Chapter 6 Essential Factors for the Provision of Sanitation Systems in Coastal Communities

This chapter identifies the essential considerations for the provision of sanitation technologies in the context of the coastal communities of Puerto Princesa. These considerations are the basis of the preliminary evaluation of low-cost sanitation systems. This evaluation identifies possible options for the case study and discusses the potential and limitations of these systems. Included in the evaluation are the generic classification of low-cost technologies provided in the World Bank studies on appropriate technology for sanitation. Expensive systems such as the chemical, freeze, packaging and incinerating toilets and the waterborne sewerage are not included in the comparative analysis.(1)

6.1 Considerations in the Provision of Sanitation Systems

In the analysis of sanitation in the coastal communities, conditions were found to vary among households, depending on the location of their houses within the coastal area, whether built on dry, transition or water zones.

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The following discussion identifies the key considerations for the choice for sanitation systems in the three zones. These considerations, as summarized in Table 6.1, include environmental, community-specific physical, social and cultural factors.

a. Site Specific Environmental Factors

In this thesis, the environmental factors are the key determinants for differentiating coastal communities from other types of communities. These factors, which include the condition of surface water and soil conditions of the coastal areas, have a direct bearing on the options for sanitary means of disposing of human waste for the community.

Surface Water Condition

The condition of Puerto Princesa bay determines the acceptability of the practice of directly disposing human waste into the water without treatment. As repeatedly mentioned in this thesis, this practice is acceptable if the following conditions are satisfied: first, water is not consumed for drinking; 2) the feces are always deposited in water and not on land; and 3) there is sufficient current for dilution.(2) The objective of these conditions is to ensure that the excreta are disposed of properly and to prevent the contact of waste to the community.

In the context of the Puerto Princesa Bay, the first requirement is not a problem since the water of the bay is saline and is not consumed as drinking water. The water quality of Puerto Princesa Bay, based on the water test conducted by the National Pollution Control Commission in March 11, 1988, revealed that the overall water quality of the bay is still excellent.(3) Although this finding indicates the unpolluted condition of the whole bay, maintaining the existing ecological balance is necessary. During the survey, the observed continued practice of disposing of human waste, wastewater and garbage along the coasts of the bay indicates an alarming pollution problem. As the community grows, this traditional habit, which used to be hygienically acceptable and satisfactory, increases pollution problems.

With the second and third conditions, the practice of direct disposal of human waste in the water regions is not as critical as that in the transition zones. In houses built above the deeper waters, waste is always deposited into the water and not on the land, and there is enough current for dilution. The problems are more critical in the transition areas where solid wastes, which are non-biodegradable, have accumulated. Compounding this problem is the extensive usage of water for domestic and personal washing which is disposed of directly into the ground and surface water. The accumulated solid wastes block the natural flow of the water thereby creating pools of stagnant waters and impeding natural flushing of other biodegradable wastes. Thus, in these areas, excreta is exposed in the environment.

Ground Condition

For parts of the community located within the elevated and transition zones, the ground condition is an important consideration in the provision of sanitation systems. The topography of the site of the coastal slums is moderately sloping or rolling. The area is very low with +3.064m. and +0.21m as the highest and lowest portions respectively above the mean lowest low water (MLLW). Thus, even on the elevated areas, internal drainage or the ability of soil to absorb water is generally low since the water table is very shallow. The clay soil is deep, poorly to very poorly drained, fine and loamy in texture.(4)

Analysis of ground conditions has to be considered to avoid groundwater contamination and pollution of the bay, because these areas have a high water table and a direct hydraulic connection to coastal waters. The disposal of human waste into the ground presents a potential hazard to the health of the community. As discussed in the previous chapter, people consume water from the well for drinking. The location of the well is fairly close to the toilets of the nearby households. Groundwater contamination promotes disease transmission from the disposal site, through the groundwater to users of well water.(5)

Disposing human waste in the coastal areas without treatment causes pollution of the bay. The site's proximity to the shore means that polluted runoff goes quickly to the coastal water basin with little time for natural purification through vegetation and soil.(6) Environmental factors such as soil type and porosity, groundwater level and hydraulics, and distance to surface water influence the degree of contamination.

