Particulates and bacteria removal by ceramic microfiltration, UV photolysis, and their combination


Aidan, A.; Mehrvar, M.; Ibrahim, T.Hassan.; Nenov, V.

Journal of Environmental Science and Health. Part A, Toxic/Hazardous Substances and Environmental Engineering 42(7): 895-901

2007


Membrane microfiltration (MF) or ultrafiltration (UF) systems of activated sludge is crucial part of a bioreactor process used in municipal wastewater treatment. In this study, both cylindrical and. at sheet ceramic membranes were used to treat municipal wastewaters. The effects of removing water turbidity and coliform bacteria from an artificial wastewater were studied by performing batch experiments by MF and ultraviolet (UV) photolysis of 254 nm wavelength. It was shown that the microfiltration had a high effect of suspended solid removal. However, the effect of bacteria removal was limited so that the rate of cfu removal was approximately 61%. Combined consecutive processes in the treatment (MF/UV and UV/MF) confirmed that a specific porosity of the ceramic filter for bacteria removal was required. The continuous membrane bioreactor (MBR) tests performed by using a MF membrane with the pore size of 0.2 mu m showed that particulate matter and microorganisms found in municipal wastewater could be effectively removed. Turbidity was decreased from 4.50 to 0.05 NTU, with a removal efficiency of greater than 98%. The permeate total suspended solid (TSS) content for the whole run was below 5 mgL(-1). The density of total coliforms was decreased more than four orders of magnitude (from around 1 x 10(5) mL(-1) to less than 5 mL(-1) in the effluent).

Journal
of
Environmental
Science
and
Health
Part
A
(2007)
42,
895-901
Copyright
©
Taylor
&
Francis
Group,
LLC
ISSN:
1093-4529
(Print);
1532-4117
(Online)
DOI:
10.1080/10934520701369941
0
Taylor
&Francis
Taylor
&Francis
Group
Particulates
and
bacteria
removal
by
ceramic
microfiltration,
UV
photolysis,
and
their
combination
AHMED
AIDAN
1
,
MEHRAB
MEHRVAR
2
*,
TALEB
HASSAN
IBRAHIM
1
,
and
VALENTIN
NENOV
3
1
Department
of
Chemical
Engineering,
American
University
of
Sharjah, Sharjah,
United
Arab
Emirates
2
Department
of
Chemical
Engineering,
Ryerson
University,
Toronto,
Ontario,
Canada
M5B
2K3
3
Department
of
Water
Treatment
Technology,
Bourgas
University,
Bourgas
8010,
Bulgaria
Membrane
microfiltration
(MF)
or
ultrafiltration
(UF)
systems
of
activated
sludge
is
crucial
part
of
a
bioreactor
process
used
in
municipal
wastewater
treatment.
In
this
study,
both
cylindrical
and
flat
sheet
ceramic
membranes
were
used
to
treat
municipal
wastewaters.
The
effects
of
removing
water
turbidity
and
coliform
bacteria
from
an
artificial
wastewater
were
studied
by
performing
batch
experiments
by
MF
and
ultraviolet
(UV)
photolysis
of
254
nm
wavelength.
It
was
shown
that
the
microfiltration
had
a
high
effect
of
suspended
solid
removal.
However,
the
effect
of
bacteria
removal
was
limited
so
that
the
rate
of
cfu
removal
was
approximately
61%.
Combined
consecutive
processes
in
the
treatment
(MF/UV
and
UV/MF)
confirmed
that
a
specific
porosity
of
the
ceramic
filter
for
bacteria
removal
was
required.
The
continuous
membrane
bioreactor
(MBR)
tests
performed
by
using
a
MF
membrane
with
the
pore
size
of
0.2
gm
showed
that
particulate
matter
and
microorganisms
found
in
municipal
wastewater
could
be
effectively
removed.
Turbidity
was
decreased
from
4.50
to
0.05
NTU,
with
a
removal
efficiency
of
greater
than
98%.
