Aerobic Water Treatment

What is aerobic wastewater treatment?

Aerobic wastewater treatment uses oxygen, microorganisms and bacteria to break down organic pollutants and nutrients (like phosphorous and nitrogen).

A mechanical aeration device, such as a compressor or air blower ensures oxygen is continuously mixed with the wastewater as part of this biological treatment process. The aerobic microorganisms feed on the organic waste in the water and convert it to biomass, water and carbon dioxide, effectively treating the pollutant.

Aerobic treatment is the opposite of anaerobic wastewater treatment, which operates in an oxygen free environment, and is used to generate biogas.

What is aerobic wastewater treatment used for?

Aerobic treatment is usually the main part of the wastewater treatment process after larger solids have been removed from the wastewater, or the secondary treatment following anaerobic treatment. Aerobic treatment processes are a reliable and efficient method for removing contamination from organic wastewater to produce high quality effluent that can safely and compliantly be discharged to main sewers or the environment. Alternatively, it can be passed through further treatment for reuse.  

Aerobic water treatment is particularly effective in industries with high levels of organic wastewater such as food and beverage, pharmaceutical and municipal.

What are the main types of aerobic water treatment?

Activated sludge (AS)

Activated sludge processes are commonly used in municipal applications for wastewater treatment. Wastewater enters an aeration tank where aerobic microorganisms break down organic material, forming flocs. These flocs settle in a separate tank, and settled solids are recycled to maintain suspended solids levels, while excess solids are disposed of as sludge.

Fixed bed bioreactors (FBBR)

Fixed bed bioreactors are tanks with chambers filled with porous material such as plastic media carriers. Wastewater flows through the chambers, forming a layer of microorganisms, promoting biofilm formation that reduces sludge and waste disposal costs. The system can be customised for processes like filtration and nitrification, making it suitable for specific wastewater treatment needs.

Moving bed bioreactors (MBBR)

Moving bed bioreactors use aeration tanks with freely moving plastic biofilm carriers. These carriers come in different shapes and sizes depending on the removal needs, and they enable the treatment of high Biochemical Oxygen Demand (BOD) wastewater in a compact space. Sludge is easily separated from the wastewater in a separate tank after the MBBR.

Membrane Bioreactors (MBRs)

MBRs are becoming increasingly utilised in water and wastewater applications when there is limited space or a need for high-quality treated water. They are an advanced wastewater treatment option which combines the best elements of activated sludge and membrane filtration to separate out suspended solids and recycle them.

Biological trickling filters

These filters work by passing wastewater through a medium designed to collect a biofilm created its surfaces that contain microorganisms to break down organic contaminants in the water. It is a simple and economical treatment method combined with further treatment for solids removal.

What are the benefits of aerobic water treatment systems?

  • Fast and efficient organic matter and nutrient removal
  • Odour prevention
  • Flexibility and adaptability
  • High quality effluent

Overall, aerobic wastewater treatment offers efficient and effective removal of pollutants, improved water quality, and the ability to adapt to different wastewater compositions, making it a widely used and preferred method in many industries.

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Improving efficiency of aerobic water treatment systems

As the aerobic water treatment process requires a constant supply of oxygen to be passed through the water, this results in high energy demands. To keep energy costs manageable regular maintenance, cleaning and monitoring is essential to ensure efficiency and maximise the lifespan of equipment.

The good news is that some modern membrane systems have sophisticated systems that operate Cleaning in Place (CIP), which allows for regular self-cleaning.   However, many in-house systems are often poorly optimised, due to complexity of programming the equipment. In recent years we have helped a number of customers reduce energy, cleaning and chemical costs significantly through review and optimisation of their equipment and processes. Read more about this in our guide to water filtration and membrane maintenance.

An increasing number of wastewater treatment plants are also incorporating anaerobic digestion into the treatment process, prior to aerobic treatment, as this generates biogas to provide energy to power operations.

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What is the difference between aerobic and anaerobic water treatment?

The choice between aerobic and anaerobic treatment depends on elements such as the composition of the wastewater, treatment objectives, desired effluent quality, and specific environmental and regulatory requirements.

These process can also be combined in sequence or parallel to achieve comprehensive wastewater treatment based on specific goals.

  • The main difference is the availability of oxygen in the process. Aerobic treatment required oxygen to be present, whilst anaerobic treatment requires it to be absent.
  • The output is different. An aerobic process results in production of biomass, heat loss and treated effluent. Anaerobic digestion produces treated effluent, heat, biomass and biogas.
  • Both processes produce sludge that can be used as fertiliser after further treatment. Anaerobic sludge can also be provided to other plants for biomass injection to boost performance or to start a new reactor.

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