How do rivers act as natural purifiers?

The holy river Ganga, I am sure that you would be familiar with this river and all my life I have been told that you lose all your sins just by taking a dip in the holy waters of Ganga, in the Hindu way of living it is believed that the bathing in the water of the Ganga redeems one’s sins.

Usually, it has been observed that all the rivers in India have carved out their path, that is not the case for River Ganga, it is the only river whose source was pre-decided, developed, and chartered by a man, not nature. King Bhagirath was the man who discovered the source and chartered its course along with cities such as Haridwar, Varanasi, Prayagraj and Patna.

According to the legend, King Bhagirath along with his grandfather King Sagar and his father King Dilip were searching for a divine waterbody only to discover failures, until they reached Gomukh that enjoys being at a unique and rare geo-point on Earth that receives heavenly radiations from the planet Jupiter turning the frozen block into divine waters, divine enough to redeem off one’s sins. The block receives moonbeams (Shiva Tatwa) in the night that helps in the freezing of water and during the day it receives the melting rays of the sun (Vishnu Tatwa) that impacts the quality of water.

Although the river Ganga might not be a natural river this rare and unique phenomenon makes it more than that “divine”.

Science or Myth?

The river Ganga might be an exception due to the aforesaid phenomenon but all the rivers share a common process of cleansing themselves, all the rivers can purify themselves ,Ganga being the most efficient purifier capable enough to cleanse one’s sin.

As human metamorphosis evolved, they started discharging sewage into natural bodies of water, thus polluting the water but the condition of water does not remain the same forever due to the natural forces of purification that act upon the pollutants and eliminate them to large extent but the self-purification capabilities have a limit to their efficiency. If humans keep on discharging wastewater heavily then that will cause the pollution of river bodies.

Natural forces of purification

  1. Dilution and Dispersion

When the organic matter content is less in volume compared to the large volume of river water, the putrescible organic matter gets dispersed and diluted reducing the menace of sewage.

When sewage of concentration Cs flows at the rate Qs into a river that has a concentration of Cr flowing at the rate of Qr then the concentration C of the resulting mix can be given by:

Cs × Qs + Cr × Qr = C (Qs + Qr)

Another form of this equation is applicable separately for finding the concentrations of impurities such as BOD, Suspended sediments, Oxygen content, etc.

  • Sedimentation:

The settleable solids in the sewage effluent settle down to the bed of the river due to the action of gravity that helps in the self-purification process.

  • Sunlight:

The sunlight helps in facilitating the bleaching and stabilizing effect of bacteria, certain microorganisms depend on the process of photosynthesis for their food they absorb carbon and release oxygen that aids in the self-purification process through oxidation.

  • Oxidation:

As soon as the sewage is discharged into the river, it triggers the process of oxidation of the organic matter hence creating a deficiency of oxygen that is filled up by the atmospheric oxygen, this process of oxidation only ends when the organic matter has completely oxidized. The process of oxidation is considered the most important action responsible for affecting the self-purification of the river.

  • Reduction:

The organic matter settled at the bottom of the river is reduced due to the process of hydrolysis either chemically or biologically, anaerobic bacteria splits the sewage content into liquids and gases, eventually leading to their ultimate stabilization by oxidation.

The self-purification forces depend on a few factors, such as temperature, turbulence, hydrography (velocity and river expanse of the river stream), available dissolved oxygen and amount and type of organic matter present, rate of reaeration.

Now for a moment, let us go back to River Ganga. In 1947 a German Scientist, Kohiman visited India and took the sample of the water of Ganga and conducted various experiments concluding that ‘The Ganga waters have a stunning quality of destroying bacteria, which I haven’t observed in the water of other rivers of the world’. A French Scientist Havel also observed Ganga Jal is capable of killing many diseases and bacteria. A study conducted by the University of Roorkee confirmed that the water of Ganga is a disinfectant, self-purifying, and can kill cholera-causing bacteria.

So Science or myth?

Well, Science according to me.

It is clear that river streams have a natural mechanism of environmental clean-up independent of human beings but human activities continuously hinder the efficiency of their mechanism that in turn is harming humans, once again indicating bad environment is bad for human business but I still believe we can turn this around.

The power, compassion, and forgiving nature of the river is described in the Rigveda 1.23.22:

Idamaph pra vahat yat kim cha duritam mayir
Yad vahambhidrudroh yad va shap utanritam

The above shloka can be translated to:

O powerful waters,
I might have violated,
The laws of nature,
Knowingly or Unknowingly,
Foolishly or impudently.
Take away whatever is wrong,
Or deficient in me.

Remember people together we can and we will Save the Planet!

Source and Reference:
Hindu Rites and Rituals, K.V Singh.
Sewage Disposal And Air Pollution Engineering, SK Garg.

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