Steady-state modeling of nutrient transformations in activated sludge treatment of pulp and paper wastewater.

摘要

Pulp and paper wastewater is often deficient in readily available macronutrients, typically nitrogen and phosphorus, whereas municipal wastewater usually contains adequate or excess quantities of these nutrients in relation to the requirements of the activated sludge microorganisms. The control of supplemental nitrogen and phosphorus dosing represents a cost reduction opportunity as well as an opportunity to reduce nutrient concentrations in the final effluent discharge, which are increasingly prescribed by environmental or governmental authorities. A wide range of pulp and paper and wastewater treatment process configurations exist industry-wide. This thesis presents a case study of an integrated TMP-newsprint mill; the methodology of the study is practical and broadly applicable.;Wastewater characterisation was carried out on a pulp and paper mill effluent for an integrated TMP-newsprint mill according to well-accepted systematic methodologies. The methodology used in this study, of rigorous data treatment, detection of pseudo-steady states, development of mass balances and the use of a pulp and paper-specific ASM1-based model, has demonstrated important insights into the nutrient transformations occurring in a well-mixed (CSTR) short-retention time AST wastewater treatment plant.;The wastewater characterisation methods highlighted major differences between the determination of COD fractions in pulp and paper wastewater and those in municipal wastewater. Calibration of the ASM-based model was exceedingly difficult for the entire range of process conditions; individually adjusted kinetic parameters were used, with an evolution of the nitrification-denitrification process rates over time. The use of the ASM-based model saturation functions as an indicator of the actual plant operating regime and of nutrient deficiency in the biomass are proposed as potentially powerful tools for the plant operators. The mill has already implemented upstream ratio control of nutrient dosing with feed-back of residual concentrations, and the proposed use of the ASM-based model will be implemented as an additional layer of control.