Designing a cost-effective and environmentally friendly system for treating industrial wastewater from a manufacturing plant that produces heavy metals and toxic chemicals involves several steps. Here's a suggested approach:1. Preliminary treatment: The first step is to remove large particles and debris from the wastewater using screens, grit chambers, and sedimentation tanks. This helps to reduce the load on the subsequent treatment processes.2. Chemical precipitation: In this process, chemicals are added to the wastewater to precipitate heavy metals and other toxic substances. Lime, for example, can be used to precipitate metals such as chromium, lead, and zinc. The precipitated solids can then be removed through sedimentation or filtration.3. Coagulation and flocculation: Coagulants and flocculants are added to the wastewater to promote the aggregation of suspended particles, forming larger flocs that can be easily removed through sedimentation or filtration. This process helps to remove additional heavy metals and toxic chemicals.4. Membrane filtration: Membrane filtration, such as ultrafiltration or reverse osmosis, can be used to remove dissolved heavy metals and toxic chemicals from the wastewater. These processes can be expensive, but they are highly effective in removing contaminants.5. Biological treatment: Biological processes, such as activated sludge or anaerobic digestion, can be used to break down organic compounds in the wastewater. These processes involve the use of microorganisms to convert the organic compounds into less harmful substances, such as carbon dioxide and water.6. Advanced oxidation processes AOPs : AOPs, such as ozonation, photocatalysis, or Fenton's reaction, can be used to further degrade toxic chemicals in the wastewater. These processes generate highly reactive radicals that can break down a wide range of pollutants.7. Sludge management: The sludge generated from the treatment processes should be properly managed to minimize environmental impacts. This may involve dewatering, stabilization, and disposal in a landfill or further treatment for resource recovery, such as energy production through anaerobic digestion.8. Monitoring and control: Implementing a monitoring and control system to ensure the proper functioning of the treatment processes is essential. This includes regular sampling and analysis of the wastewater to ensure that the treated effluent meets the required discharge standards.9. Resource recovery: To make the system more cost-effective and environmentally friendly, consider incorporating resource recovery options, such as recovering metals from the precipitated solids or generating energy from the biogas produced during anaerobic digestion.10. Continuous improvement: Regularly evaluate the performance of the treatment system and explore opportunities for optimization and the adoption of new technologies to improve efficiency and reduce costs.By implementing these steps, a cost-effective and environmentally friendly system for treating industrial wastewater containing heavy metals and toxic chemicals can be designed. This will help to minimize the environmental impact of the manufacturing plant and protect public health.