Industrial Wastewater Treatment Process | PDF
Due to the increasing civilization, it has become necessary to adopt a suitable industrial wastewater treatment process to handle liquid industrial effluents.
The world before the industrial revolution was characterized by little wastewater.
But, since the industrial revolution which boosted the economy of nations raising their standard of living, companies, and industries had a challenging problem of where to discharge their effluents after industrial processes of which they resorted to discharging of these effluents in the oceans and nearby waters.
This in turn caused a widespread of waterborne diseases like cholera, dysentery, and the likes. This caused agitations by the indigenes of the community prompting the government to look for a way to handle the situation.
The solution was that the government had to work with the industries and companies to create a suitable way of disposing of this wastewater. This brought about the creation of an industrial wastewater treatment process.
The industrial wastewater treatment process has undergone modifications as time passes newly discovered dangerous substances in the wastewater are captured in the industrial wastewater treatment process.
Industries use water for different reasons and before use, the water undergoes processes for efficient usage.
Different water treatment processes go on in the industry and although their general makeup might be similar, some of the common industrial water treatment processes include:
Boiler feedwater treatment systems – dependable at protecting the boiler unit compounds and preventing breakdowns in the pipes which occur due to the existing contaminants in the feed water.
Cooling tower water treatment systems – efficient safeguard for cooling tower elements against contaminants present in the circulation of feed water.
Raw water treatment systems – utilized during pretreatment and optimized for the feed water to enhance the product performance and process efficiency.
Wastewater treatment systems – suitable for modifying polluted streams into purified water that can be sufficiently released into treatment facilities or the environment.
It is necessary to know that an industrial treatment process is specific for its application and there are different industrial wastewater treatment processes but, if the water is used for more than one purpose or a general-purpose then, the most stringent requirement should be followed to satisfy all conditions.
What is Industrial Wastewater Treatment?
According to Wikipedia,
“Industrial wastewater treatment process describes the process used for treating wastewater that is produced by industries as an undesirable by-product.”
Industrial wastewater treatment includes electroplating rinse water processing for paint recovery, treatment of oil/water emulsions, processing wastewater containing heavy metals, oil, and grease before effluent discharge, textile wastewater, and pulp and paper wastewater.
Industrial wastewater treatment for production and manufacturing processes needs clean water as polluted water containing unwanted substances can harm the quality of the products produce.
The industrial wastewater treatment process can be used for a variety of applications be it simple or complex, effective, low-cost, and compact systems to tackle various water purification and separation needs.
The main objective of industrial wastewater treatment is to allow human and industrial effluents to be disposed of without danger to human health or damage to the environment.
Treatment of industrial wastewater is a method of recycling water as the used water undergoes some chemical processes before it can be used again.
Having known what industrial wastewater treatment is, let’s look at the reasons for industrial wastewater treatment.
Processes of Waste Water Treatment
The four processes of wastewater treatment are
- Preliminary Treatment
- Primary Treatment
- Secondary or Biological Treatment and
- Tertiary or Advanced Treatment.
1. Preliminary Treatment
preliminary treatment involves the removal of floating materials (leaves, papers, rags) and settleable inorganic solids (sand, grit), besides oily substances (fats, oils, greases).
The three major types of equipment employed in the preliminary treatment and are screeners, grit chambers, and skimming tanks, employed in preliminary screening
A screener is a device that is used to remove floating materials and suspended particles. This device has openings that are usually uniform in size. The process of screening is carried out by passing the sewage through different types of screeners with different pore sizes.
The grit chambers are used to remove heavy inorganic materials with a specific gravity of 2.4-2.7. eg. sand and ash. This process is based on sedimentation due to gravitational forces.
Skimming Tanks are used for removing great and oily materials from domestic or industrial outlets that find their entry into the sewage.
2. Primary Treatment
In primary treatment, fine suspended organic solids cannot be removed in the preliminary treatment. Primary treatment involves sedimentation or settling. In this process, sedimentation is carried twice; before the primary treatment and after the primary treatment.
