Treatment method

Acidity range (mg CaCO₃/l)

Acidity load

(kg CaCO₃/d)

Q

(l/s)

DO

(mg/l)

pH

Maximum pH attainable

Passive treatment

Aerobic wetlands

<500

≤1

Maximum permissible residence time (e.g. 1 - 5 days)

Ambient

>6

-------

Anaerobic wetlands

<500

1

Maximum permissible residence time (e.g. 1 - 5 days)

Ambient near surface and <1 mg/l below surface

>2.5

6 - 8

ALD

<500

<150

< 20

<1

>2

6 - 8

SAPS

<300

<100

< 10

<1.3

>2.5

6 - 8

Active treatment

All

1 - 10,000

1 - 50,000

No limit

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No limit

14