however, our present study suggests that measurements of only available metal contents and hydrolytic enzyme activities cannot provide a presence prediction of toxicity other extracellular and intracellular enzymes in soils amended with sewage sludge, indicating that their scientific validity is questioned.
hence, further studies are needed to explore the relevancy in using enzyme activity to reflect different types of sewage sludge and soil
this would not only overcome problems of enzyme inhibition but also would reduce a major area of public concern such as nitrate leaching, heavy metal and pathogen contamination, plant uptake of sludge borne metals and soil fertility and health