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Water treatment

political decisions and

political decisions and reforms. In 1842 Edwin Chadwick produced an important Report on the Sanitary Conditions of the Labouring Population of Great Britain. Although Chadwick did not make any specific connection between water and disease, clean water was considered part of the environmental improvements desirable for health. In 1848 one act of parliament charged government for the first time with the responsibility for safeguarding public health. According to this Act, water supplies had to be “pure, safe, and constant”. It was another fifty years before this sanitary ambition was practically fulfilled. By 1850, London’s population was close to 2.5 million. A Metropolitan water act of 1852 required that domestic water from the Thames River had to be filtered. However, the Water companies were often not fulfilling these requirements. Thus, efforts began in London and other municipalities in Britain to buy the companies. It was not until 1902 that London’s water finally came under public control. (Coffey and Reid, 1982; Hardy, 1984; Coley, 1989) It was in 1849, during the second epidemic of cholera in Britain, that John Snow’s first essay on the waterborne nature of cholera appeared, based on evidence collected and analysed on fatal cases around a well on Broad Street in London. In 1849, Snow also identified that death rates from cholera increased sharply, from 10 to 200 per 10,000 for people taking water from the farthest upstream intakes to the lowest downstream intakes, where the pollution was greater (Okun, 1996). Still, it was not until the third epidemic in 1854, that John Snow’s views on the dissemination of cholera were vindicated, and the connection between water supply and wasterborne disease was firmly established. Two water companies, the Lambeth and the Southwark and Vauxhall, served an overlapping area in London. It was found that the cholera pattern coincided with the source of WS, with the death rates 8.5 times smaller for Lambeth that had its intake upstream of sewage discharges from London (Hardy, 1984; Okun, 1996). Thus when, during the last English cholera epidemic in 1866, cholera in London showed a marked preference for the East End of the city, the implications were quickly clear to the authorities at that time (Hardy, 1984). Snow's work, and the events of 1854 and 1856, provided a firm basis upon which to establish the association between polluted water and disease. In the second half of the 19th century it was generally accepted that the solutions to the prevailing public health problems depended on improvements in the sanitary infrastructure, requiring large engineering projects. Towards the end of the century, scientific developments in the medical world started to become influential. With the development of bacteriology, after the discoveries of Pasteur and Koch in the 1880s, the germ theory became important in the fight against contagious diseases (Hardy, 1984; Coley, 1989). This stimulated interest in other issues such as water source protection, water supply, basic sanitation, hygiene education and water treatment. In general, there has been a considerable gap between the development of water treatment techniques and their practical and wide use. Sedimentation, filtration through porous vessels, and coagulation were probably the earliest forms of treatment. These techniques and others, such as, aeration, air flotation, distillation, ion exchange, softening, filtration through granular media and membranes, chemical and physical disinfection, addition of fluorides, and pH 10

adjustment, are among the technologies that have gradually become applied through the 19 th and 20 th centuries (Coffey and Reid, 1982; Droste, 1997). 2.1.1 Pioneering work in water treatment by filtration Whereas plain sedimentation improves the clarity of surface water, filtration gives much better results. Trying to improve the sand filters in copper containers used in Paris for two centuries, Joseph Amy decided to substitute sponge for sand and an alternative material for the container. In 1749 Amy, in France, was granted the first water filter patent issued by any country. These filters were to be constructed of lead, pewter, or earthenware, with filtering materials of sponge or sand. The sand was to be packed in between two plates, the lower one to serve as a false bottom to the filter, the upper to prevent disturbance of the sand when the water was poured into the vessel (Baker, 1981). In 1791 James Peacock, a London architect, was granted the first British patent on a process and apparatus for water filtration, with ascending flow to clarify the water and reverse flow to clean the filter medium. To accomplish this he proposed either three tanks, or one tank with three compartments. The first received the turbid water, from a service pipe, the second contained a stratified medium for filtration; and the third received the clarified water. In 1793 Peacock published a promotion pamphlet setting out the criteria for placing coarse material at the bottom of the filter with regularly decreasing sizes above it, so that interstitial spaces would increase in geometric ratio. Peacock’s scheme was not used at large scale in his time (Baker, 1981; Hardy, 1984). Crude versions of the slow sand filters (SSF) were used for industrial water supplies in Britain, and some may have been installed before 1790 (Baker, 1981). One of them was installed in 1804 at Paisley, Scotland, and became the first water treatment plant for a city supply. John Gibb, owner of a cotton mill in Paisley, began selling and delivering water in carts to the households from the plant he had built to treat water used for bleaching. Water from the muddy and industrially polluted River Cart flowed to a pump well through a coarse filter (23-m long, 2.4-m wide, and 1.2 m deep). A steam engine placed over the well lifted the water to an “ air-chest” about 5 m above the river, from which it was forced to the plant through about 60 m of 0.08 m bore wooden pipe. The plant was made up of sedimentation, and double filtration stages, with lateral flow, as shown in figure 2.1 (Baker, 1981). It is unknown for how long this plant was in operation, but maintenance problems due to its radial flow should had been a serious limitation for long term operation. Figure 2.1 Water treatment plant at Paisley, Scotland, 1804 (adapted from Baker, 1981). 11

