Technical Review of Water Conservation

Technical Review of Water Conservation

Long Tengrui, He Qiang
(Chongqing Jianzhu University)

1 A Survey of Water Conservation

With the uninterrupted development of society and economics, the problems of environment and natural resources are increasing, water is one of these main problems. China is a water deficient country, its water resources per capita is only 2,150m3/a (it is calculated according to the population of 13 billion), it is lower than one fourth of the world‘s per capita level. Especially the "three northern areas" (northeast, north and northwest of China) and the economically developed coastal areas, the contradictions between water supply and demand is very prominent. The concerned information stated clearly that the amount of the industrial output value being impacted by water deficiency in China has reached 230 billion RMB per year. It is forecasted till the end of this century, that the whole country‘s annual total water demand will amount to 70 billion m3, and water deficit will also amount to 7 billion m3. The deficiency of water resource has become an important factor limiting the development of China‘s economy and society.

1.1 The Connotation of Water Conservation

There are two words in English showing the concept of water conservation, they are "Saving Water" and "Water Conservation", but the meaning of the two words are somewhat different. The former means saving on water particularly. The meaning of the latter is relatively extensive, different scholars or research organizations have different understandings. But they all tend to adopt economic, social and technical means, with the purpose of satisfying social interest, to improve the co-efficient of the utilization of water resources and keep sustainable use of water resources. In the "Guidance to the Target of Water-Saving Type Cities" by China (1997), the definition of water conservation is shown as following : "Water Conservation means strengthening water management through administrative, technical and economic means; adjusting the structure of water consumption; improving water consumption technology; exercising water consumption planning and avoiding waste; building a scientific system of water consumption by applying advanced science and technology; using water resources effectively and protecting water resources to meet the demands of the sustainable development of urban economy and urban construction. In this definition, the meaning of water conservation has gone beyond the original meaning of saving water consumption. Its connotation becomes more extensive, it also includes water resources legislation, water price, management system and the concerned series of administrative management measure.

1.2 The Significance of Water Conservation

Water conservation is a global problem, even the countries with relatively abundant water resources, such as United States of American, the problem of inadequate water supply is happened frequently, too. The loss brought by inadequate water supply is enormous. At present in China besides the loss of industrial output each year owing to water-deficiency, the loss of agriculture is unmeasurable. In addition, abnormal weather conditions and water body pollution in the global scope, especially the water pollution caused by people, aggravates the situation of water resources being inadequate. Under such a situation, water conservation is of great significance:

(1) It may reduce present and future water demand and maintain sustainable utilization of water resources;
(2) To save the operating and maintenance costs of current water supply systems, cut down the construction quantity of water works, or decrease the invest of water works construction;
(3) To cut down the number sewage treatment plant being built or delay the extension of sewage disposal buildings, make current systems take in more customers‘ wastewater, so as to decrease the pollution of the receiving water body and cut costs of construction and operation;
(4) To strengthen pre-cautionary capacity against drought, short-term water-saving measures can bring immediate effects, but long-term water conservation can enhance the ability of guarding against drought in normal periods because it decreases the consumption of water resources in a large degree;
(5) It is of social significance. For the adoption of water consumption auditing and other measures may adjust water consumption differences in different areas, and avoid unfair water exploitation and other social problems concerned with water consumption;
(6) It is of obvious environmental benefit. Besides the benefits in the aspects of protecting wild living things, wet lands and beautifying environment, it also includes the benefits in the fields of safeguarding rivers‘ ecological balance and avoiding underground water pollution due to over extraction of underground water.

2 A Survey of International Water Conservation Techniques

Regardless of abundant water resources countries, such as United States of America and some European countries, or poor water resources countries of the Arabic gulf area, as an important activity and the content of water resources management, water conservation has been widely implemented throughout the world. Some mature techniques and methods of water conservation have been attained. They mainly include industrial water conservation, household water conservation, water conservation of the water supply system and other techniques of water conservation.

