A circular-economy initiative just outside the Scottish capital of Edinburgh is making waves in water filtration by producing a highly efficient filtration media from recycled glass. The Active Filter Media (AFM), made by the company Dryden Aqua, has been so successful that its production now uses a quarter of all the glass recycled in Scotland.
Dryden Aqua, founded in 1980 by marine biologist Howard Dryden, is also examining how its technology can be used in poorer countries: the company is a partner in the ECO-India research project, supported by the European Union's Seventh Framework Programme. ECO-India, which runs until August 2015, is testing innovative and cost-effective community-based water-treatment systems that will be deployed in water-stressed areas of India where the water contains high levels of arsenic, a problem that affects quarter of a billion people.
To produce AFM, Dryden Aqua takes old glass bottles, mills them to a very fine grain which has a surface area 300 times greater than sand, and gives the surface area a negative electrical charge. Pollutant particles in water flowing through an AFM filter are attracted by the charge to the surface area of the grains. The grains are also treated to be self-sterilising.
The filtration medium has been evaluated by France's Institut de la Filtration et des Techniques Séparatives as 30% more effective than sand, and 50% more effective than other crushed glass filter media, in terms of removing fine particles from water.
AFM can be used in filtration systems for drinking water, treatment of industrial wastewater, aquaculture and other applications. It can also be used to bioremediate lakes and ponds. Other environmental benefits, according to Dryden Aqua, include control of arsenic, manganese and iron in water, reduced raw material use (no need to excavate sand), use of a waste product (recycled glass) and no “biofouling” or bacteria growth on the AFM grains. The absence of biofouling means that AFM lasts for about four times as long as sand, which needs to be regularly replaced. Dryden Aqua says that the running costs of AFM filtration systems are 30% less than standard systems.
The AFM system is already used in about 100,000 installations worldwide. Future installations foreseen by Dryden Aqua could include for the textile industry in Dhaka, Bangladesh, which expects to run out of water in five years without wastewater recycling.