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Chemical Technology • May 2016
WATER TREATMENT
The costs of transporting water from the source to the
well site can quickly and dramatically exceed the simple
cost of obtaining the water [2].
Regulation of impacts on water quality
in South Africa
In South Africa the National Water Act, No 36 of 1998, states
in the preamble that one of the objects is: ”Recognising that
the protection of the quality of water resources is necessary
to ensure sustainability of the nation’s water resources in
the interests of all water users.” [3]
What this means is that hydraulic shale bed fracturing
becomes a water use, thus requiring a water use license.
The Act should be studied to understand the ramifica-
tions in more detail, in particular:
• Water use
• Prevention and remedying effects of pollution
• Determination of quantity of water which may be allo-
cated by the responsible authority
• Licences for use of water found underground on property
of another person
• Regulations on use of water
• Controlled activity
• Declaration of certain activities as controlled activities
• Water classification.
Water can be classified by the amount of TDS (Total
Dissolved Solids) per litre:
Fresh water < 1 000 mg/l TDS
Brackish water 1 000 to 10 000 mg/l TDS
Saline water 10 000 to 30 000 mg/l TDS
Brine > 30 000 mg/l TDS
While a TDS of 5 000 mg/l is the minimum threshold for a
water to be considered brine, the typical range is 30 000
to 100 000 mg/l.
In South Africa drinking water must meet the require-
ments of SANS 241 [4], which specifies, amongst other
constituents, a maximum allowable value in mg/l of Nitrate,
N<11, Sulphate, SO
4
<250, Fluoride, F<300, Chloride,
Cl<200 and Sodium as NA of about 10.
Natural formation water has been in contact with the
reservoir formation for millions of years and thus contains
minerals native to the reservoir rock. The salinity, TDS, and
overall quality of formation water vary by geologic basin.
After initial production, produced water can vary from
brackish to saline to supersaturated brine (50 000 mg/l
to >200 000 mg/l TDS) [5], and some shale gas operators
have reported TDS values greater than 400 000 mg/l.
The variation in composition changes primarily with changes
in the natural formation water chemistry.
TDS concentration is calculated as the sum of the con-
centrations for Na + , K + , Mg
2
+ , Ca
2
+ , Cl-, SO
2
-, TAL, NO
3
-,
F-, PO
4 3
- and NH
4
+ in a sample filtered through a 0,45 µm
filter [6]. See Table 2 on page 8.
One factor in shale gas water use is that operators need
this water when drilling and hydraulic fracturing activities
are occurring, requiring that the water be procured over a
relatively short period of time, and these activities will occur
year-round. Operators may need to store water for later use.
At some point, the water that is recovered from a gas well
makes a transition from flowback water to produced water.
This transition point is sometimes identified according to
the rate of return measured in m
3
/day and by looking at