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United Nations Environment Programme
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Sanitation alternatives considered in SANEX
Toilet facilities:
  • Pour-flush toilet
  • Cistern-flush toilet

On-site facilities:

  • Simple pit latrine
  • VIP latrine
  • Pour-flush latrine
  • Aquaprivy
  • Septic tank
  • Vault (vacuum cartage)
  • Seepage pit
  • Drain field

Public facilities:

  • Public toilet block
  • Overhung latrine
Resource recovery:
  • Double-vault composting toilet
  • Excreta-fed fish pond
  • Septic tank for excreta reuse
  • On-site biogas digester

Sewerage:

  • Covered stormwater drains
  • Conventional sewerage
  • Simplified sewerage
  • Settled sewerage

Off-site treatment:

  • Communal septic tank
  • Imhoff tank
  • Primary treatment
  • Waste stabilisation ponds
  • Activated sludge treatment

Reference: Loetscher (1998)

8.3 Scenarios for Sound Practices

General scenarios can be sketched based on population density to illustrate integration of technology, environmental, economic and social factors. For a low population density and where land is available around dwellings, on-site systems with on-site reuse provide householders with options that are a function of water availability, toilet type and desired reuse of blackwater and greywater. Use of a double vault composting toilet (4.1.2) and greywater for subsurface irrigation is shown in Figure 40. Maintenance requirement will be emptying the vault (say, every 6 months), windrow-composting the content with garden waste and diverting blackwater from a full vault to the one just emptied. An irrigation system for greywater needs to be checked weekly. A system requiring less householder maintenance is a septic tank with an inverted leach drain or evapotranspiration trench (4.1.5). The septic tank needs to be de-sludged every 3 to 5 years by calling a sludge contractor. This service should be available in the community for this option to operate satisfactorily including the safe disposal of the sledge by the contractor.

For a high population density, community ablutions blocks with payment for use can work well. The wastewater can be conveyed to a location where land is available for land-based treatment (4.2.4) and reuse through grazing grasses irrigated by treated wastewater. The operator of the ablutions facilities needs to ensure public health requirements for the wastewater reuse are met.

Another option for high density areas are toilet facilities in individual dwellings with wastewater collected using simplified sewerage (3.2). This can be condominial sewers or with street connections depending on community choice. Collected wastewater is treated using a series of lagoons (4.2.3), with the final lagoon employed for aquaculture (6.1.2.). Depending on land use downstream of the lagoons, wastewater can be reused further for agriculture, horticulture or tree plantation.

A well-planned sewerage system should be:

  • Energy efficient - be developed within a catchment basin to use gravity flow
  • Environmentally sound - reuse wastewater nutrients to prevent pollution
  • Economically efficient - balancing economy of scale of treatment and the cost of the sewer pipes
  • Commmunity orientated for community consultation

These requirements all point to planning for a community-scale collection, treatment and reuse of wastewater. The optimum size of the population served for a community-scale systems will depend on local conditions, which in turn are determined by local geographical (topography, climate, soil), environmental, economic and social/institutional considerations.

A futuristic scenario is depicted in Figure 40 with blackwater and kitchen biowaste collected separately to be anaerobically digested to produce energy (methane). The digested sludge is composted and reused in agriculture. Greywater is treated using wetland and separately reused.

What is clear from the above examples is that there are many technologies that are environmentally sound, from which a community can select based on their local conditions and preference.

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