Water Quality (WQ) Parameters..

What is Water Quality (WQ)?

   Water quality is a term used to describe the chemical, physical, and biological characteristics of water. Although scientific measurements are used to define a water's quality, it's not a simple thing to say that "this water is good," or "this water is bad."

These scientific measurements are known as WQ parameters.

Basically there are 3 types of water quality parameters.

   1. Physical Parameters (sample do not change while measuring)

    Ex:- Temperature, color, odor, taste, pH, turbidity, conductivity etc.

    

   2.  Chemical parameters ( Sample undergoes chemical changes)

    
    Ex:- acidity, alkalinity, BOD, COD, nitrate, sulphate, phosphate, metals, hardness, pesticides, oil/grease, phenol.

   3. Biological parameters
       Ex:- E-coli, coliform


Basically there are two methods for determine WQ parameters quantitatively. First one is the classical methods. This methods do not use instruments except balance.
    Ex:- Gravimetric, titrometric methods etc.

Other method is the Instrumental method. This methods always need instruments.

Instrumental Methods

Basic methods are,

·     Electrochemical methods

~Instrument that are used to measure electrical properties are used in this method.

~Ex: conductometry, potentiometry, voltametry and amperometry.

·     Spectroscopic methods

~Wave properties (wavelength, wave number, frequency etc.) are used as the independent variable.

~Ex: UV/ Visible, IR, NMR etc.

·     Radiochemical methods

~Measure the content of radioactive substances and radioactive properties.

·     Miscellaneous methods

~Turbidity, Circular dichroism (CD), polarimetry, refractive index (RI)

TABLE 1. INSTRUMENTAL TECHNIQUES
Method	Response
Potentiometry:	Many chemical reactions produce electric energy, a battery for example. The amount of chemical to produce a measured potential is calculated.
Coulometry:	The amount of electrical current and the duration over which it flows is a measure of the amount of chemical substance producing the current.
Conductimetry:	The number of charged chemical components in a solution determines the resistance or conductance of a solution to the passage of electrical current.
Voltammetry:	The magnitude of electric potential necessary to cause the breakdown of a chemical substance and the current resulting from that breakdown are related to the amount of chemical present.
Ultraviolet, visible, infrared, and x-ray spectometry:	The extent to which these rays are absorbed by a sample depends upon the amount of sample present
Thermogravimetry:	The loss in weight of a substance as it decomposes upon heating is proportional to the amount of substance initially present.
Nuclear magnetic resonance:	For chemicals showing magnetic properties the strength of the magnetism is related to the amount of substance present.
Nuclear activation analysis:	The amount of radioactivity produced by a substance is proportional to the amount of material emitting radiation.
Mass spectrometry:	The intensity of each component fraction present as a chemical is broken apart relates to the amount initially present.

WQ analyzing lab

Why do we need to assess the Quality of waters?

Because we must judge whether the water we use has the sufficient quality we use has the sufficient quality for the intended use. Therefore, the quality required depends on the use of water.Also water that is perfectly good to wash a car with may not be good enough to serve as drinking water at a dinner party. When the average person asks about water quality, they probably want to know if the water is good enough to use at home, to play in, to serve in a restaurant, etc., or if the quality of our natural waters are suitable for aquatic plants and animals.

BOI and CEA are the institutions that are responsible for formulated guide lines, consult parameters of other countries and also consult health aspects from certain organizations (WHO).

TABLE 2: DRINKING WATER STANDARDS (Sri Lanka Standards for potable water – SLS 614, 1983)

(Source: BOI Sri Lanka)

Highest desirable level: This is the level we would like to see. If a pollution parameter has value below the highest desirable level there will be no health problems.

Maximum permissible level: This is the legal limit. If the pollution parameter has a value above, this legal action can be taken.

Maximum tolerance limit: This is the limit above which cannot be tolerated by legal authorities.

Assessment of WQ parameters will be discussed in the next posts….