In the choice of sanitation technologies, ground conditions, particularly groundwater level, soil permeability and stability, are important considerations.(7) Some sanitation technologies, except those which can be built above the ground, are feasible when the ground water level is below one meter from the surface. Other options require permeable soil for soakaway of effluent and others require stable ground for construction.

In this context, sanitation technologies can be classified as those without soil requirements and hence, can be contained above ground, and those with soil requirements. Systems that can be built above the ground are technically feasible in the three zones of the coastal communities. Options include the composting toilets, the vault and cartage system, the bucket latrines, the shallow sewer system and the small bore sewer system. On the other hand, systems that have soil requirements include pit latrines, aqua privy and septic tank. These systems require soil conditions characterized as stable, permeable and with low ground water level. These systems are technically not feasible in coastal communities, since they can not be built on sites with adverse ground conditions.

There are cases, however, when some on-site systems are modified to suit conditions of sites characterized by high groundwater level. In the case of the pit latrine, the pit can be raised above the ground level or double pits can be built to increase capacity when excavation is difficult. This prolongs the useful life of the facility and overcomes the difficulties with high water table and groundwater pollution. In the construction of the raised pit latrine, the raised portion should be lined and rendered to prevent the seepage of foul liquid out of the pit.

b. Community Physical Factors

Community density, circulation and access networks, and available services within the community influence the selection of sanitation technologies. The implications of these factors are discussed below.

Community Density

In selecting sanitation systems, consideration of community density is critical in settlements with high density, as in the case of Puerto Princesa. On-site systems such as pit latrines, aqua privies and septic tanks require adequate space for the infiltration of waste discharged into them. These systems are not suitable for high density settlements, since high density poses danger in terms of wells for drinking water and sanitation facilities to be close together. Water seeping out of pit latrine which are bacterially and chemically contaminated will pollute the surrounding groundwater. The effluent from the septic tank, which did not permeate well through the soil, is still laden with pathogens and contaminates the nearby supply of drinking water. Hence, these systems are suitable only in low-medium density areas. Systems suitable for high density areas include the vault and cartage system, the shallow sewer system and the small bore sewer.(8)

Circulation and Access Network

As discussed in the analysis of present conditions in the coastal communities, the circulation network of the community consists of narrow footpaths on land and wooden walkways on water supported by stilts. In the selection of sanitation technologies for the community, some systems require methods for transporting waste from the place of defecation to another for waste treatment. In these technologies, waste is emptied manually or sludge is removed by a vacuum suction tanker or carts and is taken away for suitable disposal. The existing access network, consisting of narrow footpaths and walkways on stilts, poses limitations to the use of technologies requiring the use of trucks or carts for transporting waste. Access for trucks within the community is impossible.

In this context, sanitation technologies are classified according to those with waste transportation requirements and those without, with the former group at a disadvantage. Systems with waste or sludge transport requirement include bucket latrines, aqua privies, the septic tanks, the vault and cartage system and the composting toilets. On the other hand, those without transport requirement include the pit latrines, the shallow sewer system and the small bore sewer system.

Proximity and Access to Services

Households located above the waters have the least proximity to the different services that are normally situated on the dry and elevated areas of the site. Unfortunately, households occupying these areas consist of a large percentage of the community. The proximity and accessibility of services such as water supply and communal toilets to the majority of the households affect choice of sanitation options.

  • Access to Water Supply and Levels of Service

The types of water services in a given community can be hand-carried supplies, yard taps or in-house connections. These levels categorize the different sanitation options. Systems without water requirement or those requiring water only for toilet hygiene, include pit latrines, pourflush toilets, composting toilets, and their various adaptations. Those which require at least yard or household pump include septic tank and vault. More expensive systems such as cistern-flush toilets with conventional sewerage or septic tanks and soakaways are technically feasible when an in-house connection is available.(9)

In the context of the case study, the in-house connection is limited and water is usually bought or fetched from communal handpumps and hence, hand-carried. Though some households on both the transition and water zones have water connections from the city lines, water coming from this source is not consistently available and is normally collected and stored in large drums. For the majority of the households carrying water to their homes, the distance traveled by the household member fetching the water from the handpumps can be as far as 400 meters. Thus, options requiring individual in-house connections or a large amount of water for disposal are not feasible. Options are limited to systems that require at the most communal standpipes or handpumps for water service levels. Other systems that require no water or those in which water is used only for toilet hygiene are highly favorable.

