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Book Details
Abstract
Increasingly, microbial issues are commanding the attention of water treatment operators, regulators, and the media. There are many treatment options to eliminate pathogenic microbes from drinking-water. Finding the right solution for a particular supply requires sifting through a range of sometimes competing processes. Processes for removal of microbes from water include pretreatment, coagulation/flocculation/sedimentation, and filtration. Pretreatment processes include application of roughing filters, microstrainers, off-stream storage, or bank infiltration, each with a particular function and water quality benefit. Filtration can be accomplished using granular media filters, slow sand, precoat filters, membranes, or other filters. Oxidants may be added to water for a variety of purposes, including control of taste and odor compounds, removal of iron and manganese, Zebra Mussel control, and particle removal, among others. For control of microbes within the distribution system, disinfectants must interact with bacteria growing in pipeline biofilms. Models for removal of particles and microbes by granular media filtration, and equations for predicting microbial inactivation by disinfectants, can aid in the understanding and prediction of the effectiveness of treatment processes for microbial pathogens. Water Treatment and Pathogen Control is intended to provide a critical analysis of the literature on removal and inactivation of pathogenic microbes in water to aid the water quality specialist and design engineer in making important decisions regarding microbial water quality. Contents Introduction Removal Processes Inactivation (Disinfection) Processes Performance Models Treatment Variability Critical Control Strategies Conclusions Reference List
Table of Contents
| Section Title | Page | Action | Price |
|---|---|---|---|
| Cover\r | Cover | ||
| Contents | v | ||
| Foreword | ix | ||
| Acknowledgements | xiii | ||
| Acronyms and abbreviations used in the text | xv | ||
| Executive summary | xvii | ||
| 1:\rIntroduction | 1 | ||
| 1.1 PURPOSE AND SCOPE | 1 | ||
| 1.2 MULTIPLE BARRIERS | 2 | ||
| 1.3 PROCESS CONTROL MEASURES | 3 | ||
| 2:\rRemoval processes | 5 | ||
| 2.1 PRETREATMENT | 6 | ||
| 2.1.1 Roughing filters | 6 | ||
| 2.1.2 Microstrainers | 7 | ||
| 2.1.3 Off-stream storage | 8 | ||
| 2.1.4 Bank infiltration | 10 | ||
| 2.2 COAGULATION, FLOCCULATION AND SEDIMENTATION | 12 | ||
| 2.2.1 Conventional clarification | 13 | ||
| Efficiency of conventional clarification | 13 | ||
| Viruses | 15 | ||
| Protozoa | 15 | ||
| Algae | 17 | ||
| 2.2.2 High-rate clarification | 17 | ||
| 2.2.3 Dissolved air flotation | 18 | ||
| 2.2.4 Lime softening | 19 | ||
| 2.2.5 In-line coagulation | 19 | ||
| 2.3 ION EXCHANGE | 20 | ||
| 2.4 FILTRATION | 20 | ||
| 2.5 GRANULAR HIGH-RATE FILTRATION | 21 | ||
| 2.5.1 Design of granular filtration | 22 | ||
| 2.5.2 Mechanism of action of granular filtration | 23 | ||
| 2.5.3 Importance of chemical coagulation pretreatment | 23 | ||
| 2.5.4 Effect of filter media design | 24 | ||
| 2.5.5 Importance of filter backwash | 25 | ||
| 2.6 SLOW SAND FILTRATION | 26 | ||
| 2.6.1 Design and action of slow sand filters | 26 | ||
| 2.6.2 Protection provided by slow sand filtration | 30 | ||
| Removal of microbes | 30 | ||
