(1. Mentougou District Science and Technology Commission of Beijing; 2. Beijing Mentougou District Science and Technology Development Experimental Base)
Water, the creator of life, has performed the miracle of wisdom for thousands of years. It is beneficial to all things without dispute, quietly gestating all life in the world. However, with the rapid expansion of the world population, the rapid development of industry and agriculture and the acceleration of urbanization, the water crisis has become increasingly prominent in the short history of human civilization of 5000 years. According to relevant surveys, 80 countries in the world, which account for 40% of the world's population, are seriously short of water.
In the study of the future urban form-eco-city, we have given different levels of connotation to eco-city from eight aspects, such as species, resources, operation mode and the relationship between people, city and nature, and conducted in-depth research. Based on the theoretical system of eco-city construction, this paper will discuss the water resources management model of eco-city.
First, the evaluation standard of water resources function in eco-city
The biggest impact of human activities on water resources is that it is gradually reduced due to use or loss. The author's systematic thinking on the theory of eco-city construction (II) expounds the concept of eco-city as follows: from the perspective of urban function, eco-city should make its resource consumption curve run under the regional ecological supply capacity (ecological supply capacity) and ecological reduction capacity (ecological reduction capacity). As a demarcated ecological patch, a city has basically constant ecological supply capacity and ecological restoration capacity, so an important concept of an eco-city is to coordinate the relationship between resource supply, restoration capacity and human activity consumption. As the main resource that breeds life, water follows the same resource consumption standard in specific areas. From the supply point of view, in addition to ecological supply, with the rapid development of science and technology, there are mature technologies for artificial long-span water resources allocation (such as South-to-North Water Transfer Project in China and South-to-North Water Transfer Project in California, USA), but in the process of large-scale artificial natural resources allocation, ecological, economic, social and other aspects have encountered problems, which need further consideration by human beings. From the point of view of reduction, artificial reduction has played a huge role in urban sewage treatment, but in a certain historical period, the ability of artificial reduction (resource utilization) will tend to be relatively constant. Therefore, within the available range of water resources, the natural reducing capacity and artificial reducing capacity of water determine the growth limit of sustainable development of urban water resources.
In the study of eco-city, the utilization of water resources in the target area is used to evaluate the life-giving function of the city, and at the same time it is used as a guide for the development, utilization and management of water resources in eco-city. The evaluation principles are as follows:
Let the variable m be the water demand of the target city, and the radius of the target city is R.
The supply in the area with radius r is M0.
Field 1: the field with radius d minus the field with radius r, where the quantity is m 1 and d = 2r.
Domain 2: a domain with a radius of 2D minus a domain with a radius of d, where the quantity is M2 and the radius is 4R.
And so on, it is a domain n, where the number is Mn and the radius is 2nR, as shown in figure 1.
Then, the value range of this index is 0 ~ 1.
Sw is used to measure the strength of the life-giving function of the target city, that is, the sustainable degree of water resources utilization. If Sw= 1 indicates that this function is well preserved in this area, if Sw=0 indicates that this function is basically lost in this area.
Figure 1 Suitable standard of life chain domain
Second, the classification of water resources utilization
(A) the four basic functions of water in human activities
(1) constitutes life. Take human as an example, the softest part-blood contains about 80% water, the hardest part-teeth contains about 10% water, and the source of wisdom-brain contains about 85% water ... If the human body loses water to 10% ~ 20%, it will endanger life, so water is the basis of life.
(2) ensure survival. People get water through drinking or drinking, eating, metabolism of protein, fat and carbohydrate in the body every day to ensure their survival. See table 1 for the daily water demand of normal people of different ages. "One grain in the ground, ten thousand grains in the warehouse" is the most precious gift of water to mankind. Water is the air of aquatic organisms, which maintains the survival of all kinds of animals and plants, enriches the network of food chain and cultivates nutrients and energy supply for human beings. Water overcomes gravity to transport nutrients to the treetops, promotes plant photosynthesis, fixes carbon and purifies the atmosphere. Water has created various conditions for ensuring human survival.
Table 1 Daily water demand of normal people of different ages
(3) maintaining life. People's life is so inseparable from the participation of boiling water, clean and turbid, take it out and suck it in, and wash everything clean. According to statistics, the water consumption for flushing toilets, washing and showering is about 3 ~ 4.5 cubic meters per person per month. Water goes through various processes and finally forms products and services, which are needed by human life.
(4) Promote production. Production activities are the driving force to push forward the historical wheel of human society. There are traces of water in any industry. Water is used for raw materials, decontamination, power, media or temperature control, and is used in various industries.
The functional utilization classification of water is shown in Figure 2.
