Solid respirometry to characterize nitrification kinetics: a better insight for modelling nitrogen conversion in...

Area of Science:

• Environmental Engineering
• Wastewater Treatment Technologies
• Biogeochemical Processes

Background:

• Nitrification is a key process in constructed wetlands for removing ammonium.
• Accurate measurement of nitrification rates and biomass is essential for effective wastewater treatment plant modeling.
• Existing methods may not be suitable for the complex organic matter found in vertical flow constructed wetlands (VFCWs).

Purpose of the Study:

• To develop and validate an original respirometric method for measuring nitrification rates at various depths within VFCWs.
• To adapt the method for organic matter (sludge, colonized gravel) under partially saturated conditions.
• To determine autotrophic biomass concentration and maximum growth rate using the new method combined with mass balance.

Main Methods:

• A respirometric approach was employed using an on-line oxygen analyzer to measure oxygen demand in a reactor.
• The reactor contained a mixture of organic matter (sludge, colonized gravel) and a bulking agent (wood).
• Ammonium-containing liquid was applied, and gas passing through the reactor was analyzed for oxygen concentration.

Main Results:

• The study presents the overall methodology, influencing factors (sample volume, liquid properties, application frequency), and method robustness.
• The developed method successfully measured nitrification rates in VFCW organic matter.
• The combination with mass balance allowed for the determination of autotrophic biomass concentration and maximum growth rate.

Conclusions:

• A novel respirometric method enables accurate nitrification rate measurement in VFCWs.
• The method provides essential parameters (biomass concentration, growth rate) for VFCW process modeling.
• This advancement aids in optimizing the design and operation of constructed wetlands for improved wastewater treatment.