Not everyone is a water engineer. If you’re not, this section sets out a few useful definitions and concepts.


Algae are a diverse group of aquatic organisms that include photosynthetic protists, which use sunlight to produce the energy needed for their growth. Algae come in many shapes and sizes, and they can range from microscopic single-celled organisms to large macroscopic seaweeds. They live in a variety of aquatic environments, including oceans, lakes, rivers, swamps, and even the mud or gravel at the edge of a lake or stream. Algae can produce oxygen, fix nitrogen, and create energy for food webs as they photosynthesize, making them a key primary producer in aquatic and marine environments.

Algaewheel® is a cleantech biological wastewater treatment solution. It is the engine of an algal wastewater treatment plant capable of removing nutrients and cleaning water to high reuse standards.

Algal technology is the use of algae to produce both energy and other commodities such as biofuels, chemical feedstocks, pharmaceutical products, and dietary supplements. Algae are a promising source of renewable energy because they can produce a variety of energy products from simple carbon dioxide, sunlight, and water, with the only byproducts being oxygen. Additionally, algae can be cultivated in a variety of environments, both terrestrial and aquatic, and can also be used to treat wastewater and other contaminated water sources.

Aeration is the process of bringing air into a mix or environment to increase oxygen content. It is commonly used in soil preparation and water treatment to reduce odors and improve root growth. Aeration also helps with drainage and strengthens the overall structure of the soil.

Conventional Activated Sludge (CAS) is a method used to treat wastewater in municipal and industrial settings. It is based on aerating wastewater to promote the growth of microorganisms responsible for digesting and breaking down organic pollutants. The process is typically carried out in a large tank or basin called an activated sludge reactor, which combines biological and mechanical processes to convert pollutant levels to acceptable standards before discharged into the receiving environment.

Carbon dioxide is the most commonly produced greenhouse gas. Carbon sequestration is the process of capturing and storing atmospheric carbon dioxide. It is one method of reducing the amount of carbon dioxide in the atmosphere with the goal of reducing global climate change.

Algaewheel uses biological carbon sequestration. Biological carbon sequestration is the storage of carbon dioxide in vegetation such as algae, forests, as well as in soils and oceans.

The amount of organic matter present in water can be calculated by measuring the bacteria’s Biological Oxygen Demand (CBOD5), being the oxygen needed by bacteria to decompose the organic (carbon) matter in a 5-day period. A high CBOD5 level means that there is a high level of organic waste present. If the treated wastewater discharged by a treatment plant has a high content of organic components, bacteria in it will demand more oxygen from the waterway, leaving the water with less oxygen to support life. In excess, the waterway will become stagnant, adversely affecting aquatic life. 

Clean Development Mechanism (CDM) is an international emissions trading program which was introduced and adopted through the Kyoto Protocol. The program allows countries with emissions reduction commitments (Annex B countries) to meet their commitments by investing in emissions-reduction projects in non-Annex B countries which will result in a net reduction of global emissions. CDM projects are typically designed to reduce emissions of one pollutant (or a basket of pollutants) for a given amount of money or effort. The CDM enables Annex B countries to purchase these emissions reductions from non-Annex B countries. These reductions can then be used to meet emissions reduction targets of the Annex B countries.

Clarification is a process used in water treatment that involves the removal of suspended solids, flocculated particles, and microorganisms from raw water. The process helps to improve the water quality and reduces downstream processing requirements. Clarification generally involves the use of physical treatment techniques such as flocculation, settling, or filtration.

Coagulation is a process that is used in the treatment of drinking water. It involves the addition of chemicals, such as alum, ferric chloride, or polyelectrolytes, to the water to form insoluble particles called flocs. The flocs then settle out and are removed from the water. This process helps to remove impurities and reduce turbidity.

1mt of CHis equivalent to 25mt of CO2 expressed as 25mt CO2e

Carbon Dioxide equivalent

Disinfection in water treatments is the process of killing or greatly reducing the concentration of harmful bacteria, fungi, and parasites in water. It is done by adding chemical disinfectants such as chlorine, ozone, or ultraviolet light to the water. This process is used to reduce the risk of waterborne diseases.

