31. ENVR 430-2 Microbial Control Measures by Water Processes
Suggested Reading:
Brock Chapter 28- Wastewater Treatment, Water Purification, and Waterborne Microbial Diseases pp (posted as .PDF file on website)

32. Summary of Disinfectants for Microbes in Water and Wastewater
Historically, the essential barrier to prevention and control of
waterborne microbial transmission and waterborne disease.
Free chlorine: HOCl (hypochlorous) acid and OCl- (hypochlorite ion)
HOCl at lower pH and OCl- at higher pH; HOCl a more potent germicide than OCl-
strong oxidant; relatively stable in water (provides a disinfectant residual)
Chloramines: mostly NH2Cl: weak oxidant; provides a stable residual
Ozone: O3 , strong oxidant; provides no residual (too volatile and reactive)
Chlorine dioxide: ClO2,, strong oxidant; unstable residual (dissolved gas)
Concerns due to health risks of chemical disinfectants and their
by‑products (DBPs), especially free chlorine and its DBPs
UV radiation:
low pressure mercury lamp: low intensity; monochromatic at 254 nm
medium pressure mercury lamp: higher intensity; polychromatic nm)
reacts primarily with nucleic acids: pyrimidine dimers and other alterations

33. Factors Influencing Disinfection Efficacy and Microbial Inactivation
Microbe type: Resistance to chemical disinfectants:
Vegetative bacteria: Salmonella, coliforms, etc.
Enteric viruses: coliphages, HAV, SRSVs, etc.
Protozoan (oo)cysts, spores, helminth ova, etc.
Cryptosporidium parvum oocysts
Giardia lamblia cysts
Clostridium perfringens spores
Ascaris lumbricoides ova
Acid-fast bacteria: Mycobacterium spp.
Least
Most

34. Factors Influencing Disinfection Efficacy and Microbial Inactivation
Type of Disinfectant and Mode of Action:
Free chlorine: strong oxidant; oxidizes various protein sulfhydryl groups; alters membrane permeability; oxidize/denature nucleic acid components, etc.
Ozone: strong oxidant
Chlorine dioxide: strong oxidant
Combined chlorine/chloramines: weak oxidant; denatures sulfhydryl groups of proteins
Ultraviolet radiation: nucleic acid damage; thymidine dimer formation, strand breaks, etc.

35. Factors Influencing Disinfection Efficacy
and Microbial Inactivation - Bacteria
Surface properties conferring susceptibility or resistance:
Resistance: Spore; acid fast (cell wall lipids); capsule; pili
Susceptibility: sulfhydryl (-SH) groups; phospholipids; enzymes; porins and other transport structures, etc.
Physiological state and resistance:
Antecedent growth conditions: low-nutrient growth increases resistance to inactivation
Injury or in a state of “injury repair”
disinfectant exposure may select for resistant strains
Physical protection:
Aggregation; particle-association; biofilms; occlusion (embedded within protective material), association with or inside eucaryotes; corrosion/tuberculation

36. Factors Influencing Disinfection Efficacy and Inactivation - Viruses
Virus type, structure and composition:
Envelope (lipids): typically labile to disinfectants
Capsid structures and capsid proteins (change in conformation state)
Nucleic acids: genomic DNA, RNA; # strands
Glycoproteins: often on virus outer surface; typically labile to disinfectants

37. Parasite type, structure, and composition: Protozoan cysts:
Factors Influencing Disinfection Efficacy and Microbial Inactivation - Parasites
Parasite type, structure, and composition:
Protozoan cysts:
oocysts (environmentally resistant form)
some are very resistant to chemical disinfectants
Helminth ova:
some are very resistant to chemical disinfection, drying and heat
used as indicators for biosolids (Class A)

38. Effects of Water Quality on Disinfection
Particulates: protect microbes from inactivation
microbes shielded or embedded in particles
Dissolved organics: protects
consumes or absorbs (UV radiation) disinfectant
coats microbes
Inorganic compounds and ions: effects vary with disinfectant
pH: effects depend on disinfectant. 
Free chlorine more biocidal at low pH where HOCl predominates. 
Chlorine dioxide more microbiocidal at high pH

39. Disinfection: A Key Barrier Against Microbes in Water and Wastewater
Free chlorine still the most commonly used disinfectant
Maintaining disinfectant residual during treated water storage and distribution is ESSENTIAL!!
A problem for O3 and ClO2, which do not remain in water for very long and for UV, which produces no disinfectant residual
A secondary disinfectant must be used to provide a stable residual
UV radiation is a promising disinfectant because it inactivates Cryptosporidium at low doses
UV may have to be used with a chemical disinfectant to protect the water with a residual through distribution and storage.
Sequential disinfection with a strong oxidant (HOCl, O3, or ClO2) followed by monochloramine may give a synergistic effect that is more effective against microbial pathogens

40. Enteric Microbes, Water Sources and Water Treatment
Drinking water must be essentially free of disease-causing microbes, but often this is not the case.
A large proportion of the world’s population drinks microbially contaminated water, especially in developing countries
Using the best possible source of water for potable water supply and protecting this source from microbial and chemical contamination is the goal.
In many places an adequate supply of pristine water or water that can be protected from contamination is not available
The burden of providing microbially safe drinking water supplies from contaminated natural waters rests upon conventional water treatment processes.
The efficiency of removal or inactivation of enteric microbes and other pathogenic microbes in specific water treatment processes has been determined for some microbes but not others.

