Wastewater treatment: Industrial facilities generate significant amounts of wastewater with specific chemicals or process content. This is called industrial wastewater. Leaving industrial wastewater in the nature is very dangerous and vulnerable, so we need to treat industrial wastewater separately, or to remove and purify some of its impurities and then enter the municipal wastewater treatment system.
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Primary treatment: The purpose of primary treatment is to remove settleable and suspended solids, which is traditionally done by mechanical methods.
They may also be supported by chemicals, i.e. polymers that bind organic wastewater solids together and make them easier to remove.
The principles governing primary treatment are filtration, gravity and sedimentation. In conventional wastewater treatment plants, gravity and sedimentation are used to remove suspended solids.
Dense sewage solids sink to the bottom of the basin or tank, while lighter particles float to the top.
These solids are then skimmed or scraped and separated from the rest of the wastewater. This removed sludge is called raw or primary sludge and goes to sludge treatment while the effluent goes to secondary treatment.
Secondary or biological treatment
It removes carbon, nitrogen and phosphorus in the wastewater in the form of solution or particles.
Conventional biological treatment usually uses an aeration process to grow microorganisms in the wastewater, followed by a secondary sedimentation or clarification step.
This process was also known as activated sludge process at the beginning of a century ago. Today, the term “activated sludge process” can be used to describe most of the biological processes in wastewater treatment that use air or oxygen to produce a mass of microorganisms and other wastewater solids.
Secondary treatment based on the activated sludge process works as follows: Microorganisms that naturally exist or are seeded in the wastewater.
They are exposed to atmospheric air or pumped with air or oxygen. This is usually done in an aeration tank or pond.
Oxygen helps these microorganisms to produce and consume certain organic solids (fats, sugars, and other biodegradable components of food and human waste) in the wastewater.
Through reproduction, microorganisms and other organic solids become denser and form biological clots.
It then settles or suspends more easily and is separated as secondary sludge or “waste activated” (WAS) in the secondary sedimentation or clarification step.
WAS or secondary sludge goes to sludge treatment, effluent is milled or disinfected.
Tertiary wastewater treatment
Effluent from disinfection and secondary filtration treatment is usually free of dense solids or sludge
This leads to disinfection and filtration steps, sometimes referred to as “extraction” or “tertiary treatment”.
The purpose of disinfection and filtration is to ensure that wastewater before discharge into the environment
or reuse by municipalities for agricultural purposes, toilet flushing, cooling, etc., with concentrations of
It is not harmful to pathogenic microorganisms or toxic compounds.
Several processes and technologies can perform disinfection. Compounds and chemical reactions with ozonation and chlorination form insoluble compounds
which can destroy and filter microorganisms. In the case of UV rays, the radiation is used to destroy the genetic makeup of microbes.
Filtration uses a variety of filtration media to absorb insoluble compounds.
Filtration technologies include sand filters, strainers, gravity and rapid pressure filters, granular media filters, and membrane filters.
Sludge treatment in industrial wastewater
Sludge is rich in nutrients and resources, but like wastewater before disinfection and filtration, it contains harmful microorganisms and other particles that can disrupt the natural environment.
It is primarily treated to reduce these pathogens and compounds before storage or reuse.
Sludge treatment also serves to stabilize or reduce organic matter in the sludge that is naturally converted to gases (methane and carbon dioxide) in the atmosphere.
It reduces the final volume and usually the processing costs of the companies. and products and by-products of the treatment process that can be used or sold to partially offset the costs of sludge treatment.
Ideally, the sludge from primary and secondary treatment is subjected to modern sludge treatment to recover nutrients and biogas, reduce pathogens and reduce the volume of biosolids.
However, in many cases, sludge is dehydrated (and possibly calcified) before disposal or land application.
Some wastewater treatment plants can use the sludge to produce fertilizers and high-quality soil products (called Class A biosolids in the US).
