The promise comes with a rider though. Delhi Jal Board CEO Vijay Kumar says that, once the project is completed, DJB would be trapping only about 75% of the city's total sewage. At present, the river is "dead", no better than a large drain since it carries only sewage. The only time in a year when fresh water can be found in it is during the monsoon season.
"The total dissolved solids will be reduced by 70-80% while the biochemical oxygen demand (BOD) will be down by 50-70%. Changes will be visible as early as the end of 2014 since interception of sewage flowing into the Najafgarh drain, the largest one in Delhi, would be complete then," said a source.
The project was expected to be over before 2010 Commonwealth Games. It was finally inaugurated in December 2011. "By laying interceptors along the three drains, we will trap sewage from 119 sub-drains that do not lead to an STP and even open directly into Yamuna. Thus, the entire sewage load will be taken to STPs. Subsequently, the interceptors will function as independent trunk sewers. Once it starts working, the BOD, that is an extremely unhealthy 41mg/l, will fall to 12mg/l," said the DJB source.
Work was divided into six packages and awarded to three agencies. The interception network was to cost close to Rs 2,000 crore. The entire project would cost roughly Rs 6,000 crore.
Work includes augmentation of capacity of Dr Sen Nursing Home and Delhi Gate STPs from 2.2 million gallons per day to 15MGD. Thirteen drains emptying into the Bela Road and Ring Road trunk sewers will be intercepted.
But, Centre for Science and Environment, critical of the project since its inception, says interceptors will not help restore Yamuna to Class C bathing quality water, with a BOD level of 3mg/l, as ordered by Supreme Court in 2001.
"The project is full of miscalculations regarding sewage flow. The detailed project report grossly underestimates the volume of wastewater. Secondly, fresh water flows are needed to dilute the river water. Even if the entire sewage in Najafgarh and Shahdara was treated to BOD 20 mg/l, as stated by Engineers India Ltd, the Yamuna would need 18 billion litres of freshwater to dilute it to bathing level," said Sunita Narain in CSE's 'Excreta Matters: 7th State of India's Environment Report'.
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