  • Access to Communal Toilet

The analysis of the provision of communal toilet to the coastal communities indicates that the households' access and proximity to communal toilets is an important factor influencing its acceptability to the community. From a technical point of view, communal facilities may be considered the most feasible low-cost alternative for providing sanitation to the coastal slums. This facility can serve many people and is more economical on a per capita basis than are individual household facilities. This system consists of a number of latrine cubicles with shower, laundry and clothesline facilities in some cases.(10)

With this option, facilities can be built on more suitable areas, and any waste disposal system, whether on-site or off-site systems, can be used as is technically appropriate. When communal sanitation facilities become an acceptable option, determining the most strategic location of the facility is essential. The physical layout of the coastal communities is characterized by dwelling units built on mudflats and extending towards the open waters. In this context, the capacity of the facility and the distance the user has to travel from his home to the toilet are among the important factors to be considered.

As discussed earlier, with environmental considerations, the nearer the location of the facility is to the surface water, the fewer become the options for waste disposal. The adverse ground conditions make other options technically unfeasible to operate, and increase the cost of those systems which are applicable. In cases wherein a large percentage of the population is located above the water, determining the best site for the facility involves the analysis of tradeoffs among accessibility and convenience of users, the target number of users and the cost of construction.

The success of providing communal toilets does not merely depend on the ideal location and construction of the facilities. Experiences with the use of communal sanitation facilities also show that such options requires a high level of regular cleaning and basic maintenance. As in the case of the coastal communities, people prefer to use their individual overhung latrines or defecate on the surface waters than to use dirty communal toilets. The use of communal sanitation facilities becomes successful if there is a reliable party responsible for its maintenance or if there is a strong sense of community responsibility.

c. Social and Cultural Factors

Sanitation systems, even when they are properly designed, may not be appropriate when social and cultural factors affecting sanitation and hygienic practices of the community members are not considered. For instance, technologies involving re-use of excreta are unfeasible in communities where sight or handling of waste is culturally and socially unacceptable. In the same way, dry technologies are inappropriate for communities which prefer water for toilet hygiene. For the analysis of attitude in sharing toilet facilities, the level of privacy required by the community is essential. Cultural attitudes towards defecation vary; but generally, it is regarded as a private personal act. In communities that require a high level of privacy, the design of communal facilities should provide for these requirements.

Acceptability of Wastehandling

Some sanitation systems such as composting toilets and bucket latrines require wastehandling and re-use of excreta. Waste to be transported can either be the fresh excreta itself or decomposed excreta. The bucket latrine involves the handling of fresh excreta, making the system more prone to unsanitary wastehandling. The composting toilet, on the other hand, involves the handling of waste only when the excreta has been transformed into non-offensive, less harmful humus. Culturally, the most important distinction in the choice of the sanitation systems is dependent on whether the community regard human excreta as a valuable resource or view it as an unpleasant and dangerous waste product.(11)

In the context of the case study, wastehandling is culturally unacceptable. For the community, it is best to dispose of the excreta right away. When asked about the potentials of waste reuse, respondents claimed to be uninformed about the possibility. This inevitably rejects options requiring wastehandling.

User Hygienic Practices

The material used for anal cleaning affects the choice of technology. In the sanitation systems surveyed, the systems can be categorized as dry or wet systems. Dry systems, such as the composting toilets, do not allow the use of water. When water is used for anal cleaning in pit latrines built in low-permeable soil, poor perculation and water logging occurs. In wet systems such as the pour-flush and cistern flush toilets, solid materials such as rocks, mud balls, corn cobs, stones and sticks cannot be used since these materials would cause blockage problems.

In the context of the coastal communities, water is the preferred material for anal cleaning. This may be attributed to the fact that water is available to the community and that paper and other solid materials are discouraged from being thrown into the bay to prevent further pollution. For those households with toilets and treatment tanks, water and sometimes toilet papers are used. This consideration favors wet systems or those which allow the use of water at least for toilet hygiene.

