Discussion on Pure Drinking Tab Water Engineering Design

Huang Xiankui
Chongqing Institute of Architectural Design
Address: No. 31 Renhejie Yuzhong District Chongqing, China
Zip code: 400015 Tel: (O23) 63621131 Fax: (023) 63856935

Abstract Based on a case study on the project of Diwang Square of Chongqing, this paper　elaborates its engineering design features of pure tap water, the selection of water　consumption standard, purification techniques of pure drinking water, distribution of water supply system and pipeline layout.
　　Key Words pure drinking tap water, purification techniques, reverse osmosis engine, automatic control, engineering design.

　　With the development of national economy and improvement of people‘s living standard,　their consciousness of environmental protection and health protection become stronger. The　water quality requirement on daily drinking water is being increasingly high. One of the primary objectives of family environmental protection is solving the problem of drinking water quality while people hope they can drink high-quality and reliable pure water. Although city water maintains rapidly development and quality of water supply has been great improved through technical renovation of facilities, the secondary pollution of water quality during the transmission through supply pipe net, intermediate water pool and roof tank to users is still very serious. Confined to national power and economic factors, it is difficult to completely solve the quality problem of city water supply. Dual pipe water supply system is a sort of major technique to solve this problem. Namely, domestic water and drinking water are supplied with different pipes. It is not only in line with national condition, but also economic. Take Diwang Square of Chongqing for instance, the design features of pure drinking water engineering is to be presented in detail. This project is close to Jiefangbei, which is the business center of Chongqing Municipality, with its gross building area about 180,000 square meters and total structural depth about 150 meters. It consists of annex including four underground stories and nine stories overground, accessory building of 25 stories for bank office and main building of 40 stories for luxury dwelling house. The whole project integrates garage, office building, shopping center, landscape luxury house, restaurant and recreation. At the same time, there are swimming pool, tennis court large size roof garden, and hanging garden and advanced chamber at the top of ninth story of its annex. This project will be built as one of symbolic buildings of new Chongqing Municipality. Wherefore, according to the requirement of its owner, pure drinking water supply system should be designed in the dwelling part of 11th to 40th story.

1. The selection of Pure drinking water consumption standard and service discharge.
For the moment, there is no water consumption standard for residential pure pipe drinking water in our country. With reference to the relevant information both abroad and home and based on practical situation of the project, the water supply should also include water used for cooking, washing melon and fruit, beauty treatment and so on in addition to drinking water. According to above factors, water consumption standard adopts 6L per person per day. Given each family has 4.5 people and the time variation coefficient is 4.O, so the maxima of pure water consumption is 6.Om3 per day and 1.0m3 per hour.

2. Proeess design of pure drinking water
(1) Positional selection of pure drinking water facilities:
　　According to functional distribution of construction floor, facility of pure drinking water can be set in roof tank room of 43rd story and mechanical floor of 10th story. Comparatively, the water tank room on 43rd story is smaller than mechanical floor of 10th story. But through technical economy comparison, a decision bas been made to increase area of water tank room on 43rd floor and install pure water processing equipment in it. The adoption of this scheme has following advantages: it takes full advantage of hydraulic pressure of roof tank of the 43rd floor; the water supply mode of up run and underfed is adopted in pure drinking water supply network which makes pipe network circulation convenient, decreases facility usage and conserving energy.
(2) Technological Process of water purification of pure drinking water as follows:

