6. Chemical tests for levels of different types of contaminants

A typical analysis of treated water within the distribution network of Wyong Shire is shown in Table 4.

Table 4: Typical physical and chemical analysis of Wyong Shire treated water 2008 and its relationship to the 2004 NH&MRC Guidelines. (Source: Wyong Shire Council) 2004 NH&MRC Guidelines Parameter Units WSC Health Aesthetic A: Physical Characteristics pH 7.9 N/A+ 6.5 – 8.5 Hardness mg/L as CaCO3 60.6 N/A 200 Total Dissolved Solids mg/L 168 N/A 500 Conductivity uS/cm 280 True Colour Hazen Units 1.4 N/A 15 Turbidity NTU 0.28 N/A+ 5 Alkalinity mg/L as CaCO3 34 N/A B: Inorganic Chemical Characteristics Acrylamide mg/L ND 0.0002 Aluminium mg/L 0.071 N/A+ 0.2 Ammonium mg/L * N/A+ 0.5 Antimony mg/L ND 0.003 Arsenic mg/L <0.001 0.007 Asbestos mg/L * N/A+ Barium mg/L 0.047 0.7 Beryllium mg/L * N/A+ Boron mg/L .06 4 Cadmium mg/L ND 0.002 Calcium mg/L 15.6 N/A Chloride mg/L 68 N/A 250 Chromium mg/L ND 0.05 Copper mg/L 0.102 2 1.0 Cyanide mg/L ND 0.08 Fluoride mg/L 0.95 1.5 Hydrogen Sulphide mg/L * N/A+ 0.05 Iodide mg/L 0.050 0.1 Iron mg/L 0.072 N/A+ 0.3 Lead mg/L 0.002 0.01 Magnesium mg/L 5.2 N/A Manganese mg/L 0.007 0.5 0.1 Mercury mg/L ND 0.001 Molybdenum mg/L ND 0.05 Nickel mg/L ND 0.02 Nitrate as NO3 mg/L 0.965 50 Nitrite as NO2 mg/L ND 3 Selenium mg/L ND 0.01 Silver mg/L ND 0.1 Sodium mg/L 35.3 N/A 180 Sulphate mg/L 15.2 500 250 Tin mg/L * N/A Zinc mg/L 0.038 N/A+ 3 * Not routinely tested by NSW Health based on potential for presence in source waters or less than detectable quantity. N/A No health based guideline value considered necessary by NH&MRC N/A+ Insufficient data to set a guideline based on health considerations. C: Disinfection By-Products and Disinfection Agents Chlorine mg/L <0.2 5 0.6 Carbon Tetrachloride mg/L ND 0.003 Trihalomethanes mg/L 0.093 0.250 No other disinfection agents or by-products have been determined or detected. D: Organic Compounds Not tested by NSW Health. Sources for compounds listed in Guidelines unlikely to occur in catchment E: Pesticides No pesticides detected at any time in OC, OP, CPA, Triazine/Phenylurea and Glyphosate groups F: Micro-organisms 1. Routine E. coli 416 samples p/a returned a 99.3% compliance rate. 6 samples/week for 100,000 persons plus 1 sample/month per additional 10,000 persons; 98% of WSC Guideline scheduled samples should be free of thermotolerant coliforms (E. coli) .Action should be taken if any presence detected. Number of organisms is irrelevant. 2. Non-routine Giardia and Cryptosporidium No organisms detected to date. Tested monthly since July, 1998 No guideline values. If detected, advice to be sought from relevant health authority. On the Central Coast, potable water (i.e. water supplied for drinking purposes) is very safe for human consumption. Levels of all inorganic substances are well below the 2004 NH&MRC Guidelines health risk thresholds (see Table 4). Samples from the Wyong Shire distribution system in 2008 were completely free of Giardia and Cryptosporidium micro-organisms in regular monthly samplings. Based on analysis of 416 water samples over a one year period, tests for Escherichia coli bacteria returned a 99.3% compliance rate.

In summary, as far as human health is concerned, drinking water on the Central Coast is of very high quality. The aesthetic quality of Central Coast potable water is also very high but with some variation across seasons and localities within the network.

As with all water supplies, potable water on the Central Coast contains small amounts of naturally occurring minerals such as calcium, magnesium, iron and manganese. Without these substances the water would taste bland. The Central Coast water is considered soft because the concentration of calcium and magnesium is relatively low. This is because the geology of the catchments is dominated by sandstone and other sedimentary rocks.

After filtration at the Somersby and Mardi treatment plants, low levels of chlorine are added to protect the water as it travels to our homes.

The water is also fluoridated, in line with the policy of the NSW Department of Health. Water fluoridation ensures improved dental health for the entire community, regardless of a person's age, income, level of education, or ability to get dental care. A constant supply of low level fluoride can reduce the amount of cavities in children's baby teeth by as much as 60 per cent and in adults' teeth by nearly 35 per cent. At the Somersby water treatment plant, in Gosford Shire, hydrofluosilicic acid is added with precision to the water supply in liquid form through dosing pumps at a rate of 1.0 ppm. Hydrofluosilicic acid is a colourless, tasteless and odourless liquid. The dosed water is then continually monitored to ensure fluoride levels remain within the optimal concentration range. At the Mardi water treatment plant, in Wyong Shire, fluoridation is carried out by feeding sodium silicofluoride into a slurry tank and then metering it into the flow to the Clear water Tank.

The quality of water supplied to customers is regularly tested by Gosford and Wyong councils and by independent, National Association of Testing Authorities (NATA) registered, laboratories to ensure this water complies with the Australian Drinking Water Guidelines (ADWG). Tests are regularly conducted on aesthetic and health criteria to ensure the water meets the ADWG and is safe for human consumption. Most water quality concerns reported by customers are related to appearance, taste and odour and are not a health issue.

