What is industrial wastewater
Industrial wastewater refers to water that has been used in the production and manufacturing of a product and is discharged from the system as a secondary product. In another definition, industrial wastewater can be described as water that has lost its quality and characteristics during its use. Industrial wastewater is a byproduct of manufacturing plants, such as those for food, beverages, and clothing, and all factories that produce chemicals needed by humanity or use chemicals to manufacture a product. In all these factories, water is used as an important consumable in these processes.
Types of Industrial Wastewater
Industrial Wastewater Based on Pollutants
Depending on the diverse nature of industrial operations, different pollutants may be present in their wastewater, which are classified as follows.
Wastewater with Organic Matter
These wastes contain oils, organic acids, colloidal particles, proteins, and hydrocarbons. The most hazardous pollution in industrial wastewater is organic matter. Due to its high molecular weight, it is not removed by conventional treatment methods. To eliminate it, biological methods must be used. An example of this is the wastewater from the food industry.
Wastewater with Inorganic Substances
This type of industrial wastewater or effluent can contain mineral acids, nickel, zinc, cadmium, ammonia, copper, hydrogen sulfide, and free chlorine. Alternatively, this type of wastewater can be classified as chromium-containing, cyanide-containing, sulfur-containing, mercury-containing, phosphorus-containing, and radioactive wastewater due to the presence of inorganic elements.
Industrial Wastewater by Industry Type
Industrial wastewater is classified based on the type of industry or the products and materials manufactured by factories. In this article, we will highlight the most significant industries in the production of industrial wastewater.
Wastewater from the Aluminum Extrusion Industry
The aluminum extrusion process is one of the water-intensive industries that produces a large amount of wastewater. Most of this wastewater is generated during the anodizing operation for aluminum profiles. This wastewater is highly harmful to the environment and must be treated or recycled, just like other wastewater.
One of the most water-intensive industries in the anodizing (plating) sector is the aluminum industry, and for this reason, it produces a large amount of wastewater. This wastewater contains a wide and significant range of pH levels. The wastewater generated from the aluminum profile anodizing process, like other types of plating wastewater such as chrome plating, is highly toxic. Discharging it into the regular sewage system causes significant damage to the environment. On the other hand, disposing of the wastewater in ways that do not pollute the environment is very costly and not economically feasible.
Steel Industry Wastewater
The steel industry is one of the most water-intensive industries, consuming nearly 160 million cubic meters of water annually. This places it in the third-highest tier of water consumption.
Steel industry wastewater contains the following elements and substances:
Fats and oils
Neutral solids
Heavy metals in solution
Dyes
Various organic substances
Anions such as nitrate, chloride, cyanide, fluoride, phosphate, sulfate
Given the toxic substances present in industrial steel wastewater, the treatment of these effluents is of the utmost importance.
Steel industry wastewater is classified into categories such as sanitary (personal), industrial, and special effluents, such as chromium, chemical, and phenolic. Given the toxic substances present in industrial steel or metal industry wastewater, the treatment of steel industry effluent is a very important issue. The breakdown of metals is not simple, and this very reason leads to the accumulation of these highly dangerous metals in nature and the environment, causing irreparable harm.
Steel industry wastewater treatment is classified as follows:
Trash removal
Equilibration
Pumping
De-greasing
Coagulation and flocculation
Sedimentation and sand filtration
Petrochemical industry wastewater
Petrochemicals are consumer products derived from petroleum and natural gas. Wastewater from petrochemical industries contains pollutants such as proteins, phosphorus, ammonia, gasoline, carbon oil, solids, phenol, urea, carbohydrates, and many harmful algae
Petrochemical Wastewater Treatment Stages
Physical or Pre-treatment Stage
In the first stage of petrochemical wastewater treatment, large suspended and solid particles present in the industrial effluent are collected using equipment such as manual and mechanical trash racks.
Primary Treatment of Petrochemical Wastewater
In the next stage, fats, suspended particles, and colloidal particles are removed. In this stage, flocculation, sedimentation, flotation, and degreasing are performed by adding appropriate reagents.
A simple and brief explanation of wastewater flocculation is that cationic and anionic polymeric materials are used to neutralize the charge on charged particles.
Biological Treatment of Petrochemical Wastewater or Secondary Treatment
Once the effluents have passed through the previous stages and some of their pollutants have been removed, they enter the next stage for aerobic and anaerobic treatment.
Initially, anaerobic bacteria and microorganisms break down the non-degradable organic matter, and then aerobic bacteria carry out the next stage of treatment.
Wastewater from most industries contains heavy and toxic metals such as cadmium, chromium, and lead. If discharged into nature without treatment, these substances cause irreparable damage to the environment. Proper treatment of an industrial wastewater system requires a complete understanding of the components in the effluent. Before it is discharged into nature and the environment, it must be treated using advanced equipment and devices
.