Newsletter and Technical Publications
<Sourcebook of Alternative Technologies for
in Small Island Developing States>
PART B - ALTERNATIVE TECHNOLOGIES
4. TECHNOLOGIES APPLICABLE TO SMALL ISLANDS WITH SPECIFIC PROBLEMS
4.3 Wastewater Treatment Technologies and Reuse
4.3.1 Wastewater Reuse
The technology for water reuse is a combination of existing wastewater
treatment technologies and water supply treatment technologies. Processes
under the general heading of wastewater reuse range from the most
sophisticated and complex engineering processes to some of the simplest,
natural systems. Detailed descriptions of these technologies can be found
in general literature on wastewater treatment, but, for purposes of
wastewater reuse, the type of wastewater treatment technology chosen
depends on factors such as the type of wastewater; the potential use of
the reused water (for potable uses or non-potable uses); capital and
operating costs; and, existing local facilities and skills for the
maintenance and operation of the selected facility.
Extent of Use
For health and aesthetic reasons, reuse of treated sewage effluent is
presently limited largely to non-potable applications such as irrigation
and industrial cooling (UNESCO, 1991). Examples of such uses on small
islands include irrigation on the Cape Verde islands; sanitation (toilet
flushing) and garden watering in the US Virgin Islands and Fiji;
irrigation of tomato plantations, golf courses, and municipal gardens in
the Canary Islands; irrigation of a golf course on Bermuda; and,
irrigation of a golf course and use as a water source for an ornamental
pond in a bird sanctuary on Aruba. There are no known schemes in SIDS
which utilise treated wastewater from sewage systems for potable purposes.
Operation and Maintenance
Wastewater treatment facilities require a high level of operation and
maintenance, and close monitoring of discharge effluent quality to
minimise health and environmental risks associated with wastewater reuse.
Level of Involvement
This technology requires engineers and highly skilled plant operators
for both construction and operation of reuse facilities.
The costs of wastewater treatment are inevitably high, but will vary
widely according to location, type of wastewater being treated, and public
requirements governing the degree of treatment needed before reuse is
acceptable. Costs for small island applications are not readily available.
However, the main component of the cost would be the cost of the
wastewater treatment plant.
Effectiveness of the Technology
This technology can produce large quantities of low quality water which
can be used to service high water consumptive uses such as irrigation.
This use conserves the available freshwater resources for more essential
purposes including domestic use.
The potential for wastewater reuse on small islands may be limited for a
number of reasons. On very small islands, there may be insufficient land
for agriculture or industry. This limits the amount of potential
wastewater as well as the potential for its reuse; some small islands may
not have a suitable source of wastewater. If seawater flushing is already
used in sewage systems as a means of conserving freshwater, the resultant
wastewater cannot be used. Notwithstanding, opportunities do exist for the
use of wastewater on a small scale. For instance, tourist resorts can make
use of treated wastewater from package treatment plants to irrigate
gardens and lawns (UNESCO, 1991).
Wastewater reuse conserves freshwater resources, by making use of the
potentially large volumes of low quality water for irrigation and similar
Wastewater reuse carries a potential public health risk when directly
reused for potable use or indirectly reused to irrigate crops that are
commonly eaten without cooking (e.g., vegetable crops such as tomatoes and
most fruit crops). Consumers may also be unwilling to use treated
wastewater for agricultural and domestic uses. Variations in wastewater
flows and composition may lead to variable quality of the treated water
for irrigation use. Close monitoring of the treatment processes by skilled
staff is required.
Some cultures may have a problem with using wastewater to irrigate food
Further Development of the Technology
As wastewater discharge standards for urban areas, hotels, and
industries become stricter, more cost effective methods to treat
wastewater that could be reused or recycled are likely to be developed,
especially in the case of industry.
AGDRE [Australian Government Department of Resources and Energy] 1983.
Water Technology, Reuse and Efficiency, Water 2000. Australian
Government Department of Resources and Energy Report No. 10, Canberra.
Malhew, K. and G. Ho (Ed.) 1994. Workshop Papers on Localised
Treatments and Recycling of Domestic Wastewater. Murdoch University,
Shuval, H.I., B. Fattal, and P. Yekutiel 1986. State of the Art Review:
an Epidemiological Approach to Health Effects of Wastewater Reuse. Water
Science and Technology, 18(9):147-161.
UNDTCD [United Nations Department of Technical Cooperation and
Development] 1985. The Use of Non-conventional Water Resources in
Developing Countries. United Nations Natural Resources/Water Series
United Nations 1987. Non-Conventional Water Resources Use in
Developing Countries. Proceedings of the Interregional Seminar. United
Nations Natural Resources/Water Series No. 22.
UNDESD [United Nations Department of Economic and Social Development]
1992. Water Resources Management Techniques for Small Islands.
United Nations Report No. INT-88-R41, United Nations, New York.
UNESCO [United Nations Education Scientific and Cultural Organization]
1991. Hydrology and Water Resources of Small Islands, A Practical
Guide. Studies and Reports on Hydrology No. 49, UNESCO, Paris.
Vlugman, A. 1990. Country Report on Waste-Water Treatment Facilities
in Barbados. Pan-American Health Organisation (PAHO/CEPIS),