Fig. 2 Schematic diagram of water function utilization classification
(B) the use of water resources in agriculture
plant
Water constitutes the main body of plant cells, and the water content of general plant tissues accounts for 75% ~ 90% of fresh weight; Water is the reaction substance of plant metabolism and the raw material of photosynthesis. Water is the medium for various physiological and biochemical reactions and transport substances in plants; Hydrostatic pressure generated by water is used to maintain the natural posture of plants; Water is used for transpiration of plants to maintain their ecological environment. Water metabolism in plants is a process of water absorption, transportation, utilization and loss. In the whole metabolic cycle, 90% of water is used for transpiration and about 65,438+0% for photosynthesis (Table 2).
Table 2 Example of unit water consumption in planting industry
2. Animals
For animals, water is mainly used to feed livestock and poultry, keep the captive environment and clean individual animals (Table 3).
Table 3 Examples of Water Consumption for Animal Husbandry and Fishery
In addition, due to the indirect use of a lot of water in the production, processing, transportation and other links of agricultural products, this paper temporarily considers some water consumption in food processing, road transportation and other parts, and the actual water consumption of specific products needs to be analyzed in the quantitative study of industrial water consumption in eco-city.
(c) Use of water resources in industry
In industrial production, water is widely used in solvent, purification, washing, refrigeration, separation and other manufacturing processes.
1. Processing and manufacturing industry
(1) Classification of food processing and manufacturing industries and main water consumption (Table 4).
Table 4 Examples of Water Consumption in Food Processing and Manufacturing Industry
(2) Classification of textile industry and main water consumption (Table 5).
Table 5 Examples of water used in textile industry
(3) Classification of leather products and main water consumption (Table 6).
Table 6 Example of Water Consumption of Leather Products
(4) Classification of wood products processing and main water consumption (Table 7).
Table 7 Examples of Water Consumption of Wood Products
(5) Classification of paper industry and main water consumption (Table 8).
Table 8 Examples of Water Consumption of Paper Products
(6) Classification of chemical raw materials and chemical products manufacturing industry and main water consumption (Table 9).
Table 9 Examples of Water Consumption of Chemical Raw Materials and Chemicals
(7) Classification of pharmaceutical manufacturing industry and main water consumption (table 10).
Table 10 Example of Water Consumption of Medical Products
(8) Classification of rubber products industry and main water consumption (table 1 1).
Table 1 1 Examples of water consumption for rubber products
(9) Classification of plastic products industry and main water consumption (Table 12).
Table 12 Examples of Water Consumption of Plastic Products
(10) Classification of nonmetallic mineral products and main water consumption (Table 13).
Table 13 Examples of Water Consumption of Non-metallic Mineral Products
(1 1) Classification of metal smelting and rolling processing industry and main water consumption (table 14).
Table 14 Examples of Water Consumption for Metal Smelting and Calendering Products
(12) Classification of machinery and equipment manufacturing industry and main water consumption (table 15).
Table 15 Examples of Water Consumption of Mechanical Equipment Manufacturing Products
2. Extractive industries
See table 16 for an example of water consumption in the extractive industry.
Table 16 Example of Water Consumption in Mining Industry
3. Energy supply industry
See table 17 for examples of water consumption in energy supply industry.
Table 17 Examples of Water Consumption in Energy Supply Industry
4. Civil engineering construction industry
See table 18 for examples of water consumption in civil engineering and construction industries.
Table 18 Examples of Water Consumption in Civil Engineering and Construction Industry
(D) the use of water resources in the tertiary industry
1. Life service industry
See table 19 for water consumption examples of life service industry.
Table 19 Example of Water Consumption of Life Service Industry
2. Public service industry
See Table 20 for an example of water consumption in public service industry.
Table 20 Examples of Water Use in Public Service Industry
3. Circulation service industry
See Table 2 1 for an example of water consumption in circulation service industry.
Table 2 1 Examples of water consumption in circulation service industry
Three. The circulation process of water in human life and production
The water cycle of the earth is a multi-link natural process, including evaporation, atmospheric moisture transport, surface water and groundwater circulation and various forms of water storage. Precipitation, evaporation and runoff are the three most important links in the water cycle, including a series of biological cycles. Water breeds life in various cycles. As advanced intelligent creatures, human beings turn water into more food and livestock for people to eat, cotton and leather for people to cover, and metals and stones for people to live in.
(A) the circulation process of water in human life
Water enters the human body through beverage, food and metabolism, and is utilized by the human body, and then discharged by the kidney in the form of urine, the large intestine in the form of feces, the skin in the form of evaporation, and the lungs in the form of breathing, thus maintaining the balance of intake and discharge and maintaining the normal operation of biological functions. The level measurement of adults in one day is shown in Table 22. The evaporation of the skin and the moisture exhaled by the lungs enter the air, and the moisture in urine and feces constitutes a part of domestic sewage that needs to be treated. In human life, another output end of the process of making clear water turbid is kitchen waste and washing sewage.
