Multivariate data mining for estimating the rate of discolouration material accumulation in drinking water distribution systems

Particulate material accumulates over time as cohesive layers on internal pipeline surfaces in water distribution systems (WDS). When mobilised, this material can cause discolouration. This paper explores factors expected to be involved in this accumulation process. Two complementary machine learning methodologies are applied to significant amounts of real world field data from both a qualitative and a quantitative perspective. First, Kohonen self-organising maps were used for integrative and interpretative multivariate data mining of potential factors affecting accumulation. Second, evolutionary polynomial regression (EPR), a hybrid data-driven technique, was applied that combines genetic algorithms with numerical regression for developing easily interpretable mathematical model expressions. EPR was used to explore producing novel simple expressions to highlight important accumulation factors. Three case studies are presented: UK national and two Dutch local studies. The results highlight bulk water iron concentration, pipe material and looped network areas as key descriptive parameters for the UK study. At the local level, a significantly increased third data set allowed K-fold cross validation. The mean cross validation coefficient of determination was 0.945 for training data and 0.930 for testing data for an equation utilising amount of material mobilised and soil temperature for estimating daily regeneration rate. The approach shows promise for developing transferable expressions usable for pro-active WDS management

Validation of Non-residential Cold and Hot Water Demand Model Assumptions

AbstractExisting guidelines related to the water demand of non-residential buildings are outdated and do not cover hot water demand for the appropriate selection of hot water devices. Moreover, they generally overestimate peak demand values required for the design of an efficient and reliable water installation. Recently, a procedure was developed based on the end-use model SIMDEUM to derive design rules for peak demand values of both cold and hot water during various time steps for several types and sizes of non-residential buildings, i.e. offices, hotels and nursing homes. In this paper, the assumptions of building standardisation, on which the design rules are based, are validated. This was done with measurements of cold and hot water demands on a per second base and with surveys. The good correlation between the simulated water demand patterns and the measured patterns indicates that the basis of the design rules, the SIMDEUM simulated standardised buildings, is solid. Surveys were held to investigate whether the construction of the standardised buildings based on the dominant variable corresponds with practice. Surveys show that it is difficult to find relations to equip the standardised buildings with users and appliances. However, the validation proves that with a proper estimation of the number of users and appliances in only the dominant functional room of the standardised buildings, SIMDEUM renders a realistic cold and hot water diurnal demand pattern. Therefore, the new design rules based on these standardised buildings lead to reliable and improved designs of building installations and water heater capacity, resulting in more hygienic and economical installations

Duurzaam ontwerp van de aan- en afvoer van drinkwater

Het simulatiemodel SIMDEUM geeft een betrouwbare voorspelling van koud- en warmwaterverbruik in woningen, gebouwen en utiliteitsbouw en kan daardoor een cruciale rol spelen bij het bevorderen van duurzaamheid in de waterketen. Zo leiden op het model gebaseerde rekenregels tot energie-efficiënte ontwerpen van leidingwaterinstallaties. Ook maakt het model het mogelijk grijs- en hemelwatersystemen goed te dimensioneren en geeft het inzicht in de kwantiteit en kwaliteit van het afvalwater, zoals temperatuur en concentratie aan nutriënten. Deze informatie is nodig in processen waarin energie of nutriënten uit afvalwater teruggewonnen worden

Validation of non-residential cold and hot water demand model assumptions

Existing guidelines related to the water demand of non-residential buildings are outdated and do not cover hot water demand for the appropriate selection of hot water devices. Moreover, they generally overestimate peak demand values required for the design of an efficient and reliable water installation. Recently, a procedure was developed based on the end-use model SIMDEUM to derive design rules for peak demand values of both cold and hot water during various time steps for several types and sizes of non-residential buildings, i.e. offices, hotels and nursing homes. In this paper, the assumptions of building standardisation, on which the design rules are based, are validated. This was done with measurements of cold and hot water demands on a per second base and with surveys. The good correlation between the simulated water demand patterns and the measured patterns indicates that the basis of the design rules, the SIMDEUM simulated standardised buildings, is solid. Surveys were held to investigate whether the construction of the standardised buildings based on the dominant variable corresponds with practice. Surveys show that it is difficult to find relations to equip the standardised buildings with users and appliances. However, the validation proves that with a proper estimation of the number of users and appliances in only the dominant functional room of the standardised buildings, SIMDEUM renders a realistic cold and hot water diurnal demand pattern. Therefore, the new design rules based on these standardised buildings lead to reliable and improved designs of building installations and water heater capacity, resulting in more hygienic and economical installations.</p

Stochastic water demand modelling for a better understanding of hydraulics in water distribution networks

In the water distribution network water quality process take place influenced by de flow velocity and residence time of the water in the network. In order to understand how the water quality changes in the water distribution network, a good understanding of hydraulics is required. Specifically in the periphery of the network, where customers are connected, the hydraulics can change rapidly. During the night time the water is almost stagnant and the residence time increases. In the morning, when everybody gets up and flushes the toilet and takes a shower, high flow velocities can occur. During the remainder of the day flow velocities are low. The stochastic model SIMDEUM was developed to simulate water use in small time scales (1 s) and small spatial scales (per fixture). The model SIMDEUM and its applications in several hydraulic and water quality models in water distribution networks were tested against measurements within these networks. SIMDEUM enables a good model of flow velocities, residence times and the connected water quality processes in the water distribution network.Water ManagementCivil Engineering and Geoscience

Dynamic hydraulic models to study sedimentation in drinking water networks in detail

Sedimentation in drinking water networks can lead to discolouration complaints. A sufficient criterion to prevent sedimentation in the Dutch drinking water networks is a daily maximum velocity of 0.25 m s?1. Flushing experiments have shown that this criterion is a sufficient condition for a clean network, but not a necessary condition. Drinking water networks include many locations with a maximum velocity well below 0.25 m s?1 without accumulated sediments. Other criteria need to be developed to predict which locations are susceptible to sedimentation and to prevent sedimentation in future networks. More distinctive criteria are helpful to prioritise flushing operations and to prevent water quality complaints. The authors use three different numerical modelling approaches – quasi-steady, rigid column and water hammer – with a temporal discretisation of 1 s in order to assess the influence of unsteady flows on the wall shear stress, causing resuspension of sediment particles. The model predictions are combined with results from flushing experiments in the drinking water distribution system of Purmerend, the Netherlands. The waterhammer model does not result in essentially different flow distribution patterns, compared to the rigid column and quasi-steady modelling approach. The extra information from the waterhammer model is a velocity oscillation of approximately 0.02 m s?1 around the quasi-steady solution. The presence of stagnation zones and multiple flow direction reversals seem to be interesting new parameters to predict sediment accumulation, which are consistent with the observed turbidity data and theoretical considerations on critical shear stresses.Water ManagementCivil Engineering and Geoscience

Modeling the influence of district heating systems on drinking water temperatures in domestic drinking water systems within domestic properties

In this research, we investigated the influence of the heating of drinking water in the connection pipe under the influence of nearby district heating and the effect this has on water temperatures throughout the domestic drinking water system (DDWS) of a typical Dutch domestic property. We found that stagnant water in the connection pipe warms up fast, reaching the surrounding ground temperature in about 15 min, and these temperatures can be found throughout the house at taps such as the shower and the kitchen tap. Flowing water in the connection pipe is also, depending on the pipe length, heated up several degrees. The prevention of high temperatures in the soil around the connection pipe is the best measure to prevent high drinking water temperatures at the taps.Sanitary Engineerin