The sedimentation done after the primary treatment is called secondary sedimentation. It’s often necessary to use chemical coagulates to facilitate the sedimentation process and this is known as chemical precipitation or coagulation-aided sedimentation.
3. Secondary or Biological Treatment
Biological or secondary treatment is required for the removal of dissolved and fine commissural organic matter. This process involves the use of microorganisms (bacteria, algae, fungi, protozoa, rotifers, nematodes) that decompose the unstable organic matter into stable inorganic forms.
The biological treatment processes of sewage include aerobic, anaerobic and pond processes and they depend on the nature of the use of the microorganisms, the biological processes are categorized as suspended growth systems and attached growth systems.
4. Tertiary Treatment
Also known as advanced treatment, tertiary treatment is mostly needed for the removal of suspended and dissolved substances trending after the primary and secondary treatment.
Though the result of the secondary treatment is without any mistake nuisance, tertiary treatment is still needed for the following
- When the quality of the effluent to be discharged does not meet the standard requirements (particularly in the developed countries).
- When it is necessary to reuse the sewage/wastewater (reclamation of water is quite expensive, but is required in certain situations of water shortage).
They are required for the removal of nitrogen and phosphorus compounds.
There are four major processes under the tertiary treatment:
- Solids removal
- Biological nitrogen removal
- Biological phosphorus removal
Reasons for Industrial Wastewater Treatment
Just as water is useful, wastewater is useful. There are various reasons for treating industrial wastewater.
- Wildlife Habitat
- Recreation and Quality of water
- Health Concerns
- Industrial Processes
Clean water is very much needed for the survival of plants and animals that Iive in water. The industrial wastewater treatment process can help provide the necessary water that can be used in the fishing industry, sport fishing games, and future generations
Irrigation uses industrial wastewater as both a disposal method and a utilisation method making it an effective form of industrial wastewater disposal.
Water gotten from the treatment of wastewater can be used efficiently for irrigation and also, irrigation helps collect treated industrial wastewater as a way of disposing of the treated industrial wastewater
However, some measure of treatment has to be provided to industrial wastewater before it can be used for agricultural or landscape irrigation or aquaculture.
The quality of treated effluent used in agriculture has a great influence on the operation and performance of the wastewater-soil-plant or aquaculture system.
3. Wildlife Habitats
Imagine if all the industrial wastewater that was discharged into the ocean and water bodies were treated, there would be less destruction of aquatic habitats and death of aquatic wildlife.
The deposition of treated wastewater in aquatic bodies enhances life in the water and so, the treatment of wastewater improves aquatic wildlife.
The criticality and usefulness of water to land plants and animals also make it known that the treatment of industrial wastewater is good for wildlife, both land and aquatic.
4. Recreation and Quality of Life
Water is a great playground for us all. The scenic and recreational values of our waters are reasons many people choose to live where they do.
Visitors are drawn to water activities such as swimming, fishing, boating, and picnicking and so, it is needful that wastewater is treated to meet these needs.
5. Health Concerns
From the beginning of the industrial era, industrial wastewater has been known to cause various health issues like cholera and dysentery of which many have died from and are battling with now.
If it is not properly cleaned, water can carry disease. Since we live, work, and play so close to water, harmful bacteria have to be removed to make water safe through industrial wastewater treatment.
6. Industrial Processes
Water is a significant and critical ingredient in production especially the production of edibles and so treatment of industrial wastewater is very essential as these treated industrial wastewaters can be reused again for manufacturing, production, and other industrial processes.
Industrial Wastewater Treatment Process Flow Diagram
Fig. Industrial wastewater treatment process flow diagram (Conventional wastewater treatment processes)
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What Happens to Industrial Water after Treatment?
Industrial wastewater can be used for various reasons after it has passed through the industrial wastewater treatment process. Treated wastewater can be used in place of water even to the extent of drinking it.
Might sound absurd though, but industrial wastewater that has been passed through the most stringent requirements in the industrial wastewater treatment process can be used as drinking water.
Some of the uses of treated industrial wastewater include;
- Some industries, such as power-generation plants can use treated wastewater.
