Glossary
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
A
AAA
A rating system that indicates a product's rating for being economical with water or some other resource such as electricity.
Absorb
Physically or chemically assimilate (or take in) a substance, for example, as soils or plants take in water and food.
Activated Carbon
Some chemicals are attracted to fine carbon particles which are then filtered out.
Activated Sludge Process
This process involves using naturally occurring micro-organisms to feed on the organic material in the sewage. Activated sludge is a rich mixture of bacteria and minerals. The process is used in sewage treatment plants to break down organic matter and nitrogen compounds.
Acute
Severe and short lived.
Aeration
Exposure of material to air so that dissolved gases are removed; the process by which air is added to a substance.
Aerobic
Biological activity that requires the presence of oxygen.
Aerobic digestion
Breakdown of organic matter in liquid by adding oxygen or air. This is another process used in sewage treatment.
Algae
Simple photosynthetic plants that live in water or moist places.
Algal bloom
A rapid increase in the mass of one or more algae, usually caused by a change in the flow, light, temperature or nutrient levels of the water in which it lives.
Ammonia
A gas produced from a mixture of nitrogen in the air and hydrogen from methane. One source of methane is sewage.
Anaeorbic
Biological activity that takes place in the absence of oxygen.
Anaerobic digestion
Breakdown of organic matter under conditions of low air or oxygen supply.
Aquifer
A layer of porous rock that both stores water and allows it to drip through. Aquifers provide natural underground storages of water.
Audit
An assessment using measuring procedures to find out how a product or service is performing.
Australian Drinking Water Guidelines
The part of the 1996 National Water Quality Management Strategy that indicates the ideal physical, chemical and biological standards for drinking water in Australia.
Automatic urinal
A urinal system that automatically flushes every few minutes, 24 hours a day.
B
Bacteria
Bacteria are sometimes called germs. Many of them are useful for water or sewage treatment processes. Some cause disease. A huge population of them exists on human skin and in the human intestine.
Bioaccumulation
Concentration of substances, especially toxicants, in the tissue of plants and animals.
Biodegradable
Capable of being broken down by natural chemical or biological processes into simple substances not harmful to the environment.
Biodiversity
The range of soils, climate, water, plants and animals that make up the worlds of life and landscape.
Biosolids
The solids in waste water that can be removed by filters.
Biota
All living organisms in a region.
Blackwater
A combination of water, urine and faeces - what comes out of the toilet.
Blue-green algae
One form of algae (see separate listing) properly called Cyanobacteria. Blooms of blue-green algae have occurred in some important Australian waterways during drought or because of severe pollution.
BOD
Biochemical Oxygen Demand, a measure of the amount of oxygen needed to break down organic matter, such as sewage.
C
Catchment
The area of land drained by a creek or river system, or a place set aside for collecting water which runs off the surface of the land. Catchments provide the source of water for the reservoirs that collect our drinking water. Most of Melbourne's catchments are "protected": that is, they are fenced to keep out people and domestic animals and minimise the potential of pollution.
Catchment yield
The average annual volume of run-off from a catchment.
Chloramine
Ammonia is added after chlorine so that it stays in the water longer, but also provides food for aquatic algae.
Chlorine
A small amount of chlorine is used in some places to kill living things (pathogens) in the water supply that would make people sick if they drank them. However, it disappears (degrades) with time and the pathogens can regrow if the water is not covered.
Chlorophyll
A green pigment in plants, essential for photosynthesis (see separate entry).
Cigarette butts
The filter and remaining tobacco break down in weeks in fresh water but can take months in the sea.
Cistern
The part of the toilet that stores the water for flushing.
Clarifier
A structure at a sewage treatment plant for separating sludge from clearer waste water.
Coliforms
A family of bacteria (germs) which occur in large numbers in our intestines and faeces (poo). If found in water, it means the water has been recently contaminated by faeces. One coliform, Escherichia coli or E. coli, is used as an indicator of whether water is polluted by faeces.
