Stability constants and complexation capacities of complexes formed between heavy metals and extracellular polymers from activated sludge

Conditional stability constants and complexation capacities of extracellular polymers extracted from activated sludge with copper, nickel, cadmium and cobalt have been determined at high and low free metal concentrations using gel complexometry. The results compare favourably with those for other bacterial extracellular polymers, but less well with those for competing metal‐binding ligands present in sewage. The affinity of extracellular polymers for metals has been discussed in terms of their contribution to metal removal during the biological phase of wastewater treatment.