. Water Quality Assessment

The main factors affecting variation in quality are dilution, water temperature causing variation in biological activity and oxygen solubility, and seasonal changes in waste inputs.

The selection of parameters for water quality assessment is dependent on the type of receiving water, the nature of the discharges into the receiving water, water use and any legal designation relating to the system. The key parameters for physicochemical assessment of a selection of different water systems and effl uents are given below (this does not include all the parameters that are required to be monitored under various legislation (Chapter 8)):

(a) river: biochemical oxygen demand (BOD), oxygen, temperature, NH 3 , NO 3 , PO 4 , Cl, etc.;

(b) lake: oxygen (at various depths), temperature (at various depths), PO 4 , NO 3 , SiO 2 , Fe, Mn, Na, K, etc.;

(c) groundwater: Fe, Mn, NH 3 , SO 4 , As, F, conductivity; (d) estuary: oxygen, temperature, BOD, suspended solids; (e) drinking water: coliforms, Fe, Mn, toxic metals, pesticides, etc.; (f) effl uents:

(i) biodegradable – sewage, agricultural, food processing: BOD, chemical oxygen demand (COD), suspended solids, NH 3 , PO 4 , etc.,

(ii) industrial – toxic: COD, BOD, suspended solids, NH 3 , metals and/or other toxic compounds;

(g) general characteristics – typing water source: hardness, alkalinity, pH, colour, conductivity, Fe, Cl, Na, K, silica, SO 4 , temperature, etc.