A TRUE MICROBIOLOGICAL ZOO
Microorganisms are a natural asset to the health of any community.
They are
necessary for our physical health, in the synthesis of products such as acetone, glycerin,
organic acids, enzymes, alcohols and they are used in the manufacture of many drugs.
Even our food industry relies on microorganisms to help produce vinegar, sauerkraut,
pickles, alcoholic beverages, buttermilk, cheeses, yogurt and bread. From the point of
view of disposal of wastes, microorganisms are essential.
Likewise, operators of water and wastewater treatment facilities are also essential
to the health of any community. His highly under rated role is more than a “man with a
plunger”.
Wastewater treatment is a sophisticated, scientific process that requires
technical knowledge and skill. As I applaud the microorganisms that are responsible for
keeping us from drinking and swimming in our own wastes, I also applaud the operators
that tend to their needs and who know that if you treat the microorganisms right, they
will treat the water right!
Why microbiology? Wastewater treatment is a biological process! A wastewater
treatment plant is a microbiological zoo, so to speak where you house bacteria, protozoa,
metazoans and other microlife. The microorganisms do the actual breakdown and removal
of nutrients and organic material in the wastewater. They are a lot like you and I. We
perform our best when all our needs are met (food, pleasant environment etc.) and it is
the same for the microorganisms.
It is the task of the treatment system operator to provide a favorable
environment for the microorganisms; to provide for a “happy” home.
win/win partnership.
It is actually a
The treatment system provides the “food” and the favorable
environment and the microorganisms do the work of removing nutrients and providing
wastewater treatment.
Wastewater is generated from many different sources. Volumes of wastewater,
termed sewage, are generated each time it rains, or when we flush a toilet, take a shower
or wash dishes – anytime water is used. You can even predict commercial breaks during a
Super Bowl game. The sewage flow increases dramatically when everyone rushes to the
bathroom. Each day, the amount of wastewater generated can range from thousands of
gallons in a small community to billions of gallons in a large city. This sewage represents
thousands of tons of organic matter.
Where does all this water go?
Allowing this
untreated discharge that is rich in organic nutrients and rich in microorganisms, to enter
nearby lakes and streams would cause an overgrowth of algae and other aquatic
vegetation and a subsequent loss of oxygen resulting in massive fish kills.
Instead,
sewage is routed through wastewater treatment facilities where undesirable materials
and harmful microorganisms are removed.
Wastewater reclamation plants (WRPs) are designed to allow the natural process
of the breakdown of pollution to occur under controlled conditions.
These systems
include physical and chemical processes to remove solids and heavier materials such as
sticks, cans paper and trash. However, left behind is the liquid containing soluble and
insoluble organic material. The one process all WRPs have in common is the biological
treatment of this organic material or “nutrients”. That is, they rely on the use of certain
microorganisms to convert these organic nutrients into materials that are beneficial for
the environment. WRPs are designed to “house” these microorganisms and bring them in
contact with the organic nutrients in sewage. Sewage contains nutrients of every type;
phosphorus, nitrogen, sodium, potassium, iron, calcium and compounds such as fats, sugars
and proteins. Microorganisms use these substances as a “food” source for energy, for
the synthesis of cell components and to maintain life processes. The health and wellbeing of these microorganisms is critical to the adequate treatment of sewage.
As environmental regulations become more and more strict, eliminating many of the
currently used chemical treatment processes, it will become vitally important that WRP
operators are knowledgeable and are trained to maintain an environment within the
wastewater treatment system that will encourage the growth of the microorganisms best
suited to treat the water.
Many types of microorganisms can be found in the WRP
however, the types of organisms that will dominate will be the ones that are best suited
to the “environment” or conditions in the system.
WRPs are designed to foster an
“environment” that suit a certain type of microorganism. These microorganisms not only
remove organic wastes from the water, but they also “settle out” as solid material for
easy removal. WRP operators are required to maintain the right conditions in the
treatment system for the right type of microorganisms. If the right conditions are not
present, then the wrong microorganisms will dominate. These “wrong” microorganisms not
only interfere with the successful removal of wastes from the water, but they
themselves may be difficult to remove from the system.
A rich microlife exists in the WRP. Millions of millions of microorganisms enter the
facility in the raw wastewater each day.
microbiological process!
The wastewater treatment process is a
These systems are designed to create an environment for
microorganisms that remove the organic pollutants from the wastewater.
There are
several different types of microorganisms that are common in the treatment systems:
Bacteria, Protozoa and Metazoa.