- Cooling of power-generation equipment, and using wastewater for this purpose means that the facility won’t have to use higher-quality water that is best used somewhere else.
- Some non-potable uses such as washing cars, flushing toilets, cooling water for power plants, concrete mixing, artificial lakes, irrigation for golf courses and public parks, and hydraulic fracturing. Where applicable, systems run a dual piping system to keep the recycled water separate from the potable water.
- Irrigation of public parks, sporting facilities, private gardens, roadsides; Street cleaning; Fire protection systems; Vehicle washing; Toilet flushing; Air conditioners; Dust control.
- Food crops not commercially processed; Food crops commercially processed; Pasture for milking animals; Fodder; Fiber; Seed crops; Ornamental flowers; Orchards; Hydroponic culture; Aquaculture; Greenhouses; Viticulture; Industrial uses; Processing water; Cooling water; Recirculating cooling towers; Washdown water; Washing aggregate; Making concrete; Soil compaction; Dust control.
- Golf course irrigation; Recreational impoundments with/without public access (e.g. fishing, boating, bathing); Aesthetic impoundments without public access; Snowmaking.
- Aquifer recharge; Wetlands; Marshes; Stream augmentation; Wildlife habitat; Silviculture.
- Aquifer recharge for drinking water use; Augmentation of surface drinking water supplies; Treatment until drinking water quality.
Can we drink treated wastewater?
Might sound strange but, yes we can drink treated wastewater. When industrial wastewater is passed through the most stringent industrial wastewater treatment process, the outcome of the industrial wastewater treatment process can be used as drinking water.
When industrial wastewater arrives at the industrial wastewater treatment plant for the industrial wastewater treatment process to start, they are taken to a part of the o plant where Sonia and large particles are filtered.
Those solids are removed and composted, sent to a landfill, or incinerated. It then moves for grit removal where small stones, sand, and other smaller particles sink into a chamber where they are removed. These first two processes remove the water in the water but it cannot remove all.
At the secondary treatment stage, the bacteria are used to eat up p the remaining small particles in the industrial wastewater and this is through oxygenation of the water after which the water is filtered through very fine filter systems.
Chlorine is then added to the water to kill off the bacteria and the odor remaining in the wastewater. Chlorine kills about 99% of the bacteria that remain in the water after which the excess chlorine is removed and this is through dechlorination and this can be done through the use of ultraviolet lighting.
Some water treatment plants use reverse osmosis, which uses pressure to force the water through filters. These filters remove additional bacteria, remnants of prescription medications that are still present in the water, and any viruses that have made it through.
Additional chemicals are used and then UV lighting helps remove those chemicals. Once complete, you can have your drinking water from industrial wastewater.
What is the air stripping process in industrial wastewater treatment?
Air stripping is the technique of transferring volatile components is a liquid into an air stream. This method is used for the purification of majorly underground water and wastewater containing volatile compounds.
The air containing VOC must be treated in an air treatment system (e.g. active carbon installation, bio-filter).
The main set-up types are the stripping tower or stripping column and the plate stripper. The stripping tower is based on the counter-flow principle, where a vertical column is filled with packing material. The plate stripper is based on the cross-flow principle, where the liquid flow is intensively aerated via a perforated plate.
Advantages and Disadvantages
The stripping process is cheap and reliable and provides relatively good substance transfer. One of the disadvantages of this process is that it is susceptible to pollution.
Air stripping can be implemented in various sectors and a wide volume range. For example;
Air stripping is used for the removal of volatile organic substances, sulfur compounds, and NH3 in both organic and inorganic chemistry.
Air stripping is used in the pharmaceutical sector for the removal of chlorinated solvents from wastewater;
In viscose production, air stripping is the standard technique for the removal of CS2 from wastewater;
In glass engraving with ammonium-based solvents, pH supplementation and air stripping can be used for the removal of nitrogen from wastewater;
In the graphics sector, stripping is used for the removal of toluene from condensate discharged by recuperation systems;
Air stripping is implemented for the removal of chlorinated solvents like Methylene chloride in paint layers from wood.