Glossary of Terms

Aeration Chamber: The air diffusers blow the air around, encouraging the bacteria to grow, breaking down the solids

Activated Sludge: A microbial mass of bacteria, protozoa and other micro-organisms with a significant proportion of inert debris, produced when sewage is continuously aerated. Part of the still active sludge is returned to the raw sewage (hence the term activated) and the balance sent for disposal.

Aerobic: In the presence of air (free oxygen). Aeration tanks are aerobic as a result of the introduction of air.

Air gap: A physical break between the lowest level of the water inlet and the maximum fault level of an appliance, installation, feed pipe, or an inlet

Alkalinity: A measure of the buffering capacity of water. That is, the ability of water to maintain pH. Waters with high alkalinity are well buffered and because of this provide a more consistent habitat for sensitive bacteria. Water with low alkalinity is poorly buffered and subject to potentially toxic pH swings. Nitrifying bacteria need an alkalinity of at least 30-50 mg/L to remain active.

Ammonia (NH3): A form of nitrogen. In wastewater, ammonia is typically present as ammonium. Ammonia is created by the breakdown of the organic nitrogen forms of urea and faecal material.

Ammonification: An anaerobic biological process that converts organic nitrogen to ammonia.

Anaerobic: Absent air.

Anoxic: Minimal air: not enough to support aerobic treatment, but too much air to allow for anaerobic bacteria (anaerobes) to thrive.

Back-up supply: Supply of potable water that can supplement the non-potable supply when required

Bespoke: Made to individual order; custom made

Biofilm: Surface coating that is the active bacteria

Biological Treatment: A form of waste processing facility using anaerobic digestion

BOD: Biochemical Oxygen Demand. A measure of organic pollution. The amount of oxygen a sample of water will consume over a period of five days. Nitrifying bacteria thrive in environments low in BOD; denitrifying bacteria need a high BOD loading to live.

Carbonaceous bacteria: Break down carbon-based solids

Cistern: A fixed container for holding water to be used as part of a plumbing system

Coagulate: (of a fluid, esp. blood) Change to a solid or semisolid state. Cause (a fluid) to change to a solid or semisolid state: "epinephrine coagulates the blood".

COD: Chemical Oxygen Demand

Code for Sustainable Homes: A single, national standard for sustainable homes. The code uses a sustainability rating system to communicate the overall sustainability performance of a home.

Coliform: Bacteria found in the intestines, faeces, nutrient-rich waters, soil and decaying plant matter

Consent Standards: The quality of effluent as permitted by the environmental agency

Cross-contamination: Contamination resulting from the connection of pipes carrying mains water to pipes carrying non-potable water

DAF: Dissolved Air Flotation

De-nitrification: The biological conversion of nitrate (NO3) to nitrogen gas (N2).

Desludge: The process of removing sediments by draining and cleaning a tank

Down pipes: Pipes leading down from roof guttering to drains

DWF: Dry Weather Flow

EN 12566-3 - For packaged underground sewage treatment units under 50 persons sold in most of Europe. The EN12566-3 is also required for CE marking

EPP2 – Environmental Permitting Programme Phase 2 – Is part of a continuing government programme designed to improve the regulations and administrative costs concerning environmental protection and health issues.

F:M Ratio: Food to Microorganism Ratio. An expression used to describe the quantity of organic waste that bacteria consume during the wastewater treatment process. The higher the F:M Ratio, the more BOD that exists for every unit of Mixed Liquor.

Fermentation: Incomplete anaerobic digestion that produces volatile fatty acids (VFAs).

Flocculent: A substance that promotes the clumping of particles, esp. one used in treating waste water

Flows and Loads: The sizing criteria and treatment capacity of sewage treatment plants

Grease Management: Preventing the build up of grease and fat in drains

GRP: Glass Reinforced Plastic

HiPAF: High Performance Aerated Filter

Hydrolysis: Another word for Ammonification.

Influent: Water entering the sewage treatment system from the property in question

IPC: Integral Pump Chamber

Legionella: A bacterium named Legionalle pneumophila that can cause legionnaire’s disease (lung infection)

MCRT: Mean Cell Residence Time. An expression used to describe the average age of bacteria in a wastewater treatment plant. Similar, but not identical to Sludge Age.

Mg/L: Milligrams per Litre. A metric measure of concentration. Because one litre of water weighs 1,000,000 milligrams, one mg/L is equivalent to one part per million, PPM.

MGD: Million Gallons per Day. A measure of flow. Wastewater flows are typically reported in “millions of gallons per day.” Much like the term “miles per hour,” MGD is used for any period of time: week, day, hour, or even instantaneous.

Mixed Liquor: The bacteria in an aeration tank.

MLSS: Mixed Liquor Suspended Solids. A measure of concentration of the bacterial population in a wastewater treatment plant aeration tank that includes organic and inorganic matter.

MLVSS: Mixed Liquor Volatile Suspended Solids. A more precise measure of concentration of the bacterial population in a wastewater treatment plant aeration tank that includes organic matter only.

Nitrate: A form of nitrogen. In wastewater, nitrate is created by the aerobic breakdown of ammonia.

Nitrification: The biological conversion of ammonia (NH3, NH4) to nitrate (NO3).

