View all publications


Term Definition For more details see
Aerated wastewater treatment system (AWTS)

Small domestic wastewater treatment package plants commonly used for on-site treatment of household wastewater. The process typically involves:

  • settling of solids and flotation of scum
  • oxidation and consumption of organic matter through aeration
  • clarification (secondary settling of solids)
  • disinfection if followed by surface irrigation.
AS/NZS 1547:2000
Aerobic Conditions in which free oxygen (including dissolved oxygen in water) is readily available to micro-organisms such as bacteria.  
Anaerobic Conditions in which there is an absence of free oxygen (including dissolved oxygen in water) for micro-organisms such as bacteria.  
Bioaccumulation The accumulation by organisms of contaminants through ingestion or contact with skin or respiratory tissue; the net accumulation of a substance by an organism as a result of uptake from all environmental sources. As an organism ages, it can accumulate more of these substances, either from its food or directly from the environment. Bioaccumulation of a toxic substance has the potential to cause harm to organisms, particularly to those at the top of the food chain.
Biogas Principally methane and carbon dioxide produced by bacterial fermentation of organic matter.  
Biological treatment Forms of wastewater treatment such as trickling filters, contact beds and activated sludge in which bacterial biochemical action is intensified to oxidise and stabilise, the unstable organic matter present.  
Biosolids The material that remains after sludge and septage are stabilised biologically or chemically Guidelines for the Safe Application of Biosolids
to Land in New Zealand ©
New Zealand Water
Envrionment Research Foundation 2003
Blackwater Human body waste discharged either direct to a vault toilet, or through a water closet (flush toilet) and/or urinal.  
BOD Biochemical oxygen demand – the quantity of oxygen used in the biochemical oxidation of organic matter in a specified time, at a specified temperature and under specified conditions.  
BOD5 The oxygen demand associated with biochemical oxidation of carbonaceous, as distinct from nitrogenous, material. It is determined by allowing biochemical oxidation to proceed, under specified conditions, for 5 days.  
Centralised wastewater systems An urban wastewater infrastructure that takes wastewater from the source and reticulates it though pipes (sewer system) to a large central wastewater treatment plant. After the treatment plant, the treated effluent and the sludge (biosolids) are discharged into the environment at a specific location.  
Chemical treatment A wastewater treatment process designed around the chemical qualities of the wastewater and its constituents.  
Chlorination Application of chlorine to water or wastewater for disinfection or chemical oxidation of organismsby oxidising cellular material. Chlorine can be supplied in many forms, including chlorine gas, hypochlorite solutions, and other chlorine compounds in solid or liquid form. USEPA website
Clarifier A tank or basin for the purpose of reducing the concentration of suspended solids in a liquid.  
Cluster wastewater system A wastewater collection and treatment system where two or more dwellings, but less than an entire community, are served. The wastewater from each group of dwellings may be treated on-site by individual septic tanks before the septic tank effluent is transported through alternative sewer systems to a nearby off-site location for further treatment and ecosystem re-entry. In other situations the full wastewater flow from each group of dwellings may be reticulated off-site to a local treatment and ecosystem re-entry location.  
Coagulation In water and wastewater treatment, the destabilisation and initial aggregation of colloidal finely divided suspended matter by the addition of a floc-forming chemical (coagulant), or by biological processes.  
Coliform group bacteria A group of bacteria predominantly inhabiting the intestines of humans or animals, but also occasionally found elsewhere. It includes all aerobic and facultative anaerobic, Gram-negative, non-spore-forming bacilli that ferment lactose with production of gas.  
Composting toilets Toilets in which human waste (blackwater) is collected, stored and biologically degraded (composted) by predominantly aerobic micro-organisms. They require little or no water. USEPA website
Constructed wetlands Wetlands designed and constructed specifically for the treatment of wastewater.  
Cryptosporidium A single-celled parasite that lives in the intestines of animals and people. This microscopic pathogen causes a disease called cryptosporidiosis Water Quality
Information Centre
Decentralised wastewater management Where all decentralised wastewater systems are under the management supervision of a single management entity, which may be a public authority, a body corporate or other private agency. USEPA website
Decentralised wastewater systems A group of on-site and/or cluster systems where wastewater is treated and returned to the ecosystem, either on the property or on local land areas. The group of such servicing systems can be managed collectively by a single management agency under a decentralised wastewater management (DWM) programme.  
Denitrification The reduction of nitrates to nitrogen gas and oxides of nitrogen, usually under anoxic (without oxygen) conditions.  
Detention time The theoretical time required to displace the contents of a tank at a given rate of discharge.  
Digested sludge Sludge digested under aerobic or anaerobic conditions until the volatile content has been reduced to the point at which the solids are rendered less offensive and relatively non-putrescible.  
Digestive tanks See Improved septic tanks.  
Disinfection The destruction of the larger portion of micro-organisms in or on a substance with the probability that all pathogenic bacteria are killed by the agent used. AS/NZS 1547:2000
Dissolved oxygen The oxygen dissolved in water wastewater or other liquid, usually expressed in mg/L or percent saturation. Abbreviated DO.  
