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