Filtration in water treatment is a process that involves passing water through a filter or other porous material to remove impurities that could be harmful when consumed or used. This process is used for both domestic water treatment and industrial water treatment. Impurities can range from physical particles such as sand and silt to organic compounds from industrial processes, or dissolved metals such as lead, mercury, or arsenic.

Flocculation is a process that is used in water treatment to combine smaller, suspended particles into larger clumps so that they can be more easily removed from the water. These larger particles, or “flocs”, are then removed from the water by operating filters or settling basins. This process is used to clean polluted bodies of water by removing pollutants and microorganisms.

Greenhouse gasses refer to atmospheric concentrations of carbon dioxide, methane and nitrous oxide. Greenhouse gases are gases that trap heat in the Earth’s atmosphere. These gases absorb energy from the sun and re-radiate it back towards the Earth’s surface, which warms the atmosphere. This process, called the greenhouse effect, keeps the planet’s surface much warmer than it would be without these gases.

Human activities are the main driver of increases in these gasses which together are referred to as greenhouse gasses as they have given rise to sharp increases in global temperatures. The changing climate has given rise to extreme weather events including droughts which are having a serious impact on water security around the world.

GHG, including carbon dioxide, methane, nitrous oxide, and sulfur dioxide, are released as wastewater is treated with processes such as activated sludge, trickling filters, and biological aerated filters, and contribute to global warming. Technologies and processes to reduce these emissions exist, such as biological carbon sequestration or wetland technology, and wastewater treatment plants are encouraged to utilize them.

Membrane processing is a type of water treatment where water is forced through a membrane in order to remove suspended solids, organic materials, and other impurities. This type of process generally uses a pressure-driven process that works on the concentration differences between the feed water and the concentrated reject stream. Membrane processes possess many advantages, such as high purification levels, ease of operation, and low maintenance. These processes are used in a variety of water treatment applications, including industrial processes and wastewater treatment.

MBBR is an acronym for Moving Bed Biofilm Reactor, a type of wastewater treatment system. It is most commonly used in systems where considerable amounts of organic materials are present. The system works by creating an environment where microbes can attach to a medium, forming a biofilm which can then break down and remove organic materials from the wastewater.

Nature-based solutions is the sustainable management and use of natural features and processes to tackle socio-environmental issues. These issues include climate change (mitigation and adaptation), water security, water pollution, food security, human health, biodiversity loss, and disaster risk management. 

The European Commission’s definition states that these solutions are “inspired and supported by nature, which are cost-effective, simultaneously provide environmental, social and economic benefits and help build resilience. Such solutions bring more, and more diverse, nature and natural features and processes into cities, landscapes, and seascapes, through locally adapted, resource-efficient and systemic interventions”.

The National Pollutant Discharge Elimination System (NPDES) is a US federal program that regulates water pollution caused by discharges into waterways from point sources. Point sources are any identifiable source of pollution, such as sewage treatment plants, factories, industrial sites, and farm operations. The NPDES requires these dischargers to obtain permits that authorize and monitor their pollution discharges. It also regulates discharges of pollutants into streams, lakes, wetlands, and other surface waters, and also prohibits the import of pollutants into navigable waters from other sources.

Nitrous oxide, more commonly known as laughing gas, is used in water treatment to kill bacteria, viruses, and other microorganisms. It is also used to reduce the nitrate concentration in water. Nitrous oxide functions as an oxidizing agent and works by converting nitrate into nitrogen and water. In addition, it breaks down harmful substances such as hydrocarbons and other chemical pollutants.

1 metric tonne of nitrous oxide is 235 times more damaging to the atmosphere than 1 metric tonne of carbon dioxide

pH stands for potential of Hydrogen and is a measure of the acidity or alkalinity of a solution. It is measured on a scale of 0 to 14, with 7 being neutral. A solution with a pH less than 7 is acidic, while a solution with a pH greater than 7 is alkaline.

