A first of its kind analysis of the sludge found in Indian sewage treatment plants (STP), set up to treat polluted water from the Ganga, found that most of it had “high potential” for use as fertilizer, but required treatment before it could be used unrestricted in farms, or as a potential biofuel.
An emerging initiative of the National Mission for Clean Ganga, a flagship programme of the government to establish treatment facilities and prevent pollution of the river, is to derive livelihood opportunities from the river rejuvenation programme. One of the measures, under this ‘Arth Ganga’ (economic value from Ganga), is to “monetise” and reuse treated wastewater and sludge. This means converting sludge — a thick residue filtered out of STP that while rich in organic chemicals is also a repository of heavy metals, industrial effluents and bacterial contaminants — into usable products such as manure and bricks. The contaminants in sludge means that they need to be treated and dried before they can be safely disposed.
Treated sludge can be classified as class A or class B — as per the standards of the United States Environment Protection Agency — with class A being safe to be disposed of in the open and useful as organic fertilizer. Class B means that the sludge can be used in “restricted” agricultural applications, the edible parts of the crop not be exposed to the sludge-mixed soil, and animals and people not come into extensive contact. India doesn’t yet have standards classifying sludge as class A or B.
