Combining computational fluid dynamics with a biokinetic model for predicting ammonia and phosphate behavior in aeration tanks.

The aim of this study was to use computational fluid dynamics for predicting the behavior of reactive pollutants (ammonia and phosphate) in the aerobic zone of the bioreactor located at the Wschod wastewater treatment plant in Gdansk, Poland. The one-dimensional advection-dispersion equation was combined with simple biokinetic models incorporating the Monod-type expressions as source terms for the two pollutants. The problem was solved numerically by a multi-step splitting technique algorithm. The dispersion coefficient, E(L), was estimated using a statistical method and numerical optimization based on experimental data from three tracer studies. With the first method, the values of EL varied within the range 1082 to 1860 m2/h and 695 to 1355 m2/h, respectively, in sections 1 and 2 of the aerobic zone. Except for one case, deviations of the corresponding numerically optimized values of E(L) did not exceed 14%. The maximum specific rates of nitrification [r(n,max,20) = 4.6 g N/(kg VSS h)] and phosphate uptake [r(Pupt,max,20) = 13.5 g P/(kg VSS h)] at T = 20 degrees C were determined based on laboratory batch experiments. With minor adjustments of the kinetic parameters, the model was capable of accurately predicting the longitudinal profiles of ammonia and phosphate in the aerobic zone, and the simulation results were presented using the actual horizontal geometry of the bioreactor as a background.

Comparison of the effects of conventional and alternative external carbon sources on enhancing the denitrification process.

Food industry effluents are considered a potential alternative for methanol when seeking external carbon sources to enhance denitrification in municipal wastewater treatment plants (WWTPs). The aim of this study was to determine the immediate effects of dosing different carbon sources on the denitrification capability of process biomass from the Wschod WWTP in Gdansk (northern Poland). Five carbon sources, including settled wastewater, methanol, and three industrial effluents (distillery, brewery, and fish-pickling process) were tested in two kinds of batch experiments. The acclimation period of biomass to methanol also was investigated in bench-scale systems. During the conventional batch experiments, with the industrial effluents, the observed nitrate utilization rates (NURs) ranged from 2.4 to 6.0 g N/(kg VSS x h), which were only slightly lower than the rates associated with the use of the readily biodegradable fraction in the municipal (settled) wastewater [4.6 to 7.8 g N/(kg VSS x h)]. The conventional NURs observed with methanol and non-acclimated process biomass were low [i.e., 0.4 to 1.5 g N/(kg VSS x h)], and a minimum 2-week acclimation period of biomass to methanol in the bench-scale systems was needed to reach the level of 4.0 g N/(kg VSS x h). In other experiments, dosing the distillery and fish-pickling effluents at the beginning of the anoxic phase (preceded by the anaerobic phase) resulted in considerably higher (over 20%) NURs compared with the same experiments with the other carbon sources.