Water quality glossary

Our hard working team of water quality specialists closely monitor our water from the time it leaves the protected catchments right up until the point when it reaches our customers. The below water quality glossary explains some of the terms we use when measuring water quality. 

 

​Alum ​Alum, or aluminium sulphate, is used as a coagulant. Alum encourages particles in the water to stick together to form larger particles. These particles can be settled, floated or filtered out of the water.
All supplies that are treated using alum are required to be tested to ensure the aluminium concentrations do not exceed the limits set in the Victorian Safe Drinking Water Regulations and the Australian Drinking Water Guidelines
​Aluminium ​In unfiltered systems, aluminium may be present in water through natural leaching from rock and soil. In filtered systems, aluminium salts are added to the water to aid in the removal of solids and pathogens in the filtering process. Aluminium is only required to be monitored in filtered systems. Aluminium is monitored to ensure the concentration is less than 0.2 mg/L for aesthetic reasons. There is no health based target set for Aluminium.
Aluminium is a regulated parameter for filtered supplies only.
Compliance - samples must have less than 0.2 mg/L of aluminium present.
​Carbon dioxide ​Carbon dioxide is used to adjust the pH of the water. Carbon dioxide dissolved into the water and it reduces the pH. The pH can increase in the system due to the water spending long periods in cement mains during periods of low use. Carbon dioxide is used in the far ends of the system to reduce the pH of the water.
​Chlorine ​Chlorine is added to water to kill any pathogenic viruses or bacteria that may be present in the water. Chlorine is added to all of Melbourne’s drinking water supplies and is fundamental for ensuring water is safe to drink. Chlorine naturally dissipates in the water over time so South East Water adds chlorine at strategic places throughout the network to ensure there is enough chlorine in the water to prevent the regrowth of pathogens.
Compliance - the Australian Drinking Water Guidelines suggests a health limit of 5 mg/L of free chlorine.
​Chloroacetic acid ​Chloroacetic acid is a by-product produced when water is disinfected using chlorine. The chlorine reacts with naturally occurring organics in the water to produce choloroacetic acid. Chloroacetic acid is monitored for health reasons.
Chloroacetic acid is a regulated parameter.
Compliance - all samples must contain less than 0.15mg/L.
​Coagulation ​Coagulation is a process for removing particles and pathogens from the water. A coagulant, such as Alum, is added to the water and the small particles form larger particles that are easier to float or settle out of the water.
​Coliforms
Coliforms are a diverse group of bacteria which is made up of environmental coliforms which do not represent faecal contamination of the water supply. The presence of Coliforms in drinking water can be used as an indicator for operational monitoring.
Compliance - there is no limit set for Coliforms in the Australian Drinking Water Guidelines as it is used for operational purposes only.
​Colour ​Colour is caused by dissolved organic matter (humic and fulvic acids), which originate from the soils and decaying vegetation from the catchments. There are two ways to measure colour – “true” colour is measured after filtering the sample to remove the particulate matter and “apparent” colour is measured without filtration and is more like what our customers see. South East Water measures “apparent” colour.
Compliance - the Australian Drinking Water Guidelines suggest a maximum apparent colour limit, for aesthetic purposes, of 25 Hazen Units (HU).
​Copper ​Copper can occur naturally in catchments as it is widely distributed in rocks and soils as carbonate and sulphide minerals. It can also be present in drinking water from household plumbing using copper pipes. Copper can cause the water to appear blue or green. Copper is monitored for health reasons.
Compliance - the Australian Drinking Water Guidelines suggests a health limit of 2 mg/L of copper in drinking water.
​Dichloroacetic acid ​Dichloroacetic acid is a by-product produced when water is disinfected using chlorine. The chlorine reacts with naturally occurring organics in the water to produce dichloroacetic acid. Dichloroacetic acid is monitored for health reasons and is a regulated parameter.
Compliance - all samples must contain less than 0.1mg/L.