  • Page 1 and 2: Development and Evaluation of Multi
  • Page 3 and 4: ACKNOWLEDGEMENTS To my supervisor,
  • Page 5 and 6: ABBREVIATIONS ABNT: Acuavalle: ACV:
  • Page 7 and 8: SOCs: Synthetic Organic Chemicals S
  • Page 9 and 10: u c V V f Vs uniformity coefficient
  • Page 11 and 12: TABLE OF CONTENTS 1. INTRODUCTION 1
  • Page 13 and 14: 4 MULTISTAGE FILTRATION EXPERIENCIE
  • Page 15 and 16: 1 INTRODUCTION Water is essential f
  • Page 17 and 18: Table 1.2 Access to WS&S in Colombi
  • Page 19 and 20: Table 1.5 Safe drinking water cover
  • Page 21 and 22: 1.2 Multiple Barriers Strategy and
  • Page 23: 2 OVERCOMING THE LIMITATIONS OF SLO
  • Page 27 and 28: On January 14, 1829, Simpson’s on
  • Page 29 and 30: With increasing life expectancy, en
  • Page 31 and 32: Table 2.2 Treatments steps recommen
  • Page 33 and 34: In table 2.3, WHO guideline values
  • Page 35 and 36: 2.5 The Slow Sand Filtration Proces
  • Page 37 and 38: When the particles are very close t
  • Page 39 and 40: in which p 0 is the clean media por
  • Page 41 and 42: Yao et al (1971) related the remova
  • Page 43 and 44: compensate for the increase in the
  • Page 45 and 46: can be applied, but intermittent op
  • Page 47 and 48: Table 2.4 Comparison of design crit
  • Page 49 and 50: Although accepted as indirect indic
  • Page 51 and 52: 50% when the temperature falls from
  • Page 53 and 54: Figure 2.9 Flow diagram of the wate
  • Page 55 and 56: ut higher running costs, since more
  • Page 57 and 58: Headloss and flow control. Final he
  • Page 59 and 60: Figure 2.13 Influence of flow condi
  • Page 61 and 62: Operation and maintenance (O & M).
  • Page 63 and 64: in parallel (Galvis, 1983; Smet et
  • Page 65 and 66: cleaning simple, DyGF should behave
  • Page 67 and 68: case of Dortmund (Germany), the HGF
  • Page 69 and 70: Table 2.9 Data about three experien
  • Page 71 and 72: Some points of discussion about HGF
  • Page 73 and 74: and 600-800 NTU) and different filt
  • Page 75 and 76:

    the HGF units of Aesch (see table 2

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    in spite of the low removal efficie

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    order to overcome the water quality

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    full-scale units. In this research,

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    3 MULTISTAGE FILTRATION STUDIES WIT

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    in the case of UGFL. Initially, it

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    • Bigger and better-instrumented

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    l Figure 3.7 Plan view of Cinara's

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    The present research work was divid

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    Table 3.1. Design parameters, grave

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    Figure 3.9. Piezometer distribution

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    were used to collect samples for DO

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    were poured into a funnel using fil

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    H 0 : H a : Treatment levels workin

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    3.2 Results and Specific Discussion

