Aqueous release of heavy metals from two sewage sludges

Two anaerobically digested sewage sludges, one of relatively low and the other of relatively high heavy metal content, were extracted several times with water to determine the levels of Cu, Zn, and Cd that would be readily available for transport in the soil water if these sludges were applied to land. Generally, the quantity of metal released in the aqueous extracts was between 1 to 7% of the total content with Cu and Zn being released to a greater extent than Cd. The porportion of relatively mobile, non-cationic heavy metals in the aqueous extract differed in the two sludges and ranged from < 1% for Zn and Cd in one sludge to 56.2% for Cd in the other sludge.[/P ] © 1977 D. Reidel Publishing Company