Selecting appropriate treatment technologies for faecal sludge (FS) from onsite sanitation systems

Context Worldwide: FS production much larger than treated volumes In Vietnam: • Urban households required to own septic tanks • Combined onsite and centralized sanitation • FS emptying frequency up to 10 years or more Negligible FS volumes treated before discharge PURR: Partnership for Urban Resource Recovery • Developing knowledge for adequate FS treatment in urban Vietnam • Testing feasibility of anaerobic digestion for FS treatment Study goal To understand the local context and factors influencing the selection of appropriate FS treatment technologies in case study cities in Vietnam Methods Field visits in 5 cities Review of literature and legal documents Interviews with local authorities and stakeholders in charge of wastes and FS Household surveys in sewered / non-sewered, poor and rich areas (100 houses per city) Results • 73% septic tanks have less than 5 years and need to be emptied within 5 to 15 years (emptying frequency in 5 case study cities >10 years) ->FS will continue to be produced in urban Vietnam and strategies are required in short term • A variety of stakeholders and management systems exist between cities with a lack of willingness to manage FS ->Need for a coherent sanitation strategy at the national level, with geographical separation of areas with onsite/centralized systems • Different waste management infrastructures exist in each city ->Different technologies are required, even in the same country Conclusions and perspectives • Current engineering approaches and sectorial strategies are not adequate • Comprehensive context assessment is required • Possibilities for co-treatment of organic wastes with FS to optimize financial flows, public and environmental protection will be assessed

Méthodologie de la synthèse des systèmes énergétiques industriels

Raffaele Bolliger

This work presents a synthesis method that leads to the preliminary design of industrial energy systems. Such systems are composed of several technologies that transform, through a set of physical unit operations, raw materials and energy into products and energy services. The purpose of the preliminary synthesis is to define which technologies form the system, to calculate their technical characteristics, their operating conditions and their interactions, based on performance indicators such as for example the cost of the system or its environmental impact. This area is studied since a long time and many synthesis approaches are available. However, these methods have significant limitations, particularly in their ability to face the study of more and more complex systems. The main goal of the method presented in this work is to enable the study of large systems and promote the use of the experience gained from previous studies in the form of models and methodological approaches. The synthesis method of industrial energy systems is based on the overall system optimization using a model that is obtained by assembling several modules, representing each a set of physical unit operations and whose equations are formulated with the black box technique, and an integration model that can represent the possible interactions within the system. Optimization is performed using a multi-objective evolutionary algorithm, whose objective functions are defined on the basis of calculation of several performance indicators based on the model of the system. To simplify the resolution of this complex system, the optimization problem is decomposed into a master problem, responsible for calculating the characteristics of the units and their operating conditions, and an optimization slave subproblem, which selects the units being part of the system and their interconnections. To ensure its robustness, the slave subproblem is formulated as a mixed-integer linear optimization problem. The slave subproblem is formulated by using process integration techniques, which are extended in this work to allow the synthesis of multiple heat and mass transfer networks. The synthesis problem can thus be defined using an explicit superstructure or by one generated automatically, either implicit or explicit. This work also introduces a technique that greatly reduces the number of degrees of freedom of the integration model. Instead of separately optimizing each ΔTmin/2 associated with heat streams, a formula is applied to calculate their value from a reference case. The ΔTmin/2 optimization is thus reduced to the optimization of a single decision variable related to the reference case, regardless of the size of the problem. The proposed method uses a set of heterogeneous elements, including flowsheeting software for modeling physical unit operations, mathematical programming tools for the formulation of the integration problem, methods for calculating performance indicators and calculation tools such as the optimization algorithm. This work introduces new tools developed to systematically apply the proposed methodology and to automate recurring operations of data transfer and the call of the various used software. In particular, a syntax description is defined as an abstraction layer to describe and to structure the exchanged information. A computing platform has been created to support the application of the method and to ensure the data transfer between its components. Two case studies are presented to illustrate the various aspects of the synthesis method. A first case, involving the synthesis of two combined cycles, has been chosen to illustrate the different application stages of the method and to show the potential reuse of certain modules. Through the integration techniques, it has been possible to identify potential heat recovery that can increase the performance of one of the cycles beyond what had been expected by experts using conventional simulation techniques. The second case study is about the treatment of waste generated by an industrial site active in the field of fine chemicals. Waste treatment can recover different materials and energy services useful for process units, thereby reducing the quantities purchased in the market. The model of multi-network integration can easily solve the complexity of the problem of waste management in developing strategies for allocating waste to the various treatments available for different objective functions related to operating costs and environmental impact.

