专业英语PPTUnit13.ppt

WATER SUPPLY 小组成员：梁 爽 唐北怀 柏丰立 曹宏利 Total water demand on a municipal water supply system is the sum of all the individual demands during a stated period. 城市供水系统的总需水量是在某段时间内个人用水的总和。 WATER QUALITY REQUIREMENTS Water Demand Water demand in a particular community is normally specified in terms of average daily demand, defined as follows: Average daily demand=total water use in one year/365days. Units are m3/d or million m3/d, or gallons per day,or million gallons per day. 某社区需水量是按照日均需水量规定的，具体如下： 日均需水量=一年总需水量/365天 单位是m3/d或者百万m3/d，或者加仑每天，百万加仑每天 It is often convenient to express the rate of demand per person:Average daily demand=Average daily demand in community/midyear population in community. The units here may be litters per person per day or gallons per person per day. 人均需水量也很好描述:日均需水量=社区平均日需水量/年中社区人数。在这单位是每人/天/升或者是每人/每天/加仑。 The demands on a water system vary not only from year to year and from season to season, but also from day to day and hour to hour. 需水量是由于每年、每个季节、甚至是每天每时而各不相同的。 Fluctuations in Water Use WATER QUALITY STANDARDS Water contains a variety of chemical , physical, and biological substances which are either dissolved or suspended in it. 水中含有各种化学、物理、生物物质，其中有的溶解或悬浮在水中。 Water is evaluated for quality in terms of its physical, chemical, and microbiological properties. It is necessary that the tests, used to analyze the water as regards each of these properties, produce consistent results and have universal acceptance, so that meaningful comparison with water quality standards can be made. 水质评价包括物理、化学、微生物学特性。这种标准用来分析上述特性是很重要的，并且分析结果是得到大众认可的，所以与水质标准比较是有重大意义的。 Tastes, odors, color, and turbidity are controlled in public water supplies partly because they make drinking water unpalatable, but also because of the use of water in beverages, food processing, and textiles. 公共供水对水的味道，气味，颜色和浊度都有控制，因为这些因素会让水变味，不仅而此，也因为水在饮料、食品加工和纺织品中的用途所以对水的各方面都有严格管控。 Physical Chara