INFLUENCE OF CONDITIONING AGENTS ON THE DETERMINATION OF METALLIC CONTENT OF SEWAGE SLUDGE BY ATOMIC-ABSORPTION SPECTROPHOTOMETRY WITH ELECTRO-THERMAL ATOMIZATION

Conditioning agents are often used to aid the de-watering of sewage sludges prior to disposal to agricultural land. These might interfere in the electrothermal atomic-absorption spectrophotometric analysis of heavy metals. Possible interferences by inorganic and polyelectrolyte conditioners were studied at the higher rates of addition normally used in sewage practice. Analyses for cadmium, chromium, copper, nickel, lead and zinc were performed by flame and electrothermal atomisation methods in conditioned and unconditioned samples. The organic polyelectrolytes tested did not interfere, nor did most inorganic conditioners at rates of addition consistent with normal sewage treatment practice. However, interferences occurred with aluminium chlorohydrate at normal and very high addition rates, and with other inorganic conditioners at very high addition levels.