An Economical and Efficient Physico-Chemical Approach for the Reuse of Wastewater in Small and Medium Scale Paint Enterprises

This study aims to apply the concept of decentralized water treatment to develop an economically viable and stable industrial recycling technology for the treatment and reuse of wastewater from small and medium scale paint enterprises. The effects of coagulant type, coagulant dosage, pH value, coagulant aid type, and dosage, as well as hydraulic mixing parameters on the results were investigated using COD_Cr, turbidity, and coagulation settling volume ratio as the evaluation indicators during the coagulation process. The coagulation mechanism was discussed in conjunction with the analysis results of microscopic morphology and ζ potential. Activated carbon adsorption was employed as an advanced treatment method, and further studies were conducted on adsorption kinetics, adsorption isotherms, and secondary adsorption dynamic tests. Based on the indicators and constraints for recycling water, a practical treatment and reuse scheme for paint wastewater was formulated. A detailed economic analysis of the combined technology was performed using Net Present Value (NPV), considering the specific circumstances. This combined process also demonstrates high removal rates for COD_Cr (96.4%) and turbidity (99.9%) in actual wastewater. The reuse water rate is 80%, with a maximum of 5 cycles, and the economic benefit over the lifecycle is $2322. This process achieves multiple rounds of reuse for paint wastewater, conserving water resources and reducing the pressure on water treatment, thereby possessing high environmental value and economic feasibility.