The
permeate
total
suspended
solid
(TSS)
content
for
the
whole
run
was
below
5
mgL
-1
.
The
density
of
total
coliforms
was
decreased
more
than
four
orders
of
magnitude
(from
around
1
x10
5
mL
-1
to
less
than
5
mL
-1
in
the
effluent).
Keywords:
Membrane
bioreactors,
combined
processes,
ceramic
filters,
UV
photolysis,
municipal
wastewater.
Introduction
Currently,
treated
municipal
wastewater
is
discharged
to
the
environment
and
generally
it
is
considered
as
a
waste.
However,
municipal
wastewater
effluent
should
be
regarded
as
a
resource
from
which
high
quality
water
for
reuse
can
be
produced.
An
added
benefit
is
that
water
reuse
reduces
the
discharge
of
municipal
wastewater
to
the
environment
and,
thus,
it
offers
a
degree
of
source
water
protection.
In
recent
years,
applications
of
membrane
separation
techniques
in
wastewater
treatment
have
drawn
worldwide
attention
to
researchers
and
engineers.
The
membrane
bioreactor
(MBR)
process,
which
consists
of
an
activated
sludge
bioreactor
and
a
microfiltration
membrane,
is
an
emerging
biotreatment
technology
that
has
demonstrated
a
great
promise
in
water
reuse.
It
has
the
advantage
of
the
rapid
development
in
membrane
manufacturing
and
the
potential
to
fundamentally
advance
biological
treatment
Address
correspondence
to
Mehrab
Mehrvar,
Department
of
Chemical
Engineering,
Ryerson
University,
350
Victoria
Street,
Toronto,
Ontario,
Canada
M5B
2K3;
E-mail:
mmehrvar@
ryerson.ca
Received
October
16,
2006.
processes.
Possessing
advantages
such
as
excellent
effluent
quality,
a
high
biomass
concentration
without
any
concern
for
sludge
settling
problems,
a
simple
flow
configuration
and
small
footprint
demand,
MBRs
have
been
successfully
used
in
biological
wastewater
treatment
and
the
reclama-
tion
of
treated
effluents.
[11
For
the
treatment
of
domestic
wastewater,
a
sludge
con-
centration
from
3,000
to
10,000
mgL
-1
or
higher
in
mixed
liquor
suspended
solid
(MLSS)
can
be
maintained
in
an
MBR
with
a
hydraulic
retention
time
(HRT)
of
10-20
h.R
31
This
allows
large
macromolecules
to
be
in
contact
with
biomass
for
longer
period
than
that
within
a
conventional
activated
sludge
process
and
therefore,
this
leads
to
achieve
a
chemical
oxygen
demand
(COD)
or
a
biological
oxygen
demand
(BOD
5
)
removal
of
more
than
98%.
One
particular
element
of
interest
is
the
MBR
efficiency
for
the
removal
of
pathogens
in
the
treated
water.
The
effect
of
disinfection
can
be
reached
by
different
methods.
There
are
many
ap-
proaches
that
are
used
for
the
disinfection
of
water.
The
ad-
vantages
and
disadvantages
of
each
method
are
described
in
the
literature.N
Production
of
disinfected
water
with
con-
stant
high
quality
by
use
of
membrane
technology
is
a
good
alternative
for
the
conventional
treatment
techniques,
as
the
conventional
methods
of
water
treatment
have
their
own
896
Aidan
et
al.
limitations
in
their
ability
of
improved
quality
of
water.
[51
The
membranes
are
used
in
water
purification,
effluent
pol-
ishing,
virus
removal,
and
ultrapure
water
production.
Municipal
wastewaters
typically
contain
pathogenic
en-
teric
bacteria,
viruses,
and
intestinal
parasites.
Although
primary
and
secondary
wastewater
treatment
processes
eliminate
90-99.9%
of
enteric
microorganisms
and
tertiary
treatment,
such
as
filtration,
may
further
reduce
90-99%
of
these
microorganisms,
purified
wastewaters
may
still
con-
tain
high
microbial
numbers.[
61
If
a
more
efficient
elim-
ination
of
microorganisms
is
needed,
a
further
disinfec-
tion
must
be
performed
on
the
wastewater.
