Wastewater Treatment Glossary
Aeration Tank
Aeration is part of the secondary treatment process. Wastewater flowing out of the settling tanks still contains some solids and dissolved materials. Activated sludge is used to create a natural environment where microorganisms use the remaining organic material and nutrients in the wastewater as their food supply.
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Bar Screening
A bar screen (a large metal rack with bars placed at intervals) is located at the beginning of a wastewater treatment plant to remove large trash, sticks, plastic materials and rags. The captured material is then removed and disposed of in the Hartland Landfill.
Biological Aerated Filter Design
The biological aerated filter (BAF) has a 2-3m deep bed of relatively small size filter media, which provides a high surface area on which to grow a biomass. The filter bed is then submerged and the settled wastewater is pumped either upwards or downwards through the filter. A blower sends air through a diffuser at the bottom of the bed which generates bubbles that then rise through the filter and provide a steady stream of oxygen for the biomass.
Biological Oxygen Demand (BOD)
The oxygen that is required to meet the metabolic needs of aerobic (oxygen breathing) microorganisms in water that is rich in organic matter (such as water polluted with sewage).
Biomethane
A mixture of carbon dioxide and methane which is the product of the bacterial decomposition of vegetable and animal wastes.
Biosolids Recycling
Biosolids, dewatered and sanitized sludge, can be applied to land as a valuable soil amendment on crops, or used in land reclamation products and as forest fertilization.
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Carbon Neutral
An activity, such as a development project, with zero net carbon emissions. This is often achieved through carbon off-setting activities which capture an equal amount of greenhouse gases (GHG) as those released through the project. This concept may be extended to include other GHGs, measured 
in terms of their carbon dioxide equivalence; that is, the impact a GHG has on the atmosphere expressed in the equivalent amount of Carbon Dioxide (CO2), such as methane (CH4), or nitrous oxide (N2O). An example of a carbon off-setting activity could be a tree-planting initiative to capture atmospheric carbon, or adopting non-carbon releasing energy practices in lieu of burning fossil fuels. See also Carbon Positive.
Carbon Offsets
Carbon offsets are used to reduce the amount of carbon that an organization or individual emits into the atmosphere. Instead of reducing their own carbon use, they purchase an offset from an independent organization and the money is then used to fund a project that reduces carbon in the atmosphere.
Carbon Postive
The process of offsetting the amount of carbon produced by an activity with other projects, such as tree planting, or carbon reductions through energy efficiency. See also Carbon Neutral.
Collection Sewers
Each house or business that connects to a sewer in the CRD Region has a pipe that is connected to a network of underground pipes and pump stations that carry the wastewater to a processing or treatment facility.
Compact Ballasted Flocculation
A treatment process in which continuously recycled media and various additives are used to improve the settling properties of suspended solids in order to quickly form floating clusters of microbial organisms. As a result, flows can be treated at a significantly higher rate than allowed by traditional unit processes.
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Disinfection
Disinfection of effluent can take place using chlorine or ultraviolet light. Treated effluent water is held in tanks to allow sufficient time for disinfection to occur. With ultraviolet light, water passes through chambers containing ultraviolet lamps; the resulting exposure to high levels of light kills disease-causing bacteria and viruses.
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Ecosystem
A life supporting, interdependent system formed by the interaction of a community of organisms with their environment.
Effluent
Wastewater which has been separated from solids turns into effluent.
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Filtration
In tertiary treatment, a higher degree of treatment is required, so that effluent may be used in irrigation. Filtration occurs with the help of sand and crushed coal, which remove small solid particles.
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Integrated Energy Management
The combined management of solid and liquid waste streams on one site, allowing for maximum 
beneficial reuse and energy recovery. A future energy centre for the Core Area Liquid Waste Management Program could combine biosolids digestion with food waste or fats, oils and greases (FOG); producing a coal substitute and capturing biogas, biomethane and heat. Additionally, processed biosolids could be used as a soil amendment. See also Biosolids Recycling.
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Membrane Technology
Membrane technology separates treated liquid from the bacterial cells grown in solids processing tanks by membrane filtration. Some bacteria may be returned to the biological treatment stage. The rest are sent to solids treatment with the potential of being used as biosolids. See also Biosolids Recycling.
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Odour Control
Foul air can be collected using a variety of means, and odours can be removed using chemical and biological treatments.
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Pumping Systems
Most sanitary sewers move wastewater downhill by gravity to the wastewater treatment facility. In some situations, special pumps are needed to force the wastewater uphill into the facility. Pumps must be able to handle the debris, such as rocks, sand or paper, that wastewater can contain.
Process Control
The operation of complex wastewater treatment plant processes requires monitoring and testing on a continuous basis. A plant's laboratory is used for testing the quality of water as it passes through each process, as well as the sludge quality as it passes through solids handling processes. Lab data is also used to ensure compliance with regulations concerning wastewater in the CRD Region.
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Resource Recovery
Re-use or extraction of resources (e.g. water) or energy (e.g. heat) from a waste stream.
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Secondary Treatment
A level of wastewater treatment beyond primary treatment. Typically involves biological reduction in concentrations of particulate and dissolved oxygen-demanding pollutants.
Settling Tank
Primary treatment settling tanks provide an efficient process for the removal of solids that are heavy and will sink to the bottom, as well as materials that float to the surface, such as oil and grease. Settling tanks are designed to hold wastewater for several hours.
Sludge
In secondary treatment, heavy solids in wastewater fall to the bottom of settling tanks, where they become a thick slurry known as sludge. Sludge is then pumped or trucked to a solids treatment plant where it is processed into biosolids. See also Biosolids Recycling.
Solids Processing
The concentrated solids, or sludge, that are produced in a wastewater plant contain some solids and mostly water. Further dewatering is needed to turn this sludge into biosolids. To do this, settling is first used to further concentrate the solids. Second, the sludge undergoes digestion. Large tanks are 
used to mix and heat the solids. Microorganisms present in the solids use the organic material as a food source and convert it to byproducts such as methane gas. It is this gas, after being processed into biogas, which can be used as another energy source. Digestion results in stabilized biosolids that can be recycled. See also Biosolids Recycling. Filter presses and centrifuges can further dewater the biosolids after they have been digested.
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Thermal Energy
A means, or a flow, of the energy that is moving from one system or state to another. Thermal energy is the difference in temperature that occurs as the energy moves.
Total Suspended Solids (TSS)
Solids in water that can be trapped by a filter. TSS can include a wide variety of organic and inorganic material, such as silt, decaying plant and animal matter, industrial wastes, and sewage. High concentrations can lower water quality by absorbing light, making the water warmer and reducing its ability to hold oxygen necessary for aquatic life. Because aquatic plants also receive less light, photosynthesis decreases and less oxygen is produced.
Triple Bottom Line Analysis
A method to evaluate the cost and benefits of alternatives across a spectrum of social, economic and environmental attributes.
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Water Reuse
Treated effluent can be reused for industrial processes, for irrigation of crops or golf courses, and even as a non-potable water source for toilet flushing in homes and institutions. Reclaimed water that is used for irrigation can provide valuable nutrients, such as nitrogen and phosphorus, to the crops being grown.
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