Our water supply
On Monday 8 February the Vice- Chancellor of Rhodes University, Dr Saleem Badat held a forum to discuss the current water supply crisis in Grahamstown at the Barratt lecture theatre at Rhodes.
Our water supply
On Monday 8 February the Vice- Chancellor of Rhodes University, Dr Saleem Badat held a forum to discuss the current water supply crisis in Grahamstown at the Barratt lecture theatre at Rhodes.
The discussion largely revolved around the causes for the poor water quality rather than the lack of supply. Two weekends before this discussion, the Grahamstown branch of the Wildlife Environment Society of South Africa (Wessa) held a well-attended tour of the diversion weir, Glen Melville holding dam and the
James Kleynhans water purifi cation works that now almost totally supplies Grahamstown with potable
water.
Many who attended this tour had been previously unaware of how Orange River water reaches the domestic supply in Grahamstown. Here is a brief illustrated tour of how it works.
Water is diverted from the Gariep dam on the Orange River through an 86km tunnel into the headwaters of the Great Fish River and fi nds its way downstream to the vicinity of Fort Brown and the Hammanskraal weir (See photo 1).
The weir is connected by another short tunnel (2) that fi lls the Glen Melville holding dam. The Fish River fl ows over ancient sea-bed sediments so its waters are slightly brackish.
‘Slugs’ of fresher Orange River water are thus released to displace this saline water before fi lling the Glen Melville dam in the Ecca pass. Orange River water, by the time it arrives in Glen Melville lake, is turbid and brown in colour, and green-water algal blooms were evident at the time of our visit (3).
Below the Glen Melville dam the James Kleynhans WaterTreatment Works was built as an offshoot of the Lower Fish River irrigation scheme in the late 80s.
The purpose was to supply Grahamstown with drinking water in times when the Howison’s Poort dams and associated Waainek Water Treatment Works were inoperable or suffering drought conditions, as is the current situation.
The fi rst stage of the water treatment process involves fl occulation of sediments in suspension – particles dispersed in the water are clumped together so that they are easier to remove.
Makana’s Water Treatment Works normally use aluminium sulphate, but we noticed that poly- aluminium chloride (4) was in fact being used.
At the time of our visit, the pump system that was in use was leaking chemicals, and was one of the components of the process that looked shabby and ill-maintained (5).
The chlorinator had recently apparently broken down (there is only one available) and has been replaced
by the municipality.
In the interim period while a replacement was being purchased, granular chlorine, similar to that used in swimming pools was added manually to the water by the staff present at the water-works.
What happened at night is unknown. Treated water then fl ows into large rectangular concrete tanks with screens, where the sediments precipitate out (6). Large ’sandbanks’ of sediment could be seen in these tanks, which are from time-to-time manually removed.
The water then fl ows into deep sand fi lters where it is heavily aerated to remove the chlorine gas (7). The staff member who showed us around complained that these tanks should be regularly cleaned by the municipal workers, but this apparently rarely happens, and quantities of algal scum were evident on the tank sides.
Water is then reticulated to the pumps (8) which pump the treated water up the Ecca pass to Grahamstown to a concrete holding reservoir above Joza.
From there it fl ows by gravity pressure to Grahamstown East. Apparently water from this source can be reticulated throughout the city, although the pressure at its western extremity such as Rhodes, Hill 60 and the Monument is poor compared to that from the Waainek water treatment works.
The amount of water that can issue from the James Kleynhans system is relatively small, as it was designed for a population demand somewhat less than the city’s current population of about 180 000 people.
The channelised fl ow (9) is less than 50x50cm with a moderate to slow fl ow at a guesstimate around 28l/sec not much when you consider the city’s population growth from 60 000 in the 80s, and the demands of such events as the Grahamstown Festival with its infl ux of visitors.
Points of concern are the lack of backup facilities for both chlorination and fl occulation at James Kleynhans, lack of specifi c skills and training among the staff running the operation, and the shabby and apparently illmaintained nature of some of the essential equipment and tanks.
While the main control room is impressive with its computer-controlled systems for pumping the water, the purifi cation side of the operation looks a little haphazard with pumps leaking fl occulant,and odd drums of granular chlorine lying around in places (10). The design of the basic system is impressive, its current operational status is somewhat less so.
Contacts
Nikki Köhly: nkohly@yahoo.com, 046 636 1643 / Lawrence Sisitka: heilaw@imaginet.co.za, 046 622 8595 / Jenny Gon: j-gon@ intekom.co.za, 046 622 5822 / Dan Wylie d.wylie@ru.ac.za, 046 603 8409 / Nick James: nickjames@ intekom.co.za, 046 622 5757 / Strato Copteros strato@ iafrica.com, 082 785 6403
