Transcript Return Control

AS Microbiology –
Good Actors and Bad
Seth Terry, Ph.D.
Good
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Bad
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UGLY!
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A key question for operators
Of course, settleability represents only one
aspect of ‘goodness’
So, as an operator, you have to ask yourself
the question:
“Do you stand for ‘goodness’, or - for
‘badness’?”
Judge Smails, Caddyshack (1980)
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What makes a sludge “good”
Controllable settling
Appropriate microbiology
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Controllability
 Indicated by an ABSENCE of filaments
 ??????
 NO! A widespread misconception
 Sludges without filaments generally settle too
quickly, leaving behind turbid effluent
 Sludges with too many filaments generally
produce crystal clear supernatants, but settle
at rates incompatible with secondary clarifiers
 The ‘sweet spot’ lies somewhere in between
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Appropriate Microbiology
 Growing the right bugs
 To control settleability

Relative proliferation of filaments
 To achieve permit compliance

BOD oxidizers

Nitrifiers

Denitrifiers

Polyphosphate-accumulating organisms (PAOs)
 Fermenting facultative organisms
 To avoid odor

Minimizing sulfate reducing bacteria (SRBs)
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Population Control
Clearly, we would like to control the
bacterial population in our aeration tanks
We do so indirectly
Bacteria are very effective at exploiting
environmental niches
Food source, DO level, temperature, water
chemistry, metabolites from other bacteria
Environment controls population
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Microbiology Basics
‘Bugs’ Are Not ‘True Bugs’
 Two pairs of wings
 Partially hardened first
pair
 Jointed piercing and
sucking mouthparts
 Series of nymphal stages
in development
 Phylum Arthropoda,
class Insecta, order
Hemiptera
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Bugs in Wastewater Treatment
 Bacteria – Single-celled organisms
 Prokaryotes
 Lack discrete nuclear membrane
 Protozoa – Single-celled animals
 Eukaryotes
 DNA housed in nuclear membrane
 Metazoa – Multi-celled animals
 Specialization of cellular functions
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Bacterial Types
 Origin
 Enteric
 Soil
 Feed
 Final Electron Acceptor
 Aerobic respiration
 O2
 Anaerobic respiration
 Heterotrophic (organic)
 NO3-
 Autotrophic (inorganic)
 SO42-
 Growth Pattern
 Floc former
 Filament
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 CO32-
 Anaerobic fermentation
 Organic acids & alcohols
 Methane
Phylogenetic Classification
 Tending to replace out-dated system based on phenotypic
relationships, particularly in microbiology
 Latest system uses genetic differences detected by
molecular techniques (molecular chronometer)
 Root = primeval organism, the ‘Universal Ancestor’
 Domains: Bacteria, Archaea, Eukarya, (Korarchaeota)
 Kingdoms: at least 14, but probably >50!
 (Class)
 (Order)
 (Family)
 Genus: usually 93% to 95% molecular similarity
 Species: isolated monoculture
 (single bacteria culture)
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} Academic work!
Metabolic Classification
Adapted from Brock, 9th Ed.
 First distinction is
made on relation to
light
 Second distinction
may be made on
electron source
 Third distinction is
made on carbon
source for cell
growth
All Organisms
Chemotrophs:
Phototrophs:
Light not required
Light required
Chemolithotrophs:
Electrons from
inorganic chemicals
Chemolithoautotrophs:
C from CO2
(‘AUTOTROPHS’)
Chemoorganotrophs:
Electrons AND C
from organic chemicals
(‘HETEROTROPHS’)
Mixotrophs:
C from organic source
(‘HETEROTROPHS’)
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Photoautotrophs:
Photoheterotrophs:
C from CO2
(ALGEA)
C from organic source
(purple non-sulfur bacteria)
Classification Based on e--acceptor
Distinction based upon relationship to
oxygen
Class
Sub-group
Aerobes
Obligate
Relationship to O2
DO required
DO required, but only at
Microaerophilic
relatively low concentrations
DO not required, but provides
Facultative
optimum growth rate
Anaerobes Obligate
Aerotolerant
DO harmful or lethal
Organisms are indifferent to
presence of DO
Types of Metabolism
Aerobic respiration
Aerobic respiration
Aerobic/anaerobic respiration,
fermentation
Anaerobic respiration, fermentation
Fermentation
Adapted from Brock, 10th Ed.
