Parameters
A range of basic parameters are monitored to assess water quality. The following list explains the implications of these parameters for water quality.
A mobile water sampling station
Total coliforms are gram-negative rod shaped bacteria that occur naturally in the environment. Some coliform bacteria are also present in faeces. Coliforms include Escherichia, Enterobacter, Klebsiella, Citrobacter and some other species.
Escherichia coli (E. coli) is used as a more specific indicator of possible faecal contamination of water than total coliforms. E. coli in water samples should generally be removed by disinfection treatment. If E. coli is still present it can indicate that disinfection was ineffective and there is a risk of pathogens. Some laboratories also perform a test for thermotolerant coliforms (a subset of total coliforms), however testing for E. coli is preferred. Thermotolerant coliforms were formerly know as faecal coliforms.
Turbidity measures the ability of water to scatter light. Scattering is usually caused by fine material suspended in the water (including mineral and organic matter). This suspended material can interfere with disinfection.
Colour generally indicates organic material or certain metals in the water. It can interfere with disinfection and produce harmful disinfection by-products.
Salt (measured as total dissolved solids or electrical conductance) in high concentrations makes water unpalatable or unpleasant to drink.
Hardness is caused by certain dissolved mineral salts. It can affect the treatability of the water and how well soap can lather.
pH of treated water should be in the neutral range between 6.5 and 8.5. If it is above 8, chlorine disinfection becomes less effective. If pH is below 6.5, water can be corrosive and attack metals.
Metals (such as iron or manganese) can cause brown or black water, staining and discolouring of laundry and baths/sinks, and an iron or bitter taste to the water. Other metals, such as lead or mercury, can lead to long-term health problems.
Core soil sampling provides a history of sediment in lakes, including metal content
The information above is taken from the Australian Drinking Water Guidelines (National Health and Medical Research Council 2004, and the Safe Water Guide for the Australian Aid Program 2005 - www.ausaid.gov.au.
