9. Point of Use Water Filter Solutions

Whether consumers receive their water from a household well or a community water system, they may wish to treat it at its point-of-use (POU). Consumers do have the option to chose the higher quality of water that POU technologies can provide.

POU technologies treat water at single or multiple taps or for the whole house, and improve water quality in a variety of ways. Unusual taste, color, and odor or water may be corrected by POU technologies, and some POU devices also reduce harmful contaminants.

A variety of POU equipment is available for improving drinking water and other special purposes. Each technology is designed to solve one or several different water quality problems. In order to chose the right equipment, it is important to know the nature and extent of the problem.

The first step in solving a water quality problem is to have the water tested. When the safety of the water is in question, it should always be tested by a state-certified or other reputable laboratory.

Testing the water will help determine the proper treatment necessary.

10. Water Desalinization

To meet the ever-increasing demands for fresh water, especially in arid and semiarid areas, much research has gone into finding efficient methods of removing salt from seawater and brackish waters. Several processes are being developed to produce fresh water cheaply.

Three of the processes are known as multiple-effect evaporation, vapor-compression distillation, and flash evaporation. The last-named method, the most widely used, involves heating seawater and pumping it into lower-pressure tanks, where the water abruptly vaporizes (flashes) into steam. The steam then condenses and is drawn off as pure water.

One major problem in desalinization projects is the cost of producing fresh water. Using conventional fuels, plants with a capacity of 1000 gal. (3.8 million liters) per day or less produce water at a cost of $1 or more per 3800 liters. More than 500 such plants are in operation, with a total capacity of nearly 473 million liters (nearly 125 million gal) a day; however, their high costs limit their use to areas of great water scarcity. Water from conventional sources, such as wells and reservoirs, is sold for less than 30 cents per 3800 liters delivered to the home, and water for irrigation is usually priced at less than 5 cents per 3800 liters. The dual-purpose atomic power and water-desalting plants now being planned are designed to produce fresh water for between 20 and 30 cents per 3800 liters.

Notes:

1. POU technologies – методы очистки в точке водоразбора

2. POE technologies – методы очистки воды на вводе

3. ion exchange resin – ионообменная смола

4. nonpoint source – источник поверхностного стока (в отличие от точечного источника загрязнения).

Contents:

1. Lesson 1 Water…………………………………………………………… 1

2. Lesson 2 Natural water cycle …………………………………………..... 4

3. Lesson 3 Water problems …………………………………………………6

4. Lesson 4 Sources of Drinking water ……………………………………. .10

5. Lesson 5 How safe is our drinking water …………………………………14

6. Lesson 6 Water Purification (I) …………………………………………...17

7. Lesson 7 Water Purification (II) …………………………………………..20

8. Lesson 8 Water Purification (III)…………………………………………..23

9. Lesson 9 Water supply schemes……………………………………………26

10. Lesson 10 Water supply to Springfield, Illinois………………………….. 28

11. Supplementary reading ……………………………………………………30