Friday, April 19

Compressed Air Applications in Water Treatment & Wastewater Treatment

Water Treatment and Wastewater Treatment are essential industries to our world’s environment and its water supply. Whether it is supplying safe drinking water or just purified bodies of water in our environments, water and wastewater treatment facilities are utilizing compressed air every day to provide a more ecofriendly world.

Defining Water & Wastewater Treatment

Water and wastewater treatment are both processes that involve cleaning water so it can be safely reused in the environment. Water treatment is specifically treating groundwater, surface water, and rainwater to clean and disinfect it for use. This type of treatment is used when preparing water for human consumption. Wastewater treatment is the process that treats water that has been contaminated by human activity. This type of treatment is a heavier duty industrial process to clean and disinfect sewage water that requires a high level of sanitation before being released back into the environment.

How Water Treatment Works

Water treatment is a process that takes surface or ground water and purifies it for human use, whether it be for recreational usage, drinking, industrial usage, or filling environmental areas. The Centers for Disease Control and Prevention (CDC) dictates that there are 5 steps to this process:

  1. Coagulation

    This is the first step of water treatment where chemicals, like salts, aluminum, or iron, are added to the water to neutralize any dirt or dissolved particles.
  2. Flocculation

    This step gently mixes the water to help form larger and heavier particles, called flocs. Many times, more chemicals are introduced during this step to encourage flocs to form.
  3. Sedimentation

    Sedimentation is the step when the solids, or focs, are now separated from the water.
  4. Filtration

    This clear water that is now separated from any solids, or flocs, is now filtered again to separate any remaining particles from the water. Various filter materials can be used including sand, gravel, and charcoal. These filters remove any particles, germs, dust, parasites, bacteria, chemicals, or viruses from the water as it travels through. Activated carbon filters can then be used to remove any bad odors as well.
    • Ultrafiltration
      Ultrafiltration can be used in addition to regular filtration. This is where a filter membrane with extremely small pores is used. As the water flows through this membrane, only water and small, safe molecules, such as salts, can travel through. 
    • Reverse Osmosis
      Reverse osmosis is an alternative filtration method used to remove particles from the water by forcing water at high pressures through semi-permeable membranes.
  5. Disinfection

    Finally, disinfection takes the filtered water and adds one or a few chemical disinfectants, like chlorine, to kill any remaining bacteria or viruses. Water treatment plants ensure that any water to be consumed has low levels of this chemical disinfectant before it leaves their facility.

How Wastewater Treatment Works

It is no secret we have a heavily populated planet, with people utilizing water for tons of daily tasks worldwide. Many times, this used water goes to waste and is just discarded when it could be recycled and reused with purpose. In fact, the UN-Water’s 2014 World Water Development Report found that more than 80% of used water is not collected or treated! This means that this wastewater has been discarded and is sitting on Earth in its dirty state, potentially posing a threat to human and environmental health.

Wastewater treatment removes harmful particles from the water so that there is clean, safe water available for our growing populations of humans. The following contaminants are removed during the wastewater treatment process:

Suspended solids: larger pieces of particles that can cause clogs in bodies of water, channels, and other water openings.

Biodegradable Organics (BOD): BOD mixed with oxygen fuel microorganisms to grow and multiply.
Pathogenic Bacteria: These are disease causing organisms that cause issues when ingested by humans.

Nutrients: Nitrates, phosphates, and other nutrients may cause large amounts of algae, seaweed, and other fast growing eukaryotic organisms to form.
Some common elements that fall under these categories are:

  • Nitrogen
  • Phosphorus
  • Inorganic Chloramines
  • Bacteria
  • Viruses
  • Mercury or lead
  • Pharmaceuticals
  • Personal care products like harmful soaps, aerosols, etc.
  • Plastic pollutants
  • Gasoline and oil

Different forms of wastewater treatment purify this wastewater to differing levels of purification with varying intended uses. It is not a one-size-fits-all process.

Types of Wastewater Treatment

Primary Treatment

Primary wastewater treatment is the first level and delivers the lowest level of purification out of the three wastewater treatment types. It is many times considered “mechanical” treatment as it simply removes the suspended and floating solids from the sewage. Chemicals may be introduced into this process for speed and efficiency. This process serves as the first step to the next two wastewater treatment types. About 60% of the suspended solids should have been removed when primary treatment is complete.

Secondary Treatment

Secondary wastewater treatment removes over 90% of the suspended solids in the wastewater, carrying on the process after primary treatment is complete. The sewage/wastewater is aerated in secondary treatment to allow the bacteria to breakdown harmless organic matter. Once aerated, the wastewater moves to another sedimentation tank to eliminate the bacteria completely where the wastewater is disinfected with chlorine and discharged for use. Many wastewater treatment plants end their process with secondary treatment if it has met all the discharge and water quality requirements.