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Floc-Forming Bacterial Species
 Pseudomonas
 Bacillus
 Flavobacterium
 Alcaligenes
 Achromobacter
 Micrococcus
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Electron Photo of a “Floccy” Floc
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Electron Photo of a Filamentous Floc
a.k.a “The Sponge”
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Filamentous Bacterial Species
Sphaerotilus natans
Beggiatoa
Haliscomenobacter hydrossis
Microthrix parvicella
Nocardia-forms
Nostocoida limicola
Thiothrix
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Common Eikelboom “Type” Filaments
0041
0914
0092
0961
021N
1701
0675
1851
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Filament Growth Environments
Low DO
Septic/Sulfide
Organic loading rate and biodegradability
pH
Nutrient deficiency
Completely mixed, continuously fed
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F/M vs. Protozoa/Metazoa
Populations
Range
Metazoa
Shelled Am.
Carnivores
Stalks
Crawlers
Free-Swim.
Flagellates
Amoeba
Most
Common
0
.1
.2
.3
.4
F/M lb BOD/lb MLSS
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.5
.6
(Eikelboom, 2000)
Elements of Control
Environmental Factors
 Physical
 Controlled
 Chemical
 Uncontrolled
 Biological
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Physical Factors
Temperature
Mixing
DO
Hydraulics
Detention time
Mixing
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Chemical Factors
 BOD
 Form of food
 Availability of food
 Basic water chemistry
 pH
 Generally between 7.0 and 7.5
 Alkalinity
 Nitrification requirement
 Nutrients
 Toxins
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Biological Factors
Terminal electron acceptor
Aerobic
Anoxic
Anaerobic
Sludge age
Mean cell residence time (MCRT)
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Energy Production/Utilization
Bacteria
Organic
Matter
Electrons
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Final Electron Acceptors
 O2
– aerobic
 NO3- – anoxic
 SO42- – anaerobic
 CO32- – anaerobic
 Organic compounds
 Fermentation
 Alcohols
 Acids
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Energy Distribution
 Aerobic
 Anaerobic
 33%  Heat
 4.6% heat
 67% maintenance & growth
 95.4% maintenance & growth
 Maintenance
 50% high load
 Maintenance
 88.5%
 70% low load
 Growth
 50% high load
 30% low load
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 Growth
 6.9%
Food to Microorganism Ratio
F/M or F:M
lb BOD removed per lb MLVSS in system
Basis
System F/M – 24 hour period
Instantaneous F/M – Right now
 Highest at head of tank, gets smaller down the tank
Related to MCRT
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Bacterial Growth Curve
Declining Growth
Stationary
Heterotrophic Growth Curve
Log #
Viable
Organisms
Lag
Accelerated Growth
Autotrophic Growth Curve
Time
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# Viable Microorganisms
Active Microorganism Numbers
Log growth
phase
Declining
growth phase
Endogenous phase
Time or Distance Down the Aeration Tank
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Changing F/M
Q
RAS
M
F/M
F
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# Active Microorganisms
Growth Curve with Feed
Raw waste
Raw waste
Return to Aeration Tank
Length of Aeration Tank
Aeration period
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Numbers of microorganisms
Primary and Secondary Growth
Primary predominance
Secondary predominance
Secondary organisms feed
upon cell-lysis products,
primarily protein
Time
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Soluble BOD vs. Time
B.O.D. determined on settled supernatant
5-day B.O.D.
Biosorption zone
Aeration period
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Primary and Secondary Organisms
Primary
Carbohydrates
Metabolized by many different genera
Organic acids, aldehydes, ketones, alcohols
Pseudomonas
Micrococcus
Bacillus
Achromobacter
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Primary and Secondary Organisms
Secondary
Proteins
Lysis of bacterial cells
Cell contents primarily protein
Alcaligenes
Flavobacterium
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Measures of Metabolism
Direct growth methods
Micro-counting
Particle counting
Indirect methods
SOUR/Respiration Rate
ORP
Direct biochemical methods
NADH
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Oxygen utilization
SOUR vs. A-Tank Length
Distance along aeration tank
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Questions