EPFL2010

Assessment of organic waste availability and suitability for the co-digestion of faecal sludge in Vietnam

Adeline Mertenat

This Master thesis comes within the framework of the PURR project (Partnership for Urban Resource Recovery), which is a collaboration between the Department of Water and Sanitation in Developing Countries (Sandec) at the Swiss Federal Institute of Aquatic Science and Technology (Eawag), the Institute of Environmental Science and Engineering (IESE) at the National University of Civil Engineering of Hanoi (HUCE), and the Laboratory for Environmental Biotechnology (LBE) at the Swiss Federal Institute of Technology Lausanne (EPFL). The PURR project is aiming to allow a comprehensive management of faecal sludge (FS) in Vietnamese urban areas. In that perspective, anaerobic co-digestion of FS with other type of organic waste is seen as a very promising technology. As the potential benefit from FS co-digestion is closely linked with the choice of co-substrates, this Master thesis was focusing on assessing the availability and suitability of potential co-substrates produced in the two case study cities Bac Ninh and Son La. By field research and interviews, a better understanding of the actual organic waste management was established. This showed that the actual organic waste management is not in favour of FS co-digestion as such. Indeed, all organic wastes separated at production source and therefore of high quality in terms of absence of impurities with disturbing effects, are already being reused, mainly as livestock feed. The remaining organic wastes are domestic waste, which cannot be used for anaerobic digestion (AD) process due to their high level of impurities related to their mixture with non-organic wastes. However, field research also revealed that rooms for improvements do exist for a better management of organic domestic waste. Nowadays they are most of the time dumped in landfills without any treatment. A segregation step would be really relevant to implement in order to decrease the related pollution and potential resource recovery of these valuable but underexploited wastes. Nevertheless, this would require political support from local authority in order to be efficient. Based on the organic waste assessment, co-treatment scenarios and related pros and constraints for FS co-digestion when considering the local context were developed. The use of segregated organic domestic waste came out to be the most sustainable scenario but is largely compromised by actual policy. The use of unfresh fruits and vegetables from market can be considered as the best compromise between technical and contextual constraints and would require less effort to be effective. In both scenarios, local support is a key factor for their effectiveness. Based on the results of the current report, the following statement can be deduced: If local support is provided, anaerobic co-digestion would be a relevant process for FS treatment. Otherwise, other treatment processes should be investigated.