The pH of commercial water treatment systems can vary depending on the source water being treated and the treatment methods used. Generally, commercial water treatment systems aim to achieve and maintain a balanced pH of 7.0 – 7.5.

Phosphorus removal is a process used in water treatment plants to remove phosphates from wastewater or surface water. This process conventionally involves adding chemicals such as alum, lime, iron salts, or polymers to a water sample and allowing it to settle out, creating a precipitate of phosphate minerals. The sediment is then removed in a filtration or sedimentation step. This process is used to reduce the levels of phosphate in the water, which can be an excess pollutant that can cause eutrophication.

RAC (Rotating Algal Contactor) is an innovative water treatment technology. This technology uses algae-covered discs that rotate or spin inside a basin or raceway to clean and purify water. The algae removes and uptake pollutants, such as suspended solids, nutrients, organic matter and heavy metals, from the water. The rotating discs provide a laminar flow which provides an optimal environment for algal growth and removal of pollutants. The algae is then separated from the water and the clean water is then discharged.

Reflects the effectiveness of converting ammonia into nitrate 

Reverse osmosis is a water purification process that uses a membrane to remove dissolved salts, bacteria, and other impurities from water. The process works by applying pressure to a concentration gradient, forcing water molecules through a membrane that allows only smaller molecules to pass through. This process leaves behind contaminants, which are then flushed away.

Sludge (or biosolids) are the solid organic matter produced by private or municipal wastewater treatment systems that need stabilisation and disposal. It can consist of a variety of organic and inorganic materials such as bacteria, viruses, algae, protozoa, metals, and non-metals like phosphorus and nitrogen, which are all found in wastewater. Sludge is generated when wastewater is treated using physical, chemical and biological processes. Sludge needs to be managed and disposed of properly in order to protect public health and the environment.

Supernatants in water treatment are the remainder liquid that remain after sedimentation. This liquid includes dissolved chemicals that have been released from within the water, as well as from any additional drugs or chemicals used during the treatment process. The supernatant also contains suspended solids, which must be removed prior to the water being used.

Where all forms of nitrogen are also measured and regulated 

A measure of water clarity. 

Ultraviolet (UV) water treatment is a process used to disinfect water or wastewater with ultraviolet light. UV light can kill certain bacteria, viruses, and other microorganisms in water. UV treatment is used for both drinking water and wastewater. In the treatment of drinking water, it is often used in conjunction with other water filtration systems, such as reverse osmosis. In wastewater treatment, UV treatment is often used as the final disinfectant step.

VCU’s, also known as verified carbon credits, are tradable certificates that represent the right for a company or individual to emit one tonne of carbon dioxide (CO2) for a given period of time. They enable companies, governments, and other organizations to invest in sustainability and reduce their environmental impact by paying for emissions reductions elsewhere. Organizations often invest in these credits in order to offset or reduce their own emissions. The credits can be used as part of national or international emissions trading schemes, or may be traded in a voluntary carbon market.

Water re-use is the process of taking water that has either been used once for domestic, industrial, agricultural, or recreational purposes and treating it so that it can be used again either in the same application or for a different purpose. This allows for conservation of water and other resources and can help to reduce the impact of drought cycles.

Water treatment plants are facilities designed to treat water for drinking, irrigation, industrial use, or other purposes. The process of treating water typically involves the removal of pollutants and contaminants to make it safe for human consumption and use. This is usually accomplished by piping the contaminated water through multiple stages, such as flocculation, sedimentation, and filtration, in order to remove contaminants and by-products.

Watershed management is the practice of managing activities within the boundary of a watershed to improve water quality and reduce potential impacts on the environment. It involves the management of land, water, vegetation, and other features, with a goal to reduce sedimentation, enhance nutrient retention, conserve and improve wildlife habitats, and improve water conservation, water supplies, air quality and recreation opportunities. Watershed management is often critical in water treatment, as it helps prevent or reduce water pollution and protects water sources.