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Mount Darwin, Zimbabwe

van der Hoek J.P.,Waternet | van der Hoek J.P.,Technical University of Delft
Water Practice and Technology | Year: 2011

Waternet, the first water cycle company in the Netherlands, is responsible for drinking water treatment and distribution, wastewater collection and treatment, and watersystem management and control in and around Amsterdam. Waternet has the ambition to operate climate neutral in 2020. To realise this ambition, measures are required to compensate for the emission of 53,000 ton CO 2-eq/year. Energy recovery from the water cycle looks very promising. From wastewater, ground water, surface water and drinking water, all elements of the water cycle, renewable energy can be recoverd. This can be thermal energy and chemical energy. First calculations reveal that energy recovery from the water cycle in and around Amsterdam can contribute to a total reduction in green house gas emissions up to 148,000 ton CO 2-eq/year. The challenge for the coming years is to choose robust combinations of all the possibilities to fulfil the energy demand at any time. Only then the use of fossil fuel can be abandoned and the target of operating climate neutral in 2020 can be reached. © IWA Publishing 2011. Source

Ghasimi D.S.M.,Technical University of Delft | de Kreuk M.,Technical University of Delft | Maeng S.K.,Sejong University | Zandvoort M.H.,Waternet | van Lier J.B.,Technical University of Delft
Applied Energy | Year: 2016

Sieving of Dutch raw sewage over a 350μm screen, produces a cake layer called fine sieved fraction (FSF), an energy-rich material that contains mainly cellulosic fibers originating from toilet paper. The FSF biomethane potential (BMP) was studied under both mesophilic (35°C) and thermophilic (55°C) conditions, whereas the stability of the fed-batch digesters at both 35°C and 55°C was researched by varying the inoculum to substrate ratios (RI / S: 0.5-15). Results clearly showed advantages of thermophilic conditions over mesophilic conditions at all tested RI / S. Stable digestion was even possible at an RI / S of 0.5 at 55°C.Following the results of the batch tests, a compact high loaded thermophilic digester for on-site energy recovery from FSF was proposed. Based on the results of the study, high biogas production rates at high organic loading rates (OLRs) were predicted. In the energy balance calculations, surplus heat production from combined heat and power (CHP) was utilized to dry the digestate sludge before transportation to an incineration plant or for use in pyrolysis or gasification processes. Overall results showed the potential of generating 46% of the required energy for wastewater treatment via high rate FSF digestion and subsequent conversion of the bio-methane into electricity and heat. The net recoverable energy from fine sieving, anaerobic digestion of FSF, dewatering of digestate sludge and drying of dewatered digestate sludge amounted 287 MJ/ton FSF and 237 kW h electric/ton FSF at 23% TS. © 2015 Elsevier Ltd. Source

Bichai F.,Ecole Polytechnique de Montreal | Barbeau B.,Ecole Polytechnique de Montreal | Dullemont Y.,Waternet | Hijnen W.,KWR Watercycle Research Institute
Water Research | Year: 2010

The significance of zooplankton in the transport and fate of pathogenic organisms in drinking water is poorly understood, although many hints of the role of predation in the persistence of microorganisms through water treatment processes can be found in literature. The objective of this study was to assess the impact of predation by natural zooplankton on the transport and fate of protozoan (oo)cysts in granular activated carbon (GAC) filtration process. UV-irradiated unlabelled Cryptosporidium parvum and Giardia lamblia (oo)cysts were seeded into two pilot-scale GAC filtration columns operated under full-scale conditions. In a two-week period after seeding, a reduction of free (oo)cysts retained in the filter bed was observed. Zooplankton was isolated from the filter bed and effluent water on a 30 μm net before and during the two-week period after seeding; it was enumerated and identified. Rotifers, which are potential predators of (oo)cysts, accounted for the major part of the isolated zooplankton. Analytical methods were developed to detect (oo)cysts internalized in natural zooplankton isolated from the filter bed and effluent water. Sample sonication was optimized to disrupt zooplankton organisms and release internalized microorganisms. (Oo)cysts released from zooplankton after sonication were isolated by IMS and stained (EasyStain™) for microscopic counting. Both Cryptosporidium and Giardia (oo)cysts were detected in association with zooplankton in the filter bed samples as well as in the effluent of GAC filters. The results of this study suggest that predation by zooplankton can play a role in the remobilization of persistent pathogens such as Cryptosporidium and Giardia (oo)cysts retained in GAC filter beds, and consequently in the transmission of these pathogens in drinking water. © 2009 Elsevier Ltd. All rights reserved. Source