Chlorination
is
the
traditional
and
most
common
wastewater
disinfec-
tion
method
used
worldwide.
It
is
an
efficient
disinfectant
against
many
enteric
bacteria,
but
it
has
lower
efficiency
against
bacterial
spores
and
protozoan
cysts.
[71
The
use
of chlorination
has
been
decreasing,
mainly
due
to
toxic,
mutagenic
and/or
carcinogenic
disinfection
by-products
(DBPs)
as
well
as
the
formation
of
chlorine
residuals
in
the
disinfection
process.
[8
'
91
Ultraviolet
irradiation
in
the
C-region
(UV-C),
with
the
wavelength
of
254
nm
or
less,
is
also
another
important
technique
for
water
and
wastewater
disinfection.
The
num-
ber
of
plants
using
UV
disinfection
applications
has
been
increasing
in
recent
years.
UV
disinfection
typically
elimi-
nates
enteric
bacteria,
viruses,
bacterial
spores,
and
parasite
cysts
efficiently
without
producing
DBPs
or
other
chemical
residues.P
1
The
efficiency
and
reliability
of
UV
disinfection
greatly
depend
on
the
water
quality,
placing
large
demands
on
the
upstream
treatment
processes.
[111
UV-C
photolysis
makes
changes
in
the
DNA
of
the
microorganisms,
which
results
in
their
death.
Also,
if
UV
is
in
the
presence
of
hydro-
gen
peroxide,
plenty
of
hydroxyl
radicals
will
be
generated.
Hydroxyl
radicals,
in
turn,
cause
the
degradation
and
de-
struction
of
organic
matters.
[12-191
This
study
examines
the
treatment
of
municipal
wastewa-
ter
using
a
membrane
bioreactor
(MBR)
system.
The
MBR
experiments
were
preceded
by
tests
of
comparative
disinfec-
tion
efficiencies
of
UV
and
microfiltration
(MF)
techniques.
The
effectiveness
of
microfiltration
membranes
incorpo-
rated
in
MBR
was
examined
in
terms
of
organic
matter,
nu-
trients,
and
microbial
control.
Single
processes,
such
as
UV
photolysis,
membrane
processes,
and
biological
processes,
are
not
efficient
and
also
not
cost-effective
due
to
their
limi-
tations
in
the
treatment
of
wastewater
as
well
their
high
op-
erating
and
capital
costs.
It
has
been
shown
that
combined
processes,
such
as
UV
photolysis,
chemical,
or
biological
processes,
is
more
efficient
than
single
processes
alone.
[20-241
Materials
and
methods
Experimental
setup
of
the
preliminary
tests
The
preliminary
tests
were
performed
to
compare
MF
and
UV
photolysis
effects
on
removing
water
turbidity
and
col-
iform
bacteria.
The
tests
were
performed
using
an
artificial
wastewater.
The
artificial
wastewater
was
prepared
by
dilut-
ing
1
L
of
municipal
wastewater
collected
from
the
Dubai
Municipal
Wastewater
Treatment
Site,
Dubai,
United
Arab
Emirates.
The
experiments
of
this
section
were
performed
in
9
L
of
deionized
water.
Four
capsules
of
Polyseed
(Bio-
science,
Inc.)
containing
a
mixed
culture
of
microorganisms
were
added
to
the
water
system
along
with
20
g/day
bread
and
20
g/day
sugar
as
nutrient
for
one
week.
The
wastew-
ater
characteristics
after
a
two-day
period
of
incubation
contained
190
mgL
-1
BOD
5
,
3.6
mgL
-1
dissolved
oxygen
(DO),
and
659
NTU
turbidity.
The
pH
of
the
system
was
6.9.
Throughout
the
incubation
period,
the
system
was
aer-
ated
using
an
air
diffuser.
