Transcript Mass Balance and Boundary Condition Equations of the Fixed

PERFORMANCE OF A GRANULAR
ACTIVATED CARBON BIOFILTER IN
LOW STRENGTH WASTEWATER
TREATMENT
D. S. Chaudhary, H. H. Ngo and S. Vigneswaran
Environmental Engineering Group,
E. E. R & D Laboratory, Faculty of Engineering,
City Campus, Building 2, Level 6, University of Technology, Sydney,
P. O. Box 123, Broadway, NSW 2007, Australia
INTRODUCTION
 Any conventional filter with attached
biomass growth on the filter media is
known as BIOFILTER.
 Biofilter can be used in both Water and
Wastewater Treatment efficiently.
 GAC biofilter is often used in tertiary
wastewater wastewater treatment and
water treatment.
INTRODUCTION Contd……
 Biofilter is the only economical
biological treatment option in the tertiary
wastewater treatment.
 Biofilter is also economical and
environmentally friendly solution in
treating wastewater of relatively small
volume e.g. from hotel or small
communities.
INTRODUCTION Contd……
 In tertiary wastewater treatment, biofilter
can remove nutrients and dissolved
organic substances and produces
effluent of high quality for reuse purpose.
 In water treatment, it can remove
pollutants such as biodegradable and
synthetic organic materials that procure
odor and taste and cause microbial
regrowth in water distribution pipelines.
Constituents of the Wastewater Used
Compounds
Weight
(mg/L)
MnSO4
0.125
CaCl2
0.925
NaHCO3
0.875
NaCl
2.500
MgSO4.7H2O 3.750
Compounds
Weight
(mg/L)
KH2PO4
1.25
NH2.NH2.H2SO4 3.50
Glucose
16.50
Yeast Extract
1.75
Peptone
1.75
Materials and Methods
 Filter column of diameter 2 cm and
height 50 cm was employed
 The column had ports for influent feed,
effluent collection and backwashing.
 The column was packed with 5 g of
GAC (bed depth 4 = cm, porosity =
0.65, particle surface area = 1104 m2/g,
effective particle size = 0.55 - 0.75 mm)
Schematic Diagram of the experimental Set-up
For the Biofilter
Constant Head Overhead Tank
Influent Feed
Overflow Line
Port with Valve
Filter Column
(dia. 2 cm)
Valve
P
Stock Solution of
Synthetic Wastewater
Backwash Water out
Biomass attached on
GAC Pellet
Valve
Stainless Steel Mesh
Pump
Backwash Water in
Effluent out
Valve
Material and methods contd.…….
 Constant pressure head was
maintained to keep a constant filtration
rate of 1 m/h.
 The filter was backwashed at 30% bed
expansion for approximately 5 minutes
every 24 hours of filter run.
 Total organic carbon (TOC) was
measured using UV-persulphate TOC
analyser (Dohrmann, Phoenix 8000).
Material and methods contd.……
 Total adsorbed biomass as dry weight
was calculated every week.
 The synthetic wastewater was prepared
everyday and the filtration was run
continuously for 77 days.
Results and Discussion
 TOC contribution of Glucose, Peptone
and Yeast extract with inorganic
compounds was 79%, 11% and 10%
respectively.
 Biodegradation of organic substances
suggested that fresh synthetic
wastewater solution need to be
prepared everyday for filter influent.
TOC (mg/L)
Biodegradation of Organics of Synthetic
Wastewater Used
4.5
4
3.5
3
2.5
2
1.5
1
-0.0164x
y = 4.09e
2
R = 0.9844
0
5
10
15
20
Time (hr)
25
30
Performance of the GAC Biofilter
(Average influent TOC = 3.5 mg/L, Bed depth = 4 cm, Filtration rate = 1 m/h)
T O C ( m g /L )
6
E f f l u en t
I n f l u en t
4
2
0
0
10
20
30
40
T im e ( d a y s)
50
60
70
80
Biomass Growth in the GAC Biofilter
Biomass (g/g of GAC)
(Average influent TOC = 3.5 mg/L, GAC = 5 g, Filtration rate = 1 m/h)
0.1
0.05
0
0
10
20
30
40 50 60
Time (days)
70
80
90
Results and discussions contd.…….
 Minimum biomass of 0.036 g per g of
GAC was observed after 63 days of
continuous operation.
 Another set of operation conducted at 2.5
m/h filtration rate showed a biomass
growth of 0.1 g per g of GAC in 30 days.
 The decrease in biomass during 7th to
9th week of operation may be due to dieoff of microorganisms and its subsequent
removal in backwashing
Effect of Filtration Rate on the Performance
the GAC Biofilter
C/Co (in terms of TOC)
(Acclimatization period = 77 days, GAC = 5 g, average influent
TOC = 3.5 mg/L)
1
0.5
1 m/h
5 m/h
10 m/h
0
0
1
2
3
4
Time (Hours)
5
6
7
Effect of Influent Organic Concentration on the
Performance the GAC Biofilter
C/Co (in terms of TOC)
(Acclimatization period = 77 days, GAC = 5 g, Filtration rate = 1 m/h)
0.6
0.3
TOC = 3.45mg/L
TOC = 6.80 mg/L
TOC = 11.22 mg/L
0
0
1
2
3
4
Time (Hours)
5
6
7
CONCLUSIONS
 GAC biofilter can effectively be used to
produce better quality of effluent for
wastewater reuse purpose.
 The biological activity led to consistent
organic removal efficiency over a long
period of time.
 The daily backwash adopted did not seem
to affect the biological mass growth thus
effluent quality.
Conclusions contd.……
 Further works on the different concentration
and composition of attached biomass are
necessary for correct evaluation of the
biofilter.
 Further works with real wastewater are also
necessary for its practical application in the
field.
 A correct choice of filtration rate and filter
bed depth is necessary for long-term
operation with consistent and superior
effluent quality.