Tertiary Treatment

Tertiary wastewater treatment is the final treatment process that delivers the highest purification of the three wastewater treatment processes. This process is used to provide high quality water to be returned into bodies of water in the environment and sometimes, for human use. This is when inorganic compounds and bacteria are removed, such as nitrogen and parasites. The wastewater will enter a flash mixer where it is purified before being fed through sand filters. These sand filters serve to trap particles that cling together and rid the water of them as it flows through into a chlorine contact tank. The chlorine eliminates microorganisms and is then removed with sodium bisulphite before being discharged for use.

There are many different processes that can be used within each of these treatment stages to accomplish the purification process.

Applications of Compressed Air in Water Treatment Plants

Compressed air equipment is crucial to the water treatment process. Please note that sometimes an air compressor is not the only solution, but rather it’s related equipment like blowers, vacuum pumps, or oil-water separators.

Aeration: Air compressors are utilized to introduce oxygen into the water treatment plants to encourage microorganism growth. These microorganisms are used to break down any organic matter in the water.

Chemical Injection & Mixing: Air compressors use their pressurized air to both push necessary chemicals into the water and mix the chemicals in the water during the water treatment process.

Pneumatic Control: Of course, like many industries, air compressors are used to power pneumatic machinery and control systems. In water treatment plants, these pneumatic systems are used to activate valves, pumps, mixing machines, and other similar equipment.

Membrane Separation: Air compressors are used to power the pressurized filtration process to remove impurities from the water. They do this by supplying pressurized air to membrane separation equipment and machines.

Applications of Compressed Air in Wastewater Treatment Plant

As with water treatment processes, compressed air equipment is also crucial to the wastewater treatment process. Please note that sometimes an air compressor is not the only solution, but rather it’s related equipment like blowers, vacuum pumps, or oil-water separators.

Aeration: Air compressors are used to inject air into the wastewater treatment tanks to break down organic matter and any contaminant.

Back Washing & Filtration: Air compressors supply pressurized air that can pump backwash water in to force loose materials through the filter. They are also used to expand filter beds and utilize their strong pressurization to break up compacted material.

Separation: Air compressors power sludge dewatering equipment that is used to remove water from the sludge.

Sludge Drying: Air compressors are also used to blow dry air over the separated sludge to be able to keep it separated and dispose of it properly.

Desalination: Many forms of wastewater, especially those that come from the sea, are full of salt. Desalination utilizes air compressors to remove any salts or dissolved salts from the water.

Agitation: Compressed air is used to pump air into the tank and mix, or create movement, in the wastewater to prevent sedimentation or other solid particles from settling in the tanks.

Disposal: Air compressors are used to power central vacuum systems that properly dispose of wastewater. Pressurized air drives this wastewater through vacuum systems that can be pumped, collected, and drained to the proper areas.

Tank Cleaning & Maintenance: Like most industries, air compressors are also used for cleaning and maintenance in the wastewater treatment industry. It is specifically helpful to clean out digestion tanks where sludge is mixed with oxygen. Compressed air also helps in mixing these products to encourage gas yield and retention time.

Slurry Pumping: Slurry liquid is the mix of dense solids that are suspended in the water. Air compressors commonly power slurry liquid pumps that ensure slurry stays suspended while traveling through tanks in the facility so it can later be separated with ease.

Suction Pressure: Compressed air equipment, like vacuum pumps, are utilized to provide suction pressure to remove the contaminants and pump them out to designated disposal areas. They also can be used to suction the sewage and wastewater out of the sewage networks to go through the wastewater treatment process.

Purification: Air compressors are used to supply the proper amount of oxygen to properly purify the wastewater. 

Preferred Compressed Air Technology for Both Water & Wastewater Treatment

Oil-Free: Compressors that are 100% oil free ensure that the final water product is contaminant-free and all processes dealing with the air compressor are free of any oil traces. Some water treatment processes require oil free technology, especially when humans are consuming the purified water.

Reciprocating Compressors: Reciprocating compressors generate less heat during the compression process due to the positive displacement technology they use. The crankshaft is the driving mechanism inside the compressor, that drives the piston to compress the air. Both single- and multi-stage options can be beneficial depending on the pressure requirements. Due to the reduction of heat during the compression process, these compressors have a more energy efficient and safe operation.

Rotary Screw Compressors: Rotary screw air compressors also utilizer positive displacement technology but in the form of two helical screws that rotate together, never touching, creating an airtight hydraulic seal. The air that travels through these rotors becomes compressed, creating consistent pressurized air to be used. They offer high reliability and efficiency with generally low maintenance and quieter operations.

Oil-Water Separators: Oil-water separators are used to remove oils found in wastewater that presents a hazard to the environment. Wastewater passes through the separator and its filters where it undergoes treatment to separate oil, water, and sludge. Any heavy particles drop to the bottom while oil passes through the plates within the oil-water separator that collects the oil to be removed from the water.



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