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KWR
Apeldoorn, Netherlands

Weickgenannt M.,University of Stuttgart | Kapelan Z.,University of Exeter | Blokker M.,KWR | Savic D.A.,University of Exeter
Journal of Water Resources Planning and Management | Year: 2010

A method for optimizing sensor locations to effectively and efficiently detect contamination in a water distribution network is presented here. The problem is formulated and solved as a twin-objective optimization problem with the objectives being the minimization of the number of sensors and minimization of the risk of contamination. Unlike past approaches, the risk of contamination is explicitly evaluated as the product of the likelihood that a set of sensors fails to detect contaminant intrusion and the consequence of that failure (expressed as volume of polluted water consumed prior to detection). A novel importance-based sampling method is developed and used to effectively determine the relative importance of contamination events, thus reducing the overall computation time. The above problem is solved by using the nondominated sorting genetic algorithm II. The methodology is tested on a case study involving the water distribution system of Almelo (The Netherlands) and the potential intrusion of E. coli bacteria. The results obtained show that the algorithm is capable of efficiently solving the above problem. The estimated Pareto front suggests that a reasonable level of contaminant protection can be achieved using a small number of strategically located sensors. © 2010 ASCE. Source


Weickgenannt M.,University of Stuttgart | Kapelan Z.,University of Exeter | Blokker M.,KWR | Savic D.A.,University of Exeter | Sawodny O.,University of Stuttgart
Proceedings of the IEEE International Conference on Control Applications | Year: 2010

A method for the optimization of sensor locations in water distribution networks is presented with respect to effective and efficient detection of contaminations. The optimization problem is formulated as a twin-objective minimization problem with the objectives being the sensor cost and the risk of contamination. Unlike past approaches, the risk of contamination is explicitly evaluated as the product of the non-detection probability of an intrusion by a given set of sensors and the consequence of that failure (expressed as effected population). An Importance-based Sampling Method is presented and used to effectively determine the relative importance of contamination events, thus reducing the overall computation time. The above problem is solved by using the Non-dominated Sorting Genetic Algorithm II (NSGA-II). The methodology is tested on a case study involving the water distribution system of Almelo (Netherlands) and the potential intrusion of E. coli bacteria. The results obtained show that the algorithm is capable of efficiently solving the above problem. The estimated Pareto front suggests that a reasonable level of contaminant protection can be achieved using a small number of strategically located sensors. © 2010 IEEE. Source


Cornelissen E.R.,KWR | Viallefont X.D.,ESPCI ParisTech | Beerendonk E.F.,KWR | Wessels L.P.,WE Consult
Journal of Water Supply: Research and Technology - AQUA | Year: 2010

Fouling of feed spacers in spiral wound membrane elements due to particulate fouling and biofouling is one of the main operational problems of nanofiltration or reverse osmosis membrane plants. Removal of particulate fouling from spiral wound membrane elements is investigated using frequent air/water cleaning (AWC). In a pilot setup two spiral wound elements were operated in parallel and were fed by tap water containing suspended solids. The reference membrane (REF) was fed with tap water pre-filtered with a 1.0-μm cartridge filter and fouled within 50 days indicated by a 55% increase in the pressure drop. The second membrane element (AWC) was fed with unfiltered tap water (with an average turbidity of 0.3 NTU) resulting in a 73% increase in the pressure drop within a few days of operation. By using air/water cleaning, the pressure drop decreased to initial pressure drop values, indicating complete removal of particulate fouling. It was concluded that periodical air/water cleaning proved to be effective in controlling membrane spacer channel fouling as a result of particles in the feed water. © IWA Publishing 2010. Source


van den Brand T.P.H.,KWR Watercycle Research Institute | Roest K.,KWR | Chen G.H.,Hong Kong University of Science and Technology | Brdjanovic D.,UNESCO IHE | And 3 more authors.
World Journal of Microbiology and Biotechnology | Year: 2015

The activity of sulfate reducing bacteria (SRB) in domestic wastewater treatment plants (WWTP) is often considered as a problem due to H2S formation and potential related odour and corrosion of materials. However, when controlled well, these bacteria can be effectively used in a positive manner for the treatment of wastewater. The main advantages of using SRB in wastewater treatment are: (1) minimal sludge production, (2) reduction of potential pathogens presence, (3) removal of heavy metals and (4) as pre-treatment of anaerobic digestion. These advantages are accessory to efficient and stable COD removal by SRB. Though only a few studies have been conducted on SRB treatment of domestic wastewater, the many studies performed on industrial wastewater provide information on the potential of SRB in domestic wastewater treatment. A key-parameter analyses literature study comprising pH, organic substrates, sulfate, salt, temperature and oxygen revealed that the conditions are well suited for the application of SRB in domestic wastewater treatment. Since the application of SRB in WWTP has environmental benefits its application is worth considering for wastewater treatment, when sulfate is present in the influent. © 2015, Springer Science+Business Media Dordrecht. Source

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