Classification of industrial wastewater treatment processes

The effluent must be treated before discharge into water or on land. The amount of treatment required depends on the characteristics of the disposal site. The effluent can be treated in different ways. Purification processes are classified as follows.

1.PRE-TREATMENT PHYSICAL

Physical methods of industrial wastewater treatment  include the removal of materials using natural forces such as gravity, electric gravity, windward forces, and physical barriers. In general, physical purification mechanisms do not lead to changes in the chemical structure of materials. In some cases, the physical state, such as evaporation, changes, but often causes the accumulation of dispersed material, as occurs during filtration.

Physical treatment methods involve processes in which no significant chemical or biological changes occur and only physical phenomena are used to improve or treat wastewater. For example, coarse screening is done to remove larger objects and scale (or clear). In sedimentation processes, physical phenomena related to the deposition of solids by gravity act.
Sedimentation is very common for the separation of solids in refining operations and is typically used at the beginning and end of refining operations. While sedimentation is one of the most common physical treatment processes used to achieve treatment, there is another physical treatment process, including aeration, which is usually performed to supply wastewater with oxygen. However, other physical techniques are used, including filtration. The effluent passes through the filter medium to separate solids. For example, sand filters can be used to remove more solids.

2. Primary / chemical treatment

Chemical wastewater treatment methods are proposed for two types, the chemical properties of the contaminants (their tendency to react chemically) and the chemical properties of the reaction products between the contaminants and the chemicals used for the treatment, such as solubility, volatility, or others. Properties that indicate the inability of the product to remove residual suspensions in water. In general, six chemical processes can be used to treat wastewater:
1. Production of insoluble solids
2. Insoluble gas production
3. Production of colloidal suspensions, with the help of reducing the surface load
4. Production of a biodegradable substance from a non-biodegradable substance
5. Eliminate or inactivate chelating agents
6. Production of a material that can be easily removed by oxidation or reduction by one of the above methods
Chemical treatment of industrial wastewater involves the use of chemical reactions to improve water quality. The most common chemical process is chlorination. Chlorine is a chemical, a strong oxidizer, which is used to kill bacteria and thus slow down the decomposition of effluents. Another powerful oxidant used as a disinfectant is ozone. Coagulation involves the addition of a chemical, which converts the final product into an insoluble form and helps to remove suspensions from the effluent. Polyvalent metals are commonly used as chemical coagulants in wastewater treatment; Compounds containing iron (such as ferric chloride or iron sulfate), alum (aluminum sulfate) and lime (ability to neutralize) can be mentioned. Some processes may in fact be both physical and chemical in nature. For example, the use of activated carbon to absorb or remove organic matter involves both chemical and physical processes.

3. Secondary / biological treatment

Biological treatment of industrial wastewater treatment is a process in which organic matter is used as food by bacteria and other microorganisms. Almost any organic matter can be consumed as food by one or more species of bacteria, fungi, cilia, rotifers or other microorganisms. In heavy use, complex organic molecules are systematically broken down, re-emerging as new cell protoplasms. In aerobic or anaerobic systems, oxygen, which acts as an electron receptor, is required in either molecular solution or anion, such as nitrate and sulfate. Finally, reducing the amount of organic pollutants and increasing the amount of microorganisms, carbon dioxide, water and other by-products leads to microbial metabolism. In anaerobic systems, substances other than oxygen act as electron receptors.
Biological treatment methods using microorganisms, mainly bacteria, help in the biochemical decomposition of the effluent into stable end products. Microorganisms as well as more sludge are formed and the waste is converted to carbon dioxide, water and other final products. In general, biological treatment methods can be divided into aerobic and anaerobic methods based on the availability of dissolved oxygen. The solids are then removed from the effluent, and the rest is discharged to make the solids-free water tangible. In the first place, organic matter is removed, which may also include minerals. Treatment of solids and liquids that have become sludge should also be done. Finally, purification may be required to control odor, delay biological activity, or kill pathogenic microorganisms.