynamic performance is far better than conventional resin. The resin adsorption tank is designed to be 36m3, to ensure that the mass fraction of magnetic resin is 5%, the hydraulic retention time is 3h, mechanical stirring is used, and the volume flow is adjusted to 12m3/h through the return valve. The resin adopts intermittent regeneration. When a certain amount of resin accumulates in the resin precipitation tank, the resin reflux pump is started, and the resin is regenerated with 10% NaCl by mass fraction, and the remaining resin is returned to the resin adsorption tank. The COD of the effluent passing through the magnetic resin adsorption tank is controlled at about 25mg/L, and the removal rate is maintained at 40%-50%. 4. Compared with ordinary ion exchange resins, chelating resins have higher selectivity for target heavy metal ions. The adsorption mode adopts double columns in series, the adsorption volume flow is controlled at 12m3/h, and the residence time is about 30min. During operation, two columns are connected in series and one column is reserved. The desorption adopts a 4%~5% HCl solution with a mass fraction of 1%~2% NaOH for transformation. After the chelating resin is adsorbed, the COD of the effluent is <20mg/L, and the mass concentrations of Ni2+, Cu2+, and total Cr are <0.02, <0.1, <0.1mg/L, respectively.
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