Technology Vallei en Veluwe

Gamechanging technology makes wastewater treatment circular

Regional Dutch water authority Vallei en Veluwe has decided to go ahead with a game-changing new technology for municipal wastewater treatment. In contrast to conventional activated sludge treatment based on biological oxidation, the new technology separates and concentrates the organic material and nutrients. The process involves a series of physicochemical steps, resulting in clean, reusable water and several substreams that can be refined to recover commercially viable materials. A small-scale pilot showed promising results, and the water authority announced it would build a first scaled-up version with a capacity of 50 m 3 /h.

From May 2019 to June2020, water authorityVallei en Veluwe and theDutch Water Refineryconsortium (Witteveen&Bosand Royal HaskoningDHV)ran a 2.5 m 3 /h pilotinstallation with a uniqueseries of existing physicaland chemical technologiesthat included a coarsefilter, a sieve for celluloserecovery, electrocoagulation,flocculation, dissolved airflotation, nanofiltration andion exchange. The resultingeffluent was clean waterwithout nutrients, heavymetals, micro-plastics, andmicro-pollutants such aspharmaceutical residues.

Refinery of substreams

Conventional activatedsludge treatment degradesorganic matter and convertsnutrients, causing greenhousegas emissions. The remainingsurplus sludge is difficult

to handle, as it is highlydiluted and contains heavymetals. The tested series ofphysicochemical technologiestakes a completely newapproach; instead of oxidizingthe organic matter andnutrients, it extracts materialsthat can be re-used. Forexample, the toilet paper isfiltered through a sieve andrefined to recover cellulose.The recovered cellulose canbe used in asphalt to thickenthe mixture and preventthe bitumen from drippingoff the aggregate duringprocessing, transportation,and paving. Another exampleis a concentrated ammoniumstream that can be used toproduce specific fertilizers orproteins.The new technology hasno direct CO 2

, methane ornitrous oxide emissions.However, the pilot showedthat the process still usesmore electricity, and thecosts are higher compared

Clean water

A capillary nano-membranefilter removes most micropollutants,leaving only anion exchange step to removeammonium and the lastremaining pollutants. Thewater authority wants to usethis clean effluent for droughtprevention by feeding it intoa small brook that runs dryduring the summer. Usingthe clean, recovered water,the brook can meet the strictstandards of the EuropeanWater Framework Directiveall year round. Anotherpossibility being considered isto recharge the water to raisethe groundwater levels, to useit for irrigation, or for industrialapplications.

‘The consortium sees high potential for the global wastewater treatment, resource recovery and freshwater production industries.’

The water authority is nowstudying a business casearound a full-scale, newlybuiltWater Factory Wilp. Itseeks to optimize the designto recover materials from thesubstreams that meet thespecifications of potentialcustomers. The intention isto scale up the technologyand gradually increase thecapacity from 50 m 3 /h to 150m 3 /h.The consortium sees highpotential for the globalwastewater treatment,resource recovery andfreshwater productionindustries. It intends toroll out the concept ofthe ‘water and resourcefactory’ internationally forcentralized and decentralizedapplications.