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

Formation of nitrogenous disinfection by-products in 10 chlorinated and chloraminated drinking water supply systems

The presence of nitrogenous disinfection by-products (N-DBPs) in drinking water supplies is a public health concern, particularly since some N-DBPs have been reported to be more toxic than the regulated trihalomethanes and haloacetic acids. In this paper, a comprehensive evaluation of the presence of N-DBPs in 10 drinking water supply systems in Western Australia is presented. A suite of 28 N-DBPs, including N-nitrosamines, haloacetonitriles (HANs), haloacetamides (HAAms) and halonitromethanes (HNMs), were measured and evaluated for relationships with bulk parameters in the waters before disinfection. A number of N-DBPs were frequently detected in disinfected waters, although at generally low concentrations (<10 ng/L for N-nitrosamines and <10 µg/L for other N-DBPs) and below health guideline values where they exist. While there were no clear relationships between N-DBP formation and organic nitrogen in the pre-disinfection water, N-DBP concentrations were significantly correlated with dissolved organic carbon (DOC) and ammonia, and these, in addition to high bromide in one of the waters, led to elevated concentrations of brominated HANs (26.6 µg/L of dibromoacetonitrile). There were significant differences in the occurrence of all classes of N-DBPs between chlorinated and chloraminated waters, except for HNMs, which were detected at relatively low concentrations in both water types. Trends observed in one large distribution system suggest that N-DBPs can continue to form or degrade within distribution systems, and redosing of disinfectant may cause further by-product formation