Bridgewater/Inglewood (Victoria) – E.coli
26/2/20: Bridgewater/Inglewood. A routine sample collected on 26 February 2020 at the outlet of the Inglewood Basin returned a positive E. coli result of 2 Orgs/100 mL. There was no obvious root cause that could have led to secondary microbial contamination in the Bridgewater-Inglewood distribution network was identified, except possibly for low chlorine disinfectant residual in the Inglewood Basin.
A suspected performance issue at the Bridgewater WTP was investigated, but as there were no
issues found with the disinfection. process during this time, and it was verified that no out-of specification water was supplied into the network, it was concluded that the detection was not related to the performance of the WTP. Several actions are being undertaken to improve the chlorine residual in this system, including the following:
1. Completed an inspection of the integrity of the Inglewood Basin, with the assistance of a specialised contractor;
2. Optimisation of the operation of the booster chlorinator at the Basin to achieve break point chlorination without creating a chlorine overdose risk on an ongoing basis;
3. Optimisation of the chloramine residual maintained at the Bridgewater WTP.
Thermotolerant coliforms are a sub-group of coliforms that are able to grow at 44.5 ± 0.2°C. E. coli is the most common thermotolerant coliform present in faeces and is regarded as the most specific indicator of recent faecal contamination because generally it is not capable of growth in the environment. In contrast, some other thermotolerant coliforms (including strains of Klebsiella, Citrobacter and Enterobacter) are able to grow in the environment and their presence is not necessarily related to faecal contamination. While tests for thermotolerant coliforms can be simpler than for E. coli, E. coli is considered a superior indicator for detecting faecal contamination…” ADWG
Bridgewater (Victoria) – Trihalomethanes
2005/06: Bridgewater Trihalomethanes 0.380mg/L (High Level)
2006/07: Bridgewater Trihalomethanes 0.340mg/L (High Level)
2007/08: Bridgewater Trihalomethanes 0.320mg/L (High Level)
2016/17: Bridgewater Trihalomethanes 0.260mg/L (High Level)
Trihalomethanes Australian Guideline Level 0.25mg/L
Why and how are THMs formed?
“When chlorine is added to water with organic material, such as algae, river weeds, and decaying leaves, THMs are formed. Residual chlorine molecules react with this harmless organic material to form a group of chlorinated chemical compounds, THMs. They are tasteless and odourless, but harmful and potentially toxic. The quantity of by-products formed is determined by several factors, such as the amount and type of organic material present in water, temperature, pH, chlorine dosage, contact time available for chlorine, and bromide concentration in the water. The organic matter in water mainly consists of a) humic substance, which is the organic portion of soil that remains after prolonged microbial decomposition formed by the decay of leaves, wood, and other vegetable matter; and b) fulvic acid, which is a water soluble substance of low molecular weight that is derived from humus”. Source: https://water.epa.gov/drink/contaminants/index.cfm
Bridgewater – Victoria – Hardness (max levels)
2005/06: Bridgewater Hardness 440mg/L
2006/07: Bridgewater Hardness 590mg/L
2007/8 Bridgewater Hardness 690mg/L
2008/9 Bridgewater Hardness 600mg/L
2009/10 Bridgewater Hardness 520mg/L
2015/16 Bridgewater Hardness 260mg/L
2016/17: Bridgewater (Victoria) – Calcium Carbonate 240mg/L
“To minimise undesirable build‑up of scale in hot water systems, total hardness (as calcium
carbonate) in drinking water should not exceed 200 mg/L.
Hard water requires more soap than soft water to obtain a lather. It can also cause scale to form on hot water pipes and fittings. Hardness is caused primarily by the presence of calcium and magnesium ions, although other cations such as strontium, iron, manganese and barium can also contribute.”
Australian Drinking Water Guidelines 2011
Bridgewater – Victoria – Total Dissolved Solids
2005/6: Bridgewater (Victoria) – Total Dissolved Solids 2000 μS/cm (max)
2006/7: Bridgewater (Victoria) – Total Dissolved Solids 2800 μS/cm
2007/8 Bridgewater Total Dissolved Solids 3800mg/L
2008/9 Bridgewater Total Dissolved Solids 3500mg/L
2009/10 Bridgewater Total Dissolved Solids 2800mg/L
2010/11 Bridgewater Total Dissolved Solids 870mg/L
2015/16 Bridgewater Total Dissolved Solids 1300mg/L
2016/17: Bridgewater (Victoria) – Total Dissolved Solids 1200 μS/cm
“No specific health guideline value is provided for total dissolved solids (TDS), as there are no
health effects directly attributable to TDS. However for good palatability total dissolved solids
in drinking water should not exceed 600 mg/L.
Total dissolved solids (TDS) consist of inorganic salts and small amounts of organic matter that are dissolved in water. Clay particles, colloidal iron and manganese oxides and silica, fine enough to pass through a 0.45 micron filter membrane can also contribute to total dissolved solids.
Total dissolved solids comprise: sodium, potassium, calcium, magnesium, chloride, sulfate, bicarbonate, carbonate, silica, organic matter, fluoride, iron, manganese, nitrate, nitrite and phosphates…” Australian Drinking Water Guidelines 2011
Bridgewater (Victoria) – Chloride Highest Levels
2007/8 Bridgewater Chloride 910mg/L
2008/9 Bridgewater Chloride 820mg/L
2009/10 Bridgewater Chloride 720mg/L
2015/16 Bridgewater Chloride 270mg/L
2016/17: Bealiba (Victoria) Chloride 270mg/L
“Chloride is present in natural waters from the dissolution of salt deposits, and contamination from effluent disposal. Sodium chloride is widely used in the production of industrial chemicals such as caustic soda, chlorine, and sodium chlorite and hypochlorite. Potassium chloride is used in the production of fertilisers.
