The heavy metal problem can be serious when we look at untreated wastewater of mixed domestic and industrial origin. It can also be serious where sludge is produced by wastewater treatment plants which are fed by sewers collecting wastewater from domestic and industrial outlets. Most parts of Fred's article are not about this type of sludge but about the world where sewers remain an exception and fecal sludge is pumped out of the septic tanks or latrines in the backyards of houses. This is in general the poo we are producing, which should not have any elevated chemical threats. Farmers in India, but also Africa realized its value and are paying truck drivers for it. It is then usually dried for some months before use.
The heavy metal problem can be serious when we look at untreated wastewater of mixed domestic and industrial origin. It can also be serious where sludge is produced by wastewater treatment plants which are fed by sewers collecting wastewater from domestic and industrial outlets. Most parts of Fred's article are not about this type of sludge but about the world where sewers remain an exception and fecal sludge is pumped out of the septic tanks or latrines in the backyards of houses. This is in general the poo we are producing, which should not have any elevated chemical threats. Farmers in India, but also Africa realized its value and are paying truck drivers for it. It is then usually dried for some months before use.