Privacy Requirements

Privacy requirements of community members should be considered, especially in the provision of communal toilet facilities . Such requirements include how many users are served by the facility and how the users are grouped and assigned to use and maintain a particular toilet cubicle. The World Bank studies on sanitation identified three basic approaches to the design of communal sanitation blocks.(12) The first is to have a a highly public system, in which any user can enter any toilet compartment not in use at that time. Related to this is the separation of facilities for male and female users. The second is to provide a cubicle within the communal block for the exclusive use of one household. The third approach is a combination of the first two types, in which a public sanitation block is provided but reserved for the exclusive use of a large kinship group. The kinship group can be composed of several households that may belong to a patrilineal affinity or can be through camaraderie among neighbors.

In the context of the case study, experience shows that providing a highly public toilet is not at all feasible. Misuse and poor maintenance resulted since the facility is not owned by any household. Another problem associated with this approach is the non- acceptability of household members to share the facility with other households. Toilet activities are considered as very private, thus, sharing the same facilities with strangers is not at all favorable.

The second and third approaches are more feasible, as compared with the first design, since the household can guard and maintain their "private" facility. This is manifested in the case of Barangay Pagkakaisa, where the existing communal toilets are being used and maintained by the households living near the facility. However, the second approach, in which one cubicle is assigned to one household, is more expensive and unrealistic. In the coastal communities with very high density, it would be difficult to find enough space in the more elevated sites to provide all the toilet cubicles necessary. Thumbnail('nav-fig0601-sm.jpg','nav-fig0601.jpg'); ?> The third approach appears to be more realistic, since a lesser number of cubicles is provided. However, the type of social grouping per communal block will have to assessed well for this approach to be feasible.

Based on the discussion above, the important considerations for the provision of sanitation systems, whether individual or communal facilties, in the coastal communities of Puerto Princesa are summarized below. The preliminary comparative analysis of low-cost sanitation systems based on these criteria is shown in Figure 6.1.

  • Sanitation systems should be feasible in areas with adverse ground conditions to avoid contamination of surface soil, ground water and surface water.
  • System should be applicable to high density settlements.
  • System should require minimum water, with communal stand pipes or handpump as the highest water service level.
  • Waste or sludge collection, if required, should not involve large vehicles or large equipment.
  • System should not require wastehandling, most especially handling of fresh excreta.
  • Water can be used for toilet hygiene.
  • In the provision of communal toilets, special considerations include the following:
  • In determining the location of the facility, the access and proximity of households especially those located on the water zone should be considered.
  • Proper use and maintenance of the facility can be achieved if facilities are exclusively used by a group of households.
  • Household groupings based on kinship or camaraderie among neighbors are favorable.
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6.2 Sanitation systems Options

Among the criteria developed, feasibility under adverse ground conditions is the most important consideration which inevitably limits the options for the community. This factor eliminates on-site options such as the pit latrines, aqua privy and septic tanks. Hence, sanitation systems which can be built above the ground or those without soil requirements are favorable for the community. Included are the composting toilets, bucket latrine, vault and cartage, shallow sewer system and the small bore sewer system. The following discussion identifies the limitations and potentials of these sanitation options in their application to the case study.

a. Composting Toilets

Composting toilets are classified as dry, on-site systems, which have no soil requirements, and can be built above the ground.(13) They can be used under the most difficult soil and ground water conditions.(14) The term composting has been defined as a biological process for converting organic solid wastes into a humus like product whose chief use is as soil conditioner.(15) The composting process is anaerobic and requires several months, preferably a year, to make the compost safe for use as a soil conditioner.

Composting toilets can be classified into two major types, namely the continuous and the double vault composting toilets. The continuous composting toilet consists of the composting chamber situated immediately below the squatting plate. The chamber has a sloping floor above which is suspended inverted U or V shaped channels. Grass, straw, ash, sawdust and easily biodegradable household refuse as well as excreta are added to the composting chamber. The composting material slowly moves down the chamber and into a humus vault, from which it must be regularly removed.(16) Figure 6.2 illustrates this type. The double vault composting toilet has two adjacent vaults, one which is used until it is about 3/4 full, when it is filled with earth and sealed, the other vault is used. Ash and organic matter are added to the vault before it is sealed to absorb odors and moisture. The tanks are paved and are constructed above the ground so as not to be submerged by rainwater.

