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galvis

Water treatment

indicators (EPA, 1989;

indicators (EPA, 1989; Ford and Colwell, 1996). Due to the technical and economical limitations to monitor viruses and protozoa, EPA instead of Maximum Contaminant Limits (MCLs) established treatment techniques. EPA (1998) published an updated compliance technology list of filtration and disinfection alternatives to fulfil this requirement in small systems (serving less than 10,000 people). Since SSF in USA generally is used without pretreatment, the range of raw water quality appropriate for treatment by this process is narrow, However, when used with surface water of adequate quality, SSF, is considered the most suitable choice for small systems (NRC, 1997; EPA, 1998). The European Community Drinking Water Directive (EEC, 1980), implemented in 1985, does not specifically require water supplies to be disinfected. Some countries, like the Netherlands, do not require disinfectant residuals since they use good quality, microbiologically secure groundwater sources or some surface water sources from which multistage treatment has removed any harmful organisms and the amount of organic material has been minimised (Hydes, 1999; van der Kooij et al., 1999). Portugal, Spain, and the United Kingdom require all supplies to be disinfected. In UK, residual amounts are not specified because they depend on the quality of the source water, the treatment applied to the water, and the conditions of the distribution system (Hydes, 1999). The free chlorine supplied to the user must be < 0.3 mgl -1 in Austria; and in the range of 0.2-0.8, depending on pH, in Spain (Hydes, 1999). In Colombia, the free chorine in the distribution system must be in the range of 0.2-1.0 mgl -1 (Ministerio de Salud, 1998b). 2.3.1 Basic parameters for community water supply systems The establishment of standards for drinking water should reflect health risks as well as the best available scientific and technical judgement. It should also relate to economic feasibility and in-country institutional capacity and ability to provide operational skills necessary for water treatment and analysis. Standards that do not take into account practical considerations concerning the water sources, available treatment options, water surveillance practice and support available at the local level, do not contribute to improve the prevailing sanitary conditions (Lloyd and Helmer, 1991). When the standards are not met the underlying cause of why they were not met needs to be explored and remedied. One option is to establish interim objectives for the medium term and use water surveillance as a tool to orient corrective actions in those communities that are facing the highest sanitary risks. An approach for assessing and monitoring water quality in rural communities and towns with limitations in infrastructure and management capacity has been applied by Lloyd and Helmer (1991) and recommended by WHO (1993, 1997). This approach combines the use of a few water quality parameters, combined with the implementation of sanitary inspections (WHO, 1993; 1997). The basic parameters are: • E. coli counts or, as an alternative, thermotolerant coliform counts, usually referred to as faecal coliform counts • Residual chlorine (if applied) • pH (if chlorine is applied) • Turbidity 18

In table 2.3, WHO guideline values and water quality criteria of the Colombian Ministry of Health for bacteria indicators and turbidity are presented together with some other key parameters that are important for users acceptance of the service and for the application of filtration and disinfection processes. The availability of portable equipment facilitates the analysis of these parameters. Equipment for measuring turbidity, pH, residual chlorine and colour is also available in a very basic form that can be used directly by system operators with a low level of formal education. If a water source for community water supply is subject to other (agricultural or industrial) contamination not covered by the basic parameters, the national or regional health authorities need to provide additional support or training for the community to monitor these risks. Table 2.3 Guidelines and quality criteria for basic drinking water parameters (based on Lloyd and Helmer, 1991; WHO, 1993; Ministerio de Salud, 1998b) Parameter Guideline value Observations E. coli; thermotolerant (faecal) coliforms Not detectable in 100 ml If the distribution system contains between 0.2 and 1.0 mgl -1 free residual chlorine, pH

  • 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 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: Table 2.2 Treatments steps recommen
  • 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
  • Page 77 and 78: in spite of the low removal efficie
  • Page 79 and 80: order to overcome the water quality
  • Page 81 and 82: full-scale units. In this research,
  • Page 83 and 84:

    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

  • 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

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    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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