24 December 2010

Wildevoelvlei (Noordhoek/Kommetjie, Cape Town) remains in the news.  I haven’t seen the vlei this time around but given that the City has actually moved to issue such a strong warning, it must be serious.  In keeping with overseas trends, it would be useful if they would also release the associated data (algal biomass levels, toxin concentrations and etc).

As I mentioned before, the vlei is an extension of the adjacent sewage works – i.e. a maturation pond.  This situation will persist until such time as the works adopts a stringent policy of phosphorus removal.  There is an interim, off-the-shelf technology available that would address this problem, in-lake, immediately – this being the forced circulation version of the BioHavens (see elsewhere on this Blog) – namely the aptly named Leviathan!  This would turn the eastern basin of the vlei into a biological viable, non-algal dominated environment within the space of weeks – and permanently into the future.

This type of approach was suggested as a follow-up to the salting exercise back in the late-1990s – and local trials revealed that the approach was likely to work.  My experience of this type of situation is that, typically, more money is spent on trying to find a cheaper solution than the cost of the originally-proposed intervention!  The dredging of Zeekoevlei is another such example.

Wildevoelvlei biofilm generation trials, 2003

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