​DAFF ​Dissolved Air Filtration Flotation, or DAFF, is a process where particles are floated out of the water prior to filtration rather than the typical process where particles are settled out of the water prior to filtration.
Coagulant and flocculant are added to the water, as per a typical water treatment process. Instead of settling the particles out of the water, the particles are floated to the surface using fine air bubbles that have been dissolved in the water. The particles are then removed from the top of the water. The rest of the water flows through a typical sand filter bed prior to further treatment.
DAFF is used for particular types of water where the particles are very light and difficult to remove by settling. Tarago Water Treatment Plant is a DAFF plant that supplies water to the south eastern areas of Melbourne.
​E. Coli ​E. coli (Escherichia coli) indicates a high probability of recent faecal contamination. E. coli is found in large numbers in the faeces of human and other warm-blooded animals, although only a few strains of E. coli are human pathogens.
E. coli is a regulated parameter.
Compliance - All samples must have zero organisms per 100 ml with the exception of any false positive sample.
​Electrical conductivity ​Electrical conductivity is an indicative measure of the amount of dissolved salts or “saltiness” of water. Water that undergoes different types of treatment has different electrical conductivity. Closed catchment water (such as water from the Thomson Reservoir) typically has an electrical conductivity between 60-100µS. Filtered water typically has en electrical conductivity between 100-180µS. Electrical conductivity is monitored for operational and aesthetic purposes.
Compliance - Australian Drinking Water Guidelines suggest an electrical conductivity limit of 750µS for aesthetic purposes.
​Filtration ​There are many different types of filtration but they all have the same purpose - to remove particles and pathogens from the water. South East Water’s area is supplied by two filtration plants Tarago and Winneke. Tarago Treatment Plant is a Dissolved Air Flotation Filtration (DAFF) plant and Winneke is a sand filtration plant.
Different sorts of filtration are chosen for different reasons or types of water. Sand filtration, DAFF, micro-filtration and ultra-filtration are some examples of the different types of filtration.
​Flocculation ​Flocculation is a process that aids coagulation in removing particles. A flocculant, such as polyelectrolyte, is added to water once the particles in the water have been coagulated. It helps form flocs from the coagulated particles which are then easier to remove.
​Fluoride
​Fluoride can occur naturally in drinking water. In Victoria, fluoride is added to the drinking water to protect teeth against decay. The process of adding fluoride to water is called “fluoridation”. The addition of fluoride to drinking water in Victoria is a requirement of the Fluoridation Act 1973. Fluoride concentrations are monitored for health purposes.
Compliance - the concentration of fluoride must not exceed 1.5mg/L in drinking water. The annual mean for each supply source must not exceed 1.0mg/L.
​Hardness ​Hardness is a measure of particular salts (magnesium and calcium) in water. Hardness is measured in mg/L of calcium carbonate (CaCO3) equivalent ions in water. “Hard” water has a total hardness of greater than 200mg/L. “Soft” water has a total hardness of less than 60mg/L.
Hardness is monitored for aesthetic reasons.
Compliance - Australian Drinking Water Guidelines suggests total hardness should be less than 200mg/L.
​Iron ​Iron is naturally present in water from the catchment area soils. High iron levels can discolour the water. The main source of iron is through foods. Iron is monitored for aesthetic purposes.
Compliance - The Australian Drinking Water Guidelines suggest a limit of 0.3mg/L for aesthetic purposes.
​Lime ​Lime, also known as calcium hydroxide, is used to adjust the pH of the water. Lime increases the pH where as gaseous carbon dioxide is used to lower the pH. Controlling the pH is very important in the water treatment process as some process steps, such as disinfection and coagulation, need to be in a very specific pH range to be effective.
​pH ​pH is a measurement of the acidic or alkaline nature of the water. The ideal pH of drinking water is between 6.5 and 8.5. At this pH corrosion and scaling on pipes and fittings is prevented. When water spends a long time in cement mains or tanks the pH can increase and a pH value up to 9.2 for drinking water is still considered acceptable. A significant proportion of Melbourne’s mains and tanks are cement lined.