The composting toilet, which can be built above the ground is technically feasible in the three zones of the community. Application of this system, however, is critical in the transition and water zones. Within the transitional area, careful design and construction is required to avoid water infiltration into the composting chamber. One version of the composting toilet, called the Vietnamese toilet, as discussed in Chapter 3, is considered the only toilet system that functions well in the swampy and floodprone areas. It consists of two tanks for dry and anaerobic composting, built above the ground. (17) The construction of the composting vault suspended or supported above the water is theoretically feasible but would require innovation and additional cost. Watertight vaults can be prefabricated locally using labor and materials available within the community. However, no field report supports this assumption and hence, it would require an on-site application to test the feasibility of this system.

The composting toilet in general does not disturb the ecological balance of the environment as there are no dicharges of excreta into water bodies, ground water or soil. When the excreta are finally returned to the soil, they have already been transformed into humus through the decomposition that took place in the receptacle. However, although environmentally feasible, the acceptability of the composting toilet is limited by social and cultural factors. The use of composting toilets in general is successful when they receive a high degree of user care and attention and where wastehandling is acceptable.

In the context of the coastal slums, wastehandling is rejected by the community, thus, making the system not acceptable. Another limiting factor is the use of water for toilet hygiene by the community members. The composting toilet, being a dry system, does not allow the use of water. These factors restrict the application of composting toilets in the case study. The evaluation of this system is summarized in Table 6.2.

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Other systems, such as the bucket latrine, the vault and cartage system, the shallow sewer systems, and the small bore sewer system, are classified as off-site systems in which excreta are collected from individual houses and carried away from the plot to be treated and disposed of in another site. In theory, these options are feasible since problems of excreta being disposed directly to the surface waters and in soils with high groundwater levels are avoided. However, in these systems excreta will have to be disposed of safely somewhere else or will have to be re-used.

b. Bucket Latrine

Among the off-site sanitation systems, collection of excreta in buckets, pans and baskets is a common practice throughout the world. Whatever the mode of collection, the principle involves defecation into a container which is removed for disposal at frequent intervals into local surface water bodies or on land. This is the cheapest method for excreta collection in terms of capital investment; it is highly flexible and does not require any major capital outlay by the householder.(18) Figure 6.3 illustrates a typical bucket latrine.

In the context of the environmental and community physical factors, the bucket latrine is technically feasible in the coastal communities, even in the transition and water regions. The technology can be easily built or provided, it requires no water for operation and can be used in high density settlements. However, problems associated with social and cultural acceptance are involved. Major restricting factors in the usage of the bucket latrine in the communities are the rejection of wastehandling and the use of water for anal cleaning. Furthermore, the literature review indicated problems such as odor, insects, spillage and unsanitary conditions at the collection and transfer points, in the actual use of this system. Problems of transporting the excreta are amplified in the case of coastal communities where access is difficult. Thumbnail('nav-fig0603-sm.jpg','nav-fig0603.jpg'); ?> Though it is possible to make several improvements to the normal bucket latrine system by providing facilities for washing and disinfecting the buckets and by covering collection buckets with tightly fitting lids, it is still difficult in practice to ensure that the system is operated satisfactorily.(19) In this context, as summarized in Table 6.3, the usage of the bucket latrine in the case study is not feasible.

Note: Table 6.3, Fig. 6.4 and Table 6.4 are currently not available

c. Vault and Cartage System

The vault and cartage system is composed of a low-volume water flushed toilet which discharges into a sealed tank or vault in which the waste is stored for a few weeks. It is then emptied by a vacuum suction tanker and taken away for suitable disposal. The vault and cartage system overcomes the problem of the frequent emptying experienced with bucket latrines.(20) This system is illustrated in Figure 6.4.

The application of this system in the coastal communities is environmentally feasible since the system can be built above ground. However, like the composting toilet, constructing the vault above the water involves innovation and this assumption has to be verified through further studies. Other factors favoring this system are its feasibility in high density settlement, no handling of waste by the users and minimum use of water.

