The metal concentrations in the sludge are well below the permissible
limit except for Mercury. The concentration of Mercury is 0.67 in STP
sludge which is higher than the prescribed specification but lower than
the previously used compost values of 1.39. Appropriate fortification of
the dried sludge not only helps in reducing the metal content by
dilution procedure but also helps in significantly improving its quality
for usage in agriculture. The comparison of the macro and micronutrients
is shown in the table 3 below.
Table 3: Comparative analysis of nutrients in STP sludge compost and
farmyard compost