Increased insight in microbial processes in rapid sandfilters in drinking water treatment (DW BIOFILTERS)

The aim of this research project is to improve our knowledge on biological rapid sand filters as they are present in thousands groundwater based water works. This includes molecular investigations of the microorganisms responsible for the individual processes (e.g. nitrification); and detailed monitoring and experiments in the filters and laboratory to provide insight in the process mechanisms, kinetics and effect of environmental factors.

Management of the filters (e.g. backwashing, flow rate, carrier type) will be investigated at pilot and full scale, supported by mathematical models. The sustainability and climate friendliness are evaluated by life cycle assessment (LCA). Molecular methods based on qPCR are being developed and implemented to quantify bacteria in different functional groups, such as those responsible for nitrification.

This allows for development of diagnostic tools to detect if essential or core members are present or absent in a malfunctioning filter. It is meaningful to optimize the management of the filter only if they are present at relevant concentrations. Furthermore, to get insight in the complexity of the microbial community, the full microbial community is being investigated by deep sequencing.

This will also contribute to a verification of whether the selected qPCR probes include all important groups. Filters from three water works have been sampled and are currently being processed to investigate depth profiles and horizontal variation in filters. Assays for essential microbial processes such as nitrification and oxidation of manganese are currently being established.

They will provide identification of controlling parameters, bottle necks or inhibition of microbial removal of the bulk compound and the effect of filter management. Finally, a pilot plant has been established at Islevbro Water Works (operated by Copenhagen Energy) with material from the full-scale afterfilter.

After validation that the pilot plant is mimicking the full scale filter, it will be used to investigate processes at larger scales such as backwashing procedures and effect of increased load of e.g. ammonium, manganese and ferrous iron. This filter will also be used to validate the mathematical models build for the biological filters at full scale.