Reuse

Reuse in water cycle

The water sector contributes to a circular economy through the joint conduct of practice-oriented research into the reduction of raw–material use, recovery of resources and more sustainable alternatives to the materials the water sector currently uses in the treatment of water. Partners in the water sector recover resources at different points in the water cycle. The quality of the recovered resources varies considerably – partly because they originate in different sites – and their transformation into high-value commercial products, with a consistent quality and quantity, can often present a logistical and organisational challenge. The upcycling for reuse in the original application is preferred, so that a truly circular reuse is achieved. KWR researches and develops market concepts to address all these challenges, using an integrated approach that promotes the transition to a circular economy and a circular system.

Methods, tools and products

Residual streams represent a valuable source of crucial resources like water, nutrients and various other components. Existing and new applications for residuals and resources recovered from the water cycle are identified and developed, including the recovery technologies, but this does not guarantee that these residuals will also be sustainably and safely used. Concrete steps towards a responsible loop closure require a good overview of the possibilities that best dovetail with the prevailing circumstances and preconditions. In achieving this, KWR takes account, whenever possible, of the entire valorisation chain of the extraction, processing and use of the recovered residuals.

Old and new concepts

KWR combines old and new concepts, and connects different sectors from the energy-food-water nexus so that they can jointly achieve reuse. Our research translates into practical recommendations, techniques and concepts for water utilities, Water Authorities, municipalities and industry, among others.

From scenario study to practical implementation 

KWR has been involved in many inspiring examples of the safe and sustainable reuse of residuals generated in water treatment processes. The reuse sometimes occurs in the own process or elsewhere in the water cycle, but also quite regularly for applications outside of the water sector. This often involves tailored work to find the best solution and application. KWR draws on an extensive network and experience in a wide range of projects when working with you to identify new possibilities. Do you have a residual you would like to reuse, or to have reused? Would you like to know what sustainable reuse possibilities exist in your processes? KWR can give you support, ranging from scenario study to advice, and from small-scale (laboratory) tests to safe circular practical applications.

Projects around water

Waterrotonde Eerbeek

This circular water management system – the ‘waterrotonde’ (water roundabout) – treats process water from paper and cardboard mills and recovers residual products for reuse. KWR was responsible for several aspects, including the measurement of micropollutants, membrane integrity and brine management. The pilot project showed that reuse of STP effluent was a possible way to compensate for water losses in the water roundabout. Advanced technologies like nanofiltration and Electrodialysis Reversal (EDR) were used to treat and recycle water, so that, in principle, no longer any groundwater will be needed for the paper and cardboard mill.

 

Effluent reuse – MDR in the water cycle

The potential contribution of the Modular Sustainable WWTP (‘MDR’ in the Dutch abbreviation) to the optimisation of the water cycle was explored for two areas in the Province of Limburg. The MDR was originally developed by the Limburg Water Authority Company (WBL), and has since come to be known as Verdygo. This study produced a method to calculate the costs of the local implementation of Verdygo technology, using a GIS tool connected to a calculation model. The method was used to calculate the possibility of matching water demand and supply in two areas, which resulted in a number of promising business cases.

 

Closing the water cycle

To close the water cycle, organic micropollutants have to be removed from effluent. Today’s STPs are not specifically designed to remove this broad range of substances. But whenever organic micropollutants are removed from wastewater, the quality of the effluent improves considerably. This opens up the possibility, for example, of using the effluent for other, higher-value applications, rather than discharging it into surface water. A combination of ozonation with ceramic membrane filtration and biological activated carbon treatment was studied for the effluent treatment.

Projects around nutrients

KNAP

A broad consortium is researching the closure of the nutrient loops from municipal wastewater treatment and industrial process-water treatment (Closing the Loop of Nutrients from Wastewater and Process Water) (‘KNAP’ in the Dutch abbreviation). Together with the partners, we are mapping out (quantitatively and qualitatively) the recyclable fertilisers, their agricultural values, and their possible disposal routes. We are also working on a quality system with criteria which could provide a basis for assessing recycled fertilisers.

 

Micronutrients in the Resource Loop

This project laid the foundation for closing the resource loop of essential micronutrients in the entire food chain (agro-food-waste system). The focus was on the direct reuse of micronutrients via the streams containing micronutrients, and their indirect reuse following the treatment of these streams. Many micronutrients are trace elements that are indispensable for plant growth, and are therefore often added in agriculture to artificial and organic fertilisers. With a view to the circular economy, it is important that the typically linear applications of micronutrients be turned towards loop closure. The research subjects included the reuse of treatment sludge from drinking water production, reuse of the aerobic biomass from the sugar-beet industry, KGW (kitchen and garden waste) and household wastewater.

