Sewage Pollution in Tobago
(1) Sewage Pollution: A Global Perspective
By Kamau Akili and Shirley Ann James
In seeking to deal effectively with problems affecting a particular society, it is sometimes beneficial to look first at the wider picture before focussing on the specific problem. To think globally but act locally, is a course of approach that can produce significant benefits. As Tobago seeks to grapple with the growing problem of sewage pollution, it is possible that some good lessons can be learned by first having a global perspective of the problem.
Sewage is liquid waste produced by households and industries. Sewage can be subdivided into (a) Black water and (b) Grey water. Black water sewage is the stuff that comes out of toilets. Its contents may include faeces, urine, paper, condoms, tampons and water and any other material that people find convenient to flush down toilets. Grey water, on the other hand, consists of the out flow from wash basins, baths, kitchen, washing machines and sinks. The contents of gray water may include food remains, oil, detergents, dirt and water.
The problem of inadequate sewage disposal (like that of garbage disposal) is one that is the direct result of the development of human civilization and the modernization of society. When humans were hunter/gatherers who moved from place to place, sewage disposal was not a problem. Today however, the majority of the world's population of five billion plus individuals live in permanent settlements and use technology which leads to the daily production of large volumes of sewage.
The improper disposal of sewage poses risks for any society whether it is in developed North America or in underdeveloped Bangladesh. Sewage containing human feces and urine can lead to a wide variety of illnesses if such sewage is not properly treated. These illnesses include meningitis, typhoid, gastroenteritis, hepatitis, salmonella infections, cholera, bacilliary dysentery, ear infections, conjunctivitis, pneumonia, septicemia, skin rashes and diarrhoea.
Sewage also contains high levels of nutrients such as phosphate and nitrates which can lead to the "deaths "of rivers lakes and seas through eutrophication. High levels of phosphate and nitrates promote the rapid growth of algae. When these algae "bloom", die and decompose they remove dissolved oxygen from the water. The unavailability of oxygen then leads to the death of fish and other animals that need oxygen from the water. Eutrophication has occurred in a variety of locations world wide including the North American Great Lakes, Kingston Harbor in Jamaica, the Gulf of Paria in Trinidad and many rivers in Eastern Europe.
The serious negative effects that can be caused by inadequately treated sewage have been well researched and documented. This understanding has led to moves by environmental groups and governments in many countries to undertake initiatives aimed at reducing sewage pollution. The European Community for example, has developed new standards for sewage effluents released into bathing waters. In England significant progress has been achieved in the move to have "full" treatment of all sewage being released into waterways or the sea.
In looking at the various options available for sewage treatment and disposal, it has been found (in England) that it is cheaper for sewage to be fully treated than to use the traditional approach of primary or no treatment and long sewerage outfalls at sea. The application of ultraviolet light treatment and membrane filtration have been found to be quite effective and the capital costs are lower than traditional methods of primary treatment and long sea out falls.
Whilst the developed countries of Europe, North America and Asia (Japan) seem to be moving positively to solve their sewage problems, the same cannot be said for the developing countries of the world. In Africa, Asia, the Pacific, South America and here in the Caribbean, sewage treatment continues to be a major problem. This problem will not go away. In fact it will get worse. As populations grow and become more affluent, the amount of wastewater generated per person will increase. The move from pit latrines to flush toilets and from taking bucket baths to bathing with showers generally leads to increased water consumption and consequently an increased sewage output.
The biggest problem is that these developing countries do not have the amounts of money to invest in large volume sewage treatment plants. This situation has prompted extensive research into small scale, low cost methods for sewage treatment. In India for example, a variety of simple low cost methods have been developed. These include systems that have the added benefit of producing biogas that can be utilized for cooking. Over the last decade a significant amount of attention has been given to the issue of sewage pollution worldwide. A lot of research has been done and many lessons have been learned. It is now left to us to utilize the work already done to our own advantage.
(2) Sewage Pollution: A Tobago PerspectiveStephen Hayton and Kamau Akili
Like many other developing Caribbean territories, our island of Tobago is facing a growing problem of sewage pollution. Untreated or poorly treated sewage is being released into rivers and storm drains with serious implications for human health and the natural environment.
Concerns about sewage pollution in Tobago are not new. In 1982 the Institute of Marine Affairs (IMA) conducted a bacteriological survey in southwest Tobago. This survey involved tests for the presence of faecal coliform bacteria as an indