ABSTRACT
2Surface water treatment in the Netherlands receives increased attention requiring better characterisation and evaluation of the ‘algae problem’. Investigations and analysis carried out at five drinking water production locations in the Netherlands utilising surface water (amounting to 60% of the overall Dutch surface water production) show that the most significant problem are the cyanobacteria. Seasonal blooms of Microcystis aeruginosa and Oscillatoria agardhii force short- and long-term process modifications, affecting water production cost. Assessment of possible solutions suggests that, apart from the application of appropriate water quality management measures, new insights on more efficient (pre)treatment processes are critical. In treatment, the agglomeration (coagulation/flocculation) phase is considered the essential step in the removal of the algae. It should be optimised in relation to the pre-treatment preceding it (e.g. application of chemical oxidant’s, and/or microstraining), as well as to the applied solid-liquid separation treatment process. Dissolved air flotation (DAF) emerges as a feasible option given the natural tendency of algae to float. The existing discrepancies between literature and practice call for further research on process mechanisms and suggest that considerable gains can still be made in process optimisation. This research should notably increase insight into the influence of algae morphology and physiology on treatment efficiency.
