Uploaded by Muhammed Ȝteya

Water microbiology

Water microbiology
Water microbiology
 Water microbiology "Aquatic Microbiology"
 The science that deals with microscopic living organisms in fresh or salt systems
 Water sources:
1. Natural sources: Rain water, oceans, rivers, lakes, streams, ponds, springs
2. Man made sources: Dams
 Rain water: collected on the earth in the form of:
Surface water
Water present on earth surface in the
form of oceans, Rivers, Ponds, Streams
Underground water
Some of the rain water seeps through the
soil onto the non-porous rocks below
 Water cycle "Hydrologic Cycle"
 Water cycle:
 It's how the earth's water recycles itself, so the same amount of water on
the earth now equal to that at beginning.
It include:
Precipitation "Rain water"
Evaporation "from oceans, rivers, lakes, ….."
Condensation within clouds
Transpiration from plants
Water keep changing from liquid phase to vapor then back again
Water cycle occur because of Sun heat & Gravity
 Microorganism in water:
Natural water bodies as lakes & rivers & ground water contain nutrients so M.O as
bacteria, viruses, fungi take the advantage of this environment
Ex1: Bacteria
 They are adverse in nature, occur in many sizes from 1-10 µ to 500 µ
 Classified into many groups according shape, cell structure, staining
 Some bacteria are motile with flagella "Tail like structure used for movement"
Ex2: Fungi
 Called water molds or Aquatic Phycomycetes
 Soil is the common habitat of fungi, also found in aquatic environments
 On earth 1.5 million fungal sp. 3000 sp are aquatic , only 365 sp. are marine
"salt" water
Ex3: Viruses
 The smallest group of M.O, only seen under electron microscope
Dr. 3teya
2 SP. Micro
Water microbiology
 Aquatic M.O nutrition:
Aquatic M.O obtain their food in many ways
 Ex: Bacteria living near water surface where sunlight present , can produce their
own food through photosynthesis
So Aquatic M.O play a vital role in cycling of nutrients in their environments, so are
a crucial part of the food chain/ web
 Give reason: Bacteria play a vital role in aquatic M.O nutrition.
 Beneficial role of aquatic M.O to human:
 Play a role in sewage treatment
 Microscopic bacteria used to breakdown human wastes
 Harmful role of aquatic M.O to human:
 They are pathogenic so Cause serious diseases for human
 Ex: Bacteria as Salmonella typhi, S paratyphi found in water contaminated by
sewage can cause illness
 Ex2: E. coli & Enterococcus bacteria can also cause diseases
Water pollution
 It refer to contamination of water bodies as oceans, rivers, lakes, ground
water that caused by human activity
 It can be harmful to aquatic plants & M.O
 Causes of water pollution:
1- Oil pollution
2- Eutrophication
3- Global warming
4- Marine dumping
5- Atmospheric deposition
6- Underground storage leakage
7- Sewage & waste water
8- Radioactive wastes
9- Industrial wastes
Dr. 3teya
2 SP. Micro
Water microbiology
 Human activities & water pollution:
Resulting pollutants
Oil & fuel
Potential impacts
1- Decrease in light & oxygen
Nutrients, pesticides,
2- Eutrophication, nutrient
suspended matter
3- Increased stress to aquatic
Biological oxygen demand 1. Decrease in light & oxygen
2. Eutrophication, nutrient
nutrients, Organics, Bacteria,
Viruses, Turbidity, Heavy
3. Increased stress to aquatic
metals, Pesticides, Chemicals 4. Alteration of habitats
Heavy metals, Organics,
1. Increased stress to aquatic
Chemicals, Thermal pollution 2. Increased mortality
1. Decrease in oxygen
2. Eutrophication, nutrient
Nutrients, Organics,
suspended matter
3. Alteration of habitats
4. Accumulation of wastes
1. Increased stress to aquatic
Petroleum hydrocarbons
2. Mortality "Death"
Chemicals, Hydrocarbons,
1. Decrease in light & oxygen
Heavy metals, suspended
2. Alteration of habitats
 Sources of surface water pollution
2 categories according to origin
Non point source pollution "NPS"
Point source pollution "PS"
Refer to any contamination that doesn't Refer to contaminants that enter a water
originate from a single discrete source way from single identified source as pipe
It is the cumulative effect of small
Ex: discharge of sewage from a factory
amounts of contaminants gathered
