Sustainability assessment of faecal sludge treatment technologies for resource recovery in Phnom Penh, Cambodia

Selection of appropriate sustainable treatment technologies involves satisfying user requirements, quality standards on treatment and products, and specific socio-technical constraints in the intended context. Using locally adapted multi-criteria assessment (MCA), this study investigated faecal sludge treatment technologies that enable resource recovery in Phnom Penh. A four-step structured approach was applied, involving i) identification of available options, ii) prerequisite screening, iii) MCA and iv) stakeholder discussions and ranking. Data were collected in a literature review, stakeholder interviews and an online survey. Lists of suitable primary (n = 7) and secondary (n = 13) treatment technologies were compiled based on the literature. Four secondary treatment technologies (solar drying, co-composting, vermicomposting, black soldier fly larvae (BSFL) composting) were retained after prerequisite screening and subjected to MCA. Co-composting was ranked highest in MCA, since it performed well in multiple aspects, especially for health criteria. However, when economic return on investment was prioritised and a lower treatment class was accepted, e.g. USEPA Class B biosolids, the highest ranking was achieved by vermicomposting or BSFL composting. If institutional criteria were included in the assessment, solar drying would likely be the highest-ranked option, since this simple technology requires less logistically complex stakeholder arrangements than co-composting. These results show that the ranking obtained for different sludge treatment options depends on criteria weighting and tradeoffs. Considering secondary treatment options is crucial during early planning for faecal sludge management in a city of low-and-middle income countries, as the primary treatment must yield appropriate feedstock quality for the secondary treatment step

Heavy metal contamination of faecal sludge for agricultural production in Phnom Penh, Cambodia

To achieve the universal target of ‘safely managed sanitation’ set out in UN Sustainable Development Goal 6, the world needs to increase its rate of progress, since e.g. Phnom Penh, the capital of Cambodia, currently has zero percent safely managed sanitation. One way to promote safer faecal sludge management is to shift to a more circular system with nutrient recycling, but this carries the risk of heavy metal accumulation in the environment. This study analysed the concentrations of heavy metals in raw faecal sludge from various sources and assessed the appropriateness of resource recovery and reuse in relation to the heavy metal and nutrient loads in faecal sludge. A total of 42 samples collected from sludge disposal sites in Phnom Penh during the dry and rainy seasons were analysed for heavy metals and physicochemical parameters. Mean measured concentrations of heavy metals in faecal sludge samples decreased in the order Zn > Cu > Pb > Cr > Ni > Hg > As > Cd in both seasons but were higher in the rainy season, probably due partly to inflow from stormwater drains and run-off from roads during storm events. All elements analysed were within the permissible limits for application to land according to EU standards and USEPA. However, Hg and Zn concentrations exceeded the tolerance limits for local organic fertiliser and Swedish limits for compost. Faecal sludge is thus not an appropriate fertiliser considering the risk of heavy metal accumulation in relation to phosphorus recovered. Options to avoid recirculating pollutants to the environment include upstream prevention of pollution, source separation of household wastewater fractions and use of biosolids as a soil conditioner together with other fertilisers or for soil production. Additional studies are needed on these options if sanitation stakeholders are to close the nutrient loop

Dynamic Modeling to Assess Natural Wetlands Treatment of Wastewater in Phnom Penh, Cambodia: Towards an Eco-City Planning Tool

Aims: A personal computer version of the Stormwater Management Model (PCSWMM) was applied to seamlessly link urban runoff, sanitary flow, pump station operations, and a natural wastewater treatment wetland in Phnom Penh, Cambodia, as a step towards developing a planning tool that could be used to explore urban development or climate change scenarios.Study Design: PCSWMM was calibrated with measured flow and water quality data and used to estimate total phosphorus, total nitrogen, detergents, and E. coli levels at the outlet of the wastewater treatment wetland for the period May 15 to July 1, 2011.Place and Duration of Study: Phnom Penh, Cambodia; January, 2011 to March, 2012.Methodology: In support of model development, a limited water quality sampling program and bathymetric survey were conducted for the sewer and wetland system in both the dry and rainy seasons, 2011. Samples were analyzed for total nitrogen, total phosphorus, detergents, and E. coli. Sewer flow was measured continuously at 5 minute intervals to determine sanitary flow characteristics as input to the model and pump operation rules were determined through interviews with the pump operators and analysis of their data log books.Results: Consistent with past studies, the sampling showed that the wetland was effective in treating municipal waste, particularly with respect to E. coli (99% reduction from sewage inputs) and detergents (86% reduction from sewage inputs). A lower treatment efficiency was observed for total phosphorus, at around 31%, while the treatment efficiency for total nitrogen was around 71%. The wetland was divided into four zones and PCSWMM was run in continuous mode for the period May 2-July 1, 2011. The mean levels of E. coli, detergents, total phosphorus, and total nitrogen estimated by the model for that time period compared favorably with sample results from the field campaign in August, 2011.Conclusion: The naturally-occurring wetland treatment system in Phnom Penh is effective and fits well with the concepts of green infrastructure and eco-cities. PCSWMM is a useful decision-support and planning tool to explore various development and climate change scenarios in Phnom Penh

Generation and Management of Faecal Sludge Quantities and Potential for Resource Recovery in Phnom Penh, Cambodia

At the current rate of progress, there will probably still be 2.8 billion people world-wide without safely managed sanitation by 2030. To incentivise and increase implementation of sustainable faecal sludge management (FSM), especially in low and middle-income countries like Cambodia, human waste must be regarded as a resource. However, planning data, e.g. on the quantities, composition and fate of faecal sludge after leaving households, are inadequate and lack accuracy. The aim of this study was to provide baseline data for effective FSM planning by sanitation stakeholders in Phnom Penh. This was done by quantifying sludge volumes generated, transport logistics and resource recovery potential to incentivise sustainable management. Interviews were conducted with users and emptying and transportation contractors, together with collection of technical data about on-site sanitation systems. Geographical coordinates of household sampling locations and disposal sites were also mapped. The results revealed that Cheung Ek and Kob Srov wetlands are the main recipients of faecal sludge collected in Phnom Penh with the amount of 18,800 m(3) and 13,700 m(3) annually, respectively. The analysis showed that faecal sludge in Phnom Penh contains valuable resources such as nitrogen (6 tons), phosphorus (13 tons) and energy (148-165 GWh) annually, but in-depth investigations of appropriate treatment options for resource recovery are required. Detailed documentation of the location of potential recoverable resources from faecal sludge would assist decision-makers in developing action plans for sustainable FSM in Phnom Penh and similar cities

Towards Open Resources Using Services (TORUS)

L'obiettivo del progetto TORUS è quello di creare sinergie tra le scienze ambientali e il cloud computing per il processing di big-Data, per la preparazione di futuri programmi di formazione, e di progetti di ricerca in collaborazione con aziende private. In particolare l'attività è rivolta al trasferimento delle competenze tecnologiche nel campo del cloud computing e del processing di Big-Data acquisiti nell'ambito della fisica sperimentale alle scienze ambientali