However, these organics are present in relatively low concentrations. This means that there is a lot of water in wastewater which can actually be potentially recovered and reused. In our Sewer Mining project we extract water from sewage by means of forward osmosis (FO) in combination with a reconcentration system e.g. reverse osmosis (RO), to produce high-quality water and to convert the subsequent concentrated sewage into a renewable energy source (i.e. biogas). The effectiveness of FO membranes in the recovery of water from sewage has been evaluated. Stable FO water flux values were obtained with settled sewage (screened, not treated) as a feed solution. Sewer Mining could lead to a more economical and sustainable treatment of wastewater, facilitating reuse of water and energy from sewage.

State-of-the-art wastewater treatment plants (WWTP) with a primary settler collect only about 30% of the wastewater organics. Direct collection of suspended solids from wastewater by innovative fine sieving of influent can result in the removal of approximately 50% of the organics. The rest of the organic matter is currrently converted in an aerobic process and used for nutrient removal from wastewater. Aeration energy represents approximately 60% of the total energy use of a WWTP. With the 'Adsorption-Belebung' system (AB-process), developed at the University of Aachen during the energy crisis in the nineteenseventies, more organics can be collected. More than 70% of the organic matter can be trapped in the first adsorption step (A-stage). Whereas the present AB-process is equipped with intermediate settling tanks a new separation technology is put forward to collect these organics by use of dynamic filtration. Dynamic filtration is a process in which on a coarse support material (typical pore size from 3 to 500 μm), a filtering cake layer is built-up with smaller pore sizes. In the DynaFil project we work on the optimization of process conditions in the A-stage, development of sludge separation based on dynamic filtration and study digestion with dynamic filtration. The results of the project are expected to contribute to an increased sustainable energy production at WWTP plants, reduced greenhouse gas emissions, and savings in energy use, costs and space. The latest results are presented, including results from dynamic filtration experiments. The presented projects show innovative possibilities for water reuse, energy and nutrient recovery from wastewater.

Partners 

The Sewer Mining project is initiated by KWR and together with the TU Delft, Waternet, Triqua, and US-based Hydration Technology Innovations an international Innowator grant from AgentschapNL has been obtained. The DynaFil project, in which KWR (project leader), TU Delft, Waternet, STOWA, Logisticon Water Treatment, Waterboard Brabantse Delta and Bert Daamen participate, is partly funded by AgentschapNL under the Energy and Innovation Grant, Effective and Efficient Digestion chain.

 

Kees Roest  

Kees Roest completed his MSc in medical biology and his PhD in environmental sciences, focused on the microbiological aspects of anaerobic wastewater treatment systems (combining culture-dependent and culture-independent approaches). As a Marie Curie research fellow, he arranged new microbiology laboratories for the investigation of environmental bioreactor processes in Spain (Department of Chemical Engineering and Environmental Technology of the Universidad de Valladolid) and in the UK (Sustainable Environment Research Centre (SERC) of the University of Glamorgan). Currently he is working as a scientific researcher at KWR watercycle research institute in Nieuwegein, the Netherlands. His research focuses mainly on innovative wastewater & reuse technologies.

 

More information:

 kees.roest@kwrwater.nl

Grietje Zeeman (Sub-department of Environmental Technology, Wageningen Universiteit & Research Center) had tijdens haar keynote presentatie op maandag al hoge verwachtingen geschapen voor de presentaties van woensdag. Lucia Hernandez (Wetsus) en ik stonden namelijk beide op het programma (Lucia en ik hebben allebei PhD-onderzoek gedaan bij Grietje). De zaal zat daardoor zelfs voor het on-Italiaanse tijdstip van negen uur al best vol. Met een presentatie over zwart water (door mij) en over grijs water (door Lucia) werd het totale nieuwe sanitatieconcept gepresenteerd.

 

Beide presentaties gaven een overzicht van vier jaar PhD onderzoek. De discussie en vragen gingen daarom vooral over implementatievraagstukken. Er zijn nog veel aspecten die uitgezocht moeten worden. 'Socio-economische' aspecten zijn hierbij het meest belangrijk. Grietje maakte in haar presentatie onderscheid tussen ontwikkelde landen die een transitie van conventioneel naar nieuwe sanitatie moeten ondergaan. Landen in opkomst zoals Oost-Europa kunnen juist snel leidend worden op het gebied van nieuwe sanitatie, aangezien er nog geen infrastructuur voor waterzuivering aanwezig is. In ontwikkelingslanden ligt de prioriteit bij basisvoorzieningen voor hygiënisch veilige sanitatie.