(3) Pretreatment facility
Preprocess system is combined with quartz sand filter, softener and activated charcoal filter in which quartz sand filter adopts double layer filtration technique with top layer using native silica sand of granularity of O.5mm-1mm and purity greater than 97%, and under layer using natural manganous sand of granularity of 1mm-l.5mm. Its primary function is to remove subaqueous suspended matter and grain impurity and depressing water cloudiness and colority. Softener adopts cation exchange resin, which is able to depress rigidity of subaqueous calcium and magnesium ion. Husk type acticarbon is adopted in activated carbon adsorber which has the function of deodorization, color removal, heavy metal removal, organic matter removal and residual chlorine absorption. Through the pretreatment of the three devices, the reverse osmosis main engine is ensured to be in safe opetation effectively.
(4) Reverse osmosis main engine:
Reverse osmosis main engine is the key facility of pure water processing which performance would directly influence the effect of water treating. Reverse osmosis main engine is made up of secondary filter, multilevel high pressure pump, reverse osmosis membrane, TFC membrane, instruments and meters and autocontrol establishment, etc. The precision of filter element of secondary filter ware is 5um, which is able to countercheck runny grains and impurity in pretreatment to shield reverse osmosis membrane. The working pressure of multilevel high pressure pump is 1.0MP-2.0MPa which can meet desired working pressure needed for failure-free operation of reverse osmosis membrane. Reverse osmosis membrane subassembly is capable of removing 95%-98% iawater inorganic salt and organic matter, bacteria and virus of more than 99%. Thick water baffled by membrane is discharged through waste pipe with its water reclamation rate of 50%-75%. Reverse osmosis membrane adopts incense polyamide complex film which would be cleaned every half year with medicament to prolong membranous service life. This set of facility appears the advantages of compactness of layout, high automaticity, light in weight and convenience of supervision.
(5) Stertilizing equipment decontaminating apparatus
To ensure water quality, the design introduces ultraviolet disinfection facility and ozone sterilizing equipment to jointly sterilizing and disinfecting. According to the result of water quality detection, sterilizing equipment can be used either separately or conjunctively. Such facility has strong sterilization ability and the advantage of supervision convenience, and is capable to avoid side effect of producing carcinogen in traditional chlorination process.
(6) Automatic control system and protection system
The whole control system adopted import PLC programmable controller, import pressure gauge of electromagnetism compartment and liquid level controller to reach interconnected control and to completely realize internally piloting operation of complete equipment and water outlet of quartz sand filter, softener, activated carbon adsorber and reverse osmosis main engine. While systems operation comes out abnormity or failing, the devices would send out autoalarm and have relevant action to remind operating personnels make treatment in time.
3. Pipe network design of drinking pure water engineering
(1) Incorporated with construction floor and sectorization, pure water equipment was placed in water tank chamber on the 43td 800r which takes space of about 25 square meters. To take full advantage of roof tank hydraulic pressure of the 43rd floor and to conserve energy, the water supply mode of up run and underfed was adopted which also benefits to pipe periodical feeding. Water supply network is divided into two sections: Section 1 is from 11th story to 25th story which water is supplied by water purification equipment on 43rd story plus main pipe reducer; section Ⅱ is from 27th story to 40th story which is supplied by water purification equipment on 43rd story. AD branch pipe reducer is installed on lateral service piping from the 11th to 17th story and from 27th to 31st story. In this way, the subsection of water supply network has been reduced which not only save investment and story height, but also be capable of meeting hydraulic pressure value in water supply subsections of no bigger than 350kpa.To ensure pipe potable water system not come into being dead water, main riser pipe and regional loop pipe net are established for water supply, and water circulating pump as well. The caliber of lateral service piping is DN12 while caliber of water supply main pipe is DN20---DN40, and return pipe being DN20. The water velocity inside pipe network has been controlled between 0.6m/s to 1.0 m/s to prevent stemming of microbe because of too low stream velocity in pipes. Water circulating pump keeps incessant circulation flow of pipe water and circumfluence sterilizing to ensure freshness of water outlet at any moment. (For details please see pipe network layout figure).
(2) Tubing and valve
Pure drinking water riser pipe is set about against the riser pipe of living water supply system in kitchen. In each family, there are one precision pure drinking water meter and one stainless steel hydrant installed. To prevent recontamination of pipe network on water quality, high-quality polypropylene pipe for construction water supply, or PP-R, is adopted in this project. Comparing to steel pipe and copper pipe, this kind of tubing has the following advantages: Safe, hygiene, lightweight, convenience of installation, resistance to pressure, good decay resistance, little resistance, not scaling, not stemming bacteria because of lubricity of pipe wall, long performance life and pollution-free to environment in producing and construction process. It is a kind of perfect environmental protection product. All of valves are stainless steel valves. The filter of the water purification equipment and purifying box are foodstuff level stainless steel product.
4. Conclusion:
Currently, high-quality pure drinking water supply system maintains a rapid development and is being applying in some excellent residential areas, top grade dwelling houses, apartments and hotels. One of a key problems today is to research and develop new style reverse osmosis apparatus and membrane technology with great effort. As it is known, water quality requirement of living pure drinking water should be differ from commercially pure water and ultra pure water. That is to say, there is no need to remove subaqueous dissolving salt wholly or mostly from living pure drinking water. For the sake of health, there will have to be certain quantity of substances such as salinity, calcium, magnesium, sodium,
kalium , ammonium, chloride and fluoride in pure drinking water. Therefore, speeding up
the development of new style reverse osmosis apparatus and membrane technology,
changing and adjusting parameters of working pressure, temperature and specifical yield are
of important practical significance to improve water outlet quality of drinking pure water
and reserve microelement needed by human body.

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