Cryptosporidium
A genus of water-polluting protozoa which causes gastroenteritis (stomach upsets) in humans.
D
Dam
Technically, the dam is the wall that holds the water in and the reservoir is the water. Commonly, though, the words are interchanged.
Demand management
An approach to reducing the consumption of water by reducing demand for it. Demand management includes educating people about how to save water, promoting the use of household and industrial appliances that use water more economically, such as dual-flush toilets, and putting a price on water that reminds people of its true value.
Denitrification
Conversion of bound nitrogen to gaseous form.
Desalination
Removal of salts from seawater or other saline (salty) solutions.
Digester
A vessel or tank in which organic or chemical reactions take place under controlled conditions. Digesters are used in sewage treatment plants.
Dioxins
Toxic (poisonous) compounds which are by-products of the making of substances such as herbicides and disinfectants.
Disinfectants
Chemical and other processes used for disinfection (see below).
Disinfection
Any process that destroys or removes disease-causing organisms such as viruses, bacteria or protozoa. It is used as part of the purifying of drinking water.
Dissolve
When something dissolves it breaks up into particles (generally single atoms or molecules) too small to see. The solution, or liquid, appears clear.
Diversion weir
A small weir or wall across a stream or river, diverting water into a pipeline or tunnel.
DSE
Department of Sustainability and Environment, a Victorian State Government body responsible for overall management of the environment in Victoria.
Drain maintenance
When it rains, sediment and rubbish from roads and building sites is washed into the drains. The maintenance program removes this material which can block the drains.
Dual-flush toilet
A cistern that has two buttons, one of which releases only half the amount of water held in the cistern.
E
Ecology
The study of the relationships between living things and their environment (see Ecosystem).
Ecosystem
The system in which animals and plants depend on in their environment, and the environment depends on them.
Effluent
Treated sewage, the water that flows out of a sewage treatment plant. Effluent quality is assessed primarily through Biochemical Oxygen Demand (BOD), which measures the amount of oxygen required for the breakdown of the organic material contained in the effluent. Thus, effluent with very little organic matter will require very little oxygen and hence will have a low BOD. (See influent.)
Effluent irrigation
The use of effluent for watering and fertilizsing crops, fields and parks.
Enteric
Concerning the human intestines. So "enteritis" is an inflammation of the intestines. Gastro-enteritis is an inflammation of the intestines caused by something we have eaten or drunk (gastro = stomach).
Environmental flow
Water released from a reservoir to keep up water levels downstream.
Environmental Impact Statement
A statement, based on engineering, scientific and financial data, that assesses the likely impact of a project on the environment.
Environment Protection Authority (EPA)
In Victoria and other States of Australia, a State Government body whose job is to protect the air, water and land from pollution. Organisations like Melbourne Water must get a licence from the EPA to operate places such as sewage treatment plants.
Escherichia coli
A coliform (see separate entry) which indicates the presence of faeces in water.
Estuarine
Concerning an estuary, the part of an inlet or waterway that meets the sea and is subject to tidal movements. The water is usually brackish - a mixture of salt and fresh water.
Evaporation
The process by which water changes from liquid to gas or vapour and rises, forming clouds. This happens when the temperature increases over large masses of water, such as lakes and oceans.
F
Fauna
Animals and all living things in an ecosystem that are not plants (see Flora).
Filtered water
Water that has passed through sand or some other screening process to remove impurities. This usually happens before disinfection (see separate entry).
First flush
The first flow of water into the stormwater drains after rain. It often contains a lot of pollutants that built up during the dry time before the rain.
Flood flow
Flow of water from a reservoir down a spillway. This happens when the reservoir overflows because of heavy rain in its catchment.
Flood mitigation
Levee banks and other structures which hold back water in time of flood, reducing (mitigating) damage to property.
Flood plain
Low-lying land around a river which becomes inundated (covered in water) when the river level rises in time of flood.
