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Biol Process & fluidized Bed Bio Reactor with
Intermittent
Aeration
1. Purpose
The conventional municipal sewage treatment equipment primarily
contemplates to removesuspended solids and organic substance.
However, as pollution loading increase and awareness
to environmental problems grows intense, removal of nitrogen and
phosphorus has beeninvestigated. This new process has been applied
to part of municipal sewage treatment,
particularly in closed water bodies.As such an advanced
treatment process, an activated-sludge process with recirculation
of the
nitrified mixed liquor has been put into practical use. However,
this advanced activated-sludgeprocess has disadvantages such as
long retention time and requirement to circulate a large
amount of nitrifying liquid. To solve these problems, Kobe
Steel, Ltd. offers two kinds offluidized bed type biological
treatment processes for efficient removal of organic substance
and
nitrogen as well as for ease of operation control.
2. BIOL Process
2.1 Features
1) Using inorganic immobilized carrier, microorganisms are
maintained to a high concentration,thereby enabling efficient
treatment with compact equipment.
2) Return sludge which is indispensable for the activated-sludge
process is not required andcirculation of nitrifying liquid is not
required, achieving extremely easy maintenance control.
3) Stable treated water is obtained even against shock loads
such as load fluctuation.4) Excess microorganisms spontaneously
exfoliate from the carrier and flow outside of the
system. There is no trouble caused by excessive growth of
microbial layer.
2.2 Capabilities and Operating PrincipleThe flow of the BIOL
Process is illustrated as below.
The BIOL Process floats up and suspends minute inorganic carrier
in the reaction tank byaeration or by agitator, and removes organic
substance and nitrogen in wastewater by the action
of microorganisms adhering to the media.
[Nitrification]
Nitrifying bacteria oxidizes ammonia to nitrate through the
following reactions:NH4+2O2 -> NO3-+H2O+2H+
[Denitrification]
Denitrifying bacteria reduces nitrate to nitrogen gas through
the followingreactions:
2NO3-+10H -> N2+4H2O+2OH-
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3. Fluidized Bed Bio-reactor with Intermittent Aeration
3.1 Features
1) Organic matter and nitrogen can be removed simultaneously in
one single reaction tank byintermittent aeration.
2) Return sludge which is indispensable for the activated-sludge
process is not required andcirculation of nitrifying liquid is not
required, enabling extremely easy maintenance control.
3) Using inorganic immobilized carrier, microorganisms are
maintained to a high concentration,thereby enabling efficient
treatment with compact equipment.
4) Excess microorganisms spontaneously exfoliate from the
carrier and flow outside of thesystem. There is no trouble caused
by excessive growth of microbial layer.
5) Both condensability and dewaterability of generated sludge
are far better than those of the
standard activated-sludge process.
3.2 Construction and Capabilities
The outline of reactor is illustrated as below. The process flow
is described as follows:1) Raw water is continuously injected to
the bottom of the reaction section.
2) Air is fed to the lower part of the draft tube. This
fluidizes minute inorganic carrier, bringingthe reaction tank
inside to the aerobic condition. Then, organic substance is
oxidized and
decomposes by the action of microorganisms adhering to the
media, and ammonia is nitrified atthe same time.
3) When air is stopped after specified time, dissolved oxygen in
the reaction tank is depleted,while nitrate is removed through
reduction to nitrogen gas by utilizing of organic substance in
the raw water flowing into the tank.4) Finally, at the settling
section, the carrier and treated water are separated.