United States of America is the country who has done the most studies in water conservation. At the earlier time, water conservation was an emergency measure against drought and the unexpected water deficiency. In the 1970s, drawing the inspiration from the power department‘s saving on electricity, water conservation found great development in the aspects of hardware equipment and public awareness, and became basic water management measures.

Up to the 1980s, professional water conservation organizations or legislation organizations have not been built up, but various states of America have developed water conservation movement one after another. In 1990, a symposium of water conservation "CONSERV90" which was attended by main water supply companies in various states of America, it became the first national conference of water conservation and a milestone in the history of American water conservation. The conference studied and discussed various problems related to water conservation, including those of physics, economics, political and policies, after that water conservation became a feasible and permanent part of water management. At present all states think of water conservation and water consumption management as a part of the integrated water resources planning.

European countries carried out water conservation on a large scale a little later. For example, Britain is 5 to 10 years behind America. Britain set up the Company of Water Conservators in 1988, the aims are to promote the development of water conservation and environment management to satisfy the demand of the public. But it didn‘t stipulate officially to take water conservation in line with water supply planning until 1996. After that, public water supply companies nationwide carried out estimation of their water consumption and water supply planning, thus water conservation was developed to the full scale.

Arabic gulf countries are the well-known countries that are water-deficient. Since 1978, member countries of the Gulf Cooperation Council have adopted expensive substitution techniques, such as wastewater reuse and desalination of seawater, to satisfy its increasing water demand. Owing to long-term and over extraction of underground water, Saudi Arabia, Kuwait, Qatar and Bahrain and other countries have occurred the problems of over extraction of underground water resources and worsening water quality. These countries which suffer from water -deficiency have been seeking the way of guiding water resources planning and management using the principals of water conservation. At present, water conservation has been related to the fields of agriculture, industry and people‘s daily life.

2.1 Overseas Industrial Water Conservation Technology

Urban industrial water consumption occupies a bigger proportion in urban water consumption, sometimes amounting to 70%. Therefore, industrial water conservation is of great significance for urban water conservation. Urban industrial water conservation of overseas developed countries mainly lies in recycling and cooling water.

Recycling water consumption has found widely use in American industry. It was reported in 1988 and 1989 in San Jose, California, there were 15 industrial trades adopted the way of recycling water consumption. They include the food industry, finely processed metals, papers recycling and electronic industry, etc. As a result, the total water volume saved reached 560,000m3/a, with a total economic benefit 2 million USD. Among these cyclic water consumption techniques, some are to recovery and circularly utilize the water in the technical process, others are to recovery and utilize the water having been pretreated before discharging them into the sewer. It was proved that the circulation water in a factory is permitted to have a bigger fluctuation scope of water quality (reused in different production process). So recycling water is the water conservation measures should be considered first.

Many companies abroad economize on water through improving water supply system of a cooling tower. There are also some big companies such as Excel, Intel, etc. adopted ozone techniques to treat and reuse air-conditioner water or other light polluted water. As a result, wastewater discharge is reduced obviously. In addition, many factories reached the purpose of saving production water consumption through improving productive technology and production equipment.

It is shown that water consumption monitoring is valued abroad. The monitoring equipment of most industries is complete, it ensures that water conservation measures can be brought into play, at the same time it promotes to reduce leakage and avoid other wastes. Besides, it was attached much importance to carrying out water conservation education to employees. The public is the main body of the water conservation movement. The improvement of their water conservation consciousness is very important in ensuring the water conservation effect.

