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| There
are many bacteria that are not discovered and named. Racently,
new strains belong to CFB group were found and studied, these
strains were named Kaistella after our KAIST. |
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| Chryseobacterium
meningosepticum is an old name and now its reclassification
is required. With new techniques in molecular biology its new
naming is studied. |
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| Many
researchs were done on the Chlorella because of its
potential for nutrient and medical usage. In 1999 only 4 species
belong to the genus of Chlorella. In our lab, new Chlorella
species were isolated from sea and studied for registeration
as new species in Chlorella. |
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| Phototrophic
bacteria are known as nutrient- and drug-producers. Searching
new phototrophic bacteria is the first step for screening of
new active materials. |
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The
estimated total annual world capacity of pulp production was
261 million tonesand paper and paperboard production 196 million
tones in 1992. For each tone of manufactured pulp the wastewater
discharge volume ranges from 30 to 180 m3 while 20-70 m3 is
discharged per tone of paper and paperboard.
Conventional aerobic biological treatment employing aerated
lagoons and activated sludge processes is commonly used at
pulp and paper mills to remove biochemical oxygen demand (BOD)
from the effluents. These treatment methods remove also a
significant part of absorbable organic halogens (AOX); the
AOX removal ranging from 20 to 60% has been reported. However,
aerobic treatment generally has a poor effect on polychlorinated
compounds, because halogens deactivate the benzene ring for
electrophilic attack by oxygen.Under aerobic conditions, chlorinated
guaiacols and phenols can be O-methylated to the corresponding
anisoles and veratroles, which are more resistant to biodegradation
and have higher potential for bioaccumulation in fish. And
many volatile chloro-organic compounds, such as chloroform,
are likely to be removed from the effluent by stripping rather
than by biodegradation, resulting in an uncontrolled emission
of these compounds into the environment.
Studies on anaerobic treatment of bleaching plant effluent
have shown this treatment to have several advantages as compared
to aerobic treatment: polychlorinated chlorophenolics are
removed significantly, a higher AOX removal is achieved and
the phytotoxic chlorate eliminated. Furthermore, anaerobic
treatment should be a significantly more cost-efficient way
than aerobic treatment to remove BOD, providing that an efficient
conversion of organic matter into biogas can be maintained
in the process.
Lignin and chlorinated guaiacols are major components of the
wastewater generated during the chemical processing (pulping
and bleaching) of wood. In order to evaluate applicability
of anaerobic treatment for pulp mill effluent, inhibitory
effects of lignin and chlorinated guaiacols on the methanogenic
activity of anaerobic digester sludge were investigated. The
potentiality for anaerobic degradation of chlorinated guaiacols
wasalso evaluated. |
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Bacterial
sulfate reduction has been defined as a potentially cost-effective
process to remove metals from coal and metal-mine drainage.
Under anaerobic conditions, Sulfate-reducing bacteria (SRB)
oxidize simple organic compounds with sulfate and thereby
generate hydrogen sulfide and bicarbonate ions. Hydrogen sulfide
can effectively precipitate the heavy metals as metal sulfide.
Recently, for the economical treatment of metal-contaminated
wastewater, several researchers have investigated the use
of solid substrates as a source of alternative organic carbon
for bacterial sulfate reduction. The reactor packed with cow
manure could most effectively remove heavy metals in the treatment
of acid mine drainage.
The lab-scale upflow anaerobic bioreactor filled with granular
sludge and cow manure was operated and effectively removed
most of heavy metals in the order of Cu2+, Cd2+, Zn2+, Fe2+
and Mn2+ with respect to the height in the reactor. The solid
phase analysis showed that the heavy metals were mostly precipitated
in the form of metal sulfides by sulfate reduction. Distribution
of metal sulfide precipitates according to the height in the
reactor was directly related to the solubility products. This
property can be used to selectively precipitate and recover
the valuable metals from metal-containing wastewaters.
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Cyanide
is produced on a large scale for use in metal extraction,
electroplating, metal finishing, metal hardening and printed
circus board manufacturing industries. Over three billion
liters of cyanide-containing waste are generated annually
in coal coking, precious metals mining, and nitrile polymer
industries and over a billion tons of gold ore are leached
each year with cyanide. And in these industries, cyanide discharge
with various heavy metals and form metal cyanide complex.
But the metal cyanide complex is difficult to treat using
most widely used chemical methods such as alkaline chlorination.
In our lab, the degradation of different type cyanide in aerobic
treatment process was determined, and molecular biological
tool such as DGGE was used to compare population change with
the relation of cyanide type. The toxicity of different cyanide
type to sulfate reduction, the effective metal removal condition,
was determined and enriched metal complexed cyanide degrading
bacteria in sulfate reducing condition. Based on these results,
we will develop one aerobic-anaerobic recycling system to
treat both cyanide and heavy metals. |
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Groundwater
contamination is becoming a severe problem. Many different
hazardous pollutants are found in groundwater. Among them,
chlorinated ethylene, especially TCE, is one of the most frequently
detected volatile organic chemicals (VOCs) in groundwater
in the United States [1].
TCE is a halogenated aliphatic organic compound that, due
to its unique properties and solvent effects, has been widely
used as an ingredient in industrial cleaning solutions and
as a universal degreasing agent. It has been long thought
that TCE is resistant to degradation under aerobic conditions
because of its fully oxidized state. A number of monooxygenases
produced under aerobic conditions degrade TCE. Under these
conditions, there is no build up of the toxic compound vinyl
chloride, and complete mineralization is possible. An aromatic
compound such as To or phenol is required, however, for the
induction of the enzymes responsible. In other words, the
application of this system requires the presence of a suitable
aromatic compound or other inducer [2, 3]. Such a process
is known as cometabolism. When a chlorinated aliphatic hydrocarbon
is biodegraded via cometabolism, the degradation is catalysed
by an enzyme or cofactor that is produced by the organism
for other purposes. Usually the organism seems to receive
no known benefit from the degradation of the chlorinated aliphatic
hydrocarbon; in fact, the cometabolic degradation of the chlorinated
aliphatic hydrocarbon may be harmful to the organism [4].
Biological treatment of groundwater contaminated with chlorinated
compounds has been studied by a number of several research
groups [5, 6, 7, and 8]. They proposed a single-stage reactor
system to grow methanotrophic cells and degrade chlorinated
compounds simultaneously in one reactor; however the degradation
is negatively affected by competitive inhibition by substrates,
and product toxicity of chlorinated organics, which made low
efficiency. To avoid these problems a two-stage reactor has
been proposed to separate cell growth from chlorinated compound
degradation [9].
The objective of this research was to improve the efficiency
of chlorinated ethylene’s decomposition in real contaminated
groundwater through cometabolic treatment by using a single-
and two-stage reactor system.
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