Drinking Water Services
 

Drinking Water Services
Rocfort Road
Snodland
Kent ME6 5AH
0845 3454 213

email:

Drinking Water Services - Information Sheets

Water Quality Definitions


CONDUCTIVITY The electrical conductivity of water is measured in micro Siemens/cm and is the traditional indicator for mineral deposits. Pure water is not a good conductor of electricity, dissolved ions increase conductivity.

Total Dissolved Solids (TDS) Measure sthe solids content of the water source by evaporating a measured quantity of sample water and weighing the residue. Units are in mg/l

pH The acidity or alkalinity of water expressed on a scale of 0 (acid) to 14 (alkali), pH 7 is considered neutral.

HARDNESS The total dissolved calcium and magnesium salts in water. Compounds of these two elements are responsible for most scale deposits. Units are usually shown in mg/l as CaCO3

ALKALINITY The total concentration of alkaline salts (bicarbonate, carbonate and hydroxide) determined by titration with acid to pH 4.5. Units are in mg/l as CaCO3

NITRATE Concentration is in mg/l as NO3

SODIUM Concentration is in mg/l as Na+

HEAVY METALS The total of chromium, lead, copper, and other toxic metals expressed as mg/l

SUSPENDED SOLIDS The concentration of insoluble contaminants in mg/l

TURBIDITY The measure of colloidal haze present in Nephelometric Turbidity Units (NTU) or Formazin Turbidity Units (FTU)

Oxygen Absorbed (OA) Is a measure of organic contaminants determined in a four hour test at 27°C and measured in mg/l as O2. Other indicative tests could be Permanganate Value (PV), or Chemical Oxygen Demand (COD).

MICRO-ORGANISMS

 

Measures the colony forming units of total bacteria present in a fixed volume sample of water. Usually expressed as count/100ml. (bacteriological count)
A fundamental measure of purity is the bacterial count. The most common group of bacteria analysed is the COLIFORM group.


Faecal Coliforms / Coliform Organisms/ E.Coli

The COLIFORM group of bacteria includes not only organisms from the intestinal tract of warm blooded animals (faecal coli, mainly E.COLI - Escherichia Coli) but also organisms from the soil or vegetation (mainly Aerobactercleroge).

Because human faeces are a principal source of pathogenic organisms (an organism causing disease), evidence of coliforms and especially E.Coli, are an indication that pathogenic organisms could be present. However, to put all this in perspective, a single person will excrete approximately 10,000,000,000,000 coliform organisms every day.

Various pathogenic organisms are calculated to be found in various numbers of coliform levels. Allowing for safety factors, if the calculation for pathogenic organisms is 10 per 1,000,000 coliforms, the likelihood of pathogenic organisms in a sample containing 100 coliforms is 1000:1.

 

 

 

 

 


Links:

The Drinking Water Inspectorate
  DEFRA - Introduction to Water
  Water Care Syetms Ltd