Appearance

Although town drinking water supplies are generally colourless, from time to time the water's colour can change. Sometimes, it can take on a yellow or reddish/brown to almost black tint, while other times it can appear milky white or blue. This is known as discoloured water.

Incidents of discoloured water are more common during summer and periods of high demand, in low-lying areas, suburbs at the furthest end of the water supply system, dead-ends and in areas that normally experience low velocities. Until recently, the incidence of discoloured water in Gosford was increasing. This was, in part, due to the severe and ongoing drought which restricted Gosford Council's normal mains cleaning programs that remove accumulated materials from the water supply system.

In December 2007, Gosford Council launched an integrated program called Water Quality 2010 (see below) to minimise discoloured water events and the effects they have on the community.

Taste and Odour

The taste and odour of water can vary from tap to tap and can be impacted by naturally occurring minerals, Council treatment processes and internal plumbing. Personal likes and dislikes also influence the perception of taste and odour.

Some of the common taste and odour complaints are listed below.

Chlorine

Councils add chlorine to the water supply at the water treatment plants to remove harmful bacteria and protect water quality. A small residual of chlorine is generally present in drinking water once it reaches your tap and from time to time you may notice a slight chlorine taste or smell. Council carefully controls and monitors this process to ensure the residual poses no risk to health.

The consumer can eliminate the taste and smell of chlorine of drinking water by placing it in a covered jug in the refrigerator. It is recommended that this water be consumed within 24 hours. Domestic water filters or jug filters are also useful.

Musty, mouldy or earthy

Musty tastes and odours in drinking water can be caused by organic growth within water pipes.

Mould and bacteria can breed in internal plumbing when certain jointing compounds are used for domestic fittings or appliances, or when cold water pipes pass closely to hot water pipes that are not insulated.

Water pipes in areas of the supply system with low flow rates can also create an environment for organic growth.

Rust and metal

Drinking water with a rusty or metallic taste generally contains excessive iron, manganese and other metals. When these materials are present in high levels, a change in the colour of the water is also apparent.

Treatment processes remove naturally occurring iron and manganese from the water supply. However, as the water moves through the system to your tap, it may pick up material from corroding pipes not lined with cement. This may change the taste of your drinking water. A rusty or metallic taste can also occur if the internal pipes of a household are corroded. When house plumbing is corroded, water may appear clear at first, but then turn rusty or black in a few minutes.

Rotten egg smell

Rotten egg gas - hydrogen sulfide - is typically caused by decay of organic matter or chemical reactions in your plumbing, or by bacteria which change naturally occurring sulfates into hydrogen sulfide. These bacteria can be present in the water supply system, groundwater or hot water systems.

If the smell only comes from your hot water tap, there may have a problem with your hot water system. However, if the smell is strong from both hot and cold water taps when they are first turned on and diminishes after the water has run, the bacteria are probably in the water supply system. In the Wyong Shire, there is no problem of hydrogen sulfide in the town water supply

Fluoride

The taste and smell of drinking water does not change as a result of water fluoridation because the type of fluoride used to fluoridate the water supply has no taste or smell.

Household Water Quality

The quality of water delivered to your home can be affected by the nature of pipes inside your property. This is particularly so if you have corroding galvanised pipes.

While Gosford and Wyong Councils accept responsibility for the maintenance, repair and renewal of the water supply system up to the water meter on a property, it is the responsibility of homeowners to maintain the plumbing and draining on their own properties. This includes all fittings, pipes and rainwater tanks.

It is highly recommends that a licensed plumber carry out any plumbing work required within your property. The plumber should also provide the owner with a Certificate of Compliance once the work is completed, particularly for work valued at over $500.

Gosford City’s ‘Water Quality 2010’ to reduce the Incidence of Discoloured Water

Water Quality 2010 is a multi-million dollar drinking water quality management program. Launched in 2007, the main aim of the program is to reduce the incidence of discoloured water throughout the Gosford City area. In September 2008, the Federal Government announced a $4.5 million funding commitment in support of the capital works component of the program.

Capital works include improvements at the Somersby water filtration plant, upgrades to reservoirs, and refurbishment of pipelines, and as well as upgrades to the facilities for monitoring and analysing water quality.

Improvements to the Water Filtration Plant at Somersby include:  Construction of a lime and carbon dioxide dosing system to stabilise the treated water; buffering it against pH changes in the system and minimising the corrosion of cement- lined pipes.  Construction of a potassium permanganate dosing system to facilitate manganese removal from the water, thereby minimising the amount of discoloured water-causing material entering the water supply system.  Construction of a pre-chlorination system to provide an additional barrier assisting in the removal of manganese from the water.  Installation of a facility to remove wastewater containing high iron and manganese levels from the treatment process.

Improvements to the Reservoirs include:  Replacement of corroded ladders.  Refurbishment of roofing and bird-proofing.  Replacement of roof hatches where gaps in roofing are present.  Installation of devices to encourage mixing within the reservoir.

Improvements to Pipelines include:  Installation of pipe-work and valves to facilitate cleaning of large trunk mains between Somersby and North Gosford, and between Kariong and Woy Woy.  Replacement of unlined valves and hydrants in the Peninsula.

Other possible improvements may include removal of dead ends in water mains and creation of supply zones in areas where complex networks of pipes exist so as to improve water velocities through the pipes.

Upgrades to Monitoring facilities include:  Flow-meters installed in key locations throughout the system.  Installation of new in-line monitoring equipment to provide information on water quality at key locations in the system and act as early warning systems for water quality issues.  New portable monitoring equipment to allow water quality investigations at specific properties.  New laboratory analysis equipment.  New field sampling equipment.