The Biochemical oxygen demand (BOD5) test measures the amount of dissolved oxygen used by microorganisms in the biological process of metabolising organic matter in water. The more organic matter there is (e.g. in sewage and polluted bodies of water), the greater the BOD; and the greater the BOD, the lower the amount of dissolved oxygen available for higher animals such as fish. The BOD is therefore a reliable gauge of the organic pollution of a body of water. The test is performed over five days and results are reported in g/m3, using APHA method 5210 B / YSI 5000.

Chloride in the form of Cl- ion, is one of the major inorganic anions in water and wastewater.  A high chloride content may harm metallic pipes and structures, as well as having a negative effect on growing plants.  Results for Chloride using APHA4500-Cl-B are reported in g/m3.

Conductivity is a measure of the ability of an aqueous solution to carry an electric current.  It is used to indicate the presence of solutions of inorganic compounds.  Results for conductivity using APHA 2510 B are reported in μS/cm (micro Siemens per centimeter).

Contact us to discuss your requirements for Dissolved Oxygen (DO) testing, using APHA method 4500-O G.

The Ministry of Health ‘Drinking Water Standards for New Zealand 2005 (Revised 2008) stipulates that all potable water should have NO E. coli which is shown in test results as <1 MPN/100mL. E. coli can be found in water that has been polluted with faecal matter, indicating the likelihood of pathogenic bacteria.

Faecal coliforms (MPN) are a sub group within Total Coliforms and are present in the gut and faeces of warm-blooded animals. If present in food they can cause severe stomach cramps and diarrhoea.

This test is performed by APHA Compendium of Methods for the Microbiological Examination of Foods 5^th Edition 9.81 & 9.91. 

The results are available in 72 hours using a 3-replicate, 3 dilution multiple tube procedure.  This is reported as MPN/g (Most Probable Number).

Nitrogen can be found in water supplies through fertiliser run-off or the breakdown of organic matter.

Water that tastes bad or smells of Sulphur may be due to high levels of leakage from Sulphate present in some New Zealand soils.

Measurement of the pH determination is one of the most important and frequently used tests in water chemistry.  Practically every phase of water supply and wastewater treatment are pH dependent.  At a given temperature the intensity of the acidic or basic character of a solution is indicated by hydrogen ion activity and referred to as pH. On a scale of 1 – 14, pH 1 is considered strongly acidic and pH14 highly alkaline (or ‘base’).  pH 7 is described as neutral.

APHA method 4500-H+ B

Salinity is an important unit-less property of industrial and natural waters, used as a measure of dissolved salts in a given mass of solution. It is an indirect method based on the conductivity measurement as the true reading would require a complete chemical analysis which is time consuming and expensive to perform.  Results are reported in ppt (parts per thousand), using APHA method 2520 B.

Temperature is important to various tests performed in the laboratory, as well as a useful test provided in the field by our technician. Thermometers are calibrated regularly to ensure they comply with the standard and tests are conducted using APHA method 2550 B.

The alkalinity of water is its acid-neutralising capacity.  Measurements are useful in the interpretation and control of water and wastewater treatment processes, and in determining the suitability of water to be used in irrigation.  Results for Total alkalinity (using standard method APHA2320B) are reported in gCaCO3/m3.

Total hardness is the sum of the calcium and magnesium concentration, both expressed as CaCO3.  Hard water is water that has high mineral content (in contrast with "soft water"). Hard water is formed when water percolates through deposits of limestone and chalk which are largely made up of calcium and magnesium carbonates. Hard drinking water may have moderate health benefits, but can pose problems in industrial and irrigation usage, where scale formation can affect equipment that handles water. In domestic settings, hard water is often indicated by a lack of suds formation when soap is agitated in water, and by the formation of scale in kettles and water heaters.  Water softening agents may be used to soften the water. Less than 75 g/m3 (mg/L or ppm) is considered soft, 75-150 g/m3 moderately hard, 150-300g/m3 hard and greater than 300g/m3 very hard. Results are reported in gCaCO3/m3.

Tests are performed using methods: APHA 2340 C, APHA 3500-Ca B & APHA 3500-Mg 

Total Coliform counts give an indication of the contamination potential of water.

Total dissolved solids is a measure of all of the dissolved solids in the pool water, from the water source, added chemicals and atmospheric dust.  The maximum acceptable level in swimming pools is 1500ppm.

Total suspended solids (TSS) is the dry-weight of particles trapped by a filter. It can comprise a wide variety of material, such as silt, decaying plant and animal matter, industrial wastes and sewage. High levels of TSS have a deleterious effect on waterways and aquatic life. Results are reported in g/m3, using APHA method 2540 D.

Turbidity is a test of the intensity of scattered light in a sample and indicates the clarity of the water. If the sample contains debris and rapidly settling coarse sediment, the suspended solids test may be more appropriate. Results are reported in NTU (Nephelometric Turbidity Unit), using APHA method 3130 B and EPA 180.1.