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Blokker E.J.M.,KWR Watercycle Research Institute | Schaap P.G.,PWN Water Supply Company North Holland
Procedia Engineering | Year: 2015

Particulate material can accumulate in drinking water distribution systems (DWDS) and can cause discolouration. Previous research showed that temperature influences this. However, it did not explain why higher temperatures lead to a higher accumulation rates. Based on existing data collected in the DWDS of several Dutch water companies, we investigated if higher temperatures lead to more particulate material from the treatment plant, or cause higher accumulation rates within the DWDS. Continuous temperature and turbidity measurements at 6 pumping stations showed the majority of the treatment plants do not have a seasonal trend in turbidity. Filter volumes in the DWDS and high frequency particle accumulation rate measurements on numerous locations in the DWDS of one specific water company did show a seasonal effect. It is likely that higher temperatures in the DWDS can augment particulate material accumulation. © 2015 Published by Elsevier Ltd.

Blokker E.J.M.,KWR Watercycle Research Institute | Schaap P.G.,PWN Water Supply Company North Holland
Procedia Engineering | Year: 2015

Particulate material accumulates in drinking water distribution systems (DWDS) and this can cause discolouration. To minimize customer complaints it is required to understand the influencing factors and determine an appropriate flushing frequency. The accumulation rates of two comparable DWDS were examined. Area A with a constant incoming water quality experiences a steady accumulation rate; area B with a more variable incoming water quality has a variable accumulation rate. The difference in accumulation rate is proportionate to the difference in the particle loading of the two areas and is thus largely determined by the difference in incoming water quality. The water quality into a DWDS is not only determined by the treatment works, but also by the material accumulation and resupsension in the trunk mains supplying it. Monitoring the particle loading of a DWDS part can help in determining the required flushing frequency © 2015 Published by Elsevier Ltd.

Blokker E.J.M.,KWR Watercycle Research Institute | Blokker E.J.M.,Technical University of Delft | Vreeburg J.H.G.,KWR Watercycle Research Institute | Vreeburg J.H.G.,Technical University of Delft | And 3 more authors.
Drinking Water Engineering and Science | Year: 2010

An "all pipes" hydraulic model of a drinking water distribution system was constructed with two types of demand allocations. One is constructed with the conventional top-down approach, i.e. a demand multiplier pattern from the booster station is allocated to all demand nodes with a correction factor to account for the average water demand on that node. The other is constructed with a bottom-up approach of demand allocation, i.e., each individual home is represented by one demand node with its own stochastic water demand pattern. This was done for a drinking water distribution system of approximately 10 km of mains and serving ca. 1000 homes. The system was tested in a real life situation. The stochastic water demand patterns were constructed with the end-use model SIMDEUM on a per second basis and per individual home. Before applying the demand patterns in a network model, some temporal aggregation was done. The flow entering the test area was measured and a tracer test with sodium chloride was performed to determine travel times. The two models were validated on the total sum of demands and on travel times. The study showed that the bottom-up approach leads to realistic water demand patterns and travel times, without the need for any flow measurements or calibration. In the periphery of the drinking water distribution system it is not possible to calibrate models on pressure, because head losses are too low. The study shows that in the periphery it is also difficult to calibrate on water quality (e.g. with tracer measurements), as a consequence of the high variability between days. The stochastic approach of hydraulic modelling gives insight into the variability of travel times as an added feature beyond the conventional way of modelling. © Author(s) 2010.

Kruithof J.C.,Center of Excellence for Sustainable Water Technology | Martijn B.J.,Center of Excellence for Sustainable Water Technology | Martijn B.J.,PWN Water Supply Company North Holland
Water Science and Technology: Water Supply | Year: 2013

The presence of pesticides, endocrine disruptors and pharmaceuticals caused PWN to implement multiple barriers for organic contaminant control in their surfacewater treatment plants. A combination of advanced oxidation by UV/H 2O2 treatment and granular activated carbon (GAC) filtration is installed. Medium pressure UV experiments in a standard pilot reactor have been carried out into the degradation of a representative selection of pesticides found in PWN's main raw water source, the IJssel Lake. It was observed that atrazine and diuron are more sensitive to direct photodegradation while bentazone and bromacil are primarily degraded by hydroxyl radical oxidation. Addition of H2O2 increased the decay rate of all selected herbicides. Using computational fluid dynamics, irradiance distribution and kinetic models developed by Trojan Technologies Inc., an optimized UV-reactor was designed. In tests with a pilot reactor according to this new design, the predicted performance was confirmed, both for photodegradation and hydroxyl radical oxidation. During the research period, the scope broadened from pesticides to pharmaceuticals, endocrine disrupting compounds, solvents and algae toxins. At process conditions 0.56 kWh/m 3 and 6 mg/L H2O2, 80-100% degradation was achieved for compounds such as mecoprop, clofibric acid and diclofenac. A somewhat lower degradation was found for dicamba, 2, 4-D, bentazone, ibuprofen, carbamazepine and sulphametoxalol. The developed modelling was used to design a full scale UV/H2O2 system with an electric energy of 0.56 kWh/m3 for treatment of 3,000 m3/h. In a site acceptance test, degradation of atrazine was measured at two UV-doses at a fixed H 2O2 dose of 6 mg/L. The installation performed as predicted by the design models and design criteria were met. At wtp Andijk, UV/H2O2 is integrated in the existing process train, preceded by conventional surface water treatment (coagulation, sedimentation and filtration) and followed by GAC filtration providing a robust barrier against reaction products from both oxidation and photolytic degradation (assimilable organic carbon, nitrite). Replacing the conventional pretreatment by ion exchange followed by ceramicmicrofiltration will further improve the economics of UV/H2O2 treatment. Copyright © IWA Publishing 2013.

Martijn B.J.,PWN Water Supply Company North Holland | Fuller A.L.,University of New Hampshire | Malley J.P.,University of New Hampshire | Kruithof J.C.,Center of Excellence for Sustainable Water Technology
Ozone: Science and Engineering | Year: 2010

PWN considers ion exchange and ultrafiltration (IX-UF) for replacing the existing CSF pretreatment at the Andijk water treatment plant. Advanced oxidation (UV/H2O2) in combination with granular activated carbon filtration (GAC) as a non selective barrier against organic micro pollutants is operational since 2004. Effects of an improved pretreatment on the UV/ H2O2 in terms of direct photolysis, OH-radical oxidation and energy consumption are presented in this paper. NDMA and 1,4-dioxane are selected to show the impact of pretreatment on UV photolysis and hydroxyl radical oxidation, respectively. Key water quality parameters are DOC and nitrate for scavenging and competition for UV light. Compared to CSF, the electrical energy per order (EEO) for IX-UF treated water was reduced with about 50%. © 2010 International Ozone Association.

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