饮用水分配系统（DWDS）中有效的多位置水温测量

Temperature canaffect every aspectof the treatmentand the deliveryof potable water. Introduction The temperature of the drinking water delivered to a utilitiesend-customer is becoming increasingly important. Governmentsand regulators around the world are looking at ways of improvingthe overall water quality in the drinking water distribution systemsby reducing the risk of microbial contamination. At the same time,they are striving to move away from the current practice of directdisinfection of the water supply using chemical processes, such aschlorination and chloramination. “…the temperaturedependence of mostchemical reactions stemsfrom the activation energyassociated with them. Therates of chemical reactionsdecrease with decreasingtemperature. The relativeconcentrations of reactantsand products in chemicalequilibria can also changewith temperature...Temperature can, therefore,affect every aspect of thetreatment and the delivery ofpotable water.” To date, water temperature measurement carried out by a typicalutility has been sporadic, often occurring when the water entersthe drinking water distribution system (DWDS) from the treatmentplant and not at, or near to, the point of consumption. Sometimessampling is carried out at the customer’s tap as part of a regu-latory requirement, but is only performed at a very small numberof residences. This means that in some areas of the network thewater temperature may rise to the point where microbial andalgal growth can escalate, especially when there is little to no flowof water. Water temperature measurement is usually carried out using aseparate device and logged independently. However, a growingnumber of static residential and commercial meters, such as thelatest Xylem Eccus and Cordonel static water meters that utiliseultrasonic technology, can provide accurate water temperaturereadings on a near-real-time basis. Guidelines for Canadian DrinkingWater Such ubiquitous water temperature measurement, combinedwith accurate flow data, enables the utility to rapidly detect andresolve potential issues, such as initiating pipe flushing if demandis too low in a section of the DWDS. New network managementsoftware can easily incorporate this data to provide operators witha complete picture of water temperature across the network, withlittle or no additional cost above that needed to monitor existingflow and customer consumption. Why is monitoring watertemperature important? The population growth of microbes, algae, invertebrates and bioslime (aka biofilm) are all, in part, affected by the temperatureof the water in which they live. In warm climate areas, the hightemperatures of distributed water and the difficulty in maintainingdisinfectant residuals during transport over long distances maylead to microbial aftergrowth, depending on nutrient availability. While a water treatment plant can produce potable water withlittle or no contaminants at its outlet to the DWDS, there is stillan opportunity for microbes and other contaminants to enter thedistribution system. Contaminants can enter via pipe damagewhere leakage occurs, pipe repairs, poorly maintained storagetanks, air valves and hydrants. In Europe, levels of contaminationhave by and large been within acceptable limits, largely througha combination of average water temperatures being belowthose needed for accelerated population growth and/or the useof chemical additives in the water – such as Chloramines (up to4ppm in the USA) or Chlorine Dioxide (with up to 0.4ppm usedacross Europe). In countries such as Germany, Netherland and Belgium, chemicaldisinfection is avoided due to concerns about the long-termeffects on human health, as well as the potential damage toplumbing components. As a result, chemical disinfection is usedonly when there is a serious outbreak. Even disinfection efficacycan be affected by temperature, leading to difficulty in main-taining disinfectant residuals during transport over long distancesor via complex pipe networks. This can result in microbial after-growth, if sufficient nutrients are available. Overall environmental temperatures are rising due to climatechange, and governments and regulators wish to move awayfrom adding disinfectants to water, replacing them when possiblewith UV and ozone treatment processes. As a consequence,utilities must place greater emphasis on monitoring the temper-ature of the water reaching customers, as an indicator of potentialwater quality issues. Urban areas are unsurprisingly typically hotter than the rural areasthat surround them. This is due to less evapotranspiration (i.e.water evaporation to the atmosphere, either directly or via plants),heat storage and release from buildings and urban surfaces, andhuman activity or man-made heat sources. Example of howpathogens can developover time and distancefrom the utility’s watertreatment plant. While the need to ensure human health and safety is of theutmost importance, elevated water temperature can lea