 

Sustainable Airport Cities

The goal of this pilotproject was the recovery of phosphorus from Schiphol’s wastewater, so that it can be applied, without post-processing, as a fertiliser in the airport’s surrounding area. The resulting struvite was analysed for composition, pathogen contaminants and micropollutants. The results indicated that phosphorus recovery via struvite production at the Schiphol WWTP was feasible, albeit on a relatively small scale. The struvite recovered in the pilot was used as a fertiliser at the airport.

Projects around aquafer

Every year the water utilities in the Netherlands generate about 95,000 tonnes of aquafer (62,000 tonnes of liquid aquafer and 33,000 tonnes of dewatered aquafer). AquaMinerals takes this aquafer and finds outlets for it in a variety of applications, such as in biogas energy plants, STPs and as a construction material.

Production and application of granular aquafer

The transformation of dewatered aquafer into granular material makes a further extension of the sales opportunities possible. The pellets can be used as filter medium, for example in gas and air cleaning (H2S binding) or water treatment (removal of phosphorus and heavy metals). The pellets can also be used in the development of nature areas (phosphorus binding in water courses and soil).

 

Removing H2S from biogas using granular ferric (hydr)oxide

Liquid ferric (hydr)oxide (aquafer) can be transformed into aquafer pellets through granulation. These pellets can be used as filter medium for gas or air cleaning at biogas plants. The application involves binding hydrogen sulphide in the gas phase. This reduces the corrosive properties of the gas, which means that there is no longer a need for over-dosing of aquafer (iron) in the fermentation phase, since sulphide binding is only relevant in the gas phase. This also means that phosphorus remains available for recovery in the digestate. The granular aquafer can also be easily collected and replaced.

 

Application of granular ferric (hydr)oxide for arsenic and phosphorus removal

This project involved the verwijdering van fosfaat en arseen uit water generated in drinking water production. The adsorbent, which has a consistent quality and composition, can remove phosphorus and arsenic from water.

 

Polishing pellets

In this project pellets are being made from the oxidised iron from drinking water production, with a view to using them as a circular adsorption material, or Polishing Pellets. Bearing in mind KWR’s goals for surface water quality, the application of Polishing Pellets voor fosfaatverwijdering uit oppervlaktewater en/of behandeld effluent is self-evident. Pellets originating from different types of aquafer are being studied. In a simultaneous scaling-up initiative, the recipe for the Polishing Pellets is being further optimised through the testing, among others, of alternative, green binders.

 

Reuse of coagulant from aquafer (HerCauWer)

The abstraction and treatment of drinking water almost always involves the formation of aquafer (iron sludge), either through the aeration of ferrous groundwater, or through the addition of iron salts as a flocculant. By treating this iron sludge with acid one can again produce iron salts, which can then be reused as a flocculant in wastewater or drinking water treatment. In this way we can reuse the material and close the resource loop.

 

Wiser with Metal

This practical study investigates how much aquafer can be reprocessed into iron powder of a known quality. If pure enough, the iron powder can be used for a range of high-grade applications, including as a carrier material for sustainable energy. Specifically, the study is looking at the potential of this powder as a circular (metal) fuel and as a material for compact hydrogen storage.

Projects around metals

Recovery of metals

The project developed a method to measure concentrations (including sample pre-treatment) of 66 elements – including heavy and rare/earth metals – in various water streams. On the basis of the monitoring results, a decision was made to carry out experiments on the influent and (released) fly ash using ion exchange resins and (chemical) precipitation, aimed at the effective removal and/or recovery of metals like copper, zinc, cobalt, iron, lithium, titanium, palladium, wolfram, silver, gold and arsenic.

Projects around cellulose

Screencap

The essence of the innovative concept of Screencap is the recovery of solids from raw wastewater on the basis of particle size rather than density. The most significant results of the research are a 15% reduction in the aeration energy required, a 10% reduction in sludge production, and a 10% increase in the capacity of the WWTP due to the use of fine-screen technology. 

Projects around calcite

High-value reuse of lime pellets from drinking water production

About half of the drinking water in the Netherlands is softened in pellet reactors. This technology generates a residual in the form of lime pellets, which consist of a sand nucleus (seed material) and a shell of calcium carbonate (lime). By replacing the sand nucleus with one made of calcite (calcium carbonate), one produces a pure lime pellet, which consists of a single component and has a lower iron content. One thus creates a product with high-value application possibilities in industries such as glass, carpeting and paper. The (financial) returns on the lime pellets increase accordingly.