Download Importance of Microbiology in Environmental Engineering

Introduction to Environmental
Engineering
Dr. Kagan ERYURUK
Microbial Groups
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Importance of Microbiology in
Environmental Engineering
• Microbiology; a branch of biology devoted to
the study of microorganisms (microbes).
• The objects of this science; the engineering
systems of water, wastewater, solid wastes,
soil and gas biotreatment.
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1. Bacteria
• As decomposers – indispensable
ecological role by decaying organic
matter
• Natural processes are enhanced and
accelerated in stabilizing organic
wastes in treatment plants
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Reproduction and Spores
• Bacterial reproduction; by
•
•
binary fission – From one
cell
2 new cells.
Each then divide again.
Approx. every 15 – 30
mins. (doubling time)
Survival mechanism -Some
species form spores with
tough coatings that are
resistant to heat, lack of
moisture, and loss of food
supply.
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www.anselm.edu/.../ genbio/mitosisnot.html
Coliform Bacteria
• A commonly used
bacterial indicator of
sanitary quality of foods and water.
• Total coliform bacteria - commonly found in
the environment (e.g., soil or vegetation).
Generally harmless. They indicate the
presence of organic material.
• Fecal coliform bacteria- a sub-group of the
total coliform group.
Present in large
quantities in the intestines and feces of
humans and other and animals.
• Escherichia coli - a sub-group of the fecal
wqm.igsb.uiowa.edu/.../ faqsbeachenvironprof.htm
coliform group. Most E. coli are harmless
and are found in large quantities in the
intestines of humans and warm-blooded
animals.
Some strains, however, may
cause illness. (E.g. E. coli O157:H7)
• All are used as a common indicator of the
bacteriological quality of water.
E. coli
www.ericsecho.org/ whatisec.htm 6
Heterotrophic and Autotrophic Bacteria
Bacteria can be classified into 2 main groups depending
on their source of nutrients:
• Heterotrophs
use organic matter as both an energy
and a carbon source for synthesis. They are further
sub-divided into 3 groups depending on their action
toward free oxygen
– Aerobes
– Anaerobes
– Facultative
• Autotrophs oxidize inorganic compounds for energy
and use carbon dioxide as a carbon source
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Heterotrophs
• Aerobes
require
free
dissolved
oxygen
in
decomposing organic matter to gain energy for
growth and multiplication. Found in activated sludge
and trickling filters in wastewater treatment.
• Anaerobes oxidize organics in the complete absence
of dissolved oxygen by using oxygen bound in other
compounds (such as nitrate and sulfate). They
predominate in sludge digestion .
• Facultative bacteria compose a group that uses free
dissolved oxygen when available but can also live in
its absence by gaining energy from anaerobic
reaction. They are active in both aerobic and
anaerobic treatment units.
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Autotrophs
• Oxidize inorganic compounds for energy and use
carbon dioxide as a carbon source.
• Nitrifying, sulfur, and iron bacteria are of greatest
significance.
• Nitrifying bacteria oxidize ammonium nitrogen to
nitrate. Nitrification can occur in biological
secondary treatment under the conditions of low
organic loading and warm temperatures (often
avoided to reduce oxygen consumption in
treatment and to prevent floating sludge on the
final clarifier).
• Iron bacteria can flourish in some pipes (more of a
problem for water delivery pipes).
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2. FUNGI
• Microscopic non photosynthetic plants
including yeasts and molds
• Molds are aerobic and grow best in
acid solutions high in sugar content
• Fungi are found in wastewater in
small numbers but if there is large
increase in fungi concentration it is an
indication of a change in pH of the
activated sludge.
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Protozoa and
Multicellular Animals
• Protozoa- single-celled aquatic animals that multiply by
binary fission. They have complex digestive systems
and use solid organic matter as food.
• Protozoa are aerobic organisms found in activated
sludge, trickling filters, and oxidation ponds treating
wastewater.
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Viruses
• Viruses are obligate, intracellular parasites
that replicate in living hosts’ cells (i.e. not
involved in the digestion of wastewater)
• They may be involved in infecting bacterium,
but their real relevance to wastewater
treatment is in terms of infection of humans
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Algae
• Algae are microscopic photosynthetic plants of the
simplest form.
• Their relevance to most wastewater processes is
in terms of their control in the processes and at
the end of the pipe.
• Wastewater stabilization ponds support luxurious
blooms of algae to the point where the suspension
becomes self-shading.
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Bacterial Growth Requirements
1. Terminal electron acceptor
2. Macronutrients
a. carbon
b. nitrogen
c. phosphorus
3. Micronutrients
a. trace metals
b. vitamins
4. Environment
a. moisture
b. temperature
c. pH
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Growth in Pure Cultures
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• During lag phase, bacteria adapt themselves to growth
conditions. It is the period where the individual bacteria
are maturing and not yet able to divide.
• The log phase is a period characterized by cell doubling.
The number of new bacteria appearing per unit time is
proportional to the present population.
• The stationary phase is often due to a growth-limiting
factor such as the depletion of an essential nutrient, and/or
the formation of an inhibitory product such as an organic
acid.
• At death phase (decline phase), bacteria die. This could be
due to lack of nutrients, a temperature which is too high or
low, or the wrong living conditions.
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Mathematics of Growth
• log growth phase
P  P0  2 P0  2  2P0  2  2  2 P0  ....
P  P0 ( 2)
n
log P  log P0  n log 2
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Example
• Bread yeast cells divide and form 2 cells every
5 minutes. If you place 105 cells in a suitable
environment, how many cells will you have in
30 minutes?
30 minutes
n
 6 generation s
5 minutes/ge neration
P  10 2  6.4 x 106 cells
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Mixed Cultures
• Pure cultures do not exist in nature
• Log growth may occur when one organism
or group has few external limits
• Most organisms interact with other
organisms:
– competition for food and other resources
– inhibitor
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