Domestic wastewater Wastewater derived principally from dwellings, business buildings, institutions and the like and consisting of toilet wastes, and washwaters from kitchen, bathroom and laundry, but excluding commercial laundry wastes.  
Dose loading This usually refers to the method of loading from a treatment plant to the ecosystem re-entry system such as a seepage trench. Dose loading is achieved by a pump (usually activated by a float switch) or a siphon system.  
Ecosystems Communities of interacting organisms and the physical environments in which they live. Therefore, by definition, the human species and their built facilities, services and infrastructure are not separate from but are interdependent and integral parts of ecosystems.  
Ecosystem services …the conditions and processes through which natural ecosystems, and the species that make them up, sustain and fulfil human life. They maintain biodiversity and the production of ecosystem goods such as seafood, forage, timber, biomass fuels, natural fiber and many pharmaceuticals, industrial products and their precursors 20  
Effluent The liquid discharged from a wastewater system component.  
Escherichia coliform (E. coli) One of the species of bacteria in the coliform group. Its presence is considered indicative of fresh faecal contamination.  
Evapo-transpiration The process by which water in the soil matrix is both transpired through the roots and foliage of vegetation and evaporated from exposed (soil) surfaces.  
Evapo-transpiration – seepage (ETS) beds/trenches In ETS beds or trenches the treated wastewater liquid component is returned to the local ecosystem through processes of evapo-transpiration (to the atmosphere) and seepage into the sub-soils.  
Faecal coliform Bacteria present in waste from warm-blooded animals and used as an indicator of human-derived pollution.  
Faecal streptococci Often used interchangeable with enterococci, but should indicate only one group of streptococci included in the total enterococci group.  
Floc Small gelatinous masses (of mostly bacteria) formed in a liquid by the reaction of an added coagulant, through biochemical processes or by agglomeration.  
Giardia A protozoan parasite found in some waters which can infest the human intestinal tract, causing severe diarrhoea (giardiasis).  
Gravity system 1. A system of conduits (open or closed) in which the liquid runs on descending gradients from source to outlet, and where no pumping is required. (2) A water-distribution system in which no pumping is required.  
Grease trap A device for separating grease from wastewater by flotation so that it can be removed from the surface.  
Greywater Household sullage wastes – all wastewaters from kitchen, bathroom and laundry, other than blackwater. It usually contains fats and greases, organic matter, nutrients and can also contain pathogens (disease-causing micro-organisms). Sometimes referred to as sullage.  
Hybrid toilet A toilet comprising a wet vault (pedestal located over treatment tank) designed to require very low volumes (less than 300 ml/flush) for flushing.  
Hydraulic gradeline (HGL) A line, the plotted ordinate position of which represents the sum of pressure head plus elevation head for the various positions along a given fluid flow path, such as a pipeline or ground-water streamline  
Improved septic tank A septic tank with improved design and componentry. Either a dual chamber or large-capacity septic tank fitted with an effluent outlet filter. Some multi-chamber tanks have separate chambers for blackwater and greywater Sometimes referred to as digestive tanks.  
Infiltration flows Stormwater and other leakages into sewers.  
Influent The liquid wastewater entering a wastewater system component.  
Intermittent sand filter (ISF) A sand filter for treating wastewater, which is applied in intermittent doses to allow filtration and aerobic biological action. USEPA website
Imhoff Tank Two-stage wastewater treatment tank combining sedimentation of settleable solids in an upper compartment and anaerobic digestion of the settled solids in a lower compartment.  
Low-pressure effluent distribution (LPED) Following treatment, a pump dose loads through a perforated small-diameter pipe inserted within a drain coil or ceramic drain pipe laid in a trench  
Low-pressure pipe system (LPP) A shallow dispersal system for distributing treated wastewater into a good depth of topsoil. The system is a shallow, pressure-dosed soil absorption area with a network of small-diameter perforated pipes placed about 250 mm deep and in narrow trenches of around 300 mm width. This system in the NZ context may use LPED lines.  
Long term acceptance rate (LTAR) The rate at which liquid residual moves into the sub-soil from an effluent soakage system. LTAR is significantly affected by the aerobic and anaerobic biomass generated on the infiltrative surface of the soakage area, which plays a significant role in determining the appropriate loading rate for design purposes in matching effluent quality, soakage system condition and soil characteristics to achieve the long-term effective performance of a disposal system.  
Methane fermentation Fermentation resulting in conversion of organic matter into methane gas.  
Micro-organism A minute organism, either plant or animal, invisible or barely visible to the naked eye.  
Mound There are various mound systems used for further treatment and dispersal of treated wastewater within a property. These mounds are commonly filled with a particular grade of sand, but may use sphagnum peat instead. Treated wastewater is distributed along the top of the mound, and percolates through the sand or peat to the infiltration surface, which is normally at existing ground level. Such mounds are sometimes referred to as Wisconsin mounds. They are used in areas with high ground-water table and/or impermeable sub-soils. USEPA website
Nitrification The conversion of nitrogenous matter into nitrates by nitrosamines and nitrobacter bacteria.  
On-site wastewater management system