The
treatment
schemes
performed
in
the
preliminary
tests
were
as
follows:
(i)
Scheme
1:
UV
treatment
in
batch
conditions,
(ii)
Scheme
2:
Ceramic
filtration
in
semi-batch
mode,
(iii)
Scheme
3:
Ceramic
filtration
followed
by
UV
treatment
and,
(iv)
Scheme
4:
UV
treatment
followed
by
Ceramic
filtration.
The
experimental
set
up
for
the
UV
batch
system
along
with
the
natural
circulation
and
ceramic
filtration
systems
for
the
preliminary
tests
is
illustrated
in
Figure
1.
The
batch
UV
test
was
performed
using
a
cylindrical
reactor
(80
x
450
mm)
with
effective
volume
of
2
L,
in
which
the
UV
lamp
(shell
and
tube
type)
with
the
maximum
wavelength
of
250
nm
was
immersed
in
the
center
of
the
photoreactor.
The
ceramic
fil-
ter
was
a
cylindrical
microfilter
with
the
diameter
of
2.5
cm,
surface
area
of
471.24
cm
2
,
wall
thickness
of
0.65
cm,
and
the
pore
size
of
0.8
p,m.
The
ceramic
filtration
process
was
set
up
by
connecting
the
filter
to
a
vacuum
pump.
The
pro-
cess
was
carried
out
under
vacuum
pressure
of
0.06
bar
at
almost
constant
flow
rate
varying
within
31.2-31.7
cm
3
s
-1
.
The
membrane
permeability
(P)
was
calculated
as
follows:
Flow
Rate
Pressure
x
Membrane
Area
31.7cm
3
/s
x
3600s
h
62.7mmHg
x
(2
x
7r
x
2.5
x
30)cm
2
cm
=
3.86
h.mmHg
To
regenerate
the
ceramic
filter,
a
backwash
was
applied.
The
backwash
was
performed
by
applying
compressed
air
in
the
opposite
direction
of
the
water
flow.
The
quality
of
raw
and
treated
water
was
characterized
by
measuring
BOD,
pH,
colony
forming
units
(cfu),
and
the
turbidity.
Experimental
setup
of
the
laboratory
scale
MBR
tests
A
submerged
MBR,
as
shown
in
Figure
2,
was
used
in
the
experimental
study
of
this
section.
A
ceramic
flat
sheet
membrane
module
(ItN
Nanovation
GmbH,
Germany),
with
a
frame
dimension
(L
x
W)
of
12
x
12
cm
2
,
a
pore
size
P=
Power
source
Vacuum
pump
E-1
Ceramic
filter
Wastewater
Wastewater
or
water
after
ceramic
filter
IJV
light
Treated
water
DO
%
Premeate
Feed
pH
0
0
0
0
0
°°o00
0
°8
0
8
0
0
co
co
o
0
0
0
oo
0
0
8 8
a
o
0
0
71
Air
distributor
Ceramic
microfiltration
897
Fig.
1.
Experimental
set
up
used
in
the
preliminary
tests.
Left
side:
ceramic
filtration
semi-batch
set
up
with
2
L
of
wastewater
sample.
Right
side:
UV
batch
system.
of
0.2
p,m,
and
a
total
surface
area
of
0.048
m
2
,
was
im-
mersed
inside
an
activated
sludge
bioreactor.
The
bioreac-
tor
was
made
of
acrylic
plate
with
dimensions
(L
x
W
x
H)
of
15
x
3
x
30
cm
3
,
and
had
an
effective
volume
of
1
L
with
a
water
depth
of
30
cm.
A
level
controller
was
used
to
regulate
the
feeding
pump,
whilst
the
effluent
was
width-
drawn
directly
from
the
MBR
through
the
membrane
by
a
suction
pump.
Therefore,
the
system
was
operating
in
a
continuous
mode.
A
manometer
was
mounted
between
the
membrane
module
and
the
suction
pump
to
monitor
the
trans-membrane
pressure
(TMP).
The
bioreactor
was
aerated
intermittently
to
get
cyclic
aerobic
and
anaerobic
conditions
in
the
bioreactor
to
promote
nitrification
/
den-
itrification
and
biological
dephosphatation.
