This study investigates the applicability of hydroxide precipitation to complexed metal wastewaters using inorganic cations that may function as ligand sharing agents. Within this context Ca2+, Fe2+, Fe3+, Mn2+ and Mg2+ cations with the metals Cd and Cu and EDTA and NTA as ligands are used to define the systems for which theoretical and experimental evaluations are made. Results indicate that calcium is the only cation that effectively binds the ligands that makes it possible to apply the hydroxide precipitation. Fe2+ and Mn2+ are not effective due to their rapid oxidation. Mg2+ is found partly effective but may not be adequate for pretreatment purposes.

The paper provides a comprehensive coverage of the experimental information required for the activated sludge treatment of industrial wastewaters. Emphasis is placed upon the choice of parameters for organic carbon removal, the value of basic relationships between major parameters, the merit of size distribution for the evaluation of pretreatment, COD fractionation and its implication in system design, major kinetic and stoichiometric coefficients for process modelling. Relevant experimental data related to a wide range of industrial wastewaters compatible with biological treatment are provided.

Performance of sequencing batch reactors for simultaneous nitrogen and phosphorus removal is evaluated by means of model simulation, using the activated sludge model, ASM2d, involving anoxic phosphorus uptake, recently proposed by the IAWQ Task group. The evaluation includes all major process configurations with different aerobic, anoxic, anaerobic sequences, and fill conditions. Basic relationships between modelling and design based on overall process stoichiometry are established for the interpretation of nutrient profiles associated with different operation modes. A similar approach is also used for the assessment of the effect of major operating parameters on system performance.

No abstract

This study evaluated the prediction capability of Activated Sludge Model No. 2d (ASM2d), for the enhanced biological phosphorus removal (EBPR) performance of a sequencing batch reactor (SBR) receiving variable influent phosphate load. For this purpose, a laboratory-scale SBR was operated with a synthetic feed containing acetate as the sole carbon source. The experiments were conducted in four different Runs to ensure a range of different phosphate/acetate ratios in the influent. Model evaluations were carried out using concentration profiles measured throughout a representative cycle at steady state. An iterative calibration methodology was developed based on sensitivity analysis and applied to four different sets of experimental data on relevant model parameters reflecting SBR performance. ASM2d was able to predict the steady state behavior of the SBR system receiving variable influent phosphate loads only with the recalibrated parameter set. The regular changing pattern of the coefficients could be interpreted with the ability of the SBR system to sustain glycogen accumulating microorganisms, GAOs, which can store substrate under anaerobic conditions without polyphosphate energy, but deriving energy from the degradation of glycogen. Thus they are capable of prevailing at lower P/Ac ratios. The results indicate the need to include glycogen and GAOs as model components for processes involving both phosphate accumulating organisms, (PAOs) and GAOs, in order to obtain a better prediction of X(PHA) and oxygen uptake rate (OUR) profiles in the system.