Microalgae harvesting by bioflocculation: Small and large pond results

Comparison of performance between two 1,000-m2 and two 12-m2 ponds, operated under otherwise similar conditions except that one pond was screened to remove zooplankton and the other one was not so treated. Data averaged for July 1978. Note agreement in terms of productivity (grams VSS/m2/d, essentially some 90% AFDW algal biomass). (Source: Benemann et al. 1979.)

Pond

East 0.1 HA

M-3

12 sq m

West 0.1 HA

M-2 12 sq m

Experiment

Scr

eened

Unscr

eened

Pond Environment

Insolation,

Langleys/day

6

00

Culture Temp. ®C, AM

18

16

18

16

PM

26

26.

26

26

Culture pH

AM

9.5

8.6

9.4

8.5

PM

10.7

9.7

10.6

9.7

Sewage

COO, og/L

440

Total N, mg/L

51

loading and Pond Operation

Hydraulic d/в, cm/day

5.9

6.6

5.8

6.6

Dilution Rate (9/d) per day

0.33

0.33

0.29

0.33

Depth (d), cm

18

20

20

20

Mixing Velocity (M), an/sec

19

12

19

12

Culture Characteristics

VSS, mg/l

230

200

210

190

Chi. a, S of VSS

1.9

1.8

2.0

1.8

COO, mg/L

415

390

410

410

NHj-N, mg/L

3.5

7.3

4.6

8.7

Total N, mg/L

23

27

24

26

Production

Grams VSS/sq m/day

14

13

12

13

Photosynthetic Efficiency, *

1.4

1.3

1.1

1.3

Algae Removal Performance

Imhoff cone,’

VSS

88

90

87

87

24-hr,

r Chi. a

92

91

89

95

Removals,

COD

59

69

62

72

Table III. A.2. Productivity and settleability of microalgae in the 0.1-ha high-rate ponds.

Productivity (AFDW of suspended solids) averaged monthly. Varying hydraulic dilution rates and depths account for differences in productivities and harvestabilities between ponds. Algal biomass were estimated by microscopy at about 85% to more than 90% of AFDW productivity, the rest being waste derived solids. (Source: Benemann et al. 1979.)

Date

Se

st Pond

tast rono

Total Production g/m^/day

2A-hr

Imhoff Cone[8] X removal

Harvestable Production g/mvday

Total Production g/mZ/day

2A-hr

Imhoff Cone* X removal

Harvestable Production q/mZ/dav

Sept 78

25.5

92 1

23.5

8.0

85

6.В

Oct

25.5

89 і

і

22.7

11.3

71

8.0 .

N ov

11.6

27 !

3.1

9.8

83

8.1 I

Oec

A.7

70

3.3

6.6

6A

A.2

Jan 79

A.9

B5

A-2

A.7

56

2.6

Feb

6.A

02

5,2

9.3

7A

6.9 ■

liar

8.5

81

6.9

16.5

7A

12.2

Apr

15.8

76

12.0

16.2

53

816

Hay

20.1

88

17.7

21.3

7A

15.8

Jun

22.6

91

20.6

20.2

-91

18.A

Jul

22.0

92

20.2

35.5

89

31.6

Aug

21.7

88

19.1

35.6

9A

33.5

Sep

19.9

9A

18.7

35.5

87

30.9

Oct

16.3

8A

13.7

27.8

69

19.2

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