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Newsletter and Technical Publications
<International Source Book On Environmentally Sound Technologies
for Wastewater and Stormwater Management>

9.11 Case studies (Topic k)

There are a number of excellent case studies for SIDS Caribbean. These are based on papers presented at two recent workshops:

Workshop on Adopting, Applying and Operating Environmentally Sound Technologies for Domestic and Industrial Wastewater Treatment for the Wider Caribbean Region. The workshop was implemented 16-20 November 1998 in Montego Bay, Jamaica by UNEP IETC, Murdoch University of Western Australia and the UNEP Caribbean Regional Coordination Unit in Jamaica.

Workshop on Sustainable Wastewater & Stormwater Management. The workshop was implemented on the 27 E31 March 2000 in Rio de Janerio, Brazil by UNEP IETC with ABES Brazil.

Only abstracts are included below. The full papers should be consulted for details. The proceedings of the workshops are available from IETC.

9.11.1 Wastewater sector in Trinidad & Tobago: way forward for sustainable development

The author was Manherial Kerof Assisant Director Operations, Water and Sewerage Authority, Trinidad & Tobago.

Abstract

This paper aims to review the present status of the wastewater sector in Trinidad and Tobago and to address concerns regarding the sector's development after years of neglect.

Over 87% of the 1.3 million population of Trinidad and Tobago enjoy a potable water supply whilst only 30% of the population is served by centralized public and private wastewater systems. The total water production (surface and ground) amounts to 780 Mld (172 mgd) while the total volume of wastewater generated equals to 702 (155 mgd). However, the total volume of wastewater collected and treated by centralized wastewater systems averages approximately 150 Mld (33 mgd) or 21.2% of the total wastewater generated. Approximately 100 Mld (22 mgd) of wastewater is collected and treated by WASA through its 12 public wastewater systems and the remaining 50 Mld (11mgd) of wastewater being collected and treated via 148 privately owned and operated (non-WASA) systems. In general, the performance of 90% of all the wastewater plants/systems can be described as poor.

The investment within the wastewater sector has been historically low with an average of 7% of the total consolidated water and wastewater operational expenditure being spent on wastewater operations. Thus, despite the low sewerage rate (i.e. 50% of the water rate) the wastewater sector over the years has been operating at a profit at the cost of deterioration of its assets.

The major issues emerging from the analysis and review of the sector can therefore be summarized as:

  • The need for closure of the large gap which currently exists between the volume of wastewater generated and the volume of wastewater collected via the centralized systems
  • The need for closure of the large gap between the level of treatment provided and the level of treatment required as per the compulsory Trinidad & Tobago Effluent Standard TTS 417:1993. Less than 1% of wastewater collected and treated conforms to the above standard.
  • The need to reduce the proliferation of small, private wastewater systems - a situation which has resulted from the under investment in major Public Wastewater Infrastructure Development schemes over the last 35 years.
  • The high investment needs of both the Public & Private (WASA & Non WASA) Wastewater Systems due to the historic under investment in the sector.
  • The need for implementation of an effective monitoring and control system to ensure compliance with compulsory Effluent Standards.

The achievement of sustained improvement to the environment and human health in general, requires the development of a long-term strategic vision and action plan for an effective and environmentally sound Wastewater Sector.

This has been recognized at Government level as a draft report on "Development of a strategic plan for the wastewater sector in Trinidad and Tobago (August 1999 by Dilon Consulting Ltd.)", has been prepared by Inter American Development Bank (IADB), under the direction of the Government of Trinidad & Tobago.

The following is recommended in addressing the key issues identified:

  • Immediate action on institutional strengthening of the Sewerage Sector,
  • Development of a Wastewater Master Plan for Trinidad and Tobago,
  • Immediate review and increase in wastewater/sewerage tariffs to appropriate levels with respect to:
  • Domestic wastewater discharges (tariffs should be at least equal to that of water),
  • Trade effluent discharges
  • Development of Trade Effluent Discharge Regulatory Procedures and Monitoring System to control trade effluent discharged into public sewerage systems,
  • The establishment and implementation of a national Pollution Control and Monitoring Program to ensure the compliance of all wastewater systems - both public as well as private sector systems.

