Heavy metals in activated sludge

[Joe Pringle <joepringle@compuserve.com>]

Question from Exnora International in India:

We have taken up composting of vegetable wastes from the Koyambe-
du  market  in  Madras, Asias's largest  vegetable  market.   The 
Chennai  Metro  Water  Supply and Sewerage Board  has  agreed  to 
compost  the waste by using the activated sludge from the  sewage  
treatment  plant in Koyambedu. But one important issue  would  be 
`How  do  you remove heavy metals in the sludge?'  We  have  been 
writing to several people enquiring about this. Any ideas?

please CC any responses to Exnora International at: 
exnora@giasmd01.vsnl.net.in   
or   exnorain@md2.vsnl.net.in