A small-scale domestic wastewater system comprising the technologies and management protocols for the appropriate handling of household wastewater within the property boundaries of the place of origin of the wastewater. The key components of such a system include some or all of:

  • wastewater source technologies and management
  • wastewater processing technologies and management
  • technologies and management for re-entry of the processed wastewater to the in-boundary physical environment.
AS/NZS 1547:2000

USEPA website
Oxidation pond A pond used for the treatment of wastewater in which biological oxidation of organic material is carried out by natural or artificial transfer of oxygen to the water from air and from algae, and bacterial reduction is achieved by long detention and exposure to sunlight  
Oxygen demand The quantity of oxygen utilised in the biochemical oxidation of organic matter in a specified time, at a specified temperature, and under specified conditions (measured as 5-day biochemical oxygen demand – BOD5).  
Ozone treatment, or ozonation Disinfection or oxidation by ozone produced by passing air though a high-voltage discharge. USEPA website
Package plant A factory-assembled active domestic wastewater treatment plant such as an AWTS.  
Pathogens Micro-organisms that are potentially disease-causing; these include (but are not limited to) bacteria, protozoa and viruses.  
Permeability (soil) The property of a material, soil or rock that permits movement of water through it.  
Physical treatment A treatment process based on the physical characteristics of the wastewater contaminants. Examples include grit traps, macerators, screens, physical filters and sedimentation tanks.  
Population equivalent An expression of the strength of organic material in wastewater in terms of an equivalent number of persons, normally based on per capita BOD generation, but sometimes based on per capita waste volume.  
Primary treatment (1) The first major (sometimes the only) treatment in a wastewater treatment works, usually sedimentation; (2) the removal of a substantial amount of suspended matter but little or no colloidal and dissolved matter.  
Protozoa Small, one-celled animals, including amoebae, ciliates and flagellants.  
Rapid sand filter A water purification filter in which previously treated water (usually by coagulation and sedimentation) is passed downward through a filtering medium of sand, anthracite coal, or other suitable material resting on a supporting bed of gravel and an under-drainage system. The filter is cleaned periodically by reversing the flow of the water upward through the under-drain and filtering medium, sometimes supplemented by air agitation to remove mud and other impurities which have lodged in the sand.  
Recirculating sand filter A sand filter designed and operated such that its effluent can be returned to the inlet of the sand filter for further treatment. USEPA website
Residuals The by-products of waste water treatment (other than treated effluent). These include sludges, biosolids, grit, grease, fat, air emissions and odour  
Reticulation A network of pipes pumps and other devices used to transport sewage to a central point for treatment and/or disposal  
Secondary treatment (1) A more advanced treatment than primary treatment; (2) the removal of colloidal and dissolved material in wastewater, usually by biological means.  
Sedimentation The process of settling of suspended matter carried by water.  
Seepage trench A narrow trench (about 450 mm) which may be shallow (about 300 mm) or deep (about 500 mm) in which a perforated effluent distribution pipe is laid on aggregate infill. The trench is backfilled with further aggregate, geo-fabric, soil and topsoil.  
Septage The semi-liquid material that is pumped out of septic tanks, consisting of liquid, scum and sludge21 .  
Septic tank A wastewater treatment device that provides primary treatment for domestic wastewater, involving sedimentation of settleable solids, flotation of oils and fats, and anaerobic digestion of sludge. USEPA website
Sewage The spent water a community. This term is now being replaced in technical usage by the more preferable term ‘wastewater’.  
Sewerage A system of piping, with fittings, for collecting and conveying wastewater from source to treatment, and then discharge.  
Siphon An automatic, hydraulically activated system that initiates gravity flow from a sump or tank when the water reaches a specified level. No energy is required.  
Slow sand-filter A water purification filter in which water without previous treatment or chemical coagulation is passed at a slow rate downward through a fine sand medium. The filter is cleaned by scraping off and replacing the clogged layer.  
Sludge The material that settles out of wastewater primary and secondary treatment systems.  
Sphagnum peat biofilter A wastewater treatment biofilter system (normally following a septic tank or AWTS) that uses sphagnum peat as the filtering medium.  
Stormwater Rainwater run-off from impervious surfaces (roofs, roads, driveways, paths, parking lots and ground surfaces).  
Sullage An alternative term for ‘greywater’.  
Tertiary treatment The further removal of bacteria (via disinfection processes) and/or the removal of additional organic matter and suspended solids. Where nitrogen, phosphorus and eutrophying nutrient elements are removed by treatment methods, either biological or chemical, this may be called advanced treatment.  
Total Kjeldahl Nitrogen Total nitrogen in a substance determined by digesting with sulphuric acid and a catalyst; the nitrogen is reduced to ammonia, which is then measured.  
Total solids The sum of dissolved and undissolved constituents in water or wastewater (in mg/L).  
Tradewaste Tradewaste is waste water from trade or industrial processes which is discharged into the sewer. It does not include condensing water, surface water or domestic-type waste water from toilets, showers, kitchens etc
Trench vault and leaching chambers Trenches can be replaced by galleries made from PVC or other material. Treated effluent is then distributed to the infiltrating soil surface within the gallery by dose loading.  
Trickle loading This typically refers to the method by which effluent from a treatment plant, such as a septic tank, is loaded to a seepage trench. If it is displaced from the treatment tank by influent, and gravity fed to a trench, this is referred to as trickle loading. See Dose loading as the alternative and preferred method.  
Ultraviolet treatment Disinfection using light waves having wavelengths of 200–300 nm. USEPA website
Wastewater Contaminated water from domestic, commercial and industrial activities (see also Domestic wastewater).  
Waterless toilets Toilets that use no water; includes dehydrating toilets, incineration toilets and composting toilets.  
Wet-weather flow The maximum flow for which a sewerage system is designed; often referred to as ‘infiltration’ flow.  


