The aims of this ten week desk study were as follows.

1. To identify locations where a saline sewerage systems are currently being used, the level of treatment provided (if any) for saline sewage, and the effectiveness of any such treatment. To compile further evidence on the viability of use of saline water as a carrier in sewerage, and on the viability of treatment of saline sewage.

2. To contact agencies, authorities and individuals in water-short countries to establish if they have any experience or interest in the use of saline sewerage and/or the treatment of saline wastewaters.

3. To conduct investigations into the effect of salinity on equipment which will be used for saline water sewerage and/or saline wastewater treatment.

4. Preparation of recommendations for further, more detailed, research in the light of the findings.

5. Production of a report for submission to the ODA.

Phase 2

To build on the previous research, and to fill a gap in the knowledge base by seeking to establish the demand for use of saline water in urban coastal fringes.

Through an extensive literature search, the use of a questionnaire sent to several correspondents, and collaboration with water utilities and wastewater companies, a detailed picture of the world status on seawater toilet flushing has emerged.

Information was collected in two main ways:

1/ From literature reviews on specific aspects of interest.
2/ Correspondence with engineers working in locations that may have an interest in the idea of using seawater for toilet flushing.

Phase 2

Main activities:

The survey revealed that several countries currently use seawater in industrial processes. This is mainly for cooling, and hence there is generally no treatment prior to disposal. Some other countries make use of seawater for domestic uses (mainly toilet-flushing), with treatment ranging from none to secondary.

There is further interest in domestic use of seawater (indicated by whether, in times of water shortages, the use of seawater for some domestic activities would be considered). Respondents indicated a variety of perceived causes of concern about the use of seawater, including: cost of infrastructure, treatability of saline sewage, corrosion of the infrastructure, possibility of cross connections, insufficient research, and the limited value of end products (effluent/sludge).

Phase 2

The visits to the Pacific atolls (Majuro in the Marshall Islands and Tarawa in Kiribati), along with correspondence with Gibraltar and Hong Kong, led to the l conclusion that dual fresh/salt water supply systems work on a technical level.

Another separate visit was made to Gaza, which experiences chronic serious water shortages, to discuss the dual water supply option with Palestinian officials. The Palestinian water authority and other prominent organisations in Gaza were, however, sceptical about the prospects for using a dual fresh/salt water supply in Gaza, for a variety of reasons.

There was a very poor response to a questionnaire investigating the level of interest for dual water supply schemes sent to 21 organisations in urban developing areas. It is felt that the lack of response does not necessarily show a lack of potential for implementation of such dual schemes. From informal communications it appears that such systems are assumed to be unproven. The experience of the research team has undoubtedly shown that such systems can, and do, work.

One issue is therefore lack of awareness about dual supply schemes in successful operation, leading to neglect of this issue as an option. It is argued that use of dual supply schemes should be considered, along with other potable water saving options.

The perceived problems can generally be overcome, but at a cost.

Smith M.D., Parr J. and Stear R.M. (1995) Saline water for non-potable uses in coastal areas. Preliminary Report, December 1995. ODA, London

Smith, M.D., Stear, R.M., and Parr, J. Seawater for non-potable uses. (3 pages) 22nd WEDC conference; Reaching the unreached: challenges for the 21st century. New Delhi, India, 1996

Phase 2

Smith M.D., Parr J. and Stear R.M. Saline water for non-potable uses in urban coastal fringes. Draft final report, August 1996. ODA, London.

Parr, J., Smith, M.D. and Stear, R.M., ''Decreasing Freshwater Demand: Dual Supply Systems'', 23rd WEDC Conference, Durban, South Africa, September 1997, pp 0-1.

Papers were presented at two WEDC conferences in India and South Africa.

It has not yet been possible to obtain funding for further work. The greatest interest in the use of dual systems comes from small islands, for which there are limited funding opportunities. Several people have contacted the researchers to request further information, and the government of India has been considering using sea water in toilets in urban metropolitan towns, sending an engineering adviser to study the use of seawater in Hong Kong.

Tel: +44 1509 222640
Fax: +44 1509 211079
Email: m.d.smith@lboro.ac.uk