Nitrite: A form of nitrogen. In wastewater, nitrite is an intermediate chemical compound that is formed during nitrification and denitrification. Chlorination disinfection becomes difficult when effluent contains any nitrite.

Nitrogen Gas: A form of nitrogen. In wastewater, nitrogen gas is by the anaerobic breakdown of nitrate. Nitrogen gas bubbles into the atmosphere. Air is primarily nitrogen and a lesser amount oxygen.

Nitrogen: The chemical element “N.” Nitrogen exists in any number of chemical forms: organic-Nitrogen, ammonia, nitrite, nitrate, and nitrogen gas.

Non-return valve: A pipe fitting that limits flow to one direction only

ORP: Oxygen Reduction Potential. The ORP meter is an instrument for measuring biochemical activity. Positive ORP reading are generally indicative of aerobic conditions; negative ORP readings generally indicate anaerobic conditions.

Ortho-Phosphate: The most common form of phosphorus in wastewater. Can be expressed “as PO4” or “as P.”

Package Wastewater Treatment Plant: A sewage treatment plant fabricated at a factory and taken to site as complete units ready to use after installation

PAO: Phosphate-Accumulating Organism. Bacteria that provide biological phosphorus removal.

Pathogen: Any disease-producing agent, especially a virus, bacterium, or other microorganism.

Peak Flow: Maximum flow for a short period only. Usually expressed as a multiple of DWF

Permeable pavements: Pavements that allow water to drain through paved surfaces rather than running off into drains

pH: Hydrogen Ion Concentration

Phosphate: A group of phosphorus chemicals of which ortho-phosphate is by far the most common in municipal wastewater treatment.

Phosphorus: The chemical element “P.” Phosphorus exists in any number of chemical forms; however in wastewater the most common form by far is phosphate, specifically ortho-phosphate.

Population Equivalent (PE): Persons living/working/visiting a property

Potable water: Water suitable for human consumption that meets the requirements of Section 67 of the Water Industry Act 1991 [7]

Potable: Suitable for drinking.

PPM: Parts per Million. A measure of concentration. Ten thousand “parts per million” equals one percent.

Primary Treatment: The first major stage of sewage treatment in sewage works, usually involving removal of settleable solids

Public mains water: Wholesome water supplied by a water undertaker, licensed water supplier, Scottish Water or the undertaker as specified in the Water Industry Act 1991 in England and Wales, the Water (Scotland) Act 1980 [8] in Scotland, or the Water and Sewerage Services (Northern Ireland) Order 2006 [9] in Northern Ireland.

Quiescent: Being quiet, still, or at rest; inactive.

Rainwater guard: Small scale garden water storage container that collects rainwater from the roof via the drainpipe

Rainwater Harvesting: The process of collecting rainwater from the roof area of a property, filtering it, and pumping it back to the home and/or garden for use in non-potable applications.

Rainwater: Water resulting from atmospheric precipitation

Rodent barrier: Device on the holding tap overflow pipe to prevent rodents entering into the holding tank

Rota-moulded: Produced by use of polymer powder, tumbled inside the mould to produce stress free parts

Run-off: Water falling on a surface but flowing into a downpipe, drainage channel or surface water rather than permeating the ground

SAF: Submerged Aerated Filter. A form of biological filtration where the medium is completely immersed in an aerated stream of settled sewage to achieve biochemical treatment.

Secondary Treatment: The treatment of sewage by bacteria under aerobic conditions during which organic matter in solution is oxidised or incorporated into cells which may be removed by settlement

Sewage: The water borne wastes of a community

Sewerage: A system of pipes and structures for the collection and transportation of domestic and industrial wastewater

Sewage Treatment: The process of collecting sewage water from the home, filtering contaminants and treating it before pumping the environmentally safe water to a soakaway, water course or ditch.

Sludge Age: An expression used to describe the average age of bacteria in a wastewater treatment plant. Similar, but not identical, to MCRT.

Soakaway: A drainage arrangement (i.e. a pit) in permeable ground to which surplus surface water is fed and from which it soaks into the ground

SuDS: Sustainable drainage measures which alleviate flood risks both at a development site and elsewhere in the catchment

SUR1: Code for Sustainable Homes Category 4 - Surface Water Run-Off (Sur 1)

Suspended Solids: N sewage analysis, those solids retained after filtration either through filter or by centrifugation.

Telemetry: Wireless data transfer

Total – Phosphorus: A sum of all phosphorus components.

Total-Nitrogen: The sum of TKN (ammonia plus organic-nitrogen), nitrate and nitrite.

Treated Effluent: Water that has been treated by a sewage treatment system and flows from it to a soakaway, water course or ditch

TSS: Total Suspended Solids. A measure of particulate pollution, TSS describes the amount of particulate matter than can be filtered out of water.

UKRHA: UK Rainwater Harvesting Association

VFAs: Volatile Fatty Acids. Compounds formed during anaerobic fermentation that are useful as carbon sources for denitrification and as a treatment aid for biological phosphorus removal. The most common VFAs are acetic acid, propionic acid, and butyric acid, isobutyric acid, valeric acid, and isovaleric acid.

Wastewater: Water that has been used in washing, flushing, manufacturing, etc

WAT1: Code for Sustainable Homes Category 2 - Water Internal Use (Wat 1)

WAT2: Code for Sustainable Homes Category 2 - Water External Use (Wat 2)

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