The
air
was
provided
through
an
air
diffuser
at
the
bottom
of
the
re-
actor
to
generate
strong
turbulence
for
membrane
clean-
ing
through
the
aerobic
period.
For
the
experiments
using
the
flat
sheet
membrane,
seed-activated
sludge
was
col-
lected
from
the
Bourgas
Sewage
Treatment
Works,
Bour-
Membrane
filter
Fig.
2.
Membrane
bioreactor
scheme
for
the
laboratory
scale
tests.
gas,
Bulgaria,
where
the
experiments
of
this
section
were
performed,
and
placed
in
the
MBR
at
an
initial
concentra-
tion
of
1,235
mgL
-1
mixed
liquor
suspended
solid
(MLSS).
During
the
stable
operation,
the
membrane
external
fouling
was
also
observed.
During
the
laboratory-scale
MBR
operation,
the
influ-
ent
wastewater
was
a
domestic
sewage
collected
from
the
Bourgas
Sewage
Treatment
Works,
Bourgas,
Bulgaria.
The
raw
sewage
had
a
BOD
5
,
COD,
and
ammonia
nitrogen
of
approximately
150,
300,
and
12
mgL
-1
,
respectively.
Total
suspended
solids
varied
within
110-156
mgL
-1
.
The
tur-
bidity
and
total
coliform
density
were
about
4-5
NTU
and
3-4
x
10
5
mL
-1
,
respectively.
The
pH
of
the
MBR
influent
varied
from
6.5
to
7.3.
The
effluent
suction
pump
was
con-
trolled
by
a
timer
based
on
a
pre-determined
time
sequence
of
on/off
switching
to
provide
better
membrane
cleaning
with
the
aeration
and
hence,
to
minimize
the
biofouling
problem.[
251
The
general
MBR
operation
parameters
dur-
ing
its
stationary
operation
are
summarised
in
Table
1.
All
analyses
were
performed
following
Standard
Methods.
[261
Turbidity
was
monitored
by
a
turbidimeter
(LP
2000,
Hanna
Instruments).
Ammonia
nitrogen
was
analyzed
photometrically
by
nesslerization.
The
dissolved
oxygen
(DO)
was
determined
by
a
DO
probe
(RE
347
Tx
Table
1.
Operational
conditions
of
the
submerged
MBR
in
the
laboratory-scale
MBR
tests
Parameter
Value
Operation
duration
(d)
92
MLSS,
(mgL
-1
)
1235-4200
HRT
(h)
1.98-
1.66
Flux
(mL
cm
-2
h
-1
)
70-220
Organic
loading
(gCOD.g
-1
VSS.d
-1
)
0.34-1.16
NH
3
-N
loading
(g.g
-1
VSS.d
-1
)
0.016-0.054
pH
6.5-7.3
898
Aidan
et
al.
Table
2.
Quality
of
wastewater
before
and
after
treatment
by
UV
photolysis
and
cylindrical
ceramic
filter
Raw
UV
treatment
(
Scheme
1)
Ceramic
filtration
After
45th
min
After
65th
min
Parameters
wastewater
UV
treatment
UV
treatment
(Scheme
2)
Turbidity
(NTU)
659
473
452
189
Colony
forming
units/10
mL
18
3
0
7
BOD
5
(mg0
2
L
-1
)
190
180
28
meter,
EDT
Instruments).
Total
coliform
bacteria
were
enu-
merated
by
the
membrane
filtration
method,
with
Gelman
Sciences
sterilized
membrane
and
Paqua
lab
universal
in-
cubator
as
the
nutrient
medium.
Results
and
discussion
Preliminary
test
results
The
decrease
of
turbidity
and
number
of
cfu
(for
the
45th
and
65th
min)
through
the
processes
of
UV
photolytic
treat-
ment
and
microfiltration
are
summarized
in
Table
2.
