Operation period

SO₄^-2 (mg/l)

pH

COD/SO₄^-2

Sulphate loading rate

(g/Ld)

1

150

6.5

28

0.6

2

150

7.0

28

0.6

3

150

7.5

28

0.6

4

350

7.5

12

1.4

5

350

7.0

12

1.4

6

350

6.5

12

1.4

7

600

7.5

7

2.4

8

600

7.0

7

2.4

9

600

6.5

7

2.4

10^(*)

600

6.5

7

2.4

11

900

7.5

4.7

3.6

12

900

7.0

4.7

3.6

13

900

6.5

4.7

3.6

14^(*)

900

6.5

4.7

3.6

(*) Indicates a V_S of 8.5 m/h.
For the rest of the experiments Vs was 6.5 m/h