Factors limiting the application of this system are the requirements for waste collection and for a highly efficient organization for regular collection services. Normally, large collection vehicles are used to empty the tank. But in the case of coastal communities, where vehicular access is impossible, improvisation on the collection vehicle can be done. In areas, where access is difficult, smaller collection vehicles such as hand-or animal drawn carts with manually operated diaphragm pumps or small mechanically or electrically operated vehicles fitted with mechanically operated pumps can be used. Another option for this case is a pipe connection to an accessible communal vault.(21)

Though the vault system requires a minimum amount of water for maintenance, it is expensive to operate and requires a highly efficient urban local authority to organize regular vault emptying. Thus, the application of the vault and cartage in the case study is feasible as long as access to waste collection is provided. The summary of the evaluation of this system is shown in Table 6.4.

d. Shallow Sewer Systems

Among the sanitation systems included in this evaluation, the shallow sewer system proves to be the most feasible. Also known as the small diameter sewerage, this system has emerged as a result of adapting the design standards of the conventional sewerage to suit the physical conditions of urban low-income settlement, such as adverse ground conditions, high settlement density and high water consumption.(22) The system is designed to accept all household wastewaters, excreta, toilet flush water and sullage in their fresh state for off-site treatment and disposal.

As applied in the urban poor in Brazil,(23) the system consists of small diameter pipes, normally 100 millimeters, laid on flat gradients in shallow trenches. They are usually laid in backyards and narrow back alleys. Inspection chambers are built at intervals along the length of sewer lines to facilitate house connections and provide access for maintenance. Once the shallow sewer emerges from the block, various options exist: it can be connected to a conventional sewer, to a communal septic tank, or discharged straight into waste ponds. The choice depends on the site.(24) Figure 6.5 illustrates the typical layout of this system.

In the context of the coastal communities, the application of the shallow sewer system is more advantageous than the other options discussed earlier, as shown in Table 6.5. It is feasible in the three zones of the community, since the small diameter pipes can be laid even on site with adverse ground conditions and underneath the walkways built above the water. In this set-up each household, even those located above the bay, can have pourflush toilets connected to the small diameter sewer lines. For waste treatment, the small diameter sewer lines can then be connected to the city main sewer, if possible, or to communal septic tanks which can be built on sites with favorable ground conditions.

Other factors favoring this system include its feasibility in high density settlements and a minimum water requirement. It can be used with low-volume pour-flush toilets in areas where the water supply is standpipe level of service. The system requires no manual handling of waste and allows the use of water for toilet hygiene.

A significant advantage of the shallow sewer system not found in the other options is the simultaneous collection and treatment of wastewater with human waste. The system does not rely on large quantities of flushing waters for their trouble-free operation but on the high frequency with which wastewater can pass through them.(25) With the use of the this system, the large amount of wastewater is disposed of properly.

Note: Fig. 6.5, Table 6.5, Fig. 6.6 and Table 6.6 are currently not available.

e. Small Bore Sewer System

The small bore system, like the shallow sewer, is an improvised version of the sewerage system which has incorporated the requirements of high density, low-income communities. As shown in Figure 6.6, it involves the upgrading of systems using on-site leach pits or soakaways, such as the septic tank, by connecting them to small bore sewer systems so that their partially treated effluents are removed for treatment and disposed of off-site.(26) Such upgrading is possible when the level of water consumption increases, as a result of an increased or improved water supply in the community. With the effluent conveyed in a small bore sewer system partially treated, lower water flow velocities are required to prevent solid deposition within them. Hence, small diameter pipes are used and are laid at flatter gradients.(27)

Like the shallow sewer system, the small bore sewer can be built even in adverse ground conditions since waste is transported to another site for treatment. It can be applied in high density communities, requires no wastehandling or manual transportation of waste, allows the usage of water for toilet hygiene and incorporates the disposal of waste water. One limitation it has, however, as compared with the shallow sewer system, is its feasibility in the water zone. Since this system entails the usage of on-site systems such as the septic tank for each household, the construction of such tanks above the water is technically not feasible. An alternative for this is the incorporation of the shallow sewer system applied in the water zone with the small bore sewer applied in the transition and dry zones. The evaluation of this system is summarized in Table 6.6.

