Calibration of a complex activated sludge model for the full-scale wastewater treatment plant

In this study, the results of the calibration of the complex activated sludge model implemented in BioWin software for the full-scale wastewater treatment plant are presented. Within the calibration of the model, sensitivity analysis of its parameters and the fractions of carbonaceous substrate were performed. In the steady-state and dynamic calibrations, a successful agreement between the measured and simulated values of the output variables was achieved. Sensitivity analysis revealed that upon the calculations of normalized sensitivity coefficient (Si,j) 17 (steady-state) or 19 (dynamic conditions) kinetic and stoichiometric parameters are sensitive. Most of them are associated with growth and decay of ordinary heterotrophic organisms and phosphorus accumulating organisms. The rankings of ten most sensitive parameters established on the basis of the calculations of the mean square sensitivity measure (δjmsqr) indicate that irrespective of the fact, whether the steady-state or dynamic calibration was performed, there is an agreement in the sensitivity of parameters

Rotating biological contactors : a review on main factors affecting performance

Rotating biological contactors (RBCs) constitute a very unique and superior alternative for biodegradable matter and nitrogen removal on account of their feasibility, simplicity of design and operation, short start-up, low land area requirement, low energy consumption, low operating and maintenance cost and treatment efficiency. The present review of RBCs focus on parameters that affect performance like rotational speed, organic and hydraulic loading rates, retention time, biofilm support media, staging, temperature, influent wastewater characteristics, biofilm characteristics, dissolved oxygen levels, effluent and solids recirculation, stepfeeding and medium submergence. Some RBCs scale-up and design considerations, operational problems and comparison with other wastewater treatment systems are also reported.Fundação para a Ciência e a Tecnologia (FCT

The microbial ecology and bioremediation of chlorinated ethene-contaminated environments

The microbial ecology of tetrachloroethene (PCE)- and trichloroethene (TCE)-contaminated sites is complex. Fundamentally, accurate prediction of contaminant fate, the survival of dehalorespiring populations, and, thus, the performance of engineered bioremediation approaches at these sites are feasible only if the correct kinetic models are applied, and meaningful and mathematically independent parameter estimates are input into these models. A model that incorporates biomass inactivation at high chlorinated ethene concentrations, as well as the self-inhibitory and competitive inhibition effects that the elevated chlorinated ethene concentrations exert on dechlorination reactions, must be utilized to accurately predict dehalorespiring population substrate interactions and growth. The initial conditions used in batch laboratory kinetic assays, including the initial limiting substrate (S0)-to-initial biomass concentration (X0) ratio and the S0-to-half-saturation constant (KS) ratio, must be carefully selected to ensure that the parameter estimates are meaningful and independent. Kinetic assays conducted at appropriate S0/X0 and S0/KS ratios suggest that the substrate utilization kinetics of many PCE-to-dichloroethene (DCE) dehalorespirers are faster than those of Dehalococcoides mccartyi strains. Integration of mathematical simulations using appropriate dehalorespiration models and dehalorespiring co-culture experiments also showed that PCE-to-DCE dehalorespirers tend to outcompete D. mccartyi strains for higher chlorinated ethenes. Where dense nonaqueous-phase liquid (DNAPL) contamination is present, the fast substrate utilization kinetics of PCE-to-DCE dehalorespirers allow them to grow close to the DNAPL-water interface and control dissolution bioenhancement. Under excess electron donor conditions, D. mccartyi strains specialize in dehalorespiration of lesser chlorinated ethenes produced by PCE-to-DCE dehalorespirers. Maintenance of multiple dehalorespirers growing via complementary substrate interactions results in optimal utilization of electron equivalents, bioenhancement of DNAPL dissolution, and contaminant detoxification