 

Thomas Hug van Eawag, Zwitserland, gaf een interessante presentatie over hoe we decentrale/kleinschalige zuiveringen moeten en kunnen gebruiken. Een veel gehoord commentaar is dat het onderhoud van decentrale zuiveringen teveel zal kosten. Thomas benadrukte dat een voordeel van decentrale zuiveringen is dat het risico op falen (en daarmee het risico voor volksgezondheid) bij heel veel kleine zuiveringen veel kleiner is. Als één van de duizend zuiveringen faalt, dan is de impact veel kleiner dan als één hele grote zuivering faalt. Bij een groot aantal decentrale zuiveringen zul je een centrale monitoring nodig hebben. Thomas is bezig met het ontwerpen van een model zodat geschat kan worden hoe een zuivering draait. Uitdagingen hierbij zijn dan bijvoorbeeld 'hoe bepaal je of een zuivering goed draait, met welke parameters?'

 

Verder waren er veel presentaties over, uiteraard, kleinschalige zuivering, onder andere in Venetië zelf. Vanwege de ligging is het niet mogelijk om een centrale rioolwaterzuivering aan te leggen. Zo zijn er in Venetië maar liefst 7000 septic tanks! Maar steeds meer worden er geavanceerde zuiveringen met membraan bio-reactoren gebouwd in bijvoorbeeld hotels. De kwaliteit van het water in de lagune van Venetie is hierdoor de laatste jaren flink verbeterd.

 

Donderdag eindigde met een leuke verrassing: samen met Lucia werden onze presentaties en papers als een van de beste van het congres beschouwd (er waren in totaal 3 awards voor Young Professionals)! Uit handen van de burgemeester van Venetië kregen we een Venetiaans kunstwerk en een orkonde.

 

Marthe de Graaff

 

Small Sustainable Solutions 4 Water is een IWA-congres van drie groepen, te weten:

·         10th Specialezed Conference on Small Water and Wastewater Treatment System (SWWS),

·         4th Specialized Conference on Decentralized Water and Wastewater International Network (DEWSIN) en

·         3th Specialized Conference on Resources Oriented Sanitation (EcoSan).

 

Meer informatie: http://www.wastewater-venice-2011.com/

Recentelijk publiceerden Martins, A.M.P., Karahan, Ö. and van Loosdrecht, M.C.M., Effect of polymeric substrate on sludge settleability in: Water Research 45(2011)1, p.263-273.

 

Abstract
The study aims to evaluate the role of a polymeric substrate (starch) on sludge settleability. Despite being an important COD component of the wastewater, the relationship between polymeric substrates and bulking sludge has been hardly studied. The polymers are hydrolysed at a rate smaller than the consumption rate of monomers. This means that the soluble substrate resulting from hydrolysis is likely to be present at growth rate limiting concentrations. According to the kinetic selection theory this leads to bulking sludge. However, a recently postulated theory suggests that, strong diffusion limited micro-gradients of substrate concentration inside flocs lead to bulking sludge, and not a low substrate concentration as such. If the polymeric COD is first incorporated in the sludge floc and afterwards hydrolysed in the sludge floc then there is essentially no substrate gradient inside the biological flocs. The experiments showed that conditions leading to bulking sludge with monomers (glucose) did not lead to bulking when starch was used. A bulking sludge event was even cured just by substituting the monomer with starch. These results are clearly in line with a diffusion gradient--based theory for bulking sludge. Nevertheless, flocs growing on starch are more open, fluffy and porous than flocs formed on maltose or glucose, most likely because the starch needs to be hydrolysed at the surface of the micro-colonies forming the flocculated sludge. Some additional observations on occurrence of filamentous bacteria in oxygen diffusion limited systems are also discussed in this manuscript.

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V73-50MN7F0-7&_user=8139515&_coverDate=01%2F31%2F2011&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1562873167&_rerunOrigin=google&_acct=C000073631&_version=1&_urlVersion=0&_userid=8139515&md5=1baf262bab46cdf5768629bce60daa0d&searchtype=a

Recentelijk publiceerden Schriks M., Leerdam J.A. van, Linden S.C. van der, Burg B. van der, Wezel A.P. van, Voogt P. de in: Environmental Science Technology 44(2010)12, p.4766-4774.

