16593 18 tủ tài liệu bách khoa
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16593 18 tủ tài liệu bách khoa
_______CHAPTER 18______MICROBIOLOGICAL QUALITY CONTROL IN DISTRIBUTION SYSTEMSEdwin E. Geldreich, M.S.Consulting Microbiologist Cincinnati. OhioMark L 16593 18 tủ tài liệu bách khoaLeChevallier, Ph.D.Research DirectorAmerican Waler Works Service Co.Voorhees, New JerseyThe purpose of a waler supply distribution system is to deliver to each consumer safe drinking water that is also adequate in quantity and acceptable in terms of taste, odor, and appearance. Historically, the ini 16593 18 tủ tài liệu bách khoatial network of pipes was a response to present community needs that eventually created a legacy of problems of inadequate supply and low pressure as16593 18 tủ tài liệu bách khoa
the population density increased (Fronlinus. 1973: Baker. 1981). To resolve the problems caused by increasing water demand along the distribution rout_______CHAPTER 18______MICROBIOLOGICAL QUALITY CONTROL IN DISTRIBUTION SYSTEMSEdwin E. Geldreich, M.S.Consulting Microbiologist Cincinnati. OhioMark L 16593 18 tủ tài liệu bách khoarom surges of pressure. In some areas, population growth exceeded the capacity of a water resource, so other sources of water were incorporated and additional treatment plants were built to feed into the distribution network. Another response was to consolidate neighboring water systems and intercon 16593 18 tủ tài liệu bách khoanect the associated distribution pipe networks.GENERAL CONSIDERATIONSFOR CONTAMINATION PREVENTIONToday (1999), community expansion plans are more full16593 18 tủ tài liệu bách khoa
y developed and include the pnoinpprino nf utility sprvii'p so that rarpfnl rnniidpratinn k oivpn tn mpptino fntnrp18.2CHAPTER EIGHTEENdesign the pipe_______CHAPTER 18______MICROBIOLOGICAL QUALITY CONTROL IN DISTRIBUTION SYSTEMSEdwin E. Geldreich, M.S.Consulting Microbiologist Cincinnati. OhioMark L 16593 18 tủ tài liệu bách khoa to all areas while at the same time permitting any section to be isolated for maintenance. repair, or decontamination without interrupting service to all other areas.To ensure delivery of a high-quality municipal potable water supply to each consumer, managers of public water supply systems must be 16593 18 tủ tài liệu bách khoa continually vigilant for any intrusions of contamination or occurrences of microbial degradation in the distribution network. This job is complicated16593 18 tủ tài liệu bách khoa
by the very nature of the distribution system— a complex network of mains, fire hydrants, valves, auxiliary pumping, chlorination substations, storag_______CHAPTER 18______MICROBIOLOGICAL QUALITY CONTROL IN DISTRIBUTION SYSTEMSEdwin E. Geldreich, M.S.Consulting Microbiologist Cincinnati. OhioMark L 16593 18 tủ tài liệu bách khoauitable for colonization by certain microorganisms in the surviving flora. The persistence and possible growth of organisms in the pipe network are influenced by a variety of environmental conditions that include physical and chemical characteristics of the water, system age. type of pipe materials, 16593 18 tủ tài liệu bách khoa and the availability of sites suitable for colonization (often located in slow-flow sections, dead ends, and areas of pipe corrosion activity).ENGINE16593 18 tủ tài liệu bách khoa
ERING CONSIDERATIONSFOR CONTAMINATION PREVENTIONMany public water utilities make substantial efforts to expand their distribution networks to keep up _______CHAPTER 18______MICROBIOLOGICAL QUALITY CONTROL IN DISTRIBUTION SYSTEMSEdwin E. Geldreich, M.S.Consulting Microbiologist Cincinnati. OhioMark L 16593 18 tủ tài liệu bách khoa distribution network. Corrosion, unstable soil, faulting, land subsidence, extreme low temperatures, and other physical stresses often cause line breaks and necessitate repair or replacement of pipe sections. To avoid possible bacteriological contamination of lhe waler supply during lhese construct 16593 18 tủ tài liệu bách khoaion projects, a rigorous protective protocol must be followed.Distribution System Construction Practicesllic American Water Works Association has deve16593 18 tủ tài liệu bách khoa
loped standard procedures that are used, with variations, by most of the water supply industry for disinfecting water mains (AWWA. 1986). In essence, _______CHAPTER 18______MICROBIOLOGICAL QUALITY CONTROL IN DISTRIBUTION SYSTEMSEdwin E. Geldreich, M.S.Consulting Microbiologist Cincinnati. OhioMark L 16593 18 tủ tài liệu bách khoat-packing materials; (3) preliminary flushing of pipe sections; (4) pipe disinfection: (5) final flushing; and (6) bacteriological testing for pipe disinfections.Pipe sections, fittings, and valves stockpiled in yard areas or at the construction site should be protected from soil, seepages from wate 16593 18 tủ tài liệu bách khoar or sewer line leaks, stormwater runoff.and habitation by pels and wildlife (Becker, 1969; Russelman, 1969). Each of these contamination sources may16593 18 tủ tài liệu bách khoa
