Designing a cost-effective system for treating industrial wastewater involves a combination of physical, chemical, and biological processes. The goal is to remove hazardous substances, such as heavy metals and organic pollutants, while minimizing water waste and energy consumption. Here are some steps to consider:1. Preliminary treatment: This step involves screening and sedimentation to remove large particles and suspended solids from the wastewater. This can be achieved using bar screens, grit chambers, and sedimentation tanks. Preliminary treatment helps to protect the equipment and processes in the subsequent treatment stages.2. Primary treatment: This step involves the use of coagulation, flocculation, and sedimentation processes to remove suspended solids and some of the dissolved pollutants. Coagulants and flocculants are added to the wastewater to promote the aggregation of particles, which then settle out in sedimentation tanks.3. Secondary treatment: This step involves biological processes to remove organic pollutants and nutrients from the wastewater. Activated sludge, trickling filters, and rotating biological contactors are common methods used in secondary treatment. These processes involve the use of microorganisms to break down organic matter and convert it into less harmful substances.4. Tertiary treatment: This step involves advanced treatment processes to remove specific pollutants, such as heavy metals and organic compounds. Some common tertiary treatment methods include: a. Adsorption: Activated carbon or other adsorbents can be used to remove organic pollutants and heavy metals from the wastewater. b. Ion exchange: This process involves the use of ion exchange resins to remove heavy metals and other charged particles from the wastewater. c. Membrane filtration: Ultrafiltration, nanofiltration, and reverse osmosis can be used to remove dissolved solids, heavy metals, and organic pollutants from the wastewater. These processes also help to minimize water waste by recovering treated water for reuse.5. Disinfection: This step involves the use of chemical or physical methods to kill or inactivate pathogenic microorganisms in the treated wastewater. Chlorination, ultraviolet UV radiation, and ozonation are common disinfection methods.6. Sludge treatment: The solid waste generated during the treatment process, known as sludge, must be properly treated and disposed of. Sludge treatment may involve thickening, dewatering, anaerobic digestion, and composting.7. Energy recovery: To minimize energy consumption, consider implementing energy recovery systems, such as anaerobic digestion to produce biogas, which can be used to generate electricity or heat. Additionally, optimizing the operation of pumps, blowers, and other equipment can help to reduce energy consumption.8. Water reuse: Treated wastewater can be reused for various purposes, such as irrigation, cooling, and industrial processes. This helps to minimize water waste and reduce the demand for freshwater resources.By integrating these steps and technologies, a cost-effective system for treating industrial wastewater can be designed to remove hazardous substances while minimizing water waste and energy consumption. Continuous monitoring and optimization of the treatment processes will ensure the system's efficiency and effectiveness in the long run.