As a first step towards addressing the needs of the Sector, approval has been granted for the creation of a Wastewater Division within WASA. Further, the current investment trends also indicate a positive change in direction from the one of past neglect. However, further work is needed and the government of Trinidad & Tobago is committed towards improving the quality of wastewater services in the country and to the establishment of a sound and sustainable wastewater sector.

9.11.2 The Bahamas Water and Sewerage Corporation, Water Resources Management Unit (WRMU): Sustainable Wastewater and Storm Water Management.

The authors involved were Philip S. Weech, (Senior Hydrologist B.A, MSc., MIWEM, AWRA, AWWA), Glen F. Laville (AGM / Engineering & Construction, B.S.C.E, CWWA) and John A. Bowleg II (Assistant Hydrologist B.S.C.E, ASCE).

Abstract

The purpose of this paper is to show that sustainable water sector development in the Bahamas must take advantage of the peculiar hydrodynamics of the local geology, hydrology and marine dynamics. The "true" economic cost of development, as well as the long term operational and maintenance burdens of public infrastructure must be borne in mind. The model of sustainable development being proposed and explained in the paper and the model follows the notion that storm water and wastewater streams should be separated.

9.11.3 Cuba: Study cases about interrelationship sanitation, environment and sustainable management of wastewaters.

The author of the paper is Dr. Cristóbal Félix Dé}z Morejón of the Environmental Policy Directorate, Ministry of Science, Technology and Environment.

Abstract

The work mainly introduces the problem of the wastewater management, reflecting a brief panorama of the country's situation, as much in the reception as in its conduction and final disposition.

A principal case of study: the application of solution schemes of simplified sewer system or of low cost, to the local conditions;and are presented too, two also related cases: the creation of a National Center of Appropriate Technologies for Sanitation (SANITEC) that lead to the country in the search of economic solutions that protect the environment and with high social acceptance; and the particular application of stabilization ponds for the wastewater treatment coming from tourist hotels built in two keys.

The main case possesses the following characteristics:

  • Support of UNICEF and the local governments.
  • Work of a multidisciplinary team in all phases: planning, project and construction.
  • Wide participation of the town inhabitants, from the conception of the idea and project, until their construction and maintenance (that reduces the operational costs significantly). Systematic consults with the formal and not formal leaders, and in general with the residents.
  • Application of more sustainable and economical technology, with alternatives adapted to the local conditions.
  • Solution to critical environmental problems in the community that provoke dangers to the human health and cause strong contamination in the river Guaso, where wastewater spilled without control.
  • Solution to the floods caused by the rainwater.

The second case constitutes a simple presentation, with the objective to offer to the participants in the Workshop the possibility to share in a future the knowledge that SANITEC accumulates.

The third case constitutes a casuistic solution to the treatment of residual liquids in small islands with high development of the tourism, through the employment of stabilization ponds that at the moment have had good values of efficiency, and whose treated waters are used in the irrigation of the hotels gardens (reuse of the waters), like part of a complete cycle dedicated to avoid the contamination of the coastal and marine ecosystems, that have invaluable values for the tourist activity. Their reading may be of interest for the participants.

9.11.4 Barbados: Sustainable Stormwater Management

The paper is entitled Harnessing and Harvesting a Natural Resource Terrol and authored by T. Inniss, Acting head of Drainage unit, Ministry of Public Works & Transport.

Abstract

Sustainable Stormwater and Wastewater Management is an issue that should always be in the forwards of our mind. To attain this within the limits of our own social and economic development it is necessary to practice sustainability in the light of a common world market and liberalized trade. It is effective Management of available resources that has the potential to achieve the forgoing.

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