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Newsletter and Technical Publications

<Sourcebook of Alternative Technologies for Freshwater Augumentation
in Small Island Developing States>


PART C - CASE STUDIES

5.5 Sam Lord's Castle Hotel Treated Wastewater Reuse Scheme, Barbados

Introduction

Sam Lord's Castle Hotel is located in the parish of St. Philip, Barbados, on the southeastern coast of the island (Figure 44). It lies within the coral-covered section of the island, with a coral cap thickness of about 25 m. Average annual rainfall is 1 200 mm, making this is one of the driest areas on the island which has an average annual rainfall of 1 500 mm. Except for four months of the year (August to November), the average monthly evapotranspiration rate of 115 mm exceeds the monthly rainfall.

Figure 44

Figure 44. Wastewater treatment plant locations and Zone One - Water Protection Areas.

The limited groundwater resources in this area consist of a thin freshwater lens floating on top of saltwater. Due to the high irrigation water demand (water is used to irrigate lawns and garden plants) which resulted in the overpumping of the aquifer, the salinity of the groundwater had increased to a point where it was no longer considered suitable, and a decision was made to abandon the use of the well and use the treated effluent from their extended aeration, packaged sewage treatment plant for irrigation. Prior to this, the effluent from the sewage treatment plant was all disposed of by pumping into four deep boreholes. The cost of irrigation over an eight month period annually was the main driving force which led to the decision to try the effluent reuse option.

Technical Description

Effluent, consisting of kitchen, laundry, and domestic sewage from the hotel, is sent to a collection chamber from which it is pumped through a comminutor to an aeration chamber (Figure 45). No primary sedimentation is provided. The aerated, mixed liquid then flows out of the aeration chamber through a rectangular opening at one end of the aeration chamber into a clarifier chamber for gravity separation. The effluent from the clarifier chamber is passed through a 5 m deep chlorine disinfection chamber, and, after disinfection, is pumped into an automatic sprinkler irrigation system. The irrigated areas are subdivided into sixteen zones, with each zone having twelve sprinklers. Some areas are also provided with a drip-irrigation system. The sludge, which has an high water content, is pumped from the sludge chamber into the boreholes without thickening. Previously the sludge was pumped out and sent to the Bridgetown Sewage Treatment Plant for further treatment, incurring additional costs for desludging and transport. The wastewater treatment plant was designed abroad, but constructed using local contractors. The drip and sprinkler irrigation system was designed and installed, in part, by a local systems consulting company and, in part, by Sam Lord's Castle Hotel maintenance personnel. The Environmental Engineering Division (EED) of the Ministry of Health and Environment approved and monitors packaged treatment plants, and issues permits for irrigation reuse, although there is currently no controlling legislation governing reuse of wastewater in Barbados. The approval process also generally involves consultations with the Town and Country Planning Office and the Barbados Water Authority.

Figure 45

Figure 45. Wastewater treatment process for Sam Lords Castle.

Extent of Use

At present, there are twelve wastewater treatment facilities in use on Barbados, ranging in size from 13 m3/day to 170 m3/day for the hotel facilities, and to 2 700 m3/day for the Barbados Water Authority (BWA) plant. The combined total treatment capacity amounts to 3 580 m3/day. Two more BWA sewage treatment systems are planned for the south and west Coasts with the intention of providing additional water for wastewater reuse. Such reuse for irrigation of garden plants and lawn grass is presently limited to Sam Lord's Castle Hotel, St. Philip. One other hotel, 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 with reused effluent. Other applications are pending for wastewater reuse on golf courses (e.g., Westmoreland, Kingsland and Bushy Park Golf Courses), and a number of major hotels have indicated their interest in applying for permission to reuse their effluent. Plans are in place to reuse some of the treated effluent from the Barbados Water Authority Bridgetown Sewage Treatment Plant for flushing sewer lines.

Operation and Maintenance

According to a PAHO survey of wastewater treatment plants in Barbados (Vlugman, 1990), the operational status of the plant was considered to be moderate. The operations and maintenance work consists of turning on and off the pumps that do not run continuously (sludge pumps), and inspecting the system for blockages. There are no flow meters installed, and no laboratory facilities provided. Operational monitoring by the operator is limited to visual inspections and to the results of BOD and suspended solids (SS) analyses reported by the EED during their monthly inspections. Plant performance is evaluated by the operator by the colour of the mixed-liquid in the aeration chamber. He looks for a brownish colour as an indicator of good performance. The plant is about twelve years old and the operator reports few upsets, which seem to be due to grease. There are no design and construction drawings available to help with the operations and maintenance of the plant, but there are no apparent problems in obtaining spare parts.

