PANAJI: In order to prevent and control pollution level in water bodies, the Central Pollution Control Board (CPCB) has drafted categorisation of the polluted river stretches to decide the level and degree of treatment required to maintain the natural bodies at their pristine level or restore them.
The CPCB has categorised polluted river stretches in five classes from priority I to V i.e. critically polluted to non-polluted based on the amount of biochemical oxygen demand (BOD) in the water body – or the level of oxygen that plants and animals need for survival and faecal coliform (FC) contents.
The CPCB, while drafting the categorisation, has observed that the Water (Prevention and Control of Pollution) Act, 1974 does not define the level of wholesomeness to be maintained or restored in different water bodies in the country. The central board has tried to define the wholesomeness in terms of protection of human uses, and thus, taken human uses of water as base for identification of water quality objectives for different water bodies in the country.
The categorisation is based on the total score estimated for the parameters BOD (weightage – 70 per cent) and FC (weightage – 30 per cent), the monitoring location is identified as ‘polluted’ location. The score is calculated based on average BOD and FC values. If BOD is less than 3 mg/L (milligrams per litre) then the score will be 10, if it exceeds above 30 mg/L then the score will be 100. Similarly, if the FC count exceeds above 5000 MPN (most probable number) then scoring will touch maximum 100 and if it ranges between 500 MPN and 5000 MPN then scoring will be between 10 and 50.
Priority-I indicates ‘critically polluted’ if the total score is more than 90, Priority-II indicates ‘severely polluted’ if the score is between 71 and 90, Priority-III signifies ‘moderately polluted’ stretch if the total score is between 51 and 70, while Priority-IV indicates ‘less polluted’ if the total score is between 21 and 50 and Priority-V indicates ‘non-polluted’ with the total score less than 20.
After finalisation of the draft categorisation, the Goa State Pollution Control Board (GSPCB) will calculate the score based on new criteria for polluted river stretches and give the scoring.
Under the Central Pollution Control Board-sponsored national water monitoring programme, the GSPCB measured water quality of rivers at 40 locations on 16 rivers and ten beaches and among them, 21 locations did not comply with the water quality criteria with respect to feacal coliform and total coliform.
The GSPCB recently, in December last year, undertook water analysis of 39 stretches of 14 rivers and found presence of feacal coliform in all the collected samples. The highest FC count was found at two stretches of River Sal at Khareband bridge with the count ranging between 3.5 lakh and 5.4 lakh followed by River Bicholim at Baraznagar, Dhabdobo and near the bridge with 2300-13000 MPN.
The analysis report of GSPCB found the level of feacal coliform in the range of 450-4900 MPN at three stretches of River Valvanti at Tulsimala, behind Sankhali municipal market and near Vithal temple.
According to the water quality criteria prescribed by the CPCB, feacal coliform organism MPN/100ml should be 30 or less in river water without conventional treatment but after disinfection.
The data of the water quality analysis showed the feacal coliform in River Mapusa, River Mandovi, River Assonora and River Zuari did not comply with the CPCB standard. However, the analysis indicated that water quality met the desired criteria of the Biochemical Oxygen Demand (BOD), one of the most important indicators of oxygen depletion in a water body, which was observed at less the 3 mg/L in all stretches except for River Sal where values were ‘zero’.
Source:: The Navhind Times