The exercise is key as DJB runs 37 STPs on the Yamuna, with concerns over whether disinfection systems adequately reduce faecal coliform levels before discharge.
Nearly four months after the National Green Tribunal (NGT) asked the Indian Institute of Technology (IIT), Delhi, to check whether the sewage discharged into the Yamuna river after treatment is safely disinfected, the expert panel is facing hurdles in conducting the review.
The exercise is crucial because the Delhi Jal Board (DJB) operates 37 sewage treatment plants (STPs) along the Yamuna. Of these, 11 use chlorination disinfection systems, 14 have UV disinfection systems, while the rest are still undergoing technological upgradation. Concerns have been raised in the past if the bacterial loads, particularly faecal coliform levels, are brought to safe limits before discharge.
But IIT Delhi has told the NGT that it is unable to proceed with the assessment because crucial data and access to the STPs have not been provided. In a letter submitted earlier this month, the institute said its expert committee is still awaiting permission for site visits, nomination of nodal officers by DJB to coordinate plant-level information, and operational and microbial performance data from both DJB and the Delhi Pollution Control Committee (DPCC).
IIT Delhi said it had formally sought the required information through a communication dated October 27, but the data submission remains pending.
Without this information, the institute said, the expert panel cannot prepare a “technically and scientifically robust expert opinion” on the effectiveness of UV disinfection systems. It has requested the NGT to issue directions to DJB and DPCC to expedite data sharing and provide logistical support for inspections. The matter is listed for hearing before the NGT on Tuesday.
The expert committee has Prof A.K. Mittal (Head), Prof Arun Kumar, Prof V. Arya and Prof Sovik Dass from the Civil Engineering Department as its members.
In its submission, the committee noted that the performance of UV disinfection systems depends on the type of secondary biological treatment employed at STPs, as well as on the chemical and physical characteristics of the treated effluent, making a comprehensive technical evaluation essential.
The committee also flagged that it has not received a DPCC report — from July this year — referred to in earlier NGT orders. It further pointed out that while DPCC has reported non-compliance with prescribed microbial standards at 14 STPs, there is no reliable data available on the effectiveness of the UV disinfection systems installed at these plants.
A realistic assessment, the committee said, requires microbial quality data at both the inlet and outlet of UV channels.
The NGT had earlier taken note of delays in the matter. In its order dated November 11 this year, the Tribunal recorded that although IIT Delhi had informed the court in September that an expert committee had been constituted, the detailed proposal outlining the requirements of relevant documents, estimated costs and other necessary details had not been received. The Tribunal had directed its registry to issue a reminder in this regard.
The case arises from a suo motu proceeding initiated by the NGT based on a media report on the functioning of STPs along the Yamuna. According to DJB’s status report submitted in August, UV or chlorination disinfection systems have been installed at several of the 37 STPs operating along the river. However, the Tribunal has repeatedly observed that DJB has not disclosed any norms approved by a competent authority permitting the use of UV technology specifically for disinfection.
During earlier hearings, the Central Pollution Control Board (CPCB) informed the Tribunal that it prescribes only effluent quality standards and not the technology to be adopted to meet them. While manuals of the Central Public Health and Environmental Engineering Organisation (CPHEEO) list UV and ozonation as disinfection options, the NGT has said their efficacy in Delhi’s STPs must be independently verified.
A senior DJB official aware of the matter said, “The case addresses the inadequate performance of sewage treatment plants operated by the DJB along the Yamuna river. Specifically, approximately 75% of these STPs lack proper bacterial disinfection facilities, resulting in high levels of fecal coliform in treated effluent discharged into the river.”