EPA CEVRE - Chemical Wastewater Treatment System
Chemical wastewater treatment systems play a critical role in cleaning wastewater originating from industrial processes that cannot be treated using biological methods. These systems use chemical reactions to remove contaminants from the water.
The chemical treatment reactions are as follows.
Coagulation and Flocculation
These two processes are among the most fundamental steps in chemical treatment. Coagulation neutralises the electrical charges of very small solid particles and colloidal substances suspended in the wastewater, causing them to aggregate. Aluminium and/or iron salts are commonly used as coagulants for this purpose. Once their charges are neutralised, the particles are then converted into larger flocs that can easily settle during the flocculation stage by adding long-chain molecules called polymers.
Neutralisation
Maintaining the pH value of wastewater within a specific range is critical for both treatment efficiency and the protection of equipment used in subsequent stages. Highly acidic or highly alkaline wastewater is brought to the desired pH level through the neutralisation process. Substances such as sodium hydroxide (NaOH) or lime (CaO) are added to acidic wastewater, while substances such as sulphuric acid (H2SO4) are added to alkaline wastewater.
Oxidation and Reduction
These methods are used particularly for the treatment of hazardous or toxic substances. The oxidation process is used to render substances such as cyanide, phenols and certain organic pollutants less harmful. Powerful oxidants such as ozone, hydrogen peroxide or chlorine are used in this process. Reduction, on the other hand, removes heavy metal ions such as chromium and nickel from water by converting them into lower-value, less soluble compounds.
- It is highly effective in removing industrial waste that cannot be biologically treated (such as heavy metals, paint, and oil).
- The treatment process can be completed in a short time due to fast reaction times.
- Can be installed in smaller areas compared to biological treatment systems.
- The use of chemical substances increases operational costs.
- The sludge produced as a result of treatment may contain hazardous waste, and its disposal requires additional costs and regulations.
- Incorrect dosing of chemicals can reduce treatment efficiency or cause secondary pollution problems.
Chemical wastewater treatment systems are an indispensable solution for industrial facilities in terms of complying with environmental legislation and protecting natural water resources. With proper engineering and operation, these systems play a key role in returning water to the cycle in a clean state.