The pH may need to be corrected as chemicals added to the water (for example fluoride and chlorine) can change the pH. pH is monitored for aesthetic and operational purposes.
Compliance - The Australian Drinking Water Guidelines suggest a pH between 6.5 and 9.2
​pH Correction ​pH correction is the process of reducing the pH or increasing the pH to ensure it is in the optimal range. pH correction is important in the treatment process as some processes, such as disinfection, only work in a specific pH range. In water treatment in the Melbourne area, carbon dioxide is used to reduce the pH and lime is used to increase the pH.
​Polyelectrolyte ​Polyelectrolyte is a flocculant. A flocculant is added to water once the particles in the water have been coagulated. Polyelectrolyte helps the smaller particles form a floc, making it easier to remove from the water.
​Primary disinfection ​Primary disinfection refers to the first dose of a disinfectant the water receives. The water needs to be disinfected because of the presence of microbes, and some microbes are pathogenic, which means they have the ability to make humans sick. Disinfection of drinking water is the single process that has the greatest impact on drinking water safety.
There are a variety of chemicals or processes that can be used to disinfect water such as ozonation, where the gas ozone is added to the water, and ultraviolet irradiation (UV), where the water is exposed to UV light (from lamps) for a set period of time. Different disinfectants are good for destroying particular pathogens. A combination of disinfectants are often used for particular types of source water.
Chlorine gas is used as the primary disinfectant in Melbourne. Chlorine is an excellent all round disinfectant. Chlorine also remains in the water for some time, preventing the regrowth of pathogens in the water. The presence of chlorine in drinking water is important to ensure water is not re-contaminated in the transfer system and remains safe to drink all the way to the tap.
Compliance - The Australian Drinking Water Guidelines considers disinfection to be paramount to public health. The choice of disinfectant is dependant on the type and quality of the water, the type of micro-organisms, the complexity of the transfer system and the size of population served.
​Secondary disinfection
​Secondary disinfection refers to the second dose of a disinfectant water receives. Sodium hypochlorite is the main secondary disinfectant used in Melbourne. Chlorine from the primary disinfection process naturally dissipates in the water as it flows further into the network. It is important to maintain a chlorine residual throughout the network, thus secondary disinfection is used to “top up” the chlorine levels in the water.
​Sodium hypochlorite ​Sodium Hypochlorite is a chlorine disinfectant that can be used for both primary disinfection and secondary disinfection. It is often used instead of chlorine gas as it is easier and safer to handle than gaseous chlorine and is more suitable at locations that treat smaller volumes of water. Where large volumes of water are treated chlorine gas is often preferred.
​Trichloroacetic acid ​Trichloroacetic acid is a by-product produced when water is disinfected using chlorine. The chlorine reacts with naturally occurring organics in the water to produce trichloroacetic acid. Trichloroacetic acid is monitored for health reasons.
Trichloroacetic acid is a regulated parameter.
Compliance - All samples must contain less than 0.1mg/L of trichloroacetic acid.
​Trihalomethanes ​Trihalomethanes are a group of chemicals that are produced as a by-product of water disinfection using chlorine. The chlorine reacts with naturally occurring organics in the water to produce trihalomethanes. Trihalomethanes are monitored for health reasons.
Trihalomethanes are a regulated parameter.
Compliance - All samples must contain less than 0.25mg/L of trihalomethanes.
​Turbidity ​Turbidity is a measure of fine suspended material or particles in water. In a glass, a turbidity of less than 1 NTU is crystal clear, turbidity of 5 NTU will have some visible fine particles, and it would not be possible to see through a turbidity of 60 NTU. High turbidity can lessen the effectiveness of disinfection. Turbidity is a regulated parameter.
Compliance - All samples must have a 95% upper confidence limit (UCL) of the mean to be less than or equal to 5.0 NTU.

 

For more information see our Water quality fact sheets. ​


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