Environmental Engineering Reference
In-Depth Information
and in the outlet of the column reactor. In order to prevent backflow and contami-
nation, flow breakers are used between the feed line and the reactor inlet as well as
between the reactor outlet and the waste collection line. The feed is provided from
the bottom of the reactor, and effluent is collected from the top. A mixing chamber
(250 mL of volume) is located in the recycle line when needed. A mixing cham-
ber is used only when we need to achieve a high flow rate in the columns. If the
operational flow rate is small, a single pass is used. A single-pass FBCR is called a
flow-through column reactor (Fig. 1.4B).
The following protocol is used to operate FBCRs to grow biofilms:
1. Autoclave the tubings, reactor and mixing chambers.
2. Sterilize the entire system by filling it with ethanol (70% v/v) and recycling for
three hours. This is done if the filling materials do not react with alcohol.
3. Drain the reactor, and then pump 10 L of sterile deionized (DI) water through
the system to wash out the traces of alcohol.
4. Drain the reactor again and fill it with the appropriate growth medium.
5. Inoculate the reactor aseptically with 30 mL of inoculum. In the case of natu-
ral sediments, we sterilize everything except the natural sediments and we do
not inoculate, since the naturally growing bacteria will be stimulated with the
additional growth medium.
6. Operate the reactor in batch mode for at least 8 h or overnight, and then start the
flow of nutrient solution. When a single-pass reactor is used we do not run it in
batch mode. The reactor is fed with the appropriate medium all the time.
Recycle
B
A
Flow
distributor
Flow
distributor
Wast e
Effluent
Mixing
chamber
Growth
medium
Growth
medium
Glass
beads
Glass
beads
Peristaltic
pump
Peristaltic
pump
Sieves
Sieves
Flow distributor
Flow distributor
Fig. 1.4
Experimental setup (
a single column
). (
a
) A polycarbonate column filled with minerals
is operated continuously with a recycle. The recycle provides higher flow rates in the column. (
b
)
A flow through a column reactor