o Sewage is discharged into water
from a large area
without inadequate treatment
 Ex: leaching of N compounds from
o So Sewage M.O pose health threats
fertilized agricultural lands
o Wastes from domestic or wild animals
can pose a danger
Dr. 3teya
2 SP. Micro
Water microbiology
 Contamination of drinking water:
M.O may seep through soil till reach surface or ground water
Ex: Leaking from septic tanks & latrines may contaminate nearby drinking water
Another cause: The improper storage of water in household storage tanks
considered a common source of pathogens in drinking water
 Water borne microbial pathogens:
Water borne diseases
Water washed
Water based diseases o
Water related insect
Dr. 3teya
As cholera, typhoid caused by contaminated drinking
water by M.O come from animal or human wastes
As skin & eye infections caused by lack of clean water for
As Schistoma that act as human parasites
Spread in contaminated water & by eating insufficiently
cooked fish
As Mosquitoes that breed in or near water
It spread diseases as Dengue & Malaria
It not directly related to water supply or quality
2 SP. Micro
Water microbiology
 Pathogenic M.O in surface water:
 Pathogenic M.O from human & animal wastes include viruses, bacteria, protozoa
 May be found in contaminated drinking water
 May cause fatal illness
Hepatitis A, E
Norwalk virus
Rota virus
E. coli
Vibrio cholera
Gardia sp.
The classical waterborne infection cycle
Dr. 3teya
2 SP. Micro
Water microbiology
Microbial Examination of Water
The bacteriological examination of water is performed by water utilities to ensure a
safe supply of water for drinking, bathing, swimming ,domestic & industrial uses
This examination is intended to (aim to) identify water sources that contaminated
with M.O
Human fecal pathogens VARY in type & number
So testing water for presence of each type of waterborne pathogen is too time
consuming & expensive
Instead, operators test for presence of one or a few indicator M.O
The most commonly used indicator M.O are coliform bacteria
Coliform bacteria found in large numbers beside pathogenic M.O in intestinal
tracts of warm-blooded animals
Coliform bacteria are discharged from the intestinal tract with animals’ feces.
If sewage enters water, the coliform bacteria in sewage will survive in the
water for long periods of time.
The presence of coliform bacteria provide evidence that water is polluted
with sewage, & indicates the possible presence of pathogenic microbes
Characteristics of Indicators
1- A good indicator M.O should be easy to test for in lab.
2- Indicator M.O are present in greater numbers than the pathogens they indicate.
3- Indicator M.O are safer to work with in the lab than are pathogens as indicators
cause only mild illnesses.
 GIVE REASON: Coliform bacteria are good indicators
(Why Operators Prefer Coliform bacteria are good indicators?)
1- Only reproduce in animals intestines, so they will not be present in water
unless the water has been contaminated with sewage.
2- Able to survive outside animals intestines, so they will be present in
contaminated water for several days
 2 types of indicators: Total coliform bacteria & fecal coliform bacteria
Dr. 3teya
2 SP. Micro
Water microbiology
 General Characters of Coliform Bacteria
1- They are part of F: Enterobacteriaceae
2- Comprised of Gram -Ve, non spore- forming, aerobic to Facultative
anaerobic rods, which ferment lactose to acid & gas.
3- Include 2 organisms E. coli & Enterobacter aerogenes
4- Presence of E. coli & Enterobacter in water supply is evidence of fecal
5- Individual cells cannot be seen with naked eye due to small size, but colonies
can be seen
6- Some coliform bacteria naturally found in soil called non fecal coliforms
7- Coliform bacteria lives in intestinal of warm-blooded animals is called fecal
coliform bacteria
 2 major operational definitions of coliforms have been distinguished:
“Total coliforms” & “Fecal or Thermotolerant coliforms”
 Fecal or Thermo-tolerant coliforms
 Are able to grow at higher incubation Temp
 Come from the intestinal tract of a warm-blooded animal
 Considered as specific indicator of fecal contamination because total coliform
may include bacteria of non-fecal origin.