Vital M.,Eawag - Swiss Federal Institute of Aquatic Science and Technology | Dignum M.,Waternet | Magic-Knezev A.,Het Waterlaboratorium HWL | Ross P.,Technical University of Delft | And 2 more authors.
Water Research | Year: 2012

An ever-growing need exists for rapid, quantitative and meaningful methods to quantify and characterize the effect of different treatment steps on the microbiological processes and events that occur during drinking water treatment and distribution. Here we compared cultivation-independent flow cytometry (FCM) and adenosine tri-phosphate (ATP) analysis with conventional cultivation-based microbiological methods, on water samples from two full-scale treatment and distribution systems. The two systems consist of nearly identical treatment trains, but their raw water quality and pre-treatment differed significantly. All of the drinking water treatment processes affected the microbiological content of the water considerably, but once treated, the finished water remained remarkably stable throughout the distribution system. Both the FCM and ATP data were able to describe the microbiology of the systems accurately, providing meaningful process data when combined with other parameters such as dissolved organic carbon analysis. Importantly, the results highlighted a complimentary value of the two independent methods: while similar trends were mostly observed, variations in ATP-per-cell values between water samples were adequately explained by differences in the FCM fingerprints of the samples. This work demonstrates the value of alternative microbial methods for process/system control, optimization and routine monitoring of the general microbial quality of water during treatment and distribution. © 2012 Elsevier Ltd. Source

Mons M.N.,KWR Watercycle Research Institute | Heringa M.B.,KWR Watercycle Research Institute | van Genderen J.,KWR Watercycle Research Institute | Puijker L.M.,KWR Watercycle Research Institute | And 6 more authors.
Water Research | Year: 2013

Ongoing pollution and improving analytical techniques reveal more and more anthropogenic substances in drinking water sources, and incidentally in treated water as well. In fact, complete absence of any trace pollutant in treated drinking water is an illusion as current analytical techniques are capable of detecting very low concentrations. Most of the substances detected lack toxicity data to derive safe levels and have not yet been regulated. Although the concentrations in treated water usually do not have adverse health effects, their presence is still undesired because of customer perception. This leads to the question how sensitive analytical methods need to become for water quality screening, at what levels water suppliers need to take action and how effective treatment methods need to be designed to remove contaminants sufficiently. Therefore, in the Netherlands a clear and consistent approach called 'Drinking Water Quality for the 21st century (Q21)' has been developed within the joint research program of the drinking water companies. Target values for anthropogenic drinking water contaminants were derived by using the recently introduced Threshold of Toxicological Concern (TTC) approach. The target values for individual genotoxic and steroid endocrine chemicals were set at 0.01 μg/L. For all other organic chemicals the target values were set at 0.1 μg/L. The target value for the total sum of genotoxic chemicals, the total sum of steroid hormones and the total sum of all other organic compounds were set at 0.01, 0.01 and 1.0 μg/L, respectively. The Dutch Q21 approach is further supplemented by the standstill-principle and effect-directed testing. The approach is helpful in defining the goals and limits of future treatment process designs and of analytical methods to further improve and ensure the quality of drinking water, without going to unnecessary extents. © 2013 Elsevier Ltd. Source

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