Sludge Dewatering

INTRODUCTION Dewatering is a physical process integrated in the sludge line of treatment plant. It is aimed at reducing the water content and therefore the sludge volume. In this way, its transportation costs to the final destination point is reduced. On the other hand, the dewatered sludge is easier to handle and the transport process is more convenient than in the case of a sludge with higher water content. The dewatering technique chosen must be consistent with the amount and characteristics of sludges generated and with the biosolid final destination. Water present in the sludge exists in four forms (see figure): free, colloidal, intercellular and capillary. Free water can be separated from sludge by gravity as it is not associated with solids. Chemical conditioning prior to the use of mechanical tools is required in order to remove colloidal and capillary water. For intercellular water removal, the structure containing it must be broken and this can be done through heat treatment.

INTRODUCTION Odors remain at the top of air pollution complaints to regulators and government bodies around the U.S. and internationally. Ambient air holds a mixture of chemicals from everyday activities of industrial and commercial enterprises. A person’s olfactory sense, the sense of smell, gives a person the ability to detect the presence of some chemicals in the ambient air. Not all chemicals are odorants, but when they are, a person may be able to detect their presence. Therefore, an odor perceived by a person’s olfactory sense can be an early warning or may simply be a marker for the presence of air emissions from a facility. For whatever reason, it is a person’s sense of smell that can lead to a complaint. When facility odors affect air quality and cause citizen complaints, an investigation of those odors may require that specific odorants be measured and that odorous air be measured using standardized scientific methods. Point emission sources, area emission sources, and volume emission sources can be sampled and the samples sent to an odor laboratory for testing of odor parameters, such as odor concentration, odor intensity, odor persistence, and odor characterization. Odor can also be measured and quantified directly in the ambient air, at the property line and in the community, using standard field olfactometry practices, e.g. odor intensity referencing scales and field olfactometers.

It is crystal clear that, in addition to clean air, the well-being of our planet also requires that water, wastewater and the resulting biosolids (sludge) need to be managed more seriously, and in a focused, coordinated and cooperative manner. The idea for the creation of this Global Atlas of Excreta, Wastewater Sludge, and Biosolids Management originated at the IWA Biosolids Conference, “Moving Forward Wastewater Biosolids Sustainability: Technical, Managerial, and Public Synergy” held in Moncton, New Brunswick, Canada in June 2007. At this conference representatives of the International Water Association (IWA), Water Environmental Federation (WEF) and European Water Association (EWA) agreed that it would be very useful to produce a current edition of the “Global Atlas of Wastewater Sludge and Biosolids Use and Disposal” which had been published in 1996, with Peter Matthews being the original editor.