Indian rivers in danger: Brahmaputra too sound warning bell

Ranjan Kumar Padmapati

(The writer can be reached at rkpadmapati@yahoo.co.in)

Recently, the Central Pollution Control Board (CPCB) published a report on the pollution of rivers for the year 2022, which was based on 4,484 locations along the banks of the rivers spread across 28 states and seven union territories. The CPCB identified 311 polluted river stretches (PRSs) on 279 rivers. The criterion is based on the amount of biochemical oxygen demand (BOD). If it exhibits more than 3.0 mg /l, it is classified as polluted. In Assam, there are 10 PRS in total, of which one is identified as having priority at the first level and nine as having priority at the fifth level. The polluted rivers are Begi, Bharalu, Berhidihing, Dhansiri, Digboi, Kharsang, Kulsi, Mora Bhoroli, Pagladia, and Tocklai. The most polluted one is the Bharalu river, measuring BOD at 76 mg/l (3 mg/l), fluoride at 3.73 mg/l (1 mg/l), pH at 6.5 (7–8.5), and dissolved oxygen at 0.5 mg/l (6 mg/l). Figures in brackets indicate desirable limits as per the BIS standard. Basistha, another rivulet of Guwahati, is found polluting Dipor Beel, a

Unesco Ramsar site. Though the Brahmaputra is not included in the list, studies by other agencies have reported it to be a polluted river.

A report of the IJARSCT (International Journal of Advanced Research in Science, Communication, and Technology) published in November 2021 confirmed the high concentration of heavy metals like iron, chromium, lead, copper, etc., in the Brahmaputra, which are carcinogenic in nature. Those ranges exceed the acceptable limits instructed by BIS and WHO. The highest values of these heavy metals recorded are produced against each metal at different places on the Brahmaputra river banks, and their prescribed limits are indicated in brackets: iron 9.872 mg/l (0.3) and copper 54.00 micrograms/l (50) in Tezpur; lead 21.480 micrograms/l (10); and chromium 53.1 micrograms/l (50) at Pandu. These heavy metals affect most of the body organs, like the liver, brain, lung, kidney, bones, etc., to different degrees.

Yet another article by Deepa Padmanabhan (2021) reveals that the quality of the Brahmaputra water has been on the decline since 2015. The report is based on studies with a larger number of parameters over a period of 17 years, from 2003 to 2019. The water quality was affected by a high concentration of coliform bacteria at some monitoring stations along the length of the Brahmaputra. The faecal coliform level was high on different occasions at Pandu in 2017, and occasionally high at other places too. These results are confirmed by the CPCB report of 2012, and the faecal coliform bacteria level was 3000 MPB (a more probable number) per 100 millilitres, higher than the usual norm. 2,500 people may be responsible for many diseases. The tributaries in cities like Dibrugarh, Tezpur, Guwahati, etc., are dumping huge amounts of untreated sewage water into the Brahmaputra.

In a separate report by two engineers from the Assam Engineering College (Priyanka Kotoky and Bibhash Sarma, March, 2017), it is revealed that the Brahmaputra water over a stretch of 11 km starting from Ujan Bazar Ghat to Pandu Ghat is not fit for human consumption. Such impurity is caused by fertilizers, municipal waste (sewage) water, septic systems, agricultural run-off, etc. Both engineers calculated the Water Quality Index (WQI) with a larger number of parameters - temperature, P-H, dissolved oxygen, biological oxygen demand, chemical oxygen demand, suspended solids, nitrites, and nitrates) using a complex formula, and grouped the quality of the Brahmaputra water in the 4th category with a WQI of 61.71 and reported it as polluted water.

Lately, a new type of pollution has been found in the Brahmaputra sediments known as microplastic (less than 5 mm) pollution. The smaller size of microplastic (20–150 micrometres) was more abundant (531–3485 MP/kg) in the Brahmaputra, than microplastic in a range between 150 micrometres and 5 mm (20–240 MP/kg). Sources of pollution are landfills, construction debris littering, fishing, domestic use of plastic, etc. In the solid wastes, plastic is measured 9%. More than 90% of municipal solid waste is dumped improperly in open fields. Sewage canals and rivulets carry plastic materials to the rivers. Plastics are converted into micro and nanoplastics because of weathering under the exposure of ultraviolet rays from the sun. The microplastic enters the human body through different food chains. Some of the harmful effects listed are as follows: translocation to distant tissues, disruption of immunity, metabolism alteration, oxidative stress, carcinogenicity, reproductive toxicity, etc. River sediments act both as a sink and a source of heavy metals and microplastics.

A separate experiment by Tsering showed that the level of pollution due to microplastics was extremely high in 2018–19, as was the level of turbidity in 2003–2019. The UNO issued a signal of alarm on the accelerated consequences of pollution in the Brahmaputra, as reported in the journal, MDPI (Multi Disciplinary Digital Publishing Institute).

The problem of untreated sewage disposal has been accelerated by rapid urbanization on river banks and impacted by speedy population growth (20%). It is a matter of high concern that not a single sewage treatment plant is coming up in the cities of Assam. At housing complexes, it may be made mandatory to install individual sewage treatment plants with water recycling facilities. Only in Guwahati, 154 million litres of sewage are dumped into the Brahmaputra, and in all of Assam, it is 703 million litres. Other undesirable activities, such as the dumping of dead bodies into the river and religious activities like the immersion of idols (of heavy metals), etc., pollute our rivers. The PCB recorded more than 40 cases of oil spillage. Another source of river pollution (in 2014-15) in a ten-year duration recorded that it is 200 cases in Assam. Another factor is population growth on the sandbars near cities littered with plastic waste and other garbage.

The bad effect of river pollution has already been discerned. The number of river dolphins has reduced drastically to only 300 in the Brahmaputra. A local NGO, Aranyak, noted that the yield of fish has reduced to 15 kg per fisherman per day during the period of high turbidity, from 30-45 kg in the winter. A study conducted by SM Galib in the Bornoi (Bangladesh) revealed that in 8 years time after sewage water release to the river, abundance of fish and richness of species reduced to 47% and 35% respectively.

Fish population depends on P-H (acidity), dissolved oxygen, turbidity and presence of toxic substances etc. Reduction of fish yield will displace two million fishermen earning a livelihood in the entire Brahmaputra. The AINPPR under the ICAR detected pesticides, heavy metals in food chains, and contaminants in soil and water in Assam, and consequently, a PIL is pending in the Gauhati High Court.