Flora
Flowers and plants and things that look like plants, including fungi.
Flow rate
Volume of water per unit of time.
Fluoride
A chemical sometimes put into the drinking water supply to help strengthen people's teeth and reduce the number of fillings they need. There have been many arguments about whether this "fluoridation" should be done. Melbourne Water is required by State Government legislation under the Health (Fluoridation) Act 1973 to fluoridate the water supply.
G
Genus
A group of plants or animals which have a distinguishing set of characteristics in common.
Giardia
A protozoa causing diarrhoea, stomach cramps and weight loss in humans.
Giga
Denoting 10 to the power of 9, or 1,000 million. So a gigalitre of water is 1,000 million litres.
Grease trap
A hole with a grille for trapping fats, oil and grease in a drainage system. Most houses have a grease trap under an outside tap.
Greenhouse gases
Vapours, including water, in the lower atmosphere, which reflect solar radiation back to earth.
Greywater
Waste water from the kitchen, laundry and bathroom (but not the toilet). It usually contains soap, detergents and fats.
Groundwater
Water collecting below ground level in an aquifer or water table.
H
Hard water
Water that is difficult to make soap suds in because it contains calcium and magnesium salts.
Harvest
The word harvest means to collect. We harvest water just as we harvest crops. We wait for it to fall from the sky and collect the run-off in reservoirs.
Heavy metals
Dense chemical elements such as cadmium, chromium, copper, iron, lead, manganese, mercury, nickel and zinc. They can be toxic when highly concentrated.
Herbicides
Chemicals used to kill plants.
Hydrology
The study of water occurrence, distribution, movement and balances in ecosystems; the seasonal patterns of a river's flow.
I
Infiltration
The movement of water through soil or other porous material; the entry of stormwater into the sewerage system through faulty pipes.
Influent
The waste water that enters a sewage treatment plant. (See effluent.)
Irrigation
The use of water to nourish cultivated land or open space to promote the growth of vegetation.
K
Kilo
10 to the power of 3, or 1000. So a kilolitre of water is 1000 litres.
M
Manure
Animal manure, as well as human sewage contains bacteria and microscopic organisms that cause disease.
Mega
10 to the power of 6, or 1 million. So a megalitre of water is 1 million litres. Melbourne's Thomson Dam holds 1,068,000 megalitres.
Methane
A gaseous by-product of the breakdown of molecules that contain carbon. Most organisms, including humans, produce it.
Microbes
Microscopic bacteria, algae or fungi.
Micro-organisms
Microbes (see above) that live in soil, air or water. They can be useful or harmful (pathogenic).
Microfiltration
Water under pressure passes into pipes constructed of filter membranes with tiny pores too small to admit suspended solids and some pathogens.
N
Natural flow
The movement of water in accordance with gravity, without the use of devices such as pumps.
Nutrients
Substances such as nitrogen (see separate entry) and phosphorous (see separate entry) which promote the growth of plants.
Nutrient reduction
The removal of nutrients from sewage by chemical or biological processes so that the effluent does not harm the environment.
Nitrogen
Chemical element essential for the growth of plants and animals; a gas constituting 79% of the atmosphere.
Non-potable
Water that is unsafe to drink or to use in cooking.
O
Ocean outfall
A site where liquid, usually treated effluent from a sewage treatment plant, is discharged through a pipe into the ocean.
Organisms
The trees are the obvious ones. Mammals and birds live in the trees. Ants collect the seeds. Mosses and fungi live on the forest floor. Lizards eat the ants or the fungi. Millions of microbes live in the soil.
P
Pathogens
Any organism that causes disease in another.
Peak Wet Weather Flows
The maximum volumes of water flowing into a sewage treatment plant, down a waterway or through a catchment, during or soon after heavy rain.
Phosphorous
A chemical element present in rocks, soils, plants and animals. It is essential for growth and is present in many fertilisers, but through run-off it may contribute to the formation of algal blooms in waterways.
