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PART C - CASE STUDIES
5.6 Treated Wastewater Reuse Scheme in Barbados
Sam Lord's Castle Hotel is located on the southeastern coast of
Barbados, in the parish of St. Philip. It lies within the coral-covered
portion of the island, with a coral cap thickness of about 80 ft. With an
average annual rainfall of 45 inches, this is one of the driest areas of
the island (the average annual rainfall for the whole island is 60
inches). In this area, except for 4 months of the year (August to
November), the average evapotranspiration rate, 4.5 inches/month, exceeds
the monthly rainfall figures. The groundwater resources in this area
consist of a thin freshwater lens floating on top of saline water.
The hotel was formerly supplied with freshwater from a groundwater well,
but because of the high water demand, especially for the irrigation of
large expanses of lawns and garden plants, saline groundwater intruded
into it to the point where the freshwater supply was virtually exhausted.
Adecision was made then to abandon the use of the well and the hotel sent
an application to the Ministry of Health and Environment seeking
permission to use the treated effluent from its extended aeration sewage
treatment plant for irrigating lawns and garden plants. Permission for
wastewater reuse was granted and treated wastewater was diverted to
irrigation use from its former disposal site in four deep suckwells.
This technology is described in Part B, Chapter 3, "Wastewater
Treatment Technologies and Reuse."
Effluent consisting of kitchen, laundry, and domestic sewage is conveyed
to a collection chamber, from which it is pumped through a comminutor to
an aeration chamber. No primary sedimentation is provided. The aerated
mixed liquor then flows out of the aeration chamber through a rectangular
opening at one end into a clarifier for gravity separation of solids. The
effluent from the clarifier chamber is then passed through a 16-foot-deep
chlorine disinfection chamber and pumped to an automatic sprinkler
irrigation system. The irrigated areas are sub-divided into 16 zones with
12 sprinklers each. Some areas also have a drip irrigation system.
Sludge with a high water content is pumped from the sludge chamber to
the suckwells for disposal without thickening. Previously this sludge was
pumped to the Bridgetown Sewage Treatment Plant for further treatment and
additional desludging. This pumping incurred additional transportation
The packaged wastewater treatment plant was designed abroad and
constructed using local contractors. The drip and sprinkler irrigation
systems were designed and installed in part by a local irrigation system
consulting company and in part by the hotel's maintenance personnel. The
Environmental Engineering Division (EED) of the Ministry of Health and
Environment was responsible for approving, monitoring, and controlling the
operation of the packaged plant. Thus, despite the absence of effluent
standards enacted into law, some conditions were placed on the system
before permission was granted for irrigation reuse. The approval process
involved consultations with the Town and Country Planning Offices and the
Barbados Water Authority (BWA).
Extent of Use
At present, there are twelve wastewater treatment facilities in use in
Barbados, ranging in size from 2 860 gpd to 37 400 gpd for hotel
facilities and to 594 000 gpd for the Barbados Water Authority plant. The
combined total treatment capacity amounts to 786 280 gpd. Eight of these
plants are extended aeration plants, three are rotating biological
contactor plants, and one, the Barbados Water Authority plant, is a
contact stabilization plant. Two more BWA sewerage systems are planned for
the south and west coasts, with the intention of reusing their wastewater
Reuse of treated wastewater for the irrigation of garden plants and lawn
grass is limited at present to Sam Lord's Castle Hotel. Another, the
Almond Beach Village Hotel, formerly Heywoods Hotel, in St. Peter on the
west coast, is almost ready to start irrigating a 9-hole golf course.
Other applications for the reuse of wastewater on golf courses
(Westmoreland, Kingsland, and Bushy Park)are pending, and a number of
major hotels have indicated their interest in applying for permission to
reuse their effluent. In addition, plans are in place to reuse some of the
treated effluent from the BWA Bridgetown Sewage Treatment Plant for
flushing sewer lines.
Operation and Maintenance
According to the report of a survey on the Operational Aspects of
Wastewater Treatment Plants in Barbados undertaken by A. Vlugman of PAHO
in 1990, the operational status of the Sam Lord's Castle Hotel plant was
considered to be moderate. The plant is about twelve years old and the
operator reports few problems; those that have occurred are considered
minimal (due to grease). There does not seem to be any problem with
obtaining spare parts. However, no design or construction drawings are
available to help with the operation and maintenance of the plant, and the
basic skills required to operate and maintain the plant, such as some
knowledge of microbiology, some electrical/mechanical skills to repair the
equipment, and some understanding of the treatment process and the impact
of poor performance on the whole scheme, are generally lacking.
Considering the small size of most packaged wastewater treatment plants,
it may not be cost-effective for each hotel to employ a qualified
operator. However, it might be possible for a number of hotels to employ
collectively one qualified operator to look after a number of plants.
Alternatively, the Barbados Hotels and Tourism Association (BHTA) could
employ an environmental officer or sanitary engineer to oversee or advise
the various hotels on wastewater treatment and effluent reuse.
