State of the Bay Report 2011-Final.pdf - Anchor Environmental

State of Saldanha Bay & Langebaan Lagoon 2011
Activities & discharges
Figure 3.20. Monthly trends in water quality parameters Orthophosphate for effluent released from the
Saldanha WWTW Apr 2003-December 2011. Allowable limits as specified in terms of a General
Authorisation under the National Water Act 1998 are represented by the red line.
Chlorine gas, generated through a process of electrolysis, is toxic to most organisms and is
used to sterilise the final effluent (i.e. kill bacteria and other pathogens present in the effluent)
before it is released into settling ponds or the environment. Chlorine breaks down naturally through
reaction with organic matter and in the presence of sunlight, but must not exceed a concentration
0.25 mg/l in terms of the general authorisation under which the Saldanha WWTW operates. The
frequency of exceedence for this parameters since 2003 is 49.5% (i.e. nearly 50% of the readings are
above the allowable limit) (Figure 3.21).
Figure 3.21. Monthly trends in Free Active Chlorine for effluent released from the Saldanha WWTW Apr
2003-December 2011. Allowable limits as specified in terms of a General Authorisation under
the National Water Act 1998 are represented by the red line.
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