Mass balances for carbon (as COD), nitrogen, and phosphorus are excellent tools for the evaluation of WWTPs in order to estimate fluxes of these substances, to compare operational data of different WWTPs with one another and, finally, to draw conclusions of general validity. In the case of activated sludge systems, mass balances can also be very helpful for model calibration, in particular for the ‘Activated Sludge Model No. 1’ (ASM1), because this model is consequently based on balances for COD and nitrogen. Hence, the results of mass balances can be utilised directly for the estimation of model parameters. Accordingly, it is recommended to evaluate the fluxes of COD and nitrogen, before the model calibration is started. By means of mass balances only the state of equilibrium can be described. Therefore, as regards model calibration, only parameters responsible for long-term behaviour can be estimated, i.e. the heterotrophic yield YH, the fraction of biomass yielding particulate organics fP, the heterotrophic decay rate bH and the concentration of particulate inert organics XI in the influent. A correct estimate of these parameters is a prerequisite for the validity of the simulation results, not only in regard to excess sludge production and SRT, but also with respect to the oxygen consumption for carbon removal and, therefore, to denitrification capacity.

A fast and convenient method for on-line monitoring of the extraction of heavy metals from solid (environmental) matrixes was developed. By the incorporation of microcartridges filled with dried and pulverized solid samples into the conduits of a flow system and appropriate selection of the liquid flowing through the cartridge, information about the degree of leaching and in particular of the kinetics of the leaching process are obtained. The method was optimized for determination of different metals of environmental concern using in-line detection by FAAS and ICPMS.

The application of a recently proposed microanalytical flow-through system for on-line sequential extraction of heavy metals from solid samples of environmental interest is described. Using various extraction schemes (a nitric acid scheme, a two-stage extraction scheme using two reagents applied in the BCR procedure) and comparison with the common batch sequential BCR procedure, the suitability of the system for fast screening of solid environmental samples is demonstrated. By pumping leaching agents sequentially through the sample held in a micro cartridge, the different metal fractions present can be assessed in less than an hour. Method evaluation was performed using SRM 1648 urban particulate matter and BCR 701 lake sediment reference material certified for extractable metals. The need for and design of laboratory internal reference material suitable for simulating the natural (dynamic) processes of metal release into the environment is also discussed. For the first time correlation is sought between fractionation techniques and physiologically based methods for assessment of the bioaccessibility of metals in biomatrices.

No abstract