Photo-Activated Sludge System (PAS): A
novel algal-bacterial biotreatment for
nutrient rich wastewater
PhD candidate:
Angélica María Rada, MSc.
Delft, April 2015
OUTLINE
• Background and
problem statement
• Objectives
• Experimental Setup
• Results & discussion
• Conclusions
• Future works
Background & problem statement
CO2
Organic
matter
Light
Bacterial Oxidation
(OHO)
NH3
Nitrification
(AOO, NOO)
NO3-
Microalgal
photosynthesis
(PHO)
Biomass
Advantages:
•High effluent quality
•Low energy consumption
•Small areal footprint
•Technically easy to operate
P
O2
Energy intensive
activated sludge
process
Low energy
demanding algaebased natural
processes
1. Exchange of carbon dioxide and oxygen.
3. Negative effect of the algae in the microbial
growth.
4. Alterations of pH in the culture medium.
5. Exudates from the algae used as source of
carbon to the bacteria.
Photo
Activated
Sludge
System
Objectives
Main Objective
The main objective of the present research is to maximize the efficiency of the PhotoActivated Sludge System for the treatment of wastewater rich in nutrients, while
achieving a valuable recovery of biomass.
1. Key kinetics parameters.
Determination of the kinetics of the microalgae-bacteria
2. Optimal conditions of the key parameters (pH, SRT, HRT).
consortia and the differences with the known kinetics of
3. Nutrient removal mechanisms.
solely cultures of algae and bacteria.
4.Mathematical Model
Experimental Setup
Inoculums
Starting Phase – Inoculation
REACTOR 2
REACTOR 1
Medium: BG – 11
1.
Volume = 4 L
2.
N-NH4+/L = 35 mg/l
3.
PO43- = 10 mg/L
4.
Control of pH with buffer (pH 7.5)
5.
Temperature 25℃
Irradiance =1000 µmol/m2/s
1.
2.
3.
4.
5.
Scenedesmus quadricauda (10 ml)
Chlorella sp (10 ml)
Anabaena variabilis (10 ml)
Chlorococcus sp (10 ml)
Spirulina sp (10 ml)
1. Scenedesmus quadricauda
2. Chlorella sp
50 ml of Activated Sludge
3. Anabaena variabilis
(Harnaschpolder
Wastewater Treatment
4. Chlorococcus sp
Plant)
5. Spirulina sp
6. Activated Sludge bacteria
Flat Reactor
Scenedesmus quadricauda (10 ml)
Flat Panel 1
Chlorella sp (10 ml)
Anabaena variabilis (10 ml)
Chlorococcus sp (10 ml)
Flat Panel 2
Spirulina sp (10 ml)
REACTOR 3
Flat Panel 3
0.25x0.2x0.1 m for a total 1.
working
volume
Chlorella
sp (50of
ml)5 L
Flat Panel 4
Microbial communities
Mixture of algae strains
+ enriched culture of
nitrifiers
Mixture of algae strains
+ Nitrification inhibitor
Chlorella vulgaris +
Nitrification inhibitor
Activated Sludge
bacteria
Experimental Setup
Operation Periods
P
0
1
2
3
4
5
NH4-N
concentration
12.5 ((NH4)2SO4)
27.4 ((NH4)2SO4)
407.4 ((NH4)2SO4)
258.4 ((NH4)2SO4)
271.8 (NH4Cl)
294.7 (NH4Cl)
Operation
scheme
Batch
SBR
SBR
SBR
SBR
SBR
HRT
3
8
8
8
4
2
NH4-N loading rate
Operation time
(mg NH4-N /l/d)
4.1
3 days
3.4
5 days
50.9
7 days
32.3
11 days
67.9
18 days
147.3
131 days
Operation Scheme
Influent 1 (1L)
Duration: 15 min
Hour 12.15 pm
Start effluent
discharge (2L)
Duration: 15 min
Hour: 12.00 pm
Influent 2 (1L)
Duration: 15 min
Hour 12.00 am
Start settling
Stirrers turn off
Duration: 30 min
Hour: 11.30 pm
Results & Discussion - N compounds
1. Nitrogen compounds concentration
1.1 Nitrogen concentrations along the periods for R1: Microalgae-bacteria consortia
