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REGIONAL CONTEXT
 The
Brugspruit Water Pollution Control Works is located on the Brugspruit,
a tributary of the Klipspruit, draining to the upper Olifants River. The
local area was extensively mined for coal in the early part of the 1900's.
Several thousands hectares of shallow undermined land are present in the
area. The shallow undermining has had a devastating effect on the environment
and specifically on the water environment. Acid mine drainage seeping
and flowing from the old underground workings impacts directly on the
tributaries, Klipspruit and further downstream on Loskop Dam.
The water quality in the Klipspruit has been unfit for any of the recognised
users including potable and irrigation use. No significant aquatic life
has survived the poor water quality conditions. This impact is felt far
downstream.
The Department developed a water quality management plan for the Klipspruit
catchment in 1992. The management plan proposed a combination of more
stringent pollution control at source, construction of water pollution
control works and possibly future re-mining and rehabilitation of the
old mine workings.
The Department of Water Affairs and Forestry thus assumed the responsibility
on behalf of the State to remediate and install water pollution control
works to minimise the impact on the local river system.
DESCRIPTION OF THE WATER POLLUTION CONTROL WORKS
 The
water pollution control works erected by the Department involves an extensive
acid mine drainage collection and treatment system.
The collection system includes a northern and southern collector which
run along the Brugspruit, a tributary of the Klipspruit, to intercept
and collect acid mine drainage before it enters the Brugspruit. Six collection
points were constructed along the collectors and they are located at old
seep zones, mine adits and decant points. The acid mine drainage flows
under gravity to the treatment plant. The total length of the collector
pipe system is 7,8km.
The treatment plant involves a modern lime
dosing facility, which neutralises the water and removed the bulk of the
toxic metals, specifically iron, manganese and aluminium. The treatment
process includes flow balancing, pumping, lime dosing, aeration and final
clarification.
The acid mine drainage flow is quite variable and shows a distinct seasonal
pattern. The incoming flow is balanced inlined ponds. The acid mine drainage
is then pumped to a conditioning / aeration basin, where lime is added
for neutralisation. The removal of metals requires some oxygenation of
the water. The metals precipitate to form a sludge, which is separated
from the clear treated effluent in the clarifiers. Clarifiers underflow
sludge is recycled on a continuous basis, back to the conditioning/ aeration
basin.
The final effluent is stabilised with soda ash before discharge to the
adjacent Brugspruit. The collection system and treatment plant have a
combined mine water treatment capacity of 10 000 m3/day. Allowance was
also made for the future treatment of acid mine drainage collected from
the adjacent Blesbokspruit valley.
The treatment plant sludge generated in the treatment process is discharged
into specially constructed sludge lagoons.
SLUDGE LAGOONS
 The
sludge generated in the treatment process was initially classified and
required a H:h disposal facility, because of the expected high concentrations
of heavy metals, (Specifically Zn; Mn; Al (3) and Cu).
Because of the larger size of the new sludge lagoons and the low concentrations
of heavy metals the waste sludge was reclassified / delisted to a lower
hazard rating and now requires a GB+ site with a leachate management facility.
The design for the new sludge lagoons are however similar to that of
the existing lagoons. It involves a membrane lined pond system to prevent
seepage and potential contamination of the ground water and enable the
department to monitor the quantity and quality of the leachate and leakage
accurately.
Lagoon volume = 50 000 m3; depth = 5 m and area of liner = 15 000 m2
/ dam
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