Control of pH during denitrification using an encapsulated phosphate buffer

Acidic phosphate granules encapsulated within a pH-sensitive wall were used to demonstrate pH control during denitrification. Characterization of the distribution of microcapsule mass and percent potassium content of the core showed that the wall was an average of 30.3% of the total microcapsule mass. A stochastic model using Monte Carlo methods was developed describing the kinetics of release of the microcapsule core in solution. The model satisfactorily predicted the pH drop and potassium release as a function of time for experiments performed at various pH values in the absence of biological activity. Although the model only fairly predicted the actual values of pH and potassium released during the denitrification experiments, the model predicted the pH trends quite well as shown by the similar predictions in the increase and decrease in pH. The experimental data demonstrate that pH control using the microcapsules was effective because the pH rise caused by denitrification was counteracted by the release of the acidic microcapsule core.