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5 months ago

galvis

Water treatment

ecame formally

ecame formally established as WS enterprises and do not have reliable databases on these costs. Cinara, on the other hand, is also starting to promote some undergraduate and MSc dissertations to assess in a systematic and more critical way actual practical experience in the region. In spite of these limitations, the following sections present a preliminary cost analysis of MSF technology considering both initial and running costs 5.3 Cost Characteristics 5.3.1 Initial capital investment cost Factors that have an important effect on the initial investment cost in a water treatment system include: • Plant capacity • Type of plant (type of technology) • Cost of equipment (local and imported) • Design criteria and cost • Land prices • Cost of materials (local and imported) • Cost of labour • Geographic location • Transport • Climatic conditions • Level of competence and profit of constructing firms Taking the main factors as starting point, a cost model can be developed for pre-determined region, date and treatment technology. In general, the model has the following composition: C = aQ b (5.7) Ln C = Ln a + b Ln Q (5.8) In which C is cost of construction; Q is plant capacity; and a, b are coefficients. The value of the coefficient “a” corresponds to the cost of a plant with a unit capacity. The coefficient b, usually smaller than 1, indicates the economy of scale. If the value of b is closer to 1, the economy of scale is low, and as a consequence, cost efficiency will not be obtained with the increase of the size of the system. 5.3.2. Operation, maintenance and administration costs Factors that have an important effect on operation, maintenance and administration costs in a water treatment system, include: • Labour cost • Cost of consumables (local and imported) • Maintenance requirements • Energy cost • Prevailing water quality regulations • Number of users 179

Based on the practical experience with full-scale MSF plants operating by gravity in the Andean Cauca Valley, the running costs of this technology are mainly labour costs. Based on observations made during training activities and some information collected from caretakers and community based organisations, a preliminary estimation can be made of time requirements for Operation and Maintenance (O&M). Time requirements for administration seem to vary significantly between communities (Cinara, 1998). It is expected that the gradual development of more formal small enterprises for small WS systems in Colombia will contribute to improving time management and to reduce the time necessary to administer the systems, including conflict resolution inside or outside the community-based organisation. In this preliminary analysis, time required for administration is estimated as a percentage of the time required for O&M. Having an estimation of time requirement for OM&A and representative labour costs, the running cost of MSF technology in a given programme development area can be calculated. 5.4 Objectives This chapter aims to analyse and summarise information concerning the following points, although some of them are still at an exploratory stage. • To develop construction requirement models of MSF alternatives including DyGF (dynamic gravel filtration), upflow CGF (coarse gravel filtration) and SSF (slow sand filtration) stages. • To develop construction cost models of MSF alternatives, considering construction cost values of 1999 in the context of the Andean Cauca Valley. • To present preliminary information on time requirements for OM&A of MSF alternatives and to estimate OM&A costs based on labour costs in the context of the Andean Cauca Valley. • To compare initial and life cycle costs of MSF alternatives and conventional RF treatment plants. • To analyse and compare economy of scale of MSF and conventional RF plants. 5.5 Methodology 5.5.1 Initial investment cost A review of MSF systems constructed in different regions of Colombia showed that the greatest construction costs included reinforced concrete, gravel, sand, land, soil excavation, and the building including facilities for storing sand, water disinfection, and operator’s basic needs (Galvis et al, 1989; Cinara-Mindesarrollo, 1996 and 1998). Together these components represent approximately 80 percent of the direct construction cost (without including costs for administration, profits and contingencies). The remaining 20 percent is distributed between the cost of valves, fencing, illumination, accessories and pipes. Consequently, an estimate can be made of the main construction cost by relating the plant flow to the construction quantities of the different items with the greatest construction costs and multiplying these quantities by the unit cost for these items. This main direct construction cost can be then be affected by a factor (1.25) to take into account also the other (minor) direct construction costs. 180