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    3.2.2 Dynamic gravel filtration (Dy

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    Mean faecal coliform removal effici

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    Table 3.10 Comparative analysis of

  • Page 112 and 113:

    DyGF-A had flow reductions in the r

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    The experimental data used to produ

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    Previous observations were further

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    ates (figure 3.17 B). However, at t

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    Longer “initial-ripening” perio

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    Table 3.17. Descriptive statistics

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    100 Filtration rate = 0.3 mh -1 100

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    After the present experience, faeca

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    nature of the organic matter and th

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    Table 3.24 Comparative analyses of

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    3.2.4.3. Filtration run lengths and

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    deep bed filter (data not included

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    and operational considerations Pard

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    than in sand samples from other SSF

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    Step dose tracer tests were made at

  • Page 144 and 145:

    for HGFS and from 3 to 5 for HGF. T

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    Constant and declining filtration r

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    The efficiency levels summarised be

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    Surface area of CGF and SSF units.

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    community based organisations and l

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    systems. All these systems were fed

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    Parts of the suburban settlements o

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    Figure 4.2. Layout of Retiro MSF pl

  • Page 160 and 161:

    Traditionally, in the WS&S of Colom

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    Photo 4.10. Partial cleaning activi

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    Figure 4.3 Location of full-scale M

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    4.4.1.3 Main characteristics of mul

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    Figure 4.4 Layout of Restrepo MSF p

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    Figure 4.6 Layout of Javeriana MSF

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    Figure 4.9 Layout of Cañasgordas M

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    Figure 4.11. Layout of Ceylan MSF p

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    Table 4.4 Descriptive statistics fo

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    Water sources in the coffee region

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    Filterability results seem to under

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    Table 4.8 Mean removal efficiencies

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    The length of this ripening period

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    in Peru (Pardon, 1989) and Colombia

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    Photo 4.24 Drainage facilities in u

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    the Cauca Valley. This is not the c

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    Pardon (1989) reports similar evide

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    5. COST OF MULTI-STAGE FILTRATION P

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    ecame formally established as WS en

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    Models for assessing construction q

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    MSF system can then be calculated o

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    5.7 Cost Model for the Cali Area an

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    Table 5.8. Annual labour costs due

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    5.8 General Discussion The followin

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    systems. The differences between MS

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    guideline for colour is < 15 PCU (W

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    Table 6.1. Individual (at each trea

  • Page 216 and 217:

    Table 6.3. Individual (at each trea

  • Page 218 and 219:

    As shown in tables 6.1 and 6.3, col

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    UGFL 0.45 UGFS 0.45 (32;51;85) (44;

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    Table 6.4. An example of identifica

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    MSF technology showed great flexibi

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    In harmony with the new development

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    epresents the risk the community ha

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    The selection of MSF alternatives i

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    scouring and transporting away prev

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    REFERENCES ABNT, (1989) NB-592 Proj

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    Craun, G.F., Bull, R.J., Clark, R.M

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    Drinking Water Disinfection, ed. by

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    Huisman, L. (1989) Plain Sedimentat

  • Page 242 and 243:

    Mendenhall, W. and Sincich, T. (199

  • Page 244 and 245:

    Ridley, J.E. (1967) Experience in t

  • Page 246 and 247:

    Visscher, J.T. and Galvis, G. (1992

  • Page 248 and 249:

    ANNEXES Annex 1: Accessories for Mu

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    aw water. The red colour is used fo

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    Annex 2: Design of Manifolds Manifo

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    + q 2 Q1 (1.2 qn + qn) (2.2 qn) = =

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    R 1 = (total orifice area / lateral

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    0.30 0.25 0.20 0.15 0.10 0.05 0.00

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    Table A.4-2 General notation for th

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    Box A4-3. Sum of Square Error (SSE)

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    Annex 5: Residence times in coarse

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    Table A5-1 Percentage of incoming w

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    Annex 6 Number and Type of Valves N

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    Table A7-1. Descriptive statistics

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    Tables A7-3 Removal efficiencies of

  • Page 276 and 277:

    Tables A7-5 Removal efficiencies of

  • Page 278 and 279:

    Construction quantities of DyGF com

  • Page 280:

    Net present value (US$) of MSF and

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