deposit significant fecal material in the interior of pipe sections awaiting installation. Septic lank drain fields, subsurface water in areas of poor_______CHAPTER 18______MICROBIOLOGICAL QUALITY CONTROL IN DISTRIBUTION SYSTEMSEdwin E. Geldreich, M.S.Consulting Microbiologist Cincinnati. OhioMark L 16593 18 tủ tài liệu bách khoaial introduced by contaminating sources may become lodged in pipe fittings and valves. Thue cnr-l-1 citiie KếinnrviÀ? nrntứrtữd h-iRitatcxuhính r'i'.l i ÍArrVíC an/l •ítìi,' ùccAr-i-íMICROBIOLOGICAL OVALITY CONTROL IN DISTRIBUTION SYSTEMS 18.3 supply. Common-sense protective measures include providi 16593 18 tủ tài liệu bách khoang end covers for these pipe materials, drainage of standing water from trenches before pipeline assembly, and flushing of new construction or line re16593 18 tủ tài liệu bách khoa
pairs to remove all visible signs of debris and soil (Suckling. 1943; Davis. 1951).Pipe-Joining MaterialsGasket seals of pipe joints can be a source o_______CHAPTER 18______MICROBIOLOGICAL QUALITY CONTROL IN DISTRIBUTION SYSTEMSEdwin E. Geldreich, M.S.Consulting Microbiologist Cincinnati. OhioMark L 16593 18 tủ tài liệu bách khoaltiplication of a variety of bacteria in the distribution network. In these instances, although the heterotrophic plate count (11PC) and any coliform occurrences may be temporarily reduced by main disinfection, bacteria soon become reestablished from the residual population harbored in some jointpac 16593 18 tủ tài liệu bách khoaking materials. In this regrowth process, the variety of organisms and dominance of strains change, often restructuring the bacterial flora to a predo16593 18 tủ tài liệu bách khoa
minant population of Pseudomonas aeruginosa, Chromobacter strains. Enterobacter aerogenes, or Klebsiella pneumoniae. Thus, where the pattern of organi_______CHAPTER 18______MICROBIOLOGICAL QUALITY CONTROL IN DISTRIBUTION SYSTEMSEdwin E. Geldreich, M.S.Consulting Microbiologist Cincinnati. OhioMark L 16593 18 tủ tài liệu bách khoashould be made (Calvert. 1939; Adam and Kingsbury, 1937; Taylor, 1950, 1967-1968; Schoenen. 1986; Schubert. 1967). Nonporous materials such as molded or tubular plastic, rubber, and treated paper products arc preferable. Lubricants used in seals must be nonnulrilive to avoid bacterial growth in prot 16593 18 tủ tài liệu bách khoaected joint spaces. Efforts to develop bacteriostatic lubricants have resulted in the inclusion of various quaternary ammonium compounds that minimize16593 18 tủ tài liệu bách khoa
contamination from pipe joint spaces (Hutchinson. 1974). The National Sanitation Foundation (NSF international. Ann Arbor. Michigan) has proposed a t_______CHAPTER 18______MICROBIOLOGICAL QUALITY CONTROL IN DISTRIBUTION SYSTEMSEdwin E. Geldreich, M.S.Consulting Microbiologist Cincinnati. OhioMark L 16593 18 tủ tài liệu bách khoayet received final approval, some manufactures have submitted their products for testing, and in many cases the results arc available from NSF upon request.Water Supply Storage ReservoirsWater use in a community varies continuously as a reflection of the activities of the general public and local in 16593 18 tủ tài liệu bách khoadustries. While industrial uses of potable water may be more predictable, expecting water treatment operations to gear production to those frequent an16593 18 tủ tài liệu bách khoa
d sudden changes in water demand from all consumers is impractical. For this reason storage reservoirs are an essential element of the distribution ne_______CHAPTER 18______MICROBIOLOGICAL QUALITY CONTROL IN DISTRIBUTION SYSTEMSEdwin E. Geldreich, M.S.Consulting Microbiologist Cincinnati. OhioMark L 16593 18 tủ tài liệu bách khoaer during off-peak periods; equalize operational water pressures; and augment water supply from production wells that must be pumped at a uniform rate. Storage reservoirs also provide a protective reserve of drinking water to guard against discontinuance of water treatment during chemical spills in 16593 18 tủ tài liệu bách khoathe source water, flooding of well fields, transmission line breaks, and power failures. An important secondary consideration is providing adequate st16593 18 tủ tài liệu bách khoa
orage capacity for fire emergencies.Finished water reservoirs may be located near the beginning of a distribution system. but most often they are situ_______CHAPTER 18______MICROBIOLOGICAL QUALITY CONTROL IN DISTRIBUTION SYSTEMSEdwin E. Geldreich, M.S.Consulting Microbiologist Cincinnati. OhioMark L 16593 18 tủ tài liệu bách khoall 11 loi.'nl18.4CHAPTER EIGHTEENground-level reservoirs are constructed by earth embankment.The sides and bottom of such reservoirs are lined with concrete. Gunite, asphalt, or with a plastic sheet to prevent or reduce water loss in storage (Harem. Bielman. and Worth. 1976). In earthquake zones, re 16593 18 tủ tài liệu bách khoainforced concrete or a series of flat-bed steel compartments is mandatory. Reinforced concrete is often selected because of its minimal rate of deteri16593 18 tủ tài liệu bách khoa
oration from water contact. Elevated storage tanks and standpipes are constructed of steel, with an interior coating applied to retard corrosion (WadeGọi ngay
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