BACTERIA
Ninety-five
percent
of
the
microorganisms are bacteria. Bacteria are
single-celled
microorganisms
primarily
responsible for removing the organic
pollutants from the wastewater.
WRPs
are
designed
to
favor
“floc-
forming” bacteria that have the ability to remove organic pollutants and aggregate
together to form solid masses called “floc” that separates from the liquid and form the
Biosolids.
PROTOZOA
About 4% of the microorganisms in the WRP are protozoa. While bacteria do most of the
work of removing organic pollutants, the primary role of Protozoa is to remove freeswimming bacteria that do not have the ability to form floc and settle with the solids.
They help clean the water by feeding on bacteria and organic particulates in the effluent.
There are 3 major types of protozoa that are commonly present: Amoebae, Flagellates
and Ciliates.
Amoebae
Amoebae feed on organic particulates in the
wastewater.
They are rarely present in high
numbers in the WRP.
Increased numbers of
amoebae often occurs after heavy rains and
runoff wash large amounts of organic particulates
into the WRP.
Increased numbers of Amoebae
can be used as an indication of treatment system
performance problems such as low oxygen or insufficient treatment time.
Flagellates
Flagellates assist the bacteria in removing
organic pollutants from the wastewater.
Like
amoebae, they are rarely present in high
numbers. Increased numbers of flagellates can
also be used as an indication of treatment
system
performance
problems.
Increased
numbers of flagellates can indicate toxic
conditions or insufficient treatment time.
Ciliates
The primary role of ciliates is to clarify the effluent by feeding on free bacteria in
wastewater. There are 3 major groups of ciliates that are commonly found in the WRPs;
free-swimming ciliates, crawling ciliates and sessile (stalked) ciliates.
Free-swimming ciliates
Free-swimming ciliates move rapidly throughout
the wastewater feeding on bacteria.
They
contribute to effluent clarity by feeding on the
free bacteria in the water.
A high number of
free-swimming ciliates is common the WRPs. This
is generally an indication the most of the organic
pollutants have been removed by the bacteria
which are now available for feeding.
Crawling ciliates
Crawling ciliates do not have the
ability to swim. Instead they walk
along floc solids and graze on
bacteria loosely attached to the
floc.
A high number of crawling
ciliates is common in well operating
systems.
Their presence indicates
that most of the organic pollutants
have been removed.
Sessile (stalked) ciliates
Sessile ciliates have a stalk that can be
anchored to solids particles. This allows
them to remain in one place while
creating a current that will bring water
into
their
zooids
(heads).
They
contribute to the clarity of the effluent
by feeding on the free bacteria in the
water. Some species can have a single
head while colonial stalked ciliates can
have hundreds of heads. These are commonly seen in high numbers in the WRPs and
indicate that most of the organic pollutants have been removed from the wastewater.
One type of sessile ciliate called
Suctoria, develops later during the
treatment process when there are
very little bacteria left to feed on.
Instead, it attaches its “suckers” to
other small protozoa, injects a poison
that paralyzes it and feeds off of it
body fluids. Rarely are these seen in
high numbers in the WRPs.
Their
presence is an indication that the
treatment process is nearly complete.
METAZOA
Bacteria and protozoa are single-celled microorganisms that multiply by dividing into two
identical cells. Metazoa are multi-cellular microorganisms that have both male and female
species that reproduce by sexual and asexual reproduction. Metazoa commonly found in
the WRPs are rotifers, nematodes and water bears.
Rotifers
Similar to Protozoa, Metazoa do
very little to remove organic
pollutants, however they also
contribute to effluent clarity by
removing bacteria, algae and
small protozoa from the water.
They are rarely seen in high
numbers except in WRPs that have a longer treatment time. Their presence indicates
sufficient treatment.
Nematodes
Nematodes are microscopic worms that are
commonly seen in the WRPs. They
contribute very little to the overall
treatment of the wastewater and are rarely
seen in high numbers in the treatment
system. They do however; serve as
indicators of a longer treatment time.
Water Bears
Water bears are often seen in the
WRPs. They are rarely seen in high
numbers because the reproduction
time is much longer than many of the
other microorganisms. They feed on
other metazoa and protozoa and
contribute very little to the overall
treatment of the wastewater. They
are generally used as an indication of longer treatment times.
WRPs are “microbiological zoos” so to speak, made up of bacteria, protozoa, metazoa that
form an effective biological system that can reduce 95 – 99% of the organic pollutants
from the wastewater.