Inter and intra plant variability of enzyme profiles including various phosphoesterases and sulfatase of six wastewater treatment plants

• Phosphotriesterase activity is measured in sewage sludge for the first time.
• Activity sequences of various phosphoesterases were determined.
• Enzyme patterns of different process stages of one WWTP were detected.
• Specific differences between enzymatic fingerprints of aerated tanks were found.
• Variations of enzymatic activities were statistically evaluated.

Biodegradation of organic wastewater constituents by activated sludge microorganisms is based on enzymatic processes. It is supposed that wastewater treatment plants (WWTP) differ in their enzymatic fingerprints. To determine such fingerprints, activated sludges from nine aerated tanks of six WWTPs were repeatedly sampled and analyzed for the activities of l-alanine aminopeptidase, esterase, α- and β-glucosidase, alkaline phosphatase, phosphodiesterase, phosphotriesterase, and sulfatase. In one WWTP the enzymatic activities and their variations within 1 week were assayed in various process stages.Mostly the enzymatic profiles were dominated by l-alanine aminopeptidase, followed by alkaline phosphatase. They differed in variable contributions of esterase, phosphodiesterase, α- and β-glucosidase. The sulfatase activity was generally low. For the first time phosphotriesterase activity was detected in various samples, but with limited analytical validity. Particle mass-related activities of individual enzymes varied between plants by factors 2–4 and up to 11, when related to suspension volumes.