The
changes
of
cfu
and
turbidity
during
the
whole
period
of
UV
treatment
are
illustrated
in
Figures
3
and
4,
respectively.
The
colony
number
was
decreased
from
the
initial
value
of
17
to
almost
zero
cfu
in
about
1
h
by
the
UV
photolysis
alone
(see
Figure
3).
In
addition,
the
turbidity
of
the
wastewa-
ter
was
decreased
from
660
to
450
NTU
after
about
1
h
using
the
UV
photolysis
alone
(see
Figure
4).
The
results
of
reduction
in
coli
forming
units
through
the
consecutive
ce-
ramic
filtration—UV
treatment
(Scheme
3)
and
the
reverse
processes
of
UV
treatment—ceramic
filtration
(Scheme
4)
are
shown
in
Table
3.
The
obtained
results
show
that
the
MF
with
the
ceramic
filter
(0.8
µm)
is
effective
in
removing
the
turbidity
due
to
the
suspended
solids.
According
to
the
data
presented
in
Table
2,
its
efficiency
is
around
71%.
Evidently,
considering
the
BOD
5
reduction
(85%),
the
ceramic
filter
removes
most
of
the
suspended
organic
matter.
However,
the
UV
treat-
ment
on
the
turbidity
was
less
effective,
29-32%,
which
is
due
to
the
lowering
of
the
biological
activity
in
the
treated
water.
Concerning
the
colony
counting
results,
obviously
the
effect
of
UV
treatment
is
a
time-dependent
process.
Figure
3
shows
that
cfu
number
approaches
zero
at
UV
treatment
time
over
60
min.
In
spite
of
the
notable
effect
of
microfiltration
for
suspended
solids
removal,
the
effect
of
bacteria
removal
(-61%)
is
hardly
acceptable.
The
com-
bined
(MF/UV
and
UV/MF)
and
the
stand-alone
MF
treatment
processes
confirm
that
specific
porosity
of
the
ce-
ramic
filter
for
bacteria
removal
is
required.
Based
on
these
preliminary
tests,
a
flat
sheet
MF
membrane
with
lower
porosity
was
used
for
further
experiments.
Laboratory-scale
MBR
results
The
submerged
MBR
for
the
treatment
of
the
contam-
inated
wastewater
was
continuously
operated
for
more
than
18
16
14
12
10
8
6
4
2
0
0
20
40
60
80
100
Time
(min)
Fig.
3.
Colony
counts
versus
time
for
the
wastewater
treatment
using
Scheme
1
(UV
batch
system
only)
in
the
preliminary
tests.
The
colonies
were
counted
in
a
10-mL
sample.
Co
lo
ny
no.
(c
fu)
Ceramic
microfiltration
899
700
600
-
500
-
5'
.
E.
400
-
z
300
-
F.
200
100
-
0
0
20
40
60
80
100
Time
(min)
Fig.
4.
Turbidity
versus
time
for
the
wastewater
treatment
using
Scheme
1
(UV
batch
system
only)
in
the
preliminary
tests.
90
days
at
different
conditions.
During
its
steady
state
operation,
the
MBR
influent
had
an
average
COD
and
NH
3
-N
concentrations
of
300
and
14
mgL
-1
,
respectively.
The
organic
content
was
monitored
by
COD
measure-
ments.
The
first
run
was
conducted
at
continuous
aeration.
The
obtained
results
through
the
first
run
in
27
days,
as
shown
in
Figure
5,
show
that
78
to
92%
of
the
organics
were
removed
by
the
MBR
treatment,
thus
reducing
the
COD
to
an
average
of
40
mg1,
-1
in
the
effluent.
The
applied
hydraulic
retention
time
(HRT)
during
this
period
of
study
was
3.2-8.1
h.
The
observed
gradual
increase
of
HRT
was
due
to
the
membrane
fouling,
which
decreases
membrane
permeability.
The
results
show
evidently
that
the
COD
removal
rates
are
not
influenced
by
the
HRT
applied.
