Economic Assessment of Sanitation Interventions in Vietnam - WSP

Economic Assessment of Sanitation Interventions in Vietnam | Local Benefits of Improved Sanitation and HygieneA similar picture has been found for other parameters analyzed(see Figure 14). Surface water samples at sites R6 andR7 were polluted with organic matter, and the BOD andCOD values significantly exceeded the QCVN 08 standard(see horizontal red line in Figure 14). High pollution isfound in standing waters such as ponds and reservoirs, andin small flow canals, where the dilution coefficient and selfpurificationcapacity of the water bodies are limited. Morepollution is also found in places with high population density,such as sites R4, R6 and R7.BOD and COD values at R2 and R3 are much lower,even though sanitation facilities at these sites are alsonon-isolated, and pollution risks for children are stillhigh. Reasons for the better water quality at R2 and R3include better permeability of the soil (at R3), low-populationdensity (at R2), and less overflow of untreatedwastewater.Figure 15 and Figure 16 below show the extent of isolationof human excreta at urban and rural field sites. Householdsare classified ‘partially isolated’ or ‘fully isolated’, accordingto the type of sanitation systems applied.In urban areas, a ‘partially isolated’ septic tank system isthe most common application (as at rural sites, if effluentfrom septic tanks and gray water are not treated further, thesystem is considered ‘partially isolated’). Only Hai Phong(U3), Quang Ninh (U4) and Dak Lak (U5) are ‘fully isolated’sites, where wastewater treatment is applied in partof the city. Lower values for pathogens and organic matter(BOD, COD) in surface water at U3, U4, and in groundwaterat U3, U4 and U5 surveys confirm the role of improvedsanitation. A highly dense population served by anold combined sewerage system in which most wastewateris still untreated is among the reasons for low surface waterquality at Hai Phong (U3), the second largest city in NorthernVietnam.In rural areas, OD and wet pit latrines are considered ‘notisolated’. These types of toilet are also considered ‘unhygienic’according to Vietnam MOH classification (Decision08/QD-BYT-2005). No single type of sanitation system inthe surveys has been found to be ‘fully isolated’ because ofincomplete collection and treatment of wastewater flows.The septic tank receives black water from the toilet; the septictank effluent is then mixed with untreated gray water(from the kitchen, shower, etc) and discharged directly intothe soil or into a combined sewer. A similar picture is foundwith biogas digesters. Only one site (R7, Lai Xa village)had cluster wastewater treatment. However, the system wasbuilt for only a part of the village, and the combined sew-FIGURE 15: EXTENT OF ISOLATION OF HUMAN EXCRETA AT URBAN FIELD SITES (%)Daklak (U5)Quang Ninh (U4)Hai Phong (U3)Quang Nam (U2)Dong Thap (U1)0 20 40 60 80 100PercentageNot isolated ODFull isolation w/w managementNot isolated wet pit latrineBiogas digesterPartial isolation septic tankwww.wsp.org45