Abstract
In the past two decades much research effort has focused on the occurrence, effects, and risks of estrogenic compounds. However, increasing emissions of new emerging compounds may also affect the action of hormonal pathways other than the estrogenic hormonal axis. Recently, a suite of novel CALUX bioassays has become available that enables looking further than estrogenic effects only. By employing these bioassays, we recently showed high glucocorticogenic activity in wastewaters collected at various sites in The Netherlands. However, since bioassays provide an integrated biological response, the identity of the responsible biological compounds remained unknown. Therefore, our current objective was to elucidate the chemical composition of the wastewater extracts used in our previous study by means of LC-high-resolution Orbitrap MS/MS and to determine if the compounds quantified could account for the observed glucocorticoid responsive (GR) CALUX bioassay response. The mass spectrometric analysis revealed the presence of various glucocorticoids in the range of 13−1900 ng/L. In extracts of hospital wastewater−collected prior to sewage treatment−several glucocorticoids were identified (cortisol 275−301 ng/L, cortisone 381−472 ng/L, prednisone 117−545 ng/L, prednisolone 315−1918 ng/L, and triamcinolone acetonide 14−41 ng/L) which are used to treat a great number of human pathologies. A potency balance calculation based on the instrumental analyses and relative potencies (REPs) of the individual glucocorticoids supports the conclusion that triamcinolone acetonide (REP = 1.3), dexamethasone (REP = 1), and prednisolone (REP = 0.2) are the main contributors to the glucocorticogenic activity in the investigated wastewater extracts. The action of these compounds is concentration additive and the overall glucocorticogenic activity can be explained to a fairly large extent by their contribution.

As I entered the historic West Indisch Huys for the International Water and Energy Conference 2010 in Amsterdam, I was wondering. Would the impressive atmosphere of the building distract the audience from the scientific topics?

 

 

The first morning session started with Doeke Schippers (Vitens) presenting minimizing CO₂-footprint, focusing on methane productions. After this presentation it was my turn to present: Sulphate reduction in an innovative concept for saline wastewater treatment with seawater as alternative for toilet flush water (one slide is presented below). This concept contributes to reducing freshwater uses, but accessory it has advantages in wastewater treatment as well. Professor Jules van Lier (TU Delft) had doubts concerning the concept, as seawater use is related to corrosion. However, this dual system with both potable and seawater is operated successfully in Hong Kong for a half century. Moreover, the dual system is 5 times cheaper than the use of imported (from China) potable water (replacement of sewage system due to corrosion included). Thus, the use of seawater should be taken into consideration as innovative new sanitation system locally.

 

  

Learning from best practice

My presentation was followed by a presentation of my colleague Marthe de Graaff, who gave an overview of the energy in the water cycle, both on national level (Netherlands) as two case studies. During the next three sessions I switched from session to session, to attend different types of presentations.  Presentation topics varied from digestion (Jules van Lier, TU Delft and L. Bouchy, Cirsee-Suez Environnement), to Green House Gas emissions (Marlies Kampschreur, Waterboard Aa en Maas, A. Akkerman & A. Massagué, Cirsee-Suez Environnement). A few talks draw my attention. First, the presentation of my colleague at KWR Jos Frijns on 'Energy Efficiency in the European Water Industry: learning from best practices'. He explained that in European case studies significant energy savings in all parts of the water cycle were possible and a worldwide compendium is developed to guide the water industry towards opportunities of energy saving.

 

The next presentation which had my attention was about oxygen transfer in activated sludge (J. Henkel, TU Darmstadt). At first it didn't seem interesting as I am working with an anaerobic process. However, during my master thesis I worked with anaerobic/aerobic activated sludge systems. Especially, the alpha factor is influencing the aeration, determined by the floc shape of activated sludge.

 

Greywater treatment for urban water use

The third speaker Professor O. Nowak (Joanneum Research) had an interesting point of view about the name 'energy-neutral wastewater treatment'. As the investment of reactors, aerators and others has always high energy costs, the term energy-neutral doesn't fit well. He suggested that 'self-sufficient wastewater treatment plant' was a more proper term. The last presentation which had my special attention was from A. Meda (TU Darmstadt) about 'Comparison of processes for greywater treatment for urban water reuse: energy consumption and footprint'.  In this case greywater is used for toilet flushing, which is the counterpart of my study, using seawater as toilet flush water.  Off course, this system has advantages, greywater is reused and less corrosion occurs. However, instead of one wastewater stream, two separate waste streams are generated; blackwater and greywater. Moreover, two types of wastewater treatment plants are required, one for each stream.

 

This conference was very interesting and resulted in a few new ideas for my own topic. Besides it enhanced my believe in the innovative sanitation concept with seawater as toilet flush water, which should be taken into consideration when a new sanitation system is developed locally.

 

Tessa van den Brand