2014

Vers un assainissement urbain durable en Afrique subsaharienne

Halidou Koanda

Justification In Sub-Saharan Africa, excreta and wastewater disposal is characterised primarily by on-site sanitation systems. This sanitation option is more likely to increase as governments, municipalities, communities, private operators and donor agencies strive to reach the Millennium Development Goals aimed at reducing by half the proportion of people without access to basic sanitation facilities. Due to increased urban population growth in Sub-Saharan Africa, the faecal sludge volumes will increase to alarming quantities in the coming decades. An evaluation of faecal sludge management practices reveals that the main shortcomings relate to the widespread lack of involvement and foresight by the municipalities, the paucity of effective legal provisions and organization, and the absence of stakeholder coordination. Stakeholder involvement for planning and implementing faecal sludge management is virtually inexistent or excluded from urban sanitation planning processes. In the majority of situations, faecal sludge management is financially not viable. This is a major cause of the indiscriminate dumping of faecal sludge in urban areas or its untreated use in urban agriculture. These practices not only pose permanent and serious health risks but also contaminate both scarce ground and surface water. Objective and general approach On the basis of these facts, which present a real challenge to sector specialists, the overall objective of our research is to develop an innovative strategic planning approach for sustainable faecal sludge management in urban areas which allows minimising public health and environmental risks. Focus is placed on developing a reproducible methodology for stakeholder involvement, on enhancing population awareness for improved faecal sludge disposal and attributing a leading role to the dynamic private faecal sludge emptying and transport operators. These aspects form the three pillars of our search for a comprehensive methodological approach. The municipality of Ouahigouya in Burkina Faso with a population of about 65'000 inhabitants was used as pilot site to launch, implement and scientifically validate the approach. Analysis and stakeholder involvement The stakeholder-based planning approach developed in Ouahigouya relies on a combination of stakeholder identification and analysis, and participatory planning techniques (focus groups, workshops, informal meetings, all-stakeholder workshops). A quantitative survey among households allowed collecting stakeholders' proposals and evaluating suggestions for improvement of faecal sludge management and neighbourhood hygiene proposed by the population. The main steps in the stakeholder involvement approach include: Jointly clarifying the objectives of the planning process together with the stakeholders; Identifying stakeholders and their interests; Classifying stakeholders according to their importance and influence based on defined criteria and confirmed by the stakeholders themselves; Identifying the interactions between the stakeholders; Verifying the results of the stakeholder analysis by the stakeholders themselves; Choosing stakeholder involvement techniques; Implementing the chosen method of stakeholder involvement: development of faecal sludge management scenarios, acceptance of the scenarios by the stakeholders in focus groups, choice and acceptance of a basic scenario for development of the future strategy in an all-stakeholder workshop; Evaluating the chosen involvement process by the stakeholders. The experience gained with the planning methods developed and implemented in Ouahigouya reveals that the "Stakeholder analysis" method is efficient and provides answers to questions such as: Who are the important and influential stakeholders? Who should participate in the planning process and in which manner? This experience also revealed the need for capacity building of certain stakeholder categories (emptying operators, women's associations, etc.) to increase their degree of involvement in the planning process. Improvement in stakeholder involvement was achieved thanks to a combination of workshops, focus groups and other informal meetings allowing less influential stakeholders (associations of local women, horticulturists, emptiers) to share information and to freely express their opinions and concern and to defend their interests. Thus, providing an excellent example of local democracy appreciated by all stakeholders of Ouahigouya. The approach developed provides tools for policy-makers and planners to ensure an effective stakeholder involvement in the process of developing a common vision and implementation of improved urban sanitation measures. The conditions for replicating the approach developed and tested in Ouahigouya are due to participatory democracy, great commitment of the local authorities and the high motivation of the stakeholders involved. Levers for the willingness-to-improve faecal sludge management and neighbourhood hygiene The evaluation method of the willingness to improve faecal sludge management by the population was based on a combination of the planned behavior model of Ajzen and the contingent valuation method, financial analysis of the pit emptying and faecal sludge enterprise, and on focus groups of stakeholders. By focusing on local practices, perceptions and individual behavior, this method revealed that financial viability – often reduced to willingness-to-pay – is not the only factor to consider when planning improvement of sanitation practices. Willingness-to-improve is highly dependant on psycho-sociological factors such as attitude towards and beliefs in an improved neighbourhood environment, social pressure on the households by the neighbourhood as well as the subjective costs and benefits expected from improved faecal sludge management. These factors therefore present levers allowing planners and decision-makers to encourage, increase and develop the demand for improved latrine emptying services, e.g. though social marketing. Promoting private entrepreneurs According to market analysis of emptying services and stakeholders involved, small private and mainly informal enterprises play a leading role in faecal sludge management in most cities of Sub-Saharan Africa. These operators, dynamic but fragile, require an appropriate institutional, jurisdictional and economic environment based on a balanced partnership between the municipality (public) and the private sector. Our study reveals that for a company truck to be profitable, about 1'000 trips per year (at 6'000 FCFA per trip) are required or the equivalent of a city of 56'000 inhabitants. In the case of Ouahigouya, profitability is increased if the emptying operators apply the latest management and professional tools and techniques, and manage to provide emptying services in neighbouring towns. Decision support tools The research led to developing decision support tools for professionals and policy-makers. These tools facilitate the development of a tariff-oriented policy to avoid uncontrolled faecal sludge discharge into the environment, to render investments by private operators profitable, and still make emptying services accessible to low-income households. This involves: Analysis of the cost structure of 3 pit emptying companies has revealed that fuel, maintenance/repair and personnel costs make up 45%, 20% and 30%, respectively, of an enterprise's operating expenses. An Excel programme was developed to allow municipalities and private operators to determine the operating costs of emptying services. This allowed to establish a sustainable money flux between the different stakeholders involved and to define the tariffs. To prevent faecal sludge discharges in the immediate residential environment or on unauthorised sites, it might under specific circumstances prove necessary and feasible to reimburse rather than charge entrepreneurs for delivering faecal sludge to the treatment sites, hence, create a strong incentive for good emptying and haulage practice. Evaluation methods of the sludge quantities to be disposed of have been developed to allow faecal sludge planning by the municipal authorities, assessment of the potential market and return on investment by the private operators. Advantages of the approach for the population of Ouahigouya Based on the results of our study, it was possible to formulate practical recommendations for the organisation of the urban sanitation sector for the municipality of Ouahigouya – now in possession of a sustainable faecal sludge management strategy. Our study has also contributed to promoting local consultation and raising the awareness of the role and contribution of each stakeholder group, in particular the previously neglected manual emptiers in their daily efforts to improve the living conditions of the urban inhabitants. The "Strategic Excreta and Wastewater Sanitation Plan", that was developed and supported by the "Office National de l'Eau et de l'Assainissement - National Water and Sanitation Agency", provides an excellent framework for the implementation of the elaborated faecal sludge management model (as part of the this strategic plan).

EPFL2006