Sludge produced at municipal waste water treatment plants is reliable, steady and beneficial way to reuse waste. The manager of one plant in Japan is unwilling to spread the compost to agricultural fields and green belts because it contains heavy metals and human pathogenic microbiology. We searched for heavy metals and
Cryptosporidium parvum in sludge discharged from 8 night soil treatment plants in Osaka prefecture. As a result, the sludge contains a high concentration of Hg comparing other heavy metals. And we did not find out
Cryptosporidium parvum in the sludge. But many people believe that sludge can be polluted by
Cryptosporidium parvum at any time in Japan.
We proposed the reduction of Hg by changing the treatment system to shorten the sludge age and by diluting it using a wood tip and other organic substances. The sludge must be sterilized at over 60°C to prevent human pathogenic microbiology when being produced.
It is possible to produce high quality compost by changing operating procedures.
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