Dewatering and drying of fecal sludge (FS) is a key treatment objective in fecal sludge management as it reduces volume (thereby reducing emptying frequency and associated transportation costs), inactivates pathogens, and is beneficial and/or necessary to resource recovery activities such as composting and combustion as fuel. However, studies on dewatering performances of FS are limited. The physical water distribution of such matrices is not fully understood, limiting the progress in the development and optimization of FS dewatering technologies. The objective of this study is to present a gravimetric method intended to assess the dewatering characteristics and associated modelling of FS through moisture sorption isotherms. Samples were placed in airtight jars containing different saturated salt (NaOH, CaCl 2 , NaCl, KCl, K 2 SO 4 ) solutions to reproduce a range of relative humidity values (6 to 97%). Results confirmed the achievement of characteristic sigma-shaped moisture sorption isotherms with increasing moisture adsorption at higher values of relative humidity. Furthermore, experimental data best fit the three-parameter Guggenheim-Anderson-de Boer (GAB) model. This method can be replicated to contribute critical data about the characterization of fecal sludge, a seriously under-researched matrix.

In a recent article an assessment of decomposition within pit latrines measured with regard to chemical oxygen demand (COD) reductions was reported on. Some fundamental concerns were raised with regard to a key assumption of the study. The alternative perspective that is presented here does not support the study's conclusion that anaerobic processes are the dominant decomposition pathway in pit latrines. Furthermore, it is argued that their analysis and some implications of their data interpretation can be viewed in a different manner.

The drying (or dewatering) of fresh feces and fecal sludge is a productive step in the management of sanitation, waste treatment, and resource recovery services. An improved understanding of fresh feces and fecal sludge drying would contribute to the development and deployment of fecal sludge management services. However, there is a lack of available literature on the fundamental drying characteristics of fresh feces. In response to this gap, this work shares experimental results for equilibrium moisture content of fresh feces at different water activity levels (aw) and proposes the use of the Guggenheim, Anderson, and de Boer (GAB) model for predicting aw, calculating the heat of sorption, and estimating the corresponding energy requirements for drying of fresh feces. This is the first time this work has been done with fresh feces. The total heat of evaporation was significant up to a moisture content of about 0.2 kg water per kg dry solids. In addition to informing drying process design, the sorption isotherm can be used to predict microbial activity, which could improve the management of feces and fecal sludge from a public health perspective. These data in turn will be used to promote access to dignified, safe, and sustainable sanitation.

Il est admis que la production de méthane (CH4) à partir de la décomposition de la matière organique est effectuée par des microorganismes méthanogènes en condition anaérobie. C’est pour cette raison que le CH4, un gaz à effet de serre (GES) possédant un pouvoir de réchauffement global (PRG) équivalent à 25 fois celui du CO2, n’est généralement pas considéré dans les protocoles de quantification de GES concernant les procédés de traitement d’eaux usées par voie aérobie. Or, selon le type de procédé aérobie et les conditions d’opération, du méthane peut effectivement être produit. Cette note technique montre des résultats obtenus lors d’essais pilotes en laboratoire avec un biofiltre traitant du lisier de porc. Il en ressort clairement que la formation de méthane est possible avec ce type de procédé, et que les concentrations générées peuvent être non négligeables. Par conséquent, cet élément doit donc être pris en compte pour l’optimisation des procédés de traitement aérobie en rapport aux aspects liés à la réduction des GES et la lutte aux changements climatiques.

Compared to carbon dioxide (CO 2 ), methane (CH 4 ) is a strong greenhouse gas (GHG) and landfills are one of the major anthropogenic sources of atmospheric CH 4 produced by anaerobic degradation of organic waste. In Canada as in many countries around the world, programs and regulations are implemented to force capture and burning of landfill gas (LFG). However, when thermal oxidation (flaring or energetic valorisation) is not possible (i.e. low CH 4 concentration or flowrate), microbial methane oxidation by methanotrophic biofilters represents a new technology that holds great promises for GHG reduction and air pollution control of LFG. Exploratory work done in CRIQ laboratories (Quebec Canada) allowed testing different types of mediums (organic and inorganic) for the design of methanotrophic biofilters. Following this initiative, pilot scale project was undertaken in 2009. The objective was to evaluate, using a prototype installed in a closed landfill (Beauport, Quebec City), the technical and economic feasibility of implantation of methanotrophic biofilter for the treatment of LFG. Testing protocol has been implemented over a period of 83 d (from September to November 2009). The collected data were used to evaluate conversion rates (up to 80%) and the maximum elimination capacity (ECmax = 66 g CH 4 /m 3 /h). Large-scale technology demonstration work is planned for 2011-2012 to validate, over 12 months, the GHG reduction cost established for methanotrophic biofilter (CAD$16-20/t CO 2 eq).