2.2 International Household Water Conservation and Other Water Conservation Techniques

Urban household water consumption occupies a bigger proportion in urban water consumption. For example, it occupies 47% in Saudi Arabia. Urban household consumption is of great potential and its technology also has been studied thoroughly. At present, water conservation of external urban household water consumption mainly emphasizes the following aspects: (1) Urban water consumption monitoring and water consumption estimation. The purpose of carrying out water consumption monitoring is to know factual water consumption and utilization patterns, thus know the working condition of water supply system and provide the basis for the determination of rational and fair water price. The estimation of water consumption is to estimate rationally future household water consumption according to the principals of water conservation, by investigating and appraising the current condition of water consumption. (2) To adopt water-saving family sanitary facilities. Water-saving sanitary facilities are usually those of low or ultra-low rates of flow. It was indicated by the study that this kind of facilities‘ effect of economizing on water is very obvious, it can save 32% of household water if using it to replace sanitary facilities with low water utilization efficiency. Water-saving sanitary facilities including water-saving toilets, washers and shower, etc. (3) Water-saving technology of family lawn watering. According to the statistics, about 50% of the residents who have lawns in America over watering, so it is of great potential to save water. This kind of technology can reach its purpose of saving water by improving watering patterns, setting up the watering stipulations in different seasons, controlling watering time and choosing drought-resistant grass seeds. (4) Water price structure and water leakage control, including the determination of water-saving price and the control of water leakage.

Other external water conservation methods include water conservation of water works, leakage control of water supply system, water consumption auditing, rainfall management, wastewater reuse, economic incentive on water conservation, legislation, public awareness, the integrated water resources planning.

3 A Survey of Domestic Water Conservation Technique

Domestic water conservation movement is started in the early 1980s, great advances have been attained through efforts of nearly 20 years. The volume of water being saved in urban area has reached 22 billion m3 . Let‘s take Beijing city as an example. Beijing city‘s water demand on average increased 28.98% in the 1950s, 4.29% in the 1960s, 6.74% in the 1970s, 3.1% in the 1980s, 5.8% from 1991 to 1996. It is fully illustrated by the data that the effect of the water conservation measures being begun from the 1980s is very obvious.

3.1 Domestic Industrial Water Conservation Technology

Most of industrial wastewater can be reused except for a small amount being serious polluted, so industrial water conservation is also a focal point in domestic urban water conservation. Urban water intake of 10,000 RMB industrial output value in China in 1990 is 245m3/ 10,000 RMB, it decreased to 198m3/10,000 RMB in 1996. Water intake of 10,000 RMB industrial output value of Beijing, Tianjin, Dalian, Qindao and other cities are under 100m3/10,000 RMB, but there are a number of cities whose water requirements of 10,000 RMB industrial output value is up to several hundreds of cubic meters. It shows that some achievements have been attained in the work of industrial water conservation in China, but from an integral view, the level of industrial water conservation is very low. There‘s a big gap if compared with the developed countries of 20 to 30 m3/ 10,000 RMB.

In the aspects of specific water conservation technology, domestic cities mainly emphasize on the technology of water reuse, including recycling water conservation of cooling water, general recycling water conservation (recycling water consumption, closing water consumption) and technological water conservation (including cooling process reformation, technology of anhydrous and less water) etc.. These technologies have found successful applications in the trades of thermal power, iron and steel, petrochemical industry, chemical industry, printing and dyeing, paper making. Let‘s take the second stage of Baoshan Steel Company as an example, it was designed according to 95% of cyclic and recycling coefficient of utilization, the scale of its waterworks is 200,000 m3/d. If a straight-flow water supply system is adopted, then the scale will be 380 to 400 m3/ d. The effect of saving water is very obvious.

3.2 Domestic Household Water Conservation and Other Water Conservation Techniques

Generally speaking, domestic urban household water (major household water consumption) occupies about 30% of the total urban water consumption. It includes two parts: urban residents‘ houses water consumption (minor water consumption) and public water consumption. But with the fast development of society and economics, urban household water consumption will increase very soon. As far as water conservation is concerned, great potential can be exploited.

At present, main water conservation measures in China include:

(1) Water meters installation and metering. The experiences of urban household water consumption show that the installation of water meters can save more water than without using it, and each family installs a meter can save more water than that one unit having a general one. 7 large enterprises in Datong City, Shanxi province, after having changed expenses contracting system into metering charge system, household water consumption was saved 75.3%, water volume saved in each month amounts to 870,000 m3.

