CEE Oct-Dec 2012

' Water Quality Criteria and Standards For successful management of water resources it is imperative to monitor the quality of water, both in established water quality trends as well as prioritizing pollution abatement efforts Dr. B. Chakravorty c________.. . ·~.-;~:;.-: :.· .... !f:t>.:->· .:'lc...:._\~ ~ ... y Water Quality Monitoring is an important exercise, which helps in evaluati ng the nature and extent of pollution control required , and also the effectiveness of pollution control measures already in existence. The water quality trends and prioritizing of pollution control efforts is also assessed. There are many sources of water quality criteria and standards - they may originate by individual countries, or they may be issued by international bodies. Further, these various levels specified will take cognizance of the differing uses for which water quality must be maintained. The requirements, as regards suitability, of water for industrial use, for drinking, for boilers and so on, may differ widely and each may be quite demanding. The ultimate objective of the imposition of standards (which may necessitate extensive treatment prior to use) is the protection of the end users, be these by humans, animals, agriculture or industry. In the present context, however, the main considerations are in regard to safeguarding public health and the protection of the whole aquatic environment. Both have very high quality requirements, which complement each other to a great extent. For example, in general terms, if a river or lake water meets the most stringent fi shery requirements it will meet all or virtually all other environmental quality objectives (EQOs). For successful management of water resources it is imperative to monitor the quality of water both in established water quality trends as well as prioritizing pollution abatement efforts. Although all the Indian industries function under the strict guidelines of the Central Pollution Control Board (CPCB), but still the situation of environmental pollution is far from satisfactory. Different norms and guideline are given for all the industries depending upon their pollution potentials. As per Central Pollution Control Board, the inland water quality is analysed for following major parameters: The water quality monitoring resu lts are generally analysed with respect to indicator of oxygen consuming substances (Biochemical demand) and indicator of pathogenic bacteria (total coli form and fecal coli form). The organic pollution continues to be the predominant pollution of aquatic resources. The organic pollution measured in terms of bio-chemical oxygen demand (BOD) and coli form count gives the indication of extent of water quality degradation. Temperature is one of the most important ecological features. It controls behavioral characteristics of organisms, solubility of gases and salts in water. The basis of all life functions is complicated set of biochemical reactions that are influenced by physical factors such as temperature. Disease resistance is also linked to temperature . Increase in temperature also increases the rate of microbial activity. Temperature increase may become barrier to fish migration and in this way seriously affect on reproduction of species. The major sources of thermal pollution are industrial cooling systems working in a manufacturing plant or a power plant. pH is a measure of the acidity or alkalinity of water and is one of the stabl e measurements. pH is a simple parameter, but is extremely important, since most of the chemical reactions in aquatic environment are controlled by any change in its value. Anything either highly acidic or alkaline would kill marine life. Aquatic organisms are sensitive to pH changes and biological treatment requires pH control or monitoring. The toxicity of heavy metals also gets enhanced at particular pH. Thus, pH is having primary importance in deciding the quality of waste water effluent. Waters with pH value of about 10 are exceptional and may reflect contaimination by strong base such as NaOH and Ca(OH)2. The range of desirable pH of water prescribed for drinking purpose by lSI and WHO is 6.5 to 8.5. Chloride occurs in all natural waters in widely varying concentrations. Excessive chloride in potable water is not particularly harmful and the criteria set for this anion are based primarily on palatability and its potentially high corrosiveness. Chloride in excess (>250mg/L) imparts a salty taste to water and people who are not accustomed to high chlorides may be subjected to laxative effects.