Removal of Glass Particles from Compost Mixtures at Laboratory and Pilot Scales

The contamination of compost with glass presents a serious problem for the handling and re-use of this type of waste material. Most refuse can be turned into useful by-products, yet compost that is highly contaminated with glass is considered low grade and useful only for a limited range of applications, such as at turf farms and mine sites. A novel method for removing particulate glass from general waste is proposed and tested here. The two-stage process consists of a flotation and a filtration step. A rotating flotation vessel was used to separate glass particles from partially separated solid waste. A back-flushable, asymmetric, inorganic filter was tested for the treatment and reuse of the water in the separation process. The novel design proved to be robust and the separation process was found to be capable of producing high quality compost from glass contaminated samples, in both batch and continuous operation modes. The asymmetric filter produced water suitable for re-use in the same separation process. The filter performance could be restored, without damage, by short, low-pressure back-flushing. The production method for the asymmetric filter is presented in this article and the filtration and flow characteristics of a range of these novel filters are also reported.