10 months ago


Water treatment

MSF system can then be

MSF system can then be calculated on the basis of the filtration area (A). Tables 5.2 shows the main construction quantities for the different MSF component items built in reinforced concrete. Similar models can be produced for brickwork. In some hilly areas the quantities may be larger, particularly if construction in terraces is needed. The cost of the plants can be established by multiplying the quantities of the different construction items with their respective unit cost. The total sum of these items (table 5.2), plus the cost of the valves, represents around 80 percent of the cost and needs to be multiplied by 1.25 (since 100/80 equals 1.25) to estimate the total construction cost. This does not include however, costs of the water intake, transmission main or water storage and distribution. Table 5.2. Models to estimate the construction quantities of main components of MSF systems in reinforced concrete. Treatment capacity in the range of 2 to 25 ls -1 . Component UGFS (2) UGFS (3) 24

Table 5.3. Time required for conducting daily and periodic O&M tasks in MSF systems. Time is shown in full time equivalents (FTE) (1, 2) Capacity (ls -1 ) MSF Alternative 1 5 10 20 DyGF + SSF 0.2 0.4 0.7 1.0 DyGF + UGFL + SSF 0.5 0.6 0.9 1.3 DyGF + UGFS (2) + SSF 0.6 0.8 1.0 1.4 DyGF + FGDS (3) + SSF 0.7 0.9 1.2 1.5 (1) 1 FTE = time equivalent of a full-time operator. (2) Daily, periodic, and occasional activities have been considered in chapters 3 and 4. They are also described in Galvis et al (1998) and Vargas et al (1999). Table 5.4. Time required for implementing occasional O&M activities of MSF plants in fulltime equivalents (FTE). MSF Alternative Capacity (ls -1 ) 1 5 10 20 DyGF + SSF 0.01 0.06 0.11 0.22 DyGF + UGFL + SSF 0.02 0.10 0.21 0.41 DyGF + UGFS (2) + SSF 0.03 0.15 0.30 0.60 DyGF + UGFS (3) + SSF 0.04 0.20 0.40 0.79 The values in this table relate to systems with a life span extending over 10 years, as most of the occasional activities occur between a few times per year to once every five years approx. 5.6.3. Administration The time required for administrative activities is estimated at 0.3 to 0.5 FTE per month. The activities included supervision, planning, user relations, purchases, payments and meetings with sector agencies. In the five treatment plants in Cauca Valley with plant capacities between 7 and 15 ls -1 serving between 95 and 545 households (El Retiro, Cañas Gordas, Ceylan, La Marina and La Sirena), the time required for the administration of these MSF systems was in the order of 0.3 to 0.5 FTE. The estimate is assumed to be valid for plant capacities between 2 and 25 ls -1 with the lower level applying to the smaller systems. 5.6.4 Estimating overall cost The estimation of total direct construction cost can be based on tables such as 5.2 which include only items representing around 80% of direct costs, and the local unit costs. Multiply this partial direct cost by 1.25 to reach the total direct construction cost. To obtain the overall investment cost for the treatment plant, other costs need to be added to the total direct costs, such as insurance, and profit, administration and contingencies (PAC). In Colombia the value for PAC varies between 20 and 30 percent. Estimation of total staff time in FTEs per year for operation, maintenance and administration can be reached by using tables 5.3 and 5.4 and adding another 0.3 to 0.5 FTE for administration costs. The sum needs to be multiplied by the average staff’s salary and by a factor of 1.15 to obtain the total recurrent cost, as staffs make up 85 percent of the recurrent cost approx. 184