Context: 

A study by the Indian Institute of Technology (IIT), Roorkee found that the most of the sludge in Indian sewage treatment plants (STP), set up to treat polluted water from the Ganga, had high potential for use as fertilizer.

Findings of the study:

• India does not yet have standards classifying sludge as class A or B.
• Most of the sludge analysed after drying fell into the class B category. 
• Nitrogen and phosphorous levels — the basic soil nutrients — were higher than those recommended by India’s fertilizer standards (FCO, 2009). 
  • However, potassium levels in some samples were less than recommended. 
• The total organic carbon was more than 16%, again higher than FCO recommendations, but the degree of pathogens as well as heavy metal contamination was above the recommended standard.
• The sludge is required treatment before it could be used unrestricted on farms or as a potential biofuel.

Classification of the sludge:

• Treated sludge can be classified as class A or B — as per the standards of the United States Environment Protection Agency.
• Sludge belonging to the class A type is safe to be disposed of in the open and useful as organic fertilizer. 
• Class B sludge means that the sludge can be used in restricted agricultural applications, where the edible parts of the crop should not be exposed to the sludge­ mixed soil, and animals and people not come into extensive contact. 

News Source: The Hindu

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