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.

Chemical oxygen demand (COD) is defined as the amount of a specified oxidant that reacts with the sample under controlled conditions. The quantity of oxidant consumed is expressed in terms of its oxygen equivalence. Most applications of COD determine the amount of organic pollutants found in surface water (e.g. lakes and rivers) or wastewater, making COD a useful measure of water quality.  Results are reported in g/m3, using APHA method 5220 D.

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).

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

The Settlable solids (APHA 2540-F) test is used to obtain the volume of solids settling out during a fixed time period. It is reported as ml/litre.

Oil & grease is the material which is extracted from an acidified sample by a specified solvent.  The Total oil & grease (MIRINZ 829 (modified)) test is primarily performed on industrial wastewater as high levels may affect wastewater treatment systems and cause environmental degradation in waterways.  Results are reported in g/m3.

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.