Ganga water quality has improved, Govt. Tells RS
02, Jan 2019
Prelims level : Environmental Conservation Mains level : GS 3: Conservation, environmental pollution and degradation, environmental impact assessment
- The water quality of the Ganga in 2018 has “improved over last year”, according to a
written statement in the Rajya Sabha.
- The three parameters were analysed to understand the quality of water of the Ganga.
- The parameter ‘Dissolved oxygen’ showed considerable increase at 39 locations and
‘Biological oxygen demand’ showed demand reduction and also there was an overall
decrease in faecal coliform.
- These three parameters are a proxy for both the presence of aquatic life as well as microbes
that may be harmful to these biota, and are conventionally used to assess the quality of the
- Presence of organic and inorganic wastes in water decreases the dissolved Oxygen (DO) content of the water. Water having DO content below 8.0 mg/L may be considered as contaminated. Water having DO content below. 4.0 mg/L is considered to be highly polluted. DO content of water is important for the survival of aquatic organisms. A number of factors like surface turbulence, photosynthetic activity, O2 consumption by organisms and decomposition of organic matter are the factors which determine the amount of DO present in water.
- The higher amounts of waste increase the rates of decomposition and O2 consumption, thereby decreases the DO content of water.
Biological oxygen demand:
- The demand for O2 is directly related to increasing input of organic wastes and is expressed as biological oxygen demand (BOD) of water.
- Water pollution by organic wastes is measured in terms of Biochemical Oxygen Demand (BOD).
- BOD is the amount of dissolved oxygen needed by bacteria in decomposing the organic wastes present in water. It is expressed in milligrams of oxygen per litre of water.
- The higher value of BOD indicates low DO content of water. Since BOD is limited to biodegradable materials Therefore, it is not a reliable method of measuring pollution load in water.
Chemical oxygen demand:
- Chemical oxygen demand (COD) is a slightly better mode used to measure pollution load in water. COD measures the amount of oxygen in parts per million required to oxidize organic (biodegradable and non-biodegradable) and oxidizable inorganic compounds in the water sample.