Water Quality Control of the Andelse Maas Basin, The Netherlands, by Iron Dosing

The Dune Water Works of The Hague pumps yearly about 45 million cubic meters of water from the Andelse Maas Basin to the dunes for infiltration purposes. The water in the Andelse Haas Basin is strongly influenced by the Meuse river. Phosphate concentrations are so high that algal growth causes difficulties in filters and dunes. For phosphate reduction purposes, iron is dosed into the basin. Several limnological variables are monitored based on weekly measurements. A mathematical model has been developed for the description of the eutrophication in the basin. The model is time and space dependent and based on the one-dimensional dispersion-advection equation. Two separate submodels are used, one for the simulation of flow conditions and one for the algae and nutrient kinetics. The ortho-phosphate reduction is modelled as a first order process. The eutrophication model has been calibrated, verified and used for a prediction of chlorophyll-a and ortho-phosphate concentrations for the case of the shut down of the iron dosing installation. The dosing of iron appears to be a very effective way for phosphate removal. Termination of the dosing would give unacceptable high phosphate and chlorophyll-a concentrations. Present investigations are focussed upon the minimization of the amount of iron dosing.