08 February 2017
Crushed glass can out-perform sand to make for an effective alternative filter media for wastewater treatment. It is less prone to clogging with better back-washing efficiency. It’s also a sustainable alternative to sending glass to landfill. So, what is it about glass that makes it such a good alternative? More to the point, does the colour of the glass make a difference?
There are no published scientific studies that have explicitly examined the biochemical properties of recycled glass as a filter media in wastewater treatment. This is about to change, as summer student Hazel Clemens is investigating whether the physical and chemical properties of different crushed glass affects biofilm build-up. Hazel’s research is a Pioneer Project with Louise Weaver and Lee Burbery.
Green glass contains colouring additives such as chromite, iron, and lanthanum that are known antimicrobial agents. Hazel is running bio-clogging tests using different coloured glass. Hazel, Louise and Lee are betting that green glass will clog the slowest. If Hazel’s experimental results prove this is true, then there may be a commercial and environmental benefit to sorting waste glass in New Zealand.
Glass was sourced from as far as Otaki and as near as the staff Christmas celebrations. Christchurch City Council were kind enough to lend us a patch at the wastewater treatment plant to set up the column experiment. Crushed glass media is dosed with freshly supplied effluent from the clarifiers. Rates of clogging and biofilm build-up are being monitored.
Time will tell whether the Three Boys green glass is the way to go for filter media. The CSC groundwater lads are certainly hoping so!