Unit 2.3 Consumption for Various Purposes



Read the text and answer the following questions:

1) What are the main uses of water furnished to a city?

2) What practice may have a considerable effect upon total water consumption?

3) What are industrial water requirements?

4) Does the actual amount of water used for extinguishing fires greatly figure in the average consumption?

5) What type of water is classified as “unaccounted for”?

6) What are the reasons of “unaccounted for” water?

7) What is the percentage of the “unaccounted for” water in a system?

The water furnished to a city can be classified according to its ultimate use or end. The uses are:

Domestic. This includes water furnished to houses, hotels, etc., for sanitary, culin­ary, drinking, washing, bathing, and other purposes. It varies according to living conditions of consumers, the range usually being considered as 75 to 380 1 (20 to 100 gal) per capita per day, averaging 190 to 340 1 (50 to 90 gal) per capita. These figures include air conditioning of residences and irrigation or sprinkling of privately owned gardens and lawns, a practice that may have a considerable effect upon total consumption in some parts of the country. The domestic consumption may be expected to be about 50 percent of the total in the average city; but where the total consumption is small, the propor­tion will be much greater.

Commercial and Industrial. Water so classified is that furnished to industrial and commercial plants. Its importance will depend upon local conditions, such as the existence of large industries, and whether or not the industries patronize the public waterworks.. Self-supplied industrial water requirements are estimated to be more than 200 percent of municipal water supply demand.

 Public Use. Public buildings, such as city halls, jails, and schools, as well as public service—flushing streets and fire protection—require much water for which, usually, the city is not paid. Such water amounts to 50 to 75 1 per capita. The actual amount of water used for extinguishing fires does not figure greatly in the average consumption, but very large fires will cause the rate of use to be high for short periods.

Loss and Waste. This water is sometimes classified as " unaccounted for," although some of the loss and waste may be accounted for in the sense that its cause and, amount are approximately known. Unaccounted-for water is due to meter and pump slippage, unauthorized water connections and leaks in mains. It is apparent that the unaccounted-for water, and also waste by cus­tomers, can be reduced by careful maintenance of the water system and by universal metering of all water services. In a system 100 percent metered and moderately well maintained, the unaccounted-for water, exclusive of pump slippage, will be about 10 percent.

The total consumption will be the sum of the foregoing uses and the loss and waste.

1. Read the text again and give the summary of it using the following phrases:

• The text deals with…

• It covers such points as…

• It is pointed out that…

• The information is of (no, little, great) interest to…

 

Unit 2.4 Periods of Design and Water Consumption Data Required

Discuss in pairs:

1) What factors does the design period depend on?

2) How long can be the design period?

Read the text and see if your ideas are right.

The economic design period of a structure depends upon its life, first cost, ease of expansion, and likelihood of obsolescence. In connection with design, the water consumption at the end of the period must be estimated. Overdesign is not conser­vative since it may burden a relatively small community with the cost of extrava­gant works designed for a far larger population. Different segments of the water treatment and distribution systems may be appropriately designed for differе periods of time using differе capacity criteria.

1. Development of source. The design period will depend upon the source. For groundwater, if it is easy to drill additional wells, the design period will be short, perhaps 5 years. For surface waters requiring impoundments, the design period will be longer, perhaps as much as 50 years. The design capacity of the source should be adequate to provide the maximum daily demand anticipated during the design period, but not necessarily upon a continuous basis.

2. Pipe lines from source. The design period is generally long since the life of pipe is long and the cost of material is only a portion of the cost of construction. Twenty-five years or more would not be unusual. The design capacity of the pipe line should be based upon average consumption at the end of the design period with consideration being given to provision of suitable velocities under all an­ticipated flow conditions.

3. Water treatment plant. The design period is commonly 10 to 15 years since expansion is generally simple if it is considered in the initial design. Most treat­ment units will be designed for average daily flow at the end of the design period since overloads do not result in major losses of efficiency. Hydraulic design should be based upon maximum anticipated flow.

4. Pumping plant. The design period is generally 10 years since modification and expansion are easy if initially considered. Pump selection requires knowledge of maximum flow including fire demand, average flow, and minimum flow during the design period.

5. Amount of storage. The design period may be influenced by cost factors peculiar to the construction of storage vessels, which dictate a minimum unit cost for a tank of specific size. Design requires knowledge of average consumption, fire demand, maximum hour, maximum week, and maximum month, as well as the capacity of the source and pipe lines from the source.

6. Distribution system. The design period is indefinite and the capacity of the system should be sized to accommodate the maximum anticipated development of the area served. Anticipated population densities, zoning regulations, and other factors affecting per capita flow should be considered. Maximum hourly flow including fire demand is the basis for design.

1. Notes to the text:

Obsolescence – моральный износ

to drill – бурить

velocity – скорость

flow – поток

expansion – расширение

overload – чрезмерная нагрузка

2. Match the words in two columns and make the collocations:

1) water                    a) demand

2) distribution          b) wells

3) to drill                  c) capacity

4) ground                 d) system

5) surface                 e) treatment

6) daily                     f) water

7) design

3. Match the following English expressions to their Russian ones:

1) first cost a) подземные воды
2) surface water b) обеспечивать
3) criteria c) первичные затраты
4) ground water d) система распределения
5) distribution system e) критерии
6) to provide f) наземные воды

4. Read the text again and answer the questions:

1) What is the purpose of water treatment and distribution systems design?

2) What is the design period for surface water?

3) What should the design capacity of the pipe line be based upon?

4) What is hydraulic design based upon?

5) What does pump selection require?

6) How should the distribution system be sized to?

 5. Complete the following sentences using the text:

1) Different segments of the water treatment and distribution systems are designed for…

2) The design capacity of the pipe line should be based upon…

3) The economic design period of a structure depends upon…

4) Pump selection requires knowledge of…

5) Maximum hourly flow is…

6. Look through the text again and find English equivalents for the following words and word combinations:

1) насосная станция

2) трубопровод

3) очистительное сооружение

4) распределительная система

5) запроектированная мощность источника

6) природная скорость

7) условия потока воды

8) потеря эффективности

9) видоизменение и расширение

10) факторы стоимости

7. Discuss in pairs:

1) Required data to waterworks design.

2) Key elements of pumping plant construction.

Part III


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