20 GC Daily, S Alexander, PR Ehrlich, et al. Ecosystems services: benefits supplied to human societies by natural ecosystems. Ecol 1997, 2:2-16.

21 R Crites, G Tchobanoglous. Small and Decentralised Wastewater Management Systems. McGraw Hill, Boston, 1998.

Māori Glossary

Hapū – subtribe

Iwi – people; tribe

Kaimoana – seafood

Kaitiaki – guardian; caretaker; trustee

Kaitiakitanga – guardianship

Kaumātua – elders

Kawa – protocol

Mātaitai reserve – an identified traditional fishing ground established under regulation 23 of the Fisheries (Kaimoana Customary Fishing) Regulations 1998

Mana whenua – the authority of iwi or hapü by virtue of traditional occupation

Manaakitanga – the act of caring for others, ie, visitors

Manuhiri – visitors

Marae – the traditional meeting place of the Mäori people

Mauri – life force; life essence; life principle

Paru – mud; dirt; dirty

Rāhui – a conferment of tapu to restrict access to an area

Taiapure – a local fishery area in estuarine or littoral coastal waters (Fisheries Act 1983)

Tangata whenua – local people

Taonga – treasures; anything highly prized

Tapu – sacred; forbidden

Tino rangatiratanga – self determination; self management

Urupū – cemetary; burial ground

Wāhi tapu – a place sacred to Māori in the traditional, spiritual, religious, ritual or mythological sense

Wairua – spirit

Whānau – family


Durie, M.H. (1998) Te Mana Te Käwanatanga: The Politics of Mäori Self-Determination. Oxford University Press.

Kawharu (ed.), Waitangi: Mäori and Päkeha Perspectives of the Treaty of Waitangi (1989) Ryan, P.M. (1989) The Revised Dictionary of Modern Mäori. Heinemann Education

Tauroa, H & P. (1986) Te Marae: A Guide to Customs and Protocol. Reed Books.

Waitangi Tribunal, Kaituna River Report (1984)

Waitangi Tribunal, Wänanga Capital Establishment Report (1999)