Level of Involvement

Government involvement in this programme is as a licensing, monitoring and controlling authority through the Ministry of Health and Environment's Environmental Engineering Division (EED) which is charged with the responsibility of approving and monitoring the performance of wastewater treatment package plants. The plant is privately owned and operated except for monthly inspection checks and sampling for BOD and SS analysis by the EED.

Costs

Figures on cost are not available.

Effectiveness of the Technology

During 1989 and 1990, BOD and SS removal efficiencies of 86% and 83%, respectively, are achieved. While two chlorine tablets are put into the chlorination chamber each week, regardless of effluent quality or quantity, there are no data available from which to evaluate, in detail, the effectiveness of the disinfection of effluent. Notwithstanding, from an aesthetic point of view, the irrigation of lawns and plants seems to be very successful, as evidenced by the lush greenery, which is a great improvement compared to the period before the effluent reuse programme began.

Suitability

Due to the karst nature and topography of the coral-rock groundwater aquifer system, only properly-treated wastewater would be suitable for reuse, to avoid groundwater contamination. Thus, very few facilities produce treated wastewater suitable for this type of application. However, the hotel belt, where this technology is most likely to be used, is located along the south and west coasts, downstream of the line of public supply wells, and poses little threat of contamination to the groundwater. The hotel belt is also in close proximity to the treatment plants.

Advantages

The use of the treated effluent results in substantial savings in irrigation water costs, assuming that the Hotel would otherwise have disposed of the same effluent and purchased water from the Barbados Water Authority's public water supply system. Reuse also makes this additional volume of freshwater, not consumed for irrigation use, available for other domestic purposes.

Disadvantages

Inadequate operation and maintenance may pose some health risks. WHO suggests the use of primary, secondary, and sand filtration, or equivalent, treatment of wastewater intended for reuse in situations where there is possible human contact with effluent. The present application does not fully meet these guidelines, and full compliance could result in increased water costs. The potential impacts associated with the implementation of the technology include contamination of groundwater, human skin irritations caused by bacteria or virus in inadequately disinfected effluent sprayed on lawns or garden plants, and mineral build up in soil, none of which are presently monitored on an adequate and continuous basis. However, due to the close proximity of the irrigated area to the coast, there is little risk to the domestic groundwater supply, although the flow to sea could still adversely affect the marine system. The timing of the irrigation has also been designed to minimise the health risks associated with potential contact by the hotel guests with the lawns and garden plants.

Further Development of the Technology

The technology is well-developed. However, local engineers and scientists need to familiarize themselves with the technology as used on Barbados and make necessary modifications for its practical application in the Barbados situation. There is also a need to evaluate the effectiveness of the disinfection process (chlorination by gas or chlorine tablets) in eliminating both bacteria and viruses. Considering the small size of most of the wastewater package plants, it may not be cost-effective for each hotel to employ a qualified operator; however, it may be possible for a number of hotels to team up to employ one qualified operator to look after a number of plants or to employ an Environmental Officer or Sanitary Engineer through the Barbados Hotels and Tourism Association (BHTA) to oversee or advise the various hotels on wastewater treatment and effluent reuse. Special training programmes, including attachment to BWA wastewater treatment facilities, could be developed to improve plant performance and monitoring.

Information Sources

Contacts

B.J. Mwansa, Project Manager, Barbados Water Resources Management and Water Loss Studies, "Invermark", Hastings, Christ Church, Barbados. Tel. (809) 430-9372/3, Fax: (809) 430 - 9374.

Scofield Alleyne, Maintenance Engineer, Almond Beach Village Hotel, St. Peter, Barbados.

Wilfield Moore, Maintenance Officer, Sam Lords 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.

Bibliography

Vlugman, A. 1990. Country Report in Waste-Water Treatment Facilities in Barbados. Pan-American Health Organisation (PAHO/CEPIS), Washington.

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