Field: Sustainable water cycle
Global Technical function: Filtrating, Separating
Technical Function Unit: Bio filtrating, Cleaning, Cooling

DENUTRITOR

DENUTRITOR is a bio filtrating device which reduces biofouling in water systems by removing compounds that cause the growth of microbial populations. This biofilter has been developed within the AQUAFIT4USE  large-scale project. This pan-European initiative, funded under the 7th Framework Programme (FP7), a grant funding programme, aims to make industries more independent of the supply of water for their production processes. New technologies, tools and methods for sustainable water supply, use and discharge in the main water consuming industries, i.e. “water fit-for-(re)use”, have been developed.

Biofouling (or biological fouling) is the unwanted accumulation of microorganisms, plants, algae and/or animals on wet surfaces, due to the presence of inorganic nutrients and organic compounds which are dissolved in the water. Biofouling causes various damages to industrial systems (e.g. membrane bioreactors, pipelines and heat exchangers) among other corrosion, spoiling of food products, energy losses and clogging of equipment. As a result, biofouling generates huge economic impacts (in 2006, the costs of fouling in industrial nations were estimated between 0.17% and 0.25% of their Gross Domestic Product) and leads to health risks due to the accumulation of pathogenic microorganisms.

Current biofouling control strategies (e.g. specific design without dead ends, use of biocides, mechanical cleaning) often turn out to be inadequate, expensive or even damaging for equipment or the environment. To overcome these problems, Deltares and TNO (The Netherlands) have developed an innovative filtrating device which is a cheap, effective and environmentally sustainable technique for biofouling prevention and water treatment. Working like a traditional biofilter, microorganisms degrade “Assimilable Organic Carbon” (AOC) and “Biodegradable Organic carbon” (BOC) and remove other nutrients from the water. In this way, the source of biofouling is removed and the potential re-use for water is therefore enhanced. Furthermore, in the present device, microorganisms degrade the AOC/BOC substrates on fillers composed of reticulated polyurethane (PUR) foams. Because PUR foams have a very high porosity with a high specific surface area, the treatment of water can be performed at a low hydraulic retention time.

A pilot installation has been tested so that the technology readiness level is estimated to 7 on the TRL scale. The focus was on biofouling prevention in membrane systems and cooling water systems as well as on sustainable water cycle achievement in general. During the
pilot testing period, the robustness of the device and the chemical and biological quality of the produced waters were monitored. The pilot installation was operated for eleven months so that about 3000 m3 of water was treated. It showed that up to 92% of the biofouling potential had been removed. As a result, re-use of waste water effluent for major water consuming processes such as chemical synthesis and steam production can lead to a significant decrease of the drinking water consumption.

The system is of particular interest when performed within an integrated device. Such a device encompasses several levels of treatment, each one focussing on specific substances. A first separating stage removes insoluble precipitates; a second biological treatment occurs, which can be followed by an Advanced Oxidation Process (or AOP like the ozone/AOP process) which cracks down hardly biodegradable organic compounds. Finally, the biofouling potential of the effluent and the salts are removed.

All types of waters with low Chemical Oxygen Demand (COD) and particle content can be treated. Several industrial sectors are in the scope: the chemical industry, drinking water production and energy production.