SANEX™ was developed at the Advanced Wastewater Management Centre (AWMC) at the University of Queensland, Australia. The project was co-funded by the Swiss Development Cooperation (SDC). The software runs in the MS Windows operating environment and can be downloaded at no cost from

http://www.awmc.uq.edu.au/download/sanex/ 

To explain how SANEX™ works this article uses a simplified sewerage demonstration project for a low-income community in Malakasari, east Jakarta.

The SANEX™ Interface

The main screen (Figure 1) is divided into three sections: navigation, where criteria can be accessed; a section where the question for the currently selected criterion is displayed; and a list of feasible alternatives that is updated based on user input.

Figure 1: The main screen

1. Level of community involvement
2. Level of community motivation
3. Community requirements regarding convenience and status
4. Community requirements regarding resource recovery
5. Coordination of construction activities
6. Management abilities of local authorities
7. Local availability of construction services and commodities
8. Construction impediments

In order to express the TAC, the most expensive alternative is assumed to cost 100%; all other alternatives are then calculated relative to this figure. Clicking on any of the buttons labelled with the index names sorts alternatives accordingly.

Figure 2 Graphical output screen

SANEX™ can also output more detailed information such as a summary of the sub-indices ratings, capital costs and annual recurrent costs. A built-in comprehensive encyclopaedia enables less experienced users to work with the software.

The total population size of the Malakasari community is about 36,000 people. However, the project was designed to serve only a fraction, namely 3000 people in 474 houses. In this area the population density is about 300 persons per hectare. The demonstration project consisted of a simplified sewerage network and a treatment plant with anaerobic and aerobic contact process units. The author visited the project in 1996 and again early in 1998. Then construction of the sewerage system and the plant was largely completed and house connections were being installed.

SANEX™ divides the evaluation process into two steps:

1. Screening: An initially large set of sanitation systems is screened to eliminate infeasible alternatives.
2. Comparison: The merits of the remaining alternatives with regards to beneficiaries’ situation and preferences are compared. As explained in the previous section, the composite indices ‘implementability’ and ‘sustainability’ are calculated to facilitate the ranking of alternatives.

This stage incorporates 21 criteria, addressing largely technical issues. If the outcome for a criterion is worse than a given threshold, some alternatives are eliminated. In order to pass the screening evaluation, a sanitation system must fulfil all criteria. Failing one leads to its rejection, even if it is acceptable with regards to all other criteria.The following list outlines critical issues in the Malakasari community and explains how SANEX™ interpreted user input to determine the feasibility of alternatives.

1. Planners indicated that dwellers wanted at least on-plot, preferably in-house toilets. SANEX™ did therefore not allow public toilet blocks or facilities shared with neighbours.
2. The use of cartage systems was precluded by narrow street access to many dwellings, which would hinder the convenient removal of nightsoil.
3. The new facilities had to be suitable for receiving combined black- and greywater. The implications of this requirement are linked to the design population density and the water supply systems. SANEX™ assumes that two thirds of the population growth are accommodated by increased population density and one third by area expansion. For Malakasari, assuming a constant population growth of 3% per year throughout the project design life of 15 years thus resulted in a design population density of over 400 persons per hectare. This density precluded the use of septic tanks connected to soakaways, which would receive toilet effluent and, as a result of piped water supply, large volumes of greywater of around 100 L per person and day. Given the large absorption areas required in this situation, SANEX™ limits the application of septic tanks connected to soakaways to populations less dense than 100 persons per hectare.
4. Simple sanitation systems like latrines and aquaprivies can only accept small volumes of greywater (i.e. up to about 30 L per person and day) and thus were also not feasible.
5. In summary, SANEX™ considered the following systems appropriate: conventional sewerage, simplified sewerage, and settled sewerage. This result does not take into consideration affordability, which is discussed in the next section.

The second evaluation stage uses 29 socio-cultural, technical and financial criteria to rate those alternatives that passed the screening stage. Results for the Malakasari community were as follows:

1. The fact that beneficiaries were willing to allocate only 1% of their income to improved sanitation and were not ready to contribute in kind suggests a lack of motivation. Residents seemed to be content with their situation and saw no pressing need for improvement.
2. The community was not sufficiently involved in the decision making process. Participatory activities were restricted to updating the community on project aims and progress mainly via their leaders.
3. Residents complained that street surfaces damaged during pipe laying were not re-sealed properly. Also, to connect houses, floor covers had to be partly removed, but subsequently were not properly replaced. For example, some house owners said that original tiles were only partly replaced by tiles of other patterns or colour. Clearly, the resulting aesthetic effects were no incentive to the remaining households to connect.
4. These concerns apply to a similar extent to all three systems identified as feasible during the screening stage.
5. Because SANEX™ does not include the treatment technology used in the Malakasari project, comparison of cost estimates was only possible for the simplified sewerage network. Local authorities had estimated that costs of the complete system (including house connections) would be 631,973,000& Rp (1995). By comparison, the SANEX™ estimate in Indonesian currency was 592,596’000& Rp (1995). Costing results for the other two systems considered software feasible by the software were 1,378,130,000& Rp for conventional sewerage and 289,407,348& Rp for settled sewerage (excluding septic tanks).

Basically, the evaluation results from SANEX™ confirmed the assessment of local planners. But the software also showed that, since most houses already had septic tanks in place, the installation of settled sewerage would likely have been a less costly alternative. However, planners did not like this option, saying that residents could not be trusted to properly maintain and empty their tanks. Also, since most septic tanks were installed by house owners, the assumption was that most tanks probably would require upgrading. When attending a community information evening, the author found several of the outcomes from the comparison stage confirmed. Community leaders said that for most households disadvantages from connecting to the sewerage network outweighed advantages. In fact, displaying mainly an ‘out of sight out of mind’ attitude with little concern for their environment, the only consequences of connecting that most residents clearly saw were service fees and construction-related hassles. Some also hinted that the project was generally seen as a government effort imposed on their community and that they had been content with the situation as it was before.

The author:

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