Reactor 1 - Microalgae-bacteria consortia
475
P1
450
P2
P3
P4
P5a
P5b
425
375
350
325
Increase of
Alkalinity (171d)
300
275
250
225
200
175
150
125
100
75
50
25
EFF - NH4
EFF-NO2
EFF-NO3
INF
195
190
180
185
175
170
165
160
155
150
145
140
135
130
125
120
115
110
105
95
100
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
5
Day
10
0
0
N-compounds concentration (mg/L)
400
Results & Discussion - N compounds
1. Nitrogen compounds concentration
1.2 Nitrogen concentrations along the periods for R2: Microalgae consortia
Reactor 2 - Microalgae consortia
475
P1
450
P2
P3
P4
P5a
P5b
425
375
350
Increase of
Alkalinity (171d)
325
300
275
250
225
200
ATTU
addition
(184d)
175
150
125
100
75
50
25
EFF - NH4
EFF-NO2
EFF-NO3
INF
195
190
185
180
175
170
165
160
155
150
145
140
135
130
125
120
115
110
105
95
100
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
5
Day
10
0
0
N-compounds concentration (mg/L)
400
Results & Discussion - N compounds
1. Nitrogen compounds concentration
1.3 Nitrogen concentrations along the periods for R: Cholerra Vulgaris
Reactor 3 - Chlorella Vulgaris
475
P1
450
P2
P3
P4
P5a
P5b
425
375
350
Increase of
Alkalinity (171d)
325
300
275
250
225
200
175
150
125
100
75
ATTU
addition
(184d)
50
25
EFF - NH4
EFF-NO2
EFF-NO3
INF
195
190
185
180
170
175
165
160
155
150
145
140
135
130
125
120
115
110
105
95
100
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
5
Day
10
0
0
N-compounds concentration (mg/L)
400
Results & Discussion - N compounds
1. 2 Ammonium removal rate for microalgae and nitrifiers
Ammonium
removal rate
- Reactor
2
3
Reactor
1 - Ammonium
removal
rate
140
P1
P1
P2
P3
P4
130
P5b
Ammonium Removal algae
Periods
mgFSA-N/L/d
R1
R2
R3
64.6
64.0 64.2
4
30.0
32.5 34.0
5a
41.9
40.1 47.6
5b
120
110
100
90
80
70
60
Ammonium Removal bacteria
mgFSA-N/L/d
Increase of
R1 Alkalinity
R2
R3
(171d)
0.84
--3.21
--32.14
---
Microalgae-Bacteria allows us to have higher ammonium conversion rates!!!
50
40
30
ATTU
addition
ATTU
(184d)
Increase of addition
Alkalinity (171d)(184d)
20
10
Ammonium removal rate - algae
Ammonium removal rate - nitrifiers
195
190
185
180
175
170
165
160
155
150
145
140
135
130
125
120
115
110
105
95
100
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
5
Day
10
0
0
Ammonium removal rate (mgNH 4-N/L/d)
Ammonium removal rate (mgNH 4-N/L/d)
P5a
Results & Discussion - N compounds
1. 2 Suspended solids
ReactorReactor
Reactor
1 - Microalgae-bacteria
Microalgae
consortia
consortia
32--Chlorella
Vulgaris
5.5
P1P1
P4 P4P4
P2P2
P2 P3 P3
P3
P5a
P5a
P5b
5.0
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
TSS - R3
R1
R2
VSS - R3
R1
R2
165
160
155
150
140
145
135
130
125
120
115
110
105
95
100
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
5
Day
10
0.0
0
Solids concentrations (g/L)
4.5
Results & Discussion - N compounds
1. 2 Suspended solids
ReactorReactor
Reactor
1 - Microalgae-bacteria
Microalgae
consortia
consortia
32--Chlorella
Vulgaris
5.5
P1P1
P4 P4P4
P2P2
P2 P3 P3
P3
P5a
P5a
P5b
Period
5.0
3
4
5a
5b
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
TSS - R3
R1
R2
VSS - R3
R1
R2
165
160
155
150
140
145
135
130
125
120
115
110
105
95
100
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
5
Day
10
0.0
0