41. Watershed Protection: Planning the Future of our Source Water Austin, Texas
Does your utility need assistance in developing a source water protection plan? Attend this all-new seminar to learn about Source Water Plans in detail, as well as how to determine source water susceptibility and how to develop emergency plans. You'll also explore the impact of public participation and education as a vital component of Source Water Protection.
You'll Learn:
What is a Source Water Protection Plan (SWPP)?
Federal, State, and Local Government Roles in Source Water Protection Plans
Delineation of Source Water Protection Areas
Contamination
Determining Source Water Susceptibility
SWP Area Management
Development of Emergency Plans
Public Participation and Education
Source Water Assessment Program Implementation
Funding Options

42. STORAGE:
Reservoirs,
lakes

43. Water Treatment Processes: Storage
Reservoirs, aquifers & other systems: store water / protect it from contamination
Site specific with respect to factors influencing microbial reductions
detention time
temperature
microbial activity
water quality
sunlight
sedimentation
land use
precipitation
runoff or infiltration
Household storage and collection is practiced in some places
Stored volumes are relatively small and storage times are short
contamination during collection and storage is a problem
Point-of-use water treatment reduces pathogens enteric disease

44. Water Storage and Microbial Reductions
Microbial reductions by storage reduces microbe levels over time by natural antimicrobial processes and microbial death or die-off (bacteria)
One study in The Netherlands showed human enteric viruses in surface water were reduced by 400-1,000-fold when storage was for 6‑7 months.
Protozoan cyst reductions by storage are also expected but data are limited.
Data from the ICR indicates lower protozoan levels in reservoir or lake sources than in river sources

45. Chemical Coagulation- Flocculation
Removes suspended particulate and colloidal
substances from water, including microorganisms.
Typically, add alum (aluminum sulfate), ferric chloride, or sulfate to the water with rapid mixing and controlled pH conditions
Insoluble aluminum or ferric hydroxide and aluminum or iron hydroxo complexes form
These complexes entrap and adsorb suspended particulate and colloidal material.
Slow mixing (flocculation) is then used to promote the aggregation and growth of the insoluble particles (flocs).
Resulting floc particles are subsequently removed by gravity sedimentation (or direct filtration)

46. Microbial Reductions by Chemical Coagulation-Flocculation
Enteric microbes reductions In laboratory and pilot scale field studies:
90 to >99% using alum or ferric salts as coagulants
other studies report much lower removal efficiencies by coagulation‑flocculation.
Conflicting information may be related to PROCESS CONTROL
coagulant concentration, pH and mixing speed during flocculation.
Expected to reduce enteric microbe concentrations of water by 90-99% if critical process variables are adequately controlled
Microbes are NOT inactivated by chemical coagulation
Infectious microbes remain in the chemical floc
The floc removed by settling and/or filtration must be properly managed to prevent pathogen exposure.
Recycling back through the plant is undesirable
Filter backwash must be disinfected and disposed of properly.

47. Filtration of Drinking Water
Widely used to remove suspended particles (turbidity) incl. microbes.
Historically, two types of granular media filters:
Slow sand filters: uniform bed of sand; low flow rate <0.1 GPM/ft2
Rapid sand filters: 1, 2 or 3 layers of sand/other media; >1 GPM/ft2
Membrane filters: more recent development and use in drinking water
microfilters: several tenths of mM to mM diameter pore size
nano- and ultra-filters: retention based on molecular weight cutoff
Typically 1, ,000 MWCO
Reverse osmosis filters: pore size small enough to remove dissolved salts; used to desalinate (desalt) water as well as particle removal
Adsorbers and filter-adsorber systems:
Granular activated carbon adsorption: remove dissolved organics
Sand and granular activated carbon filter-adsorber:
reduces particles and organics

48. Slow Sand Filters
Less widely used for large municipal water supplies in the USA
Effective and still widely used in Europe and for smaller water supplies.
Filter water through a 3‑ to 5‑foot deep bed of unstratified sand at a flow rate of about 0.05 gallons per minute per square foot.
Biological growth that develops in the upper surface of the sand is primarily responsible for particle and microbe removal.
Filters are effective without pretreatment of the water by coagulation‑flocculation.
Filters are periodically cleaned by removing, cleaning and replacing the upper few inches of biologically active sand (Schmutzdecke)

49. Microbial Reductions by Slow Sand Filtration
Quite effective in removing enteric microbes from water.
Virus removals >99% in laboratory models of slow sand filters.
Lab studies: reovirus removals of up to 4 log10; no infectious viruses recovered from filter effluents
Field studies:
naturally occurring enteric viruses removals
97 to >99.8 percent; average 98% overall;
Comparable removals of E. coli bacteria.
Virus removals= 99‑99.9%; high bacteria removals
Parasite removals: Giardia lamblia cysts effectively removed
Expected removals ~ 99%

50. Microbe Reductions by Rapid Granular Media Filters
Ineffective in removing enteric microbes unless
preceded by chemical coagulation‑flocculation.
Enteric microbe removals of 90->99 % achieved.
Field (pilot) scale studies: rapid sand filtration preceded by iron coagulation‑flocculation
virus removals of <50% (poor control?).
Giardia lamblia: removals not consistently high; related to the efficiency of turbidity removal; >99% removals reported when optimized.
Removal may not be high unless turbidity is reduced to <0.2 NTU.
Lowest removals shortly after filter backwashing
Microbes primarily removed in filter by entrapped floc particles.
Overall, can achieve ~90% microbial removals from water
when preceded by chemical coagulation‑flocculation.