The taste threshold of chloride in water is dependent on the associated cation but is in the range 200–300 mg/L. The chloride content of water can affect corrosion of pipes and fittings. It can also affect the solubility of metal ions.
In surface water, the concentration of chloride is usually less than 100 mg/L and frequently below 10 mg/L. Groundwater can have higher concentrations, particularly if there is salt water intrusion.
Based on aesthetic considerations, the chloride concentration in drinking water should not exceed 250 mg/L.
No health-based guideline value is proposed for chloride.” 2011 Australian Drinking Water Guidelines
2007/8 – Bridgewater Victoria) – Turbidity
2007/8 – Bridgewater (Victoria) – Turbidity 6.5NTU (max)
2018/19: Bridgewater-Inglewood (Victoria) – Turbidity 7.2NTU (max)
Chlorine-resistant pathogen reduction: Where filtration alone is used as the water treatment
process to address identified risks from Cryptosporidium and Giardia, it is essential
that filtration is optimised and consequently the target for the turbidity of water leaving
individual filters should be less than 0.2 NTU, and should not exceed 0.5 NTU at any time
Disinfection: A turbidity of less than 1 NTU is desirable at the time of disinfection with
chlorine unless a higher value can be validated in a specific context.
Aesthetic: Based on aesthetic considerations, the turbidity should not exceed 5 NTU at the
Bridgewater – Victoria – Iron
2007/8 Bridgewater Iron 0.67mg/L
2008/9 Bridgewater Iron 0.48mg/L
2015/16 Bridgewater Iron 0.41mg/L
Based on aesthetic considerations (precipitation of iron from solution and taste),
the concentration of iron in drinking water should not exceed 0.3 mg/L.
No health-based guideline value has been set for iron.
Iron has a taste threshold of about 0.3 mg/L in water, and becomes objectionable above 3 mg/L. High iron concentrations give water an undesirable rust-brown appearance and can cause staining of laundry and plumbing fittings, fouling of ion-exchange softeners, and blockages in irrigation systems. Growths of iron bacteria, which concentrate iron, may cause taste and odour problems and lead to pipe restrictions, blockages and corrosion. ADWG 2011
2007/10 – Bridgewater (Victoria) – Sodium
2007/8 Bridgewater Sodium 510mg/L
2008/9 Bridgewater Sodium 390mg/L
2009/10 Bridgewater Sodium 360mg/L
should not exceed 180 mg/L….The sodium ion is widespread in water due to the high solubility of sodium salts and the abundance of mineral deposits. Near coastal areas, windborne sea spray can make an important contribution either by fallout onto land surfaces where it can drain to drinking water sources, or from washout by rain. Apart from saline intrusion and natural contamination, water treatment chemicals, domestic water softeners and
sewage effluent can contribute to the sodium content of drinking water.” ADWG 2011
Bridgewater (Victoria) – Aluminium
According to the ADWG, no health guideline has been adopted for Aluminium, but that the issue is still open to review. Aluminium can come from natural geological sources or from the use of aluminium salts as coagulants in water treatment plants. According to the ADWG “A well-operated water filtration plant (even using aluminium as a flocculant) can achieve aluminium concentrations in the finished water of less than 0.1 mg/L.
The most common form of aluminium in water treatment plants is Aluminium Sulfate (Alum). Alum can be supplied as a bulk liquid or in granular form. It is used at water treatment plants as a coagulant to remove turbidity, microorganisms, organic matter and inorganic chemicals. If water is particularly dirty an Alum dose of as high as 500mg/L could occur. There is also concern that other metals may also exist in refined alum.
While the ADWG mentions that there is considerable evidence that Aluminium is neurotoxic and can pass the gut barrier to accumulate in the blood, leading to a condition called encephalopathy (dialysis dementia) and that Aluminium has been associated with Parkinsonism dementia and amyotrophic lateral sclerosis, the NHMRC, whilst also acknowledging studies which have linked Aluminium with Alzheimer disease, has not granted Aluminium a NOEL (No Observable Effect Level) due to insufficient and contradictory data. Without a NOEL, a health guideline cannot be established. The NHMRC has also stated that if new information comes to hand, a health guideline may be established in the future.
In communication with Aluminium expert Dr Chris Exley (Professor in Bioinorganic Chemistry
The Birchall Centre, Lennard-Jones Laboratories, Keele University, Staffordshire UK) in March 2013 regarding high levels of Aluminium detected in the South Western Victorian town of Hamilton
“It is my opinion that any value above 0.5 mg/L is totally unacceptable and a potential health risk. Where such values are maintained over days, weeks or even months, as indeed is indicated by the data you sent to me, these represent a significant health risk to all consumers. While consumers may not experience any short term health effects the result of longer term exposure to elevated levels of aluminium in potable waters may be a significant increase in the body burden of aluminium in these individuals. This artificially increased body burden will not return to ‘normal’ levels when the Al content of the potable water returns to normal but will act as a new platform level from which the Al body burden will continue to increase with age.