Authors: Yogesh Upadhyaya and Sandeep Achantani
You might have seen the pictures- waters of Yamuna lapping the shores gently, birds flying around and best of all, the color blue and not black. Did the lockdown really clean up Yamuna and what could we learn from that? Central Pollution Control Board (CPCB) recently released a report on this subject and our reading of the report suggests that it is not the lockdown that has cleaned the water. However, there is a lot that can be learned from this small report.
First, let us understand the geography of the river in Delhi.
Yamuna in Delhi
The river Yamuna enters Delhi at Palla. It flows for twenty-two kilometer till the Wazirabad barrage, where all of its water is stopped for use of citizens of the city. Twenty-three major drains enter the river downstream of the Wazirabad Barrage and except for monsoons, all the water in the river comes from these drains. We give below, the schematic of the river in the city, as depicted in the CPCB report.
The Najafgarh and Shahdara drains contribute most of the water (80%) as well as pollution (74% of average BOD load — see the note at the end of this post to quickly understand various pollution measures). There are 41 Sewage Treatment Plants to clean this drain water, of which 33 are operational. The operational capacity is 2801 Million Liters per Day (MLD) of which only 2254 MLD is utilized. This, when the average daily discharge is 3026 MLD.
The CPCB tested the water quality at three places in the Yamuna river, and in Najafgarh and Shahdara drains. They compared it to the quality observed in earlier periods. The results of the test were informative.
Results of water testing
Broadly speaking, there was a sharp improvement in the water quality at Nizamudin and upstream of Okhala, as seen in the BOD and COD levels, although both were still higher than norms. There was a slight improvement in BOD and COD levels in Najafargarh drain, as compared to a year ago, but a worsening in the quality of water in Shahdra drain. Most importantly, in both cases, the levels of pollutants were way over the standards!
This is not surprising. According to CPCB, industries in Delhi generate only 36 MLD (Million liters per day) of effluents and contribute less than 5% of the BOD load. Furthermore, there are a few Effluent Treatment Plants to handle this load. The lockdown was for industries and not households. People in the households kept washing their dishes and clothes and did not stop defecating and urinating just because their movements were restricted.
So how is it that there was improvement in water quality in the river although there was no improvement in the water in the main contributing drains?
Excess snow melt
Around a year back, one of us had written a post on cleaning of Ganga and the main message of the post was that there was a hard problem and a harder problem in cleaning water bodies.
· Less Goo: The hard problem was to stop filth and pollutants from homes, commercial establishments, industries and farms to flow to the water body.
· More flow: The harder problem was to take less water from the water body for agricultural, industrial and residential activities. If there is more flow in a water body, it cleans itself. If there is less flow, the water remains dirty.
This year saw excess snow melt in upper reaches of the river and hence there was excess water. The excess water was more than that could be stored at Wazirabad and hence, it was released downstream. This water diluted the shit from the drains the empty into the river and made it better.
Most of the pollutants entering the Yamuna in Delhi are from residences. Without severely reducing this load, there is no way the Yamuna in the city can be cleaned up. It is only in monsoon that the river flows freely and gets cleaned up a little.
While reading the report, a few questions came up our mind which we will try to answer in the coming months.
· If the main source of pollution is the drains and domestic waste then, why is it not getting solved with STPs? There has been a lot of investment by the government in the last two decades on STPs and yet there is no visible result.
· Why is the STP capacity utilization below operational capacity? Why is operational capacity below installed capacity? STPs are simple. We believe that a typical STP has the following stages
o Filter large solids using grills
o Push air through water to encourage decomposition of organic substance
o Let suspended solids settle at bottom
o Dispose settled solids
o Filter water through gravel beds, etc.
This is not technologically complex and once an STP is set-up, there is no reason it should stop running.
· Why would Delhi spend money on cleaning the water when it does not have to drink it? The city extracts the water for its use upstream of where it dumps its filth. So, its own pollution does not impact its drinking water and aesthetics is much less powerful motivator than health. If we track the river back to source, we will find that this story repeats itself in many cities upstream. It is in no one’s interest to clean the river after they have extracted water from it for their own use. This is similar to problems faced by people living in apartment blocks. If the bathroom above you leaks and that causes problems in your bathroom, it is possible that your upstairs neighbor does not heed your pleas to get it fixed.
· How can we increase the flow of water in the river? This is not easy. More than 90% of water of the river is taken for agriculture in non-monsoon season. Farmers probably cannot change their dependence on this water without capital subsidy for more efficient irrigation methods like drip irrigation.
· The 4–5 measures that CPCB used in this report may not be comprehensive. For example, it mentions POP idols as polluters. But such specific pollutants many not be captured by Ph, SS, DO, BOD and COD. These measures may not fully capture presence of pollutants arising from fertilizer and pesticides runoff and from industrial activities also.
Note: Pollution measures used by CPCB
Suspended Solids (SS): This is a measure of solids suspended (not dissolved) in water. It is expressed in mg / l. Note that reducing these solids will also reduce the BOD.
Conductivity: Conductivity of water is a measure of dissolved solids. Many salts, when dissolved in water, increase its conductivity.
Biochemical Oxygen Demand (BOD): It measures the amount of oxygen required by microorganisms in the sewage to break down the organic content contained in the sewage. When a high BOD sewage is released into a water body, it takes away dissolved Oxygen from it. The Oxygen is needed by fishes and other aquatic life and they die when a high BOD pollutant is released into the water body.
Dissolved Oxygen: Directly measures the dissolved Oxygen levels in water.
Chemical Oxygen Demand: A measure similar to BOD but less specific in the sense that it measures everything that can be chemically oxidized, rather than just levels of biologically oxidized organic matter.
Acidity (ph): Acidity of the water
AskHow India has begun its work on the topic, “How can we clean our water bodies?” and this is the first post under it. We hope you point out our errors and also help us answer the questions we have raised in this post.
Modifications / Changes: The title of the piece changed from “Has the lockdown cleaned Yamuna?” to “Has the lockdown cleaned Yamuna? No!” for greater clarity on June 17, 2020.
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