51. Cryptosporidium Removals by Sand Filtration
Type
Rate (M/hr)
Coagulation
Reduction
% (log10)
Rapid, shallow 5 No
65 (0.5)
Yes
90 (1.0)
Rapid, deep 6
(5.0)
Slow
0.2
(2.7)

52. Reverse Osmosis Membrane Filter Plant
Osmosis: the natural tendency is for water to move through the membrane from the dilute to the concentrated solution until chemicals reach equal concentrations on both sides of the membrane

53. Removal Effect of the Water purifier for Home Use against Cryptosporidium parvum Oocysts
Toshihiro MATSUI1), Junko KAJIMA2) and Takashi FUJINO1)
1) Department of Infectious Diseases, Kyorin University School of Medicine 2) Research and Study Department, Japan Association of Parasite Control
ABSTRACT.  The removal effects of the faucet mounted type water purifier for home use were examined against Cryptosporidium parvum oocysts. The water purifier is composed of a layer of granular activated carbon and the hollow fiber membrane filter. The cartridges were unused, 25%, 50% and 75% flow down by Arizona-dust of U. S. A. Two respective cartridges were used of the examination. The faucet and the water purifier were connected by anti-pressure tube, and 3.0 × 107 oocysts of Cryptosporidium parvum were injected into anti-pressure tube while water was running. Twenty liter of collected purified water was examined under the fluorescent microscope. Any oocysts in the purified water collected from all cartridges were not found. Therefore, we considered this purifier as an effective one in removing Cryptosporidium oocysts from drinking water.
From 2004 Journal of Veterinary Medical Science 66:941-43

54. Cryptosporidium Reductions by Membrane Filtration
Type
Pore Size
Log10 Cryptosporidium
Reduction
A, MF
0.2 µm
>4.4
B, MF
C, MF
0.1 µm
4.2->4.8
D, UF
500 KD
>4.8
E, UF
300 KD
F, UF
100 KD
MF = microfilter filter; UF = ultrafilter
Jacangelo et al., JAWWA, Sept., 1995

55. Contaminant Removal by Granular Activated Carbon
Good removal of chemical and microbial contaminants
Mode of removal: fissures adsorb chemicals/particles
Problem: what to do with material after use? Hazardous material !!

56. Water Softening
“Hard” Water: contains excessive amounts of calcium and magnesium ions
iron and manganese can also contribute to hardness.
Hardness ions are removed by adding lime (CaO) and sometimes soda ash (Na2CO3) to precipitate them as carbonates, hydroxides and oxides.
This process, called softening, is basically a type of coagulation‑flocculation process.

57. Microbial Reductions by Softening Treatment
Softening with lime only (straight lime softening); moderate to high pH
ineffective enteric microbe reductions: about 75%.
Lime‑soda ash softening
results in the removal of magnesium as well as calcium hardness at higher pH levels (pH >11)
enteric microbe reductions >99%.
Lime‑soda ash softening at pH 10.4, 10.8 and 11.2 has produced virus reductions of 99.6, 99.9 and percent, respectively.
At lower pH levels (pH <11), microbial removal is mainly a physical process
infectious microbes accumulate in the floc particles and the resulting chemical sludge.
At pH levels above 11, enteric microbes are physically removed and infectivity is also destroyed
more rapid, extensive microbe inactivation at higher pH levels.

58. Drinking Water Treatment for Pathogen Control: The Multiple Barrier Approach
Pathogen reductions are best achieved by
using a series of treatment processes
Typical water treatment process train for surface water:
Source water management and protection (Storage)
Coagulation-flocculation-sedimentation
Rapid granular medium filtration
Disinfection
Can you estimate the microbial reductions at each
stage of treatment and overall by such a system?
Will it be the same for all classes of microbes?

59. Study Points: Wastewater treatment processes Disinfection
Primary (settling), secondary (biological), tertiary (disinfection) treatment
Waste liquid treatment (aerobic); waste solids treatment (anaerobic)
Alternative systems: Facultative oxidation ponds, Constructed wetlands, On-site septic systems, etc.
Disinfection
Kinetics (First-order, Retardant, and Multi-hit)
Disinfectant types (chemical vs. physical disinfectants)
Factors that effect disinfection
Water treatment processes
Chemical (coagulation-flocculation, lime softening)
Physical (slow sand filtration, rapid granular media filtration, membrane filtration)