Comparatively,
the
lower
rates
of
organic
matter
removal
were
recorded
to
be
78%
at
the
lowest
influent
COD
concentration,
namely
at
influent
COD
concentration
of
135
mgL
-1
.
During
this
run,
the
ammonia
nitrogen
influent
and
effluent
concentrations
were
observed
as
depicted
in
Figure
5.
Despite
the
fluctuation
of
NH
3
-N
concentration
Table
3.
Colony
count
results
for
Scheme
3
(ceramic
filtration
semi-batch
followed
by
UV
treatment)
and
Scheme
4
(UV
batch
followed
by
ceramic
filtration)
in
the
preliminary
tests
Time
of
UV
treatment
(min)
19.5
34.5
49.5
15
8
Scheme
4**
30
4
45
2
*The
cfu
values
for
the
ceramic
filter
influent
and
effluent
were
18
cfu/
10
mL
and
9
cfu/10
mL,
respectively.
**The
cfu
value
for
the
UV
reactor
influent
was
17
cfu/
10
mL.
in
the
MBR
influent,
the
NH
3
-N
concentration
was
usually
below
0.1
mg1,
-1
in
the
effluent.
Such
high
effect
of
nitrification
was
observed
in
another
MBR
study.
[271
The
obtained
results
in
this
study
may
be
attributed
to
the
high
solid
retention
time
(SRT)
allowing
greater
accumulation
of
nitrifying
bacteria
in
the
reactor,
thus
performing
nitrification
at
a
faster
rate.
Combined
effects
of
organic
carbon
assimilation,
nitrification,
and
bio-dephosphatation
The
second
set
of
experiments
were
conducted
in
condi-
tions
of
sequential
change
(every
two
hours)
of
DO
concen-
tration
in
the
bioreactor.
Every
two
hours,
the
air
supply
was
terminated.
A
typical
daily
change
of
dissolved
oxy-
gen
concentration
(DO)
is
depicted
in
Figure
6.
Similar
to
Run
1,
the
process
was
studied
at
different
HRT.
Within
this
run,
the
HRT
applied
was
in
the
range
of
1.98-11.66
h.
0
influent
COD
-e-
Effluent
COD
—0—
influent
NH3-N
—A—
Effluent
N113-N
0
5
10
15
20
25
30
Time
(days)
Fig.
5.
Quality
of
wastewater
before
and
after
treatment
using
flat
sheet
ceramic
membrane
for
the
laboratory
scale
membrane
bioreactor
system.
The
effluent
NH
3
-N
after
2
days
was
below
0.1
mg1,
-1
C
is
the
concentration
in
terms
of
mgL-1.
Integrated
Processes
Scheme
3*
cfu/
10
mL
1
0
0
400
350
300
250
r
200
C.
)
150
100
50
0
9
8
7
—6
cp
5
E
4
0
in
3
2
1
0
E
12
10
8
6
4
2
0
.........
A
-
A-
A..
..•-
A-
....
-
.
A
.
A
-
*
M—
NO3
influent
9—
NO3
effluent
- -
NH3-N
influent
A
NH3
-N
effluent
Aidan
et
al.
900
Influent
-
9
-
Effluent
0
5
10
Time
(days)
15
20
9
10
11
12
13
14
15
Time
(h)
16
17
18
Fig.
8.
Phosphate
changes
as
a
function
of
time
using
flat
sheet
ceramic
membrane
for
the
laboratory
scale
membrane
bioreactor
system.
P
is
the
phosphate
concentration
in
terms
of
mgL
-1
.
Fig.
6.
A
typical
dissolved
oxygen
(DO)
concentration
strategy
in
the
flat
sheet
ceramic
membrane
bioreactor
for
the
laboratory
scale
membrane
bioreactor
system.
The
effects
of
continuous
membrane
fouling
resulted
in
an
increase
of
HRT
applied.
The
obtained
results
show
that
during
the
entire
period
of
the
run,
the
efficiency
related
to
the
COD
removal
was
above
84%.
The
highest
recorded
rate
of
COD
removal
was
90%.
