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galvis

Water treatment

eporting procedures for

eporting procedures for the key service indicators it is not possible to make valid comparisons and it is also difficult to identify key problems and set priorities. However, some project reports and institutional data show that many systems provide neither the continuity nor the quality that is needed. In fact, in the great majority of small communities disinfection is not practised at all, and Reiff (1988) has indicated that around 70% of all disinfection units in Latin America are not working properly. In Peru, it was found that 100% of small WS included in a experimental water surveillance study failed to meet basic drinking water quality criteria (Lloyd & Helmer, 1991). In Ecuador more than 75% of their drinking water supply depends on surface water (Foster et al, 1987). Problems of continuity, quantity or quality were identified in the majority of WS systems included in participatory evaluations in Ecuador (Visscher et al., 1996) and Bolivia (Quiroga et al., 1997). Besides, most of these reports show that the organisations responsible for providing the WS&S services do not manage to cover even the cost of operation and maintenance. This situation usually leads to inadequate functioning and eventually to abandoning of the infrastructure, representing a considerable loss of investment and high political and socioeconomic cost. In January 1991, beginning in Peru, epidemic cholera invaded the Americas for the first time in the 20 th century, resulting in 391,219 cases with 4,002 deaths by the end of the year. In 1992, 353,811 cases with 2,396 deaths were reported in 19 countries. In 1993 the total number of registered cases declined to 206,259 (Traverso, 1996). However, in Colombia the number of cases were presenting a tendency to increase, with 1,002 in the year 1994, 1,783 in the year 1995, and 2,453 in the first half of the year 1996 (OPS/PAHO, 1997). It was noted by the World Health Organisation that: “The [epidemic] outbreaks of cholera [throughout] the countries of Central and South America are an ample reminder of how quickly the adverse health impacts of unsatisfactory water supply and basic sanitation appear and accelerate. The question is not only one of providing facilities, although it is of prime concern in the first instance, but also of sustaining them through adequate provision for operation and maintenance of systems, and ensuring their proper utilisation through adequate health and hygiene education” (WHO, 1996). 1.1 An Overview of the Water Supply and Sanitation Sector in Colombia In Colombia, between 1975 and 1993, US$ 2.8 billion was invested in WS&S sector. Coverage values increased 25% for both piped connections (51 to 76%) and sewerage systems (38 to 63%). These values only include “conventional” solutions. In fact, by 1993 the access to sanitation should be 74%, including 8% access to septic tanks and 3% access to latrines. The main advances started in the 1990s with the sector receiving an average investment of 0.5% of the GNP of the country (the GNP per capita in 1995 was 1910 US$ for Colombia and 3320 US$ for Latin America). During the decade of the 1980s the Latin American countries invested on average 0.2% of their GNP (DNP, 1995; OPS/PAHO, 1997; WB, 1997). Nevertheless, by 1994, 8.6 million Colombians still did not have access to piped water supplies and 9.3million lacked access to sanitation. Following the international pattern, the situation was worst in the smaller cities and the rural areas as illustrated in table 1.2. 2

Table 1.2 Access to WS&S in Colombia in 1985 and 1993 (DNP, 1995; Ministerio de Salud, 1998a; DANE, 1993). Year 1985 1993 Type of Settlement Population Access (%) Population Access (%) (Millions) Water Sewerage (Millions) Water Sewerage 4 Major cities 8.0 89 82 10.3 88 84 Capitals and cities > 10 5 5.5 71 63 7.5 88 78 Other urban areas 6.2 82 63 8.8 84 69 Rural areas 10.4 12 2.4 10.8 44 19 TOTAL 30.1 58 47 37.4 76 63 1 1. The total access to sanitation was 74%: sewerage 64%; septic tanks 8%; latrines 3% Now this is especially relevant because of the decentralisation process in the WS&S sector. By 1993 there were 3.3 million people in the urban part of 860 municipalities in Colombia, which had less than 12,500 people in their urban area (table 1.3). The problems in the main cities were concentrated in their urban-fringe areas where the “conventional” , centralised, type of technologies are not viable technically and economically. In Bogota alone it is estimated that 0.6 million people do not have access to water supply and one million to sanitation (Marín, 1995). Furthermore like in the other Andean countries, part of the population already covered are facing problems due to the poor performance of the systems. Table 1.3 Distribution of Colombian municipalities by population ranges (DANE, 1993) Ranges based on the number of inhabitants Number of municipalities in each range % Urban population in each range < 2,500 419 40 558,110 [2,501 – 5,000) 226 21 881,672 [5,001 – 12,500) 215 20 1’865,606 [12,501 – 30,000) 103 10 2’097,759 [30,001 – 100,000) 62 6 1’140,888 [100,001 – 500,000] 27 2 6’728,248 > 500,001 5 1 11’006,250 TOTAL 1,057 100% 24’278,533 In 1993 the total (urban plus rural) population of Colombia was 37’448,000 In an evaluation of 49 projects financed by FINDETER and other national agencies, problems of sustainability were identified (FINDETER, 1996; Restrepo et al, 1998). These problems were related to different factors throughout the whole cycle of the projects, such as poor technology selection or specification, managerial or technological limitations at local level to operate the systems or insufficient support from the national or departmental agencies. Because of its geography and topography, Colombia has an annual average rainfall of 3,000 mm, with 88% of the territory presenting values higher than 2,000 mm. These values are above the average of 1600 mm/year for South America, and the global average of 900 mm/year (Ministerio del Medio Ambiente, 1996). As shown in table 1.4, the Temperate Zone, between 1,000 and 3,000 m above sea level (masl), represents 35% of the surface of the country, with 34% of the water offer, and supporting 66% of the population. Besides, 38% of the agriculture and the livestock farming and significant part of the factoring also take place in this zone. By the year 2016, if the present pattern of increasing demand and reducing offer 3

  • 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: 1 INTRODUCTION Water is essential f
  • Page 19 and 20: Table 1.5 Safe drinking water cover
  • Page 21 and 22: 1.2 Multiple Barriers Strategy and
  • Page 23 and 24: 2 OVERCOMING THE LIMITATIONS OF SLO
  • Page 25 and 26: adjustment, are among the technolog
  • 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
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    case of Dortmund (Germany), the HGF

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    Table 2.9 Data about three experien

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    Some points of discussion about HGF

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    and 600-800 NTU) and different filt

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    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

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    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

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    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

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    Table 6.3. Individual (at each trea

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    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

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    Mendenhall, W. and Sincich, T. (199

  • Page 244 and 245:

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

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    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

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    Tables A7-5 Removal efficiencies of

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    Construction quantities of DyGF com

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    Net present value (US$) of MSF and