 Total Coliforms operationally defined in 2 different methods:
1- Most probable number "MPN" or Multiple Tube Technique
2- Membrane Filter Technique
Most probable number "MPN" or Multiple Tube Technique
3 Steps: Presumptive, Confirmed, Completed tests
1- The presumptive test:
 Series of lactose broth tubes are inoculated with measured amounts of the
tested water sample
 Gas production in any tube is presumptive evidence of presence of coliform
 MPN of coliforms in 100 ml of the water sample can be estimated by the
number of positive tubes.
2- The Confirmed test:
 In order to confirm the presence of coliforms, it is necessary to inoculate EMB
(Eosin methylene blue) agar plates from positive presumptive tube.
 Methylene blue in EMB agar inhibit gram +Ve organisms & allow growth of
gram –Ve coliforms
Dr. 3teya
2 SP. Micro
Water microbiology
 Coliforms "E.coli & E. aerogenes" produce colonies with dark centers can be
distinguished from one another by the size and color of the colonies.
 E. coli colonies : Small & have green metallic sheen,
 E. aerogenes colonies: Large pinkish colonies.
If only E. coli or if both E. coli & E. aerogenes appear on the EMB plate, the test is
If only E. aerogenes appears on the EMB plate, the test is negative
This due to that : E. coli is an indicator of fecal contamination, as it is not
normally found in water or soil, whereas E. aerogenes found in nature outside of
the intestinal tract
3- The Confirmed test:
 It occur using the organisms which grew on the confirmed test media.
 These organisms are used to inoculate nutrient agar slant & tube of broth
 After 24 hours at 37 C, the lactose broth is checked for gas production, &
nutrient agar slant checked by gram stain
If the organism is gram –Ve, Nonspore-forming rod-shaped produces gas in
lactose tube so the test is POSITIVE "Coliforms present in the water sample"
Dr. 3teya
2 SP. Micro
Water microbiology
The Membrane Filter Technique
 MF technique defines total coliforms as
 All organisms that produce colony with golden green metallic sheen within 24
hours of incubation at 35°C on Endo-type medium containing lactose & are
aerobic or facultative anaerobic, gram-negative, non- spore- forming rods
In this method, measured volume of sample "or sample dilution" are vacuum filtered
though bacterial filter has pore size of 0.47 µm that retain the bacteria
Then the filter Incubated 24 hrs, at 35C in petri dish with nutrient medium "Endotype medium containing lactose"
If bacteria present, it will grow on the upper surface of membrane.
After 24 hrs, Total coliforms produce colony with golden-green metallic sheen
"+Ve test"
Ex of fecal coliforms fond in soil: Citrobacter, Enterobacter, Kleibsiella
The total coliforms separated into those of fecal and non-fecal origin.
 Fecal Coliforms
 At higher incubation temperature of 44.5°C. coliforms of only fecal origin will
 Non fecal Coliforms from environmental sources can’t grow at elevated Temp.
 Fecal Coliforms can be defined as gram -Ve, non-spore forming, rod shaped
bacteria which ferment lactose with production of gas at 44.5 C within 24h
 Any kind of Coliform bacteria not to be tolerated in finished (treated) drinking water.
Dr. 3teya
2 SP. Micro
Water microbiology
Drinking Water Treatment Process
 Treatment of drinking water by municipal water systems involve few key
1. Aeration: water mixed to liberate dissolved gases & to suspended particles in water
2. Flocculation: Materials & particles present in drinking water (clay, organic
material, metals, microorganisms) are quite-small, so will not settle down without
 To help the settling process, coagulating compounds are added to water, so
the suspended particles “stick” to coagulants & creating large heavy clumps of
3. Sedimentation: Water is left undisturbed to allow the heavy clumps & coagulants
to settle out.
4. Filtration: Water run through series of filters that trap & remove particles still
remaining in water.
 Beds of sand or charcoal are used to accomplish this task.
5. Disinfection: Water now free of particles & M.O
 Water treated to destroy any remaining disease-causing pathogens.
 This occur chlorination (Used to eliminate pathogens in swimming pools),
ozone, or ultraviolet radiation.
 The water is now safe to drink & sent to pumping stations for distribution
 Chlorine:
 Inactivate M.O by damaging its cell membrane.
 Once cell membrane is weakened, chlorine can enter the cell & disrupt cell
respiration & DNA activity (2 processes that are necessary for cell survival)
 It can cause problems if its use is not controlled very carefully
 When used as a control on the disease-producing bacteria, the idea is to disinfect
and not sterilize the effluent.
