The water quality of two stretches of the Ganga passing through Bihar and Uttarakhand, which were polluted earlier, has now improved and is of bathing standard with the biological oxygen demand (BOD), which ascertains the health of a river, found to be in check, according to official data.
The BOD is an important parameter for assessing water quality. It deals with the amount of oxygen consumption by biological organisms. The lower the value, the better the water quality.
The water quality of the Ganga is assessed in accordance with the primary water quality standard for outdoor bathing, which is when the BOD is less than 3 mg per litre, along with other factors.
According to the data shared with PTI of the Ganga river water quality comparison between 2015 and 2021, the BOD level of the river flowing through Uttarakhand (Haridwar to Sultanpur) and Bihar (Buxar to Bhagalpur) is below 3 mg per litre, which falls in the unpolluted category.
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Even in the other two stretches of the Ganga flowing in Uttar Pradesh (Kannauj to Varanasi) and West Bengal (Triveni to Diamond Harbour), the BOD level is in the lowest of the pollution category — category-5 (3-6 mg per litre), National Mission for Clean Ganga (NMCG) Director General G Asok Kumar said.
According to official data, there was an improvement in 2021 in comparison to 2015, when the BOD of the Ganga flowing through Bihar was in category-2 (7.8-27 mg per litre) and that of the stretch of the river flowing through Uttar Pradesh was in category 3 (3.8-16.9 mg per litre).
However, not much change was seen in the BOD level of the river flowing through West Bengal between 2015 and 2021. In 2015, the BOD level between Triveni to Diamond Harbour was in category-5 (3.1 to 5.8 mg per litre) and in 2021, it remained in the same category with a slight improvement in the BOD level, which was recorded between 1.3 and 4.3 mg per litre.
The water bodies that have a BOD level of more than 6 mg per litre are considered as polluted and identified for remedial action.
Other parameters that are used to measure the health of a river are also dependent upon the BOD level. For example, if the BOD exceeds 6 mg per litre, the dissolved oxygen, which is the amount of oxygen present in the water, is reduced below the desired levels. More the dissolved oxygen, better the health of a water body.
Kumar said to improve the water quality of the river flowing through Uttar Pradesh, especially Kanpur, the focus is on getting sewage treatment plants (STPs) running.
”We also found that a lot of industrial effluents come in in Kanpur. So we are now coming out with common effluent treatment plants to tackle it. We are in the process of rehabilitating many of the STPs in those areas too,” he told PTI.
Common effluent treatment plants (CETPs) are treatment systems specifically designed for collective treatment of effluents generated from small-scale industrial facilities in industrial clusters.