Modelling and dynamic simulation of a pilot-scale moving bed bioreactor for the treatment of municipal wastewater: model concepts and the use of respirometry for the estimation of kinetic parameters.

A model for the simulation of a moving bed bioreactor (MBBR) used for the treatment of municipal wastewater is proposed. The model includes attachment of particulates to the biofilm and detachment of biofilm into the bulk liquid. The growth kinetics are modelled with the activated sludge model no. 1 (ASM1). Respirometry was used for the estimation of kinetic parameters. The resulting respirograms featured the typical endogenous and exogenous respiration phases and the respirogram shapes were as expected from analogous respirometry with activated sludge. The estimated parameter set was used for modelling and simulation of the pilot-scale MBBR. The main proportion of biomass in the MBBR was found to be attached as biofilm on the carrier elements (4.1 -4.6 g dm-3) and only a small amount was suspended in the bulk liquid (0.15gdm(-3)). Attachment and detachment rates were estimated to be 4.8-7.5g m(-2) d(-1) 1for attachment and 6.5-7.5g m(-2) d(-1) for detachment. The biofilm age was estimated to be 1.8-2.7d. The model was used to predict effluent quality parameters and a good fit of the simulated data to the measured data originating from a four-days-long measurement campaign was obtained.

Complexation of Copper(II) with Carbonate Ligands in Aqueous Solution: A CW and Pulse EPR Study.

The pH dependent complexation between copper and (13)C-labeled carbonate ligands in aqueous solution is investigated by optical spectroscopy and continuous wave and pulse EPR. The small (13)C hyperfine coupling observed in the pulse EPR spectra at low temperature and pH 5.5 is assigned to weak, monodentate coordination of carbonates to the Cu(2+) ion. The (13)C hyperfine couplings found at pH 6.5 and 8 are of the same magnitude as twice the nuclear Larmor frequency (matching range) and are assigned to bidentate coordination of carbonate. The larger coupling for the bidentate complexes is explained by a higher covalency of the pi bonding in the four-membered ring. The elongation of the axial bonds to the water ligands caused by coordination of carbonate ligands in the equatorial plane of the copper complex leads to smaller proton couplings. The observation of both mono- and bidentate coordination at pH 6.5 and 8 by pulse EPR at low temperature is in contradiction to the calculated concentrations of copper-carbonate complexes at room temperature. Although equilibrium shifts during the freezing of the samples cannot be excluded, the basic mechanisms of mono- and bidentate complexation observed in frozen solution should also apply in aqueous solution at ambient temperature.