(2) To adopt water-saving facilities, including water-saving toilets, washers and showers, etc. But there is still a long way to go if hoped all these facilities are not only convenient to use, but also have water conservation effect and in the mean time they can be widely used.

(3) Urban water-saving irrigation. With the improvement of people‘s living standards, urban green space will increase constantly, and urban water consumption of irrigation is increasing year by year. At present China is popularizing the new techniques of sprinkling irrigation, micro sprinkling irrigation and drip irrigation. They will save 30 to 50 % on water than the original ground irrigation, at the same time it will save a large number of labor forces.

4 Water Conservation Technology Recommended to Shijiazhuang City

Shijiazhuang is the provincial capital of Hebei province. Its city nature is: an important hub of communications, a coastal provincial capital city whose industrial system which is relative complete in range and service sector is well developed. At present it has formed an industrial system which is complete in range, with the emphasis on the trades of textile, medicine, electron, machinery, chemical industry, building materials and food industry. Its agriculture is well equipped and township enterprises are developed very fast. It is planned that in the year 2000, the total population of the whole city will be 3.51 million, and the water demand will be 578 million m3, gross industrial and agricultural value of output amounts to RMB 63.26 billion RMB; In 2010, the total population of the whole city will be 5.01 million, water demand will be 784 million m3, gross industrial and agricultural value of output amounts to 155.9 billion RMB.

Water resources in Shijiazhuang City include surface and underground water resources. According to the study of Shijiazhuang Construction Committee, the available volume of surface water in the whole city shown as following: 413million m3 in average year (in rainfall ), 326 million m3 in a especially drought year. The total volume of underground water exploitable is 926 million m3. The research results of the Planning and Design Institute in Shijiazhuang indicate that surface water resources can be used is only 127million m3 /a, the volume of underground water is between 240million m3 to 250million m3. It can be calculated that the quantity of water resources in Shijiazhuang City is only 370 million m3, if compared with the water demand in the year 2000 and 2010, there is a gap of 208 million m3 and 414 million m3. Therefore, the situation of water-deficiency in Shijiazhuang City is very serious, water conservation is of practical or immediate significance. Considering this situation, suggestions are made in this report: (1) It must be aware the seriousness and harmfulness of water-deficiency of this city. Water deficiency and the pollution of water quality has not only influenced people‘s daily life, but also become a factor limiting the development of society and economics of the whole city. (2) Water conservation is a comprehensive problem, all effective administrative and technical means must be brought into play, such as, engineering techniques, legislation and law, organization construction, economic incentive, social means, etc.. (3) Attaching much importance to industrial water conservation. Shijiazhuang is a city whose industry is relative developed, but its water consumption of 10,000 RMB industrial output value reached 313 m3 in 1989, it is planned to drop to 120 m3 / 10,000 RMB in 2000. It‘s water consumption of 10,000 RMB industrial output value is the highest one among the northern cities that are similar in water resources, so it is of great potential in water conservation. (4) Water conservation consumption of household water also must be paid attention to. Per capita water consumption in Shijiazhuang City is a little more than average cities in Hebei province, it amounts to 137 L/(Capita.d) in 1990, it is 200 L/ (Capita.d) in the year of 2000 according to the plan, it is still of great potential in water conservation. At the same time awareness and education of water conservation must be strengthened, especially the ideology education of water conservation must be done for the school students.

In summary, the deficient situation of water resources of Shijiazhuang City is very serious, but it also must be seen that the potential of water conservation is very big. Therefore, take Shijiazhuang as a model city of water conservation is typical and is of significance. To analyze the potential of water conservation of the cities and use the advanced experiences in domestic and abroad for reference, and make a good job of water conservation of China‘s model city, it is of great significance to release the deficient situation of water resources in China. This report suggested that specific projects in water conservation should be established and carried out the construction of model project.