It
was
confirmed
that
the
changes
of
HRT
do
not
have
influence
on
COD
removal.
During
the
second
run,
the
effect
of
nitrogen
removal
was
also
monitored.
As
Figure
7
shows,
ammonia
was
oxidized
to
a
high
extent
so
that
its
effluent
concentration
was
lower
than
0.1
mgL
-1
.
Nitrogen
in
different
forms
was
balanced
reasonably
well
with
most
of
the
ammonia
being
converted
to
nitrate
and
subsequently
denitrified
to
free
nitrogen
(81-
83%).
The
residual
nitrite
was
always
lower
than
200
AgL
-1
.
Nitrite
accumulation,
which
may
occur
in
the
biofiltration
process,
was
not
observed
in
the
MBR
treatment.
The
mon-
itoring
of
effluent
phosphorous
content
also
showed
an
un-
expected
high
effect
of
its
removal.
A
stable
effect
of
phos-
phorous
removal,
above
94%,
was
recorded,
as
depicted
in
Figure
8.
30
25
0
5
10
15
20
25
30
Time
(days)
Fig.
7.
Changes
of
NO
3
and
NH
3
-N
as
a
function
of
time
using
flat
sheet
ceramic
membrane
for
the
laboratory
scale
membrane
bioreactor
system.
C
is
the
concentration
in
terms
of
mgL
-1
.
The
sludge
concentration
in
the
MBR
was
increased
from
around
1,235
to
4,200
mgL
-1
in
MLSS,
while
the
ratio
of
volatile
suspended
solid
to
suspended
solid
(VSS/SS)
was
nearly
constant
at
0.90.
Following
the
bio-flocculation
pro-
cesses
in
MBR
and
membrane
separation,
particulate
mat-
ter
and
microorganisms
were
effectively
removed
from
the
effluent.
Turbidity
was
decreased
from
4.50
to
0.05
NTU,
with
removal
efficiency
of
greater
than
98%.
The
perme-
ate
total
suspended
solid
(TSS)
content
for
the
whole
run
was
below
5
mg1,
-1
.
The
density
of
total
coliforms
was
de-
creased
more
than
four
orders
of
magnitude
from
around
1
x
10
5
mL
-1
to
less
than
5
m1,
-1
in
the
effluent.
The
experimental
results
suggest
that
the
MBR
process
can
be
both
technically
and
economically
feasible
for
water
reuse.
Conclusions
Both
cylindrical
and
flat
sheet
ceramic
membranes
were
effective
in
obtaining
high
quality
water
from
municipal
wastewater.
This
can
help
in
the
scarce
resources
of
wa-
ter
by
water
reuse
which
will
reduce
the
discharge
of
mu-
nicipal
wastewater
to
the
environment
and
thus,
offers
a
degree
of
source
water
protection.
The
batch
comparative
studies
of
MF
and
UV
effects
on
removing
wastewater
tur-
bidity
and
coliform
bacteria
from
an
artificial
wastewater
showed
a
high
effect
of
microfiltration
for
suspended
solids
removal.
It
was
shown
that
the
effect
of
bacteria
removal
was
limited
(the
rate
of
cfu
removal
was
around
61%)
in
uti-
lizing
MF
membranes
with
pore
size
of
0.8
p,m.
The
com-
bined
treatment
processes
(MF/UV
and
UV/MF)
confirm
that
specific
porosity
of
the
ceramic
filter
for
bacteria
re-
moval
was
required.
The
continuous
MBR
tests
performed
with
flat
ceramic
MF
membrane
with
pore
size
of
0.2
p,m
showed
that
particulate
matter
and
microorganisms
of
mu-
nicipal
wastewater
could
be
effectively
removed.
Specifi-
cally,
the
removal
efficiency
with
respect
to
turbidity
was
greater
than
98%,
while
the
density
of
total
coliforms
was
decreased
more
than
4
orders
of
magnitude,
from
around
1
x
10
5
mL
-1
to
less
than
5
mL
-1
in
the
effluent.
Ceramic
microfiltration
901
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