State of the Bay Report 2010-Final - Anchor Environmental

Anchor Environmental
Until recently the Langebaan WWTW did not discharge any effluent into the sea as all of it
was used it to irrigate the local golf course. However, increasing volumes of effluent received by this
plant is yielding more water than is required for irrigation and some of this is now discharged into
the Bay. There are nine sewage pump stations in Saldanha Bay and two conservancy tanks, all of
which are situated on the western border of Small Bay. The conservancy tanks are positioned
adjacent to the Yacht Club. There are eighteen sewage pump stations in Langebaan situated
throughout the town, many of which are near the edge of the lagoon, and three conservancy tanks
spread around the edge of the lagoon at Oosterwal, Stofbergsfontein and Oudepos (Figure 4.17).
Sewage effluent can enter the Saldanha/Langebaan marine environment via three routes,
namely;
Discharge of treated sewage effluent in the Bok River which drains into Small Bay
Overflow of sewage pump stations as a result of pump malfunction of power failures
Seepage or overflow from septic or conservancy tanks
Historically a number of these pump stations used to overflow from time to time directly
into the Bay when the pumps malfunctioned. This has now a rare event, however, as much of the
associated infrastructure has been upgraded recently and is now regularly maintained.
The Saldanha WWTW operates under an exemption issued by the Department of Water
Affairs (DWAF) in terms of the Water Act of 1956 which authorises the release of a total volume of
958 000 m 3 per year. Table 4 shows the general standards as specified under the Water Act 54
(1956), and the revised general limits specified under the National Water Act 36 of 1998 for various
other parameters and substances contained in the released waters of the WWTW of Saldanha and
Langebaan.
4.3.6.1 Water quality parameters associated with the Saldanha WWTW
Trends over time for water quality parameters associated with effluent from the Saldanha
WWTW are shown in Figure 4.18-Figure 4.19. Before 2005, the daily volume discharged never
exceeded 2000 m 3 , but volumes of effluent released have subsequently been increasing steadily
over time and are now approaching the maximum annual limit allowed in terms of the exemption
issued by DWAF. Numbers of faecal coliforms in the effluent from the WWTW exceeded allowable
limits specified on 14 occasions since 2003 (15% of the time) (Figure 4.18). Allowable limits for Total
Suspended Solids were exceeded on 12% of the occasions on which measurements were made, and
measurements for Chemical Oxygen Demand (COD) exceeded allowable limits 28% of the time
(Figure 4.18). Chemical Oxygen Demand is commonly used to indirectly measure the amount
of organic compounds in water. A worrying sign is the levels of Ammonia Nitrogen discharged
which are consistently above the allowable margin of 3 mg/l; allowable limits being exceeded 94% of
the time. Nitrate Nitrogen limits were exceeded on 19% of the occasions (Figure 4.19).
Table 4.5. General standards as specified under the Water Act 54 (1956) and revised general limits
specified under the National Water Act 36 of 1998.
SUBSTANCE/PARAMETER GENERAL STANDARDS
UNDER THE WATER ACT
GENERAL LIMIT FOR
GENERAL AUTHORISATION
State of the Bay 2010: Saldanha Bay and Langebaan Lagoon 70