Solids concentrations (g/L)
4.5
R2
R3
g/m2/d
22.75
13.50
20.06
36.33
g/m2/d
12.19
26.50
32.36
58.17
Results & Discussion - N compounds
3. Nitrogen removal rates and biomass growth rate of algae and Nitrifiers
3.1 Nitrogen removal rates and biomass growth rate of Nitrifiers
Period
Ammonium
loading rate
HRT
4
5a
5b
mgFSA/L/d
67.9
149.7
142.8
1/d
4
2
2
Based on
Rxbacteria
substrate
Rs bacteria
µ
µmax
mgVSS/L/d mgFSA-N/L/d 1/d
1/d
0.07
0.84
1.94 1.99
0.55
3.21
0.94 0.95
28.34
32.14
0.19 0.19
Measured
2.0
Max specific growth rate of nitrifiers
1.5
y = 2.6538x + 1.0873
R² = 0.9997
2.5
1.0
0.5
0.0
1.5
-0.5
1.0
-1.5
-1.0
-2.0
0.5
-2.5
-3.0
0.0
0
10
20
30
Ammonium loading rate (mgFSA-N/L/d)
40
-3.5
-1.6
-1.4
-1.2
-1.0
-0.8 -0.6 -0.4
Log (1/Rsb)
-0.2
0.0
0.2
Log (µm/Y)
µmax
2.0
Results & Discussion - N compounds
3. Nitrogen removal rates and biomass growth rate of algae and Nitrifiers
3.2 Nitrogen removal rates and biomass growth rate of algae
Periods
3
4
5a
5b
Periods
3
4
5a
5b
Periods
3
4
5a
5b
Ammonium
loading rate
mgFSA/L/d
32.3
67.9
149.7
142.8
Ammonium
loading rate
mgFSA/L/d
32.3
67.9
149.7
142.8
Ammonium
loading rate
mgFSA/L/d
32.3
67.9
149.7
142.8
Reactor 1 - ALGAE
HRT
1/d
8
4
2
2
VSS
Rxalgae
gVSS/L mgVSS/L/d
1.6
1639.7
0.5
478.2
0.5
534.8
2.1
2085.0
Measured
Rs algae
mgFSA/L/d
29.5
64.6
30.0
41.9
Based on substrate
µ
µmax
1/d
1/d
0.19
0.19
1.47
1.47
0.61
0.61
0.22
0.22
Reactor 2 - ALGAE
HRT
1/d
8
4
2
2
Measured Based on substrate
Rs algae
µ
µmax
gVSS/L mgVSS/L/d mgFSA-N/L/d
1/d
1/d
1.8
227.5
29.7
0.18
0.18
0.5
135.0
64.0
1.28
1.28
0.4
178.2
32.5
0.99
0.99
0.7
357.2
40.1
0.61
0.61
VSS
Rxalgae
Reactor 3 - ALGAE
HRT
1/d
8
4
2
2
Measured Based on substrate
Rs algae
µ
µmax
gVSS/L mgVSS/L/d mgFSA-N/L/d
1/d
1/d
0.9
109.4
29.8
0.37
0.37
0.5
131.5
64.2
1.32
1.32
0.3
161.4
34.0
1.14
1.14
0.8
391.7
47.6
0.66
0.66
VSS
Rxalgae
Results & Discussion - N compounds
3. Nitrogen removal rates and biomass growth rate of algae and Nitrifiers
3.2 Nitrogen removal rates and biomass growth rate of algae
1.4
1.2
R1
0.8
R2
0.6
R3
0.4
0.2
0.0
0
25
50
75
100
125
Ammonium loading rate (mgFSA-N/L/d)
Ammonium conversion rate (mg
mgFSA-N/L/d)
µmax
1.0
150
175
Algae ammonium converstion rate
(mgFSA-N/L/d)
Specific growth rate - algae
1.6
70
Algae ammonium conversion rate per
biomass concentration
Rsalgae R1
Rsalgae R2
Rsalgae R3
60
50
40
30
20
10
0
0
1000
2000
Net ammonium conversion rate per
biomass concentration
80
70
60
Rs R1
50
40
30
20
10
0
0
3000
Biomass concentration (mgVSS/L)
1000
2000
3000
Biomass concentration (mgVSS/L)
4000
4000
Conclusions
• Coupling bacteria with algae process increase the efficiency of
ammonium removal without external aeration
• Ammonium removal rates of 70 mg/L/d by algae and bacteria at
HRT of days
• Higher ammonium removal at higher solid concentrations (3 g/L)
• Reduction in the specific growth rate of alga and nitrifiers when in a
microalge-bacteria system
• The algae biomass has presented tolerance at high concentration of
NO2-N
Challenges!!!
1. More accurate and precise determination of the
kinetic parameters
2. More accurate determination of algae biomass
and bacterial biomass
3. Modelling of the Microalgae –bacteria system
THANKS FOR YOUR
ATTENTION!
1