 Disinfection : the process of killing disease-producing bacteria.
 Sterilization : the process of killing all living organisms.
 If an attempt were made to sterilize the effluent, the biological life in the receiving
waters would likely be destroyed.
 The best method for controlling the disinfection process & preventing harm to
aquatic life by over-chlorination is to maintain a specific chlorine residual
Dr. 3teya
2 SP. Micro
Water microbiology
level in the effluent
 Chlorine residual:
 The amount of available chlorine in water after a given time of contact (20
min at peak flow, 30 min at average flow) under specific conditions including
PH & Temp
 Chlorine Residual Testing
 The presence of Residual chlorine in water indicate that:
1- Sufficient amount of chlorine was added initially to water to inactivate bacteria
& some viruses that cause diarrheal disease
2- Water is protected from recontamination during distribution
 The presence of Residual chlorine is correlated with the absence of disease causing
M.O & thus is a measure of the water portability
 Demand chlorine:
 The amount of chlorine that firstly react with organic matter & metals so not
available for disinfection
 Total chlorine:
 The remaining chlorine conc. after chlorine demand. It divided into
1. Combined chlorine:
 The amount of chlorine reacted with nitrate & un-available for disinfection
2. Free chlorine:
 Amount of chlorine available for disinfection, to inactivate disease causing
M.O, a measure to determine the water portability
The microbiology of piped distribution systems
 The drinking-water distribution system provides a habitat for M.O, which sustained by
organic & inorganic matter present in pipes & water.
 M.O may be introduced into distribution system during Drilling, servicing, repairing
 It aimed to prevent contamination from fecal material that present near pipes
or contaminate surface or soil water.
 Bacteria present in the water & on surfaces are harmless, but they are at the base
of a food-chain for free-living organisms as fungi, protozoa, worms, crustaceans.
 These organisms may be present in a distribution system, even in the presence of
residual "disinfectant”
Dr. 3teya
2 SP. Micro
Water microbiology
 Biofilm
 Complex structure adhering to surfaces that are regularly in contact with water,
consisting of colonies of bacteria & other M.O as yeasts, fungi, protozoa that
secrete mucilaginous protective coating which encase them
 Biofilms formed on solid, liquid surfaces or soft tissue in living organisms,
and are typically resident to conventional methods of disinfection.
 Example: Dental plaque, algal mats on water bodies
 Pathogenic biofilms in the body causing disease as cystic fibrosis and otitis
 They are beneficial in treating sewage, industrial waste, contaminated soil.
 Iron bacteria & sulfur bacteria
 They are small living organisms that naturally occur in soil, surface water,
groundwater, may be introduced into the distribution system during Drilling,
servicing, repairing
1- Iron Bacteria
 More common than sulfur bacteria
 Oxidizing agents that combine iron or Mn dissolved in ground water with oxygen
 Signs that indicate iron bacteria problem:
1- Water may has yellow, red, orange color
2- Rusty slime deposits in toilet tanks
3- Strong smell resemble foul oil
2- Sulphur Bacteria 2 categories of sulfur bacteria
Sulfur oxidizing bacteria
Sulfur reducing bacteria “SRBs”
- Live in oxygen-deficient environments.
Convert sulfide into sulfate,
- They break down sulfur compounds,
producing dark slime that can clog
producing H2S gas.
- H2S gas is foul-smelling, highly corrosive
Iron & sulfur bacteria cause problems as
Undesirable color, stains or deposits
stained plumbing fixtures & laundry
Unpleasant tastes & odors
Restrict water flow in distribution lines
Plugged water treatment equipment.
Dr. 3teya
2 SP. Micro
Water microbiology
* There are two major types of waste water treatment plants,
biological plants, and physical/chemical.
1. Biological plants
A Are mainly used to treat combined domestic and industrial
wastewater from municipalities,
the biological plants use micro-organisms to treat the waste
water-almost the same process that occurs naturally.
However at the biological treatment plants, the wastewater is
being treated under controlled conditions: -> This is to ensure that
the water is
placed back into the environment
Dr. 3teya
2 SP. Micro
Water microbiology
Dr. 3teya
2 SP. Micro
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