The operation and maintenance required consists of turning the pumps
that do not run continuously (such as the sludge pumps) on and off, and
checking to ensure that all systems are running smoothly without any
blockages. There are no flow meters installed and no laboratory facilities
of any kind are provided to document the technical performance of the
plant. Any operational monitoring of plant and process by the operator is
limited to visual inspections. Plant performance is evaluated by the
operator on the basis of the color of the mixed liquor in the aeration
chamber; a brownish color is an indicator of good performance.
Nevertheless, BOD and TSS analyses are done monthly during inspections by
Level of Involvement
The only government involvement in this program is licensing, monitoring
and administrative control, exercised through the EDD, which is charged
with the responsibility of approving and monitoring the performance of
packaged wastewater treatment plants. The Sam Lord's Castle Hotel plant is
entirely privately owned and operated, except for the monthly inspections
and sampling for BOD and TSS conducted by the EED.
As this plant is privately owned and operated, cost figures are not
Effectiveness of the Technology
Based on 1989 and 1990 results, BOD and TSS removal efficiencies of 86%,
and of 98% and 83%, respectively, are achievable. Data on the
microbiological quality of the effluent are not available; two chlorine
tablets are put into the chlorination chamber each week, regardless of
effluent quality or quantity. Hence there is need to evaluate in detail
the effectiveness of the disinfection before the effluent is used for
irrigation. However, from an aesthetic point of view, the irrigation of
lawns and plants seems to be very successful, as evidenced by the lush
greenery surrounding the hotel. This is a great improvement compared to
the period before the effluent reuse program was put into place.
The applicability of this technology depends on the nature of the land.
In Barbados, owing to the karstic nature and topography of the coral rock
aquifer system, groundwater contamination by reused wastewater can be
avoided only if the wastewater is properly treated. At present, there are
very few facilities with a suitable effluent quality. However, the hotels
in the belt along the south and west coast, down gradient from the line of
public water supply wells, would be obvious candidates for application of
this reuse technology, posing the least danger of contamination to the
groundwater. The hotel belt also has the advantage of being situated next
to the BWA wastewater treatment plants.
- The use of the treated effluent results in substantial savings in
irrigation water costs and reduces the likelihood of water pollution,
assuming that the effluents would otherwise have been disposed of
through sea outfalls.
- This technology eliminates the need to use potable water supplied by
the BWA public domestic supply system for irrigation and makes it
available for other uses.
- Inadequate operation and maintenance may pose some health risks.
- The WHO criteria on wastewater reuse for recreational purposes with
possible human contact may not be fully met in this case. These criteria
(effluents should not contain more than 100 coliform organisms/100 ml in
80% of samples, and should not contain chemical contaminants that lead
to the irritation of mucous membranes and skin) require primary and
secondary treatment and sand filtration, or the equivalent. Provision of
such treatment would significantly increase the cost of this technology.
- The potential environmental impacts associated with this technology
are contamination of groundwater, human skin irritations caused by
bacteria or viruses in inadequately disinfected effluent sprayed on
lawns or gardens, and mineral buildup (salination) in the soil, none of
which are currently monitored on an adequate and continuous basis.
(Because of the proximity of the application area to the coast, there is
little risk to the domestic groundwater supply from the Sam Lord's
Castle Hotel reuse scheme; however, the flow to the sea could still
adversely affect the coastal marine ecosystem. In this case, the
irrigation is timed to minimize the health risk to the hotel guests.)
Further Development of the Technology
The technology is well developed; however, local engineers and
scientists need to familiarize themselves with it and evaluate its
suitability for use elsewhere in Barbados, with any necessary
modifications. There is also a need to evaluate the effectiveness of the
disinfection process (chlorination by gas or chlorine tablets) in
eliminating bacteria and viruses. It is very probable that, in future,
more hotels will want to reuse effluent from the packaged treatment
plants, especially in the light of proposals to change the domestic water
tariff structure. Special training programs, in association with the BWA
wastewater treatment facilities, should be developed to improve plant
performance and monitoring.
B. J. Mwansa, Project Manager, Barbados Water Resources
Management and Water Loss Studies, "Invermark," Hastings, Christ
Church, Barbados. Tel. (809)430-9372 / 430-9373. Fax (809)430-9374.
Scofield Alleyne, Maintenance Engineer, Almond Beach
Village Hotel, St. Peter, Barbados.
Wilfield Moore, Maintenance Officer, Sam Lord's Castle
Hotel, St. Philip, Barbados.
Sylvan Catwell, Senior Environmental Engineering
Assistant, Ministry of Health and Environment, EED, Culloden Road, St.
Michael, Barbados. Tel. (809)436-4820.
Vlugman, Anthony 1990. Country Report on Waste-Water Treatment
Facilities in Barbados. PAHO. Washington, DC