Photosynthesis
The process by which plants use chlorophyll (see separate entry) to convert light energy to chemical energy.
Planning controls
Flood plains and other flood prone areas are mapped and identified on council planning schemes so that new housing and industrial developments aren't a risk to public health and safety.
Pollution
Pollution is anything that would harm us and other living things in an environment. Water pollution generally includes chemicals, bacteria and viruses, other micro-organisms and rubbish. These are called pollutants.
Potable
Water that is safe to drink and to use in cooking.
Primary treatment
The first stage of treating sewage, usually the removal of big solids such as pieces of wood, as well as rags and plastics.
Protozoa
Microscopic animals, sometimes pathogenic in humans. They include Giardia and Cryptosporidium, which live in water.
Protected catchment
Protected catchments have no farms, no houses, no factories, so they provide water free of any pollutants these and other human activities produce. Most of Melbourne's catchments are protected.
R
Retarding basins
Retarding basins are used where hard surfaces in urban areas lead to rapid build up of stormwater. This flow can be temporarily stored in a basin and released more slowly, preventing flooding downstream.
Reticulation
A network, water pipes, for example, which delivers a service or commodity. A water system of this kind is called a reticulated supply. Other reticulated services include electricity and telephony.
Restrictor
A plumbing device which restricts the flow of water.
Retro-fitting
The fitting of new appliances or features after the initial installation.
Reuse
Recycling of effluent for use by industry or in agriculture or horticulture.
Run-off
Rainfall water which flows from a catchment into a river, stream, lake or reservoir.
Rural Catchment
Water that runs off a rural catchment contains the chemicals used by farmers, as well as animal wastes that dissolve in run-off water.
S
Saline
Salty. The salinity levels in water affect its usefulness for a range of purposes, and its harmfulness to the environment.
Secondary treatment
The removal of organic matter from waste water in a sewage treatment plant using aerobic biological processes.
Sedimentation
The process by which suspended particles in waste water settle to the bottom.
Sewage and sewerage
Sewage is the waste carried in our sewers. Sewerage is the system of pipes, pumps and treatment plants to manage sewage.
Sludge
Sludge is the inorganic suspended solids (see separate entry) which settle out from sewage.
Soft water
Water with light concentrations of calcium and magnesium, and which lathers readily with soap or detergent.
Stormwater
Rainfall which runs off roofs and roads and other surfaces and flows into gutters, streams and waterways where it eventually flows into the bays. This water can carry with it all sorts of contaminants. Some are obvious such as plastic bags or detergents from people washing their cars, others are not so obvious such as nutrients and heavy metals.
Suspended Solids
Some substances, such as soil, have particles that cannot dissolve. The bigger particles settle if the water is not disturbed, but some are too small to settle out and stay suspended. These particles are big enough to scatter light and make the water appear murky. Solids such as mud can be removed by letting the water stand for several years or by filtering it.
T
Tertiary treatment
The further processing of waste water in a sewage treatment plant which may involve further reduction in nutrient levels, filtration, use of constructed wetlands and higher levels of disinfection.
Toxic
Harmful, destructive or deadly to living things.
Toxicants
Poisonous substances, including harmful concentrations of otherwise useful elements such as nitrogen and phosphorous.
Turbidity
The degree of resistance to light in water caused by the presence of suspended solids which scatter or absorb the light, making the water look muddy or cloudy.
V
Vermiculture
The cultivation of worms to break down waste. The worm casts contain recovered nutrients which can then be used for fertilizer or soil conditioning.
W
Waste water
Any water which has been used at least once and cannot be used again without being treated.
Water table
The level of water in an aquifer.
Wetlands
Low-lying areas of land regularly or permanently covered with either fresh or salt water. They occur naturally, and can be constructed. Melbourne Water's Western Treatment Plant at Werribee has one of the world's largest constructed wetlands. They have become the habitat for a large range of bird life.