This chapter cited the factors influencing the selection of sanitation technologies for the case study. Factors include environmental, community specific physical, social and cultural factors. Environmental factors, such as the condition of the surface water and soil are considered as the preliminary factors for the selection of sanitation technologies for the case study. Conditions of the surface water justify whether the practice of disposing of waste into the water is still acceptable. The soil conditions of the site, characterized by high ground water level and poor permeability, favor those systems without soil requirements and those that can be built above the ground.

The other essential factors include community specific physical, social and cultural factors. Physical factors include community access networks, access to water supply and communal toilets. The poor access networks in the community limit options of those technologies not requiring the use of large trucks to collect sullage or waste. The level of water service in the community, consisting mostly of hand-carried water supply from communal standpipes or bought from neighbors, limit options not requiring in-house water connection. Social and cultural factors, on the other hand, include the user's requirements such as acceptability of waste handling, hygiene habits and required privacy level.

In the evaluation of the various sanitation systems based on the developed criteria, it can be concluded that the options for the community are narrowed down to those systems that can be built even with adverse ground conditions. These options include the composting toilets, the bucket latrine, the vault and cartage, the small bore sewer and the shallow sewer system. Social and cultural factors eliminate the bucket latrine and the composting toilets. The vault and cartage options are potentially feasible, except in the water zone, as long as the access to waste collection is provided. The application of the small bore system is only feasible within the elevated and transition zones of community. Among the systems discussed, the shallow sewer system proves to be the most appropriate based on the developed criteria.

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1. The chemical, freeze and packaging toilets are considered expensive modern variations of the bucket latrine, which involve the conservation of waste for some time without too many adverse environmental effects and allow later treatment elsewhere. Incinerating toilets requires the use of oil, gas, or electricity for operation. These toilets are expensive to purchase and to operate. Nimpuno, 1984, p.268.

2.McGarry, 1977, pp. 247-248.

3.PIADP, 1989.

4.Puerto Princesa City Profile, 1989.

5. Charles G. Gunnerson, et.al., Appropriate Sanitation Alternative: A Planning and Design Manual, (Baltimore: John Hopkins University Press, 1982), pp. 21-22.

6. Clark, 1974.

7. Gunnerson, et. al., 1982, p.42.

8. Kalbermatten, et. al., 1980, pp. 44-45.

9. Ibid., et. al.,1980, p.37.

10. Gunnerson, 1982.

11.Uno Winblad; and Wen Kilama, Sanitation Without Water, Monograph (Stockholm: Swedish International Development Authority, 1980), p. 23.

12. Kalbermatten, et.al.,1980, p.141.

13. Gunnerson, et. al, 1982, pp.40-41.

14. Winblad, 1980, p.3.

15. C.G. Golueke, Composting, (Emmaus: Rodale Press, 1976), as quoted in, Witold Rybczynski, Chongrak Polprasert, and Michael McGarry, Low Cost Technology Options for Sanitation: A State-of-the-Art Review and Annotated Bibliography, (Ottawa: International Development Research Centre, 1978), p.16.

16. Witold Rybczynski, Chongrak Polprasert, and Michael McGarry, Low Cost Technology Options for Sanitation: A State-of-the-Art Review and Annotated Bibliography, (Ottawa: International Development Research Centre, 1978), p.18.

17. Nimpuno, pg.275-276.

18. McGarry, 1977, p.254.

19. Ibid., 1977, p. 254.

20. Cotton,et. al., 1991, p. 85.

21.Gunnerson,et. al, 1982, p.118-119.

22. Sinnatamby, 1990, p.146-147.

23. For detailed description of the shallow sewer system in Brazil, see for example: Cheri Hart, "Classy 'Condo' Sewers for Brazil's Urban Poor, UNDP, March 1991, pp.16-20. For detailed information regarding the design, operation and maintenance of shallow sewer systems, with relevant case studies, see for example UNCHS, " The Design of Shallow Sewer Systems", Nairobi, Kenya, 1986

24. Hart, 1991, p.18.

25. Sinnatamby, 1990, p. 150.

26. Ibid., 1990, p.144.

27.Ibid., 1990, p.144.

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