Trace elements in biological waste treatment

The importance of trace elements for microbial growth and metabolism is well recognized. However, their importance in the operation of biological waste treatment processes is not usually considered or understood fully. It is often assumed that the concentration of trace elements present in a wastewater will be sufficient for good treatment. This assumption may not be valid, because the types and concentrations of trace elements in a wastewater vary with location and time. Trace elements may also be removed from the wastewater by various means, including adsorption and hydrogen sulfide precipitation. For these reasons, trace element deficiencies may occur, and treatment problems, including the occurrence of filamentous organisms, may result. An argument supporting this thesis, along with an analysis of the role of trace elements in the activated sludge process, is presented. Recommendations and alternatives for overcoming problems that may be caused by trace element deficiencies are offered.