Extracellular enzyme activities and nutrient availability during artificial groundwater recharge

Area of Science:

• Environmental Science
• Microbiology
• Hydrogeology

Background:

• Natural organic matter (NOM) removal is crucial for drinking water production via artificial groundwater recharge (AGR).
• Biodegradation significantly contributes to NOM removal during AGR.
• Understanding microbial processes, specifically extracellular enzyme activities (EEAs), is vital for optimizing AGR systems.

Purpose of the Study:

• To investigate the biodegradation of NOM and nutrient availability for microorganisms in an AGR aquifer.
• To determine the relationship between EEAs and nutrient concentrations along a flow path in an AGR system.
• To assess the role of microbial enzymes in NOM removal during AGR.

Main Methods:

• Measurement of specific extracellular enzyme activities (alpha-d-glucosidase, beta-d-glucosglucosidase, phosphomonoesterase, leucine aminopeptidase, acetate esterase) using fluorogenic substrates.
• Determination of nutrient concentrations along the flow path in the AGR aquifer and reference groundwater.
• Comparison of enzyme activities and nutrient levels in basin water, sediment, and pore water.

Main Results:

• Significant increases in enzymatic hydrolysis rates (EEAs) were observed within 10m of the recharge basin.
• EEA changes correlated with decreases in nutrient concentrations, suggesting nutrient regulation of enzyme synthesis.
• Phosphorus was identified as a likely limiting nutrient at this AGR site.
• Extracellular enzymes demonstrated synergistic and cooperative functioning.

Conclusions:

• Microbial extracellular enzyme activities play a critical role in natural organic matter removal during artificial groundwater recharge.
• Nutrient availability directly influences the synthesis and activity of extracellular enzymes in aquatic environments.
• Phosphorus limitation impacts microbial degradation processes in this specific AGR system.
• The synergistic action of extracellular enzymes enhances the efficiency of NOM biodegradation.