Basic Chemistry Terms and Tests
pH
This is a scale of numbers from 0 to 14 which describes the amount of hydrogen ions dissolved in a water or chemical solution.
pH = -Log10 [H+]
The negative log to the base 10 of the hydrogen ion concentration.
Acids have a very low pH as they have a high concentration of free hydrogen ions. These are liquids like battery acid or nitric acid that is sometimes used in metal cleaning products.
Alkaline liquids like ammonia-based bleaches or peroxide solutions have a very high pH.
Both acids and alkaline solutions can cause severe burns, which is why they are normally recommended to be handled using gloves and solutions available to the public are much less concentrated than those used in the lab.
Water supplied from our taps or in creeks and streams is usually in the neutral range – that is 6.5 – 8.5 pH.
Conductivity
Conductivity describes the capacity of a liquid or solid to conduct an electronic current. Conductivity is measured in Siemens per centimetre (S/cm). Reticulated water in Hervey Bay has an average conductivity of 230 micro Siemens per centimetre (µS/cm) – very low conductivity.
In waters, a high conductivity indicates a large amount of dissolved material – sea water has a very high conductivity. A low conductivity indicates the water is quite pure with very little dissolved material.
Hardness
Hardness is a test used to determine the amount of dissolved calcium and magnesium sulphates that may be dissolved in the liquid. These ions can cause scaling of pipe work and can contribute to some taste issues in relation to drinking water supplies.
The term 'hard water' indicates levels greater than 200 mg/L and these waters do not lather very easily. The lab is often asked about the hardness of our tap water supply by people wanting to install dishwashers as they may need to add water softening agents to prevent damage to these machines.
The water supply for Hervey Bay is very soft (low hardness) and therefore softeners are not required.
Water that is too low in these ions is considered to be potentially corrosive to plumbing systems. Levels less than 50 – 60 mg/L are deemed potentially corrosive.
Free chlorine
This test enables drinking water providers like Wide Bay Water to control the amount of the potentially dangerous chemical 'chlorine' that has to be added to our treated drinking water to ensure it is free of dangerous bacteria.
The National Health and Medical Research Council states that Free Chlorine levels less than 5 mg/L are safe for consumers.
Wide Bay Water tries to ensure Free Chlorine levels are kept less than about 2 mg/L but sometimes this is not always possible. If there is a large rainfall event the dam gets very churned up and it is much harder to remove all the suspended material that may harbour bacteria.
One of the most difficult aspects of this component of our water supply is that people react very differently to these breakdown products of chlorine. Some people are 'super sensitive' and can strongly detect extremely low levels that other people would not notice at all. Some may even suffer severe allergic reactions which makes it very difficult for providers to ensure disinfection of the water supply and keep consumers happy at the same time.
True colour and turbidity
These tests are very commonly used to describe a water sample and are very self-explanatory. If the drinking water was discoloured or cloudy it would not be considered as very good quality. There are tests and instruments that can be used to assign values to these very subjective terms and Wide Bay Water uses these to regulate treatment systems.
Dissolved metals
There are very many metals and metal compounds that exist in any water sample. Most of them are dissolved from rocks in the environment by rain and end up in our water supplies.
Most dissolved metals are present in such low levels as to be virtually undetectable even using the most sophisticated instruments.
The major metals Wide Bay Water monitors are iron, manganese, copper and zinc.
Iron and manganese are present in significant amounts in the environment and are not hazardous to health but may contribute to problems within the distribution system. Iron is the major component of rust which is basically iron oxide.
Iron and manganese
Most of the environmental iron and manganese are removed during the treatment process but trace amounts (less than 0.3 mg/L) may enter the distribution system. Over time, these trace amounts can build up in microscopic dead flow parts of a pipe system until they reach a mass or size where they are dislodged and appear in our water as very small, hard black or brown particles. These particles will sink to the bottom in a glass of water.
Many people using bore water will have noticed brown stains appearing on brickwork or concrete that has been regularly washed with bore water. Most bore waters contain quite high levels of dissolved iron and manganese but when the water comes into contact with bricks or cement that are basically alkaline materials, the pH of the water is changed and these metals can no longer stay dissolved but solidify out of solution and cause this staining.
Copper and zinc
Copper and a small amount of zinc are used in the plumbing of a household and in valves within the system. Monitoring levels of these metals can help us to identify potential problem areas where valves may need replacement. A customer may notice a blue or greenish residue in the bath or basin from copper being dissolved into the water.
The occurrence of these residues is generally as a result of the breakdown of the copper pipes within a hot water system. The high pressure and heat within a hot water system will accelerate the breakdown of low-quality pipe work and generally the system will need to be replaced.
Aluminium
Aluminium gets some very bad press as it is reported to be linked with Alzheimer’s Disease. The guidelines indicate levels less than 0.2 mg/L to be safe for drinking water.
A compound called Alum which contains aluminium is used in the treatment plant to remove the very fine dirt and leaf particles from the raw water that comes from the dam, so it is not surprising that trace amounts may be found in our drinking water.
The lab routinely monitors Hervey Bay’s drinking water for aluminium and it is kept at levels less than 0.1 mg/L.
Lead
In Hervey Bay, we have no such industrial sources of lead and there is no detectable level of lead in our environmental water supplies.
Where there is a concern at the potential for lead poisoning, a doctor should order a blood test to confirm the presence of lead and an investigation conducted into possible sources within the person’s environment.
Dissolved oxygen
Any liquid open to the air will contain a proportion of dissolved gaseous oxygen as well as the oxygen associated with the water molecule. This oxygen is used by fish and other water organisms.
Where this oxygen level is low, water can become stagnant and cause fish deaths.
Algae can contribute to the levels of dissolved oxygen as they process light and CO2 to produce oxygen. Often ponds that are high in algae will be super saturated with dissolved oxygen.
Dissolved Oxygen (DO) is used as an indicator to shown the general health of water body or as one of the requirements of EPA licence to discharge effluent water into the environment.