| Removal of turbidity | 31 | ||
| 2.7 PRECOAT FILTRATION | 32 | ||
| 2.7.1 Removal of microbes | 32 | ||
| 2.7.2 Importance of chemical pretreatment | 33 | ||
| 2.8 MEMBRANE FILTRATION | 33 | ||
| 2.8.1 Microfiltration | 35 | ||
| 2.8.2 Ultrafiltration | 36 | ||
| 2.8.3 Nanofiltration and reverse osmosis | 37 | ||
| Bench-scale study | 37 | ||
| Pilot-scale study | 38 | ||
| Full-scale studies | 38 | ||
| 2.9 BAG, CARTRIDGE AND FIBROUS FILTERS | 39 | ||
| 3:\rInactivation (disinfection) processes | 41 | ||
| 3.1 FACTORS AFFECTING DISINFECTION | 41 | ||
| 3.2 PRETREATMENT OXIDATION | 43 | ||
| 3.3 PRIMARY DISINFECTION | 44 | ||
| 3.3.1 Chlorine | 44 | ||
| Mode of action | 44 | ||
| Effectiveness of chlorine against bacteria and viruses | 45 | ||
| Effectiveness of chlorine against protozoa | 47 | ||
| By-products of disinfection with chlorine | 50 | ||
| 3.3.2 Monochloramine | 50 | ||
| Mode of action | 50 | ||
| Effectiveness of monochloramine | 52 | ||
| By-products of disinfection with monochloramine | 52 | ||
| 3.3.3 Chlorine dioxide | 52 | ||
| Mode of action | 52 | ||
| Effectiveness of chlorine dioxide against bacteria and viruses | 53 | ||
| Effectiveness of chlorine dioxide against protozoa | 53 | ||
| By-products of disinfection with chlorine dioxide | 54 | ||
| 3.3.4 Ozone | 55 | ||
| Mode of action | 55 | ||
| Effectiveness of ozone against bacteria and viruses | 55 | ||
| Effectiveness of ozone against protozoa | 56 | ||
| Effectiveness of ozone against algal toxins | 58 | ||
| 3.3.5 Ultraviolet light | 58 | ||
| Mode of action | 58 | ||
| Effectiveness of UV against bacteria and viruses | 58 | ||
| Effectiveness of UV against protozoa | 59 | ||
| Guidelines and standards relating to the use of UV | 61 | ||
| 3.3.6 Mixed oxidants | 61 | ||
| Sequential disinfection | 61 | ||
| 3.4 SECONDARY DISINFECTION | 62 | ||
| 3.4.1 Maintenance of water quality in the distribution system | 62 | ||
| 3.4.2 Factors affecting microbial occurrence | 62 | ||
| Disinfectant residual and disinfectant level | 62 | ||
| Biostability | 63 | ||
| Corrosion control and pipe materials | 64 | ||
| Pressure, cross-connection control and maintenance | 64 | ||
| 3.4.3 Other non-chlorine disinfectants | 65 | ||
| 4:\rPerformance models | 67 | ||
| 4.1 REMOVAL PROCESS MODELS | 67 | ||
| 4.1.1 Transport | 68 | ||
| 4.1.2 Attachment | 68 | ||
| 4.1.3 Effects of process variables on removal efficiency | 68 | ||
| Particle size | 69 | ||
| Pretreatment with chemical coagulants | 71 | ||
| Filtration rate | 71 | ||
| Filter medium size and depth | 72 | ||
| Temperature | 72 | ||
| 4.2 DISINFECTION MODELS | 72 | ||
| 4.2.1 Integrated disinfection design framework | 74 | ||
| 5:\rTreatment variability | 75 | ||
| 5.1 EFFECTS OF PROCESS VARIABILITY | 76 | ||
| 5.2 RELATIONSHIPS BETWEEN TREATMENT PROCESSES | 76 | ||
| 5.3 DYNAMIC NATURE OF TREATMENT PROCESSES | 77 | ||
| 5.4 EFFECTS OF CHANGES IN RAW WATER QUALITY | 78 | ||
| 5.5 VARIABILITY DUE TO PROCESS MEASUREMENTS | 78 | ||
| 6:\rProcess control | 81 | ||
| 6.1 RISK ASSESSMENT AND PROCESS CONTROL | 82 | ||
| 6.2 SOURCE WATER PROTECTION | 83 | ||
| 6.3 COAGULATION, FLOCCULATION AND CLARIFICATION | 85 | ||
| Coagulation | 85 | ||
| Flocculation | 87 | ||
| Clarification | 88 | ||
| 6.4 FILTRATION | 88 | ||
| 6.5 DISINFECTION | 90 | ||
| 6.6 DISTRIBUTION SYSTEM | 91 | ||
| 7:\rReference list | 93 | ||
| Index | 107 |