The Australian Drinking Water Guidelines 2011 (ADWG) provide a framework for the management of drinking water supplies. They are a reference for what defines safe, good quality water, how it can be achieved and how it can be assured. They are concerned both with safety from a health point of view and with aesthetic quality. Guideline values for microbial, physical and chemical characteristics are provided for water utilities to work towards.
In the Bega Valley Shire, drinking water samples are taken from 100 separate sampling locations (taps) throughout the year for microbial analysis across the 4 water supply systems. These water samples are analysed for E.coli and total coliforms. Free chlorine and total chlorine are also analysed at these sites.
Drinking water samples are also taken from 28 separate sampling locations throughout the year for physical and chemical analysis across the 4 water supply systems. These water samples are analysed for pH, turbidity, total dissolved solids, hardness, colour, fluoride, sulphate, nitrate, nitrite, iron, manganese, other metals and heavy metals.
All analyses are undertaken at the NSW Department of Health Division of Analytical Laboratories in Sydney, apart from field analyses for free and total chlorine.
Between 1 July 2017 and 30 June 2018, 100% compliance with the ADWG guideline values was achieved for all analytes except for total coliforms (1 exception from 381 samples), iron (5 exceptions from 33 samples), lead (1 exception from 33 samples), aluminium (1 exception from 33 samples) and turbidity (9 exceptions from 389 samples). Of these, only the exception for lead is related to health considerations. All other exceptions are related to aesthetic water quality considerations and are not health related.
This high level of compliance is due to the high quality of local source water, sound disinfection systems for each water supply system and regular monitoring and maintenance.
Sampling and analysis of water quality for compliance with the ADWG guideline values shows Bega Valley Shire to have a very high quality of water (refer above). Nevertheless, there are factors and occurrences that detrimentally affect water quality at certain times and for some customers. The main causal factors, water quality issues and systems where these issues arise are shown in the table below.
|Main causal factors affecting water quality||Water quality issues||Water supply systems where this is an issue|
|Rainfall run-off in catchment areas||Turbid water with sediment solids enters, settles and accumulates in the water supply network. Solids periodically re-mobilise and increase the water turbidity for some customers.||Tantawanglo-Kiah (north), Brogo-Bermagui, Bemboka|
|Dissolved iron and manganese in groundwater||Hydroxides of iron and manganese form, enter, settle and accumulate in the water supply network. Solids periodically re-mobilise and increase the water turbidity for some customers.||Bega-Tathra, Tantawanglo-Kiah (south)|
|Algae in dams||Algae and other organics when chlorinated may impart a musty taste and smell to the water. Some species of blue-green algae are toxic and there is a risk that a toxic species may bloom in the future.||Tantawanglo-Kiah, Brogo-Bermagui|
|Dam turnover||Occurs autumn each year in Brogo Dam, operated by Water NSW. Turbid, coloured and iron rich water rises from low water levels to the surface. In the one to two weeks following, this water flows downstream to the Brogo-Bermagui system pump intake and into the system.||Brogo-Bermagui|
|Soft source water||Soft water is believed to contribute to the corrosion of pipework, including household copper pipes, causing elevated copper levels in the water at some properties. Health advice for copper in drinking water is available in the ADWG (p145, pp525-527) and on the NSW Health web site.||All systems|
|Biofilm growth in pipes||Biofilm growth may impart a musty taste and smell to the water. Biofilm may periodically slough away, causing coloured and turbid water to be experienced by some customers.||All systems|
Water mains and reservoirs on each system need to be cleaned periodically (flushing and vacuuming) to remove sediment (clays, iron hydroxide, carbonates, organic matter). The majority of dirty water issues are due to the re-suspension of sediment that has accumulated within parts of the system. Chlorine residuals can be variable at some locations due to the long detention times in the system.
There are currently no water treatment plants for the 4 water supply systems in the Bega Valley Shire. Water is extracted and chlorine added (fluoride is also added to water for the Bega-Tathra system). Rechlorinaton is also undertaken in locations where and when monitoring shows the level of chlorine residual to be lower than required.
Water treatment plants are planned to improve the consistency and quality of water supplied by each supply system. Water treatment plants will improve customer levels of service, compliance with ADWG water quality indicator values and enable source and storage water quality risks to be managed more effectively. The construction of water treatment plants will come at a significant capital cost, estimated at around $60 million. Water treatment plants will also lead to higher ongoing operational costs and higher customer water bills.
Use water from the cold water tap for drinking and cooking. Hot water systems may contain more dissolved minerals and metals, due to the heating process.
Copper pipes are used extensively in plumbing systems in Australia (and internationally). Drinking water can contain elevated metals such as copper and sometimes lead when left standing in pipes for extended periods. In this case, it is a good idea to flush cold taps for 2-3 minutes before using the water for drinking or cooking. This will lower the levels of copper and other metals that may be present in the water. This ‘first-flush’ of water can be used for washing up, watering plants, or other non-drinking uses.
The NSW Government considers fluoridation of community water supplies an effective way to deliver fluoride to all members of the community. In the Bega Valley Shire, only the Bega-Tathra water supply system is fluoridated. The other three systems remain non-fluoridated. Any changes to the water supply in the Bega Valley Shire in regard to fluoride will be made with community consultation.