Table 22 Adult Daily Level Measurement
Manure, as a fertilizer source and soil conditioner, was used in agriculture, which can be traced back to before the Southern Song Dynasty. At least in the early 1980s, China maintained a good material circulation relationship between urban and rural areas. However, since 1980s, the agricultural utilization of urban manure has been increasingly hindered, and it has been treated as real waste through solid-liquid separation, solid landfill and liquid input into sewage treatment plants (Figure 3).
Fig. 3 the circulation process of water in human life
(B) the water cycle in human production process
1. Water cycle process in agricultural production
The circulation process of water in planting industry is shown in Figure 4. The circulation process of water in aquaculture is similar to the industrial production in Figure 5.
Fig. 4 water cycle process of planting industry
2. Recycling process of water in industrial production
The circulation process of water in industrial production is shown in Figure 5.
Fig. 5 Circulation process of water in industrial production
3. Water cycle process of service industry
The circulation process of water in service industry is shown in Figure 6.
Fig. 6 Circulation process of water in service industry
Four. Water resources management of eco-city
In the human-centered cycle, water is used to form various material components, and most of them return to nature in the form of sewage and wastewater. The water resources management of eco-city will strive to find an effective breakthrough point and gradually improve the sustainable degree of water resources utilization of eco-city.
Natural reduction of water refers to the process that harmful substances in water are degraded and removed by natural organisms such as vegetation, animals and microorganisms without human interference after sewage enters land and water. As shown in fig. 7, the time I2 required for the natural reduction of the accumulated sewage M2 in the time t2 is called the natural treatment cycle of water. The natural treatment period of water is directly proportional to the accumulation time and quantity of sewage and wastewater, that is, T2 = m t.
Fig. 7 Natural treatment cycle and manual treatment cycle of water
Artificial water reduction refers to the process of separating or converting pollutants contained in sewage into harmless substances by physical, chemical and biological methods through manual intervention, thus purifying sewage. As shown in fig. 7, within the time of t 1, the time I 1 required for artificially reducing the accumulated sewage quantity M 1 is called the artificial treatment cycle of water. The artificial treatment cycle of water is not only related to the accumulation amount and time of sewage, but also related to the development of human sewage treatment technology (denoted by K), that is.
Generally speaking, T 1 < T2, which makes the artificial reduction cycle shorter than the natural reduction cycle, is also to improve the treatment efficiency of urban sewage and wastewater. In the artificial treatment of sewage and wastewater, it is often accompanied by the flow of energy and funds, as shown in Figure 8.
Fig. 8 Urban sewage and wastewater treatment cycle
There is a critical value t0 in the process of wastewater formation, that is, the accumulated amount of wastewater is M0 at T0. At T0, the pollutants in sewage increase in the form of physical accumulation, and its content will not cause harm to other species; When T0 is exceeded, each pollutant will have various biochemical reactions, and its content or reacted substances will seriously threaten other species. We call the sewage treatment cycle within T0 as harmless treatment cycle, and the sewage treatment cycle outside T0 as harmful treatment cycle. T0 is a factor related to time, cumulative amount, temperature, light and oxygen content (Figure 9 and Figure 10).
Figure 9 Harmless Cycle and Harmful Cycle
Figure 10 Thoughts on Water Resources of Eco-city
Water is the source of life and records all kinds of information about the evolution of human civilization. Since ancient times, human beings and various species have alternated from generation to generation, and only water is eternal and endless. With the intensification of human plunder, water has recorded a dangerous signal, punishing human beings with drought, flood and abandonment.
Verb (abbreviation of verb) conclusion
The management goal of water resources in eco-city should be to realize the short-distance water supply in the city as far as possible, to reduce sewage and wastewater through natural reduction and artificial reduction in the harmless period, to shorten the energy flow and capital flow brought by sewage and wastewater treatment as much as possible, and to realize the sustainable process of water resources from source to treatment.
The difference between sewage and clean water is the difference in physical and chemical properties of other molecules generated by water molecules. The form of water molecular structure under the action of different information should be a sign of water health. The health of this kind of water affects the living conditions of human beings or determines human health in a certain sense.
refer to
[1] Wang Ruihui, Ma,,, Ruchun,. Seven garden plants in Beijing and their typical green water allocation. Forestry Science, April 2008 44( 10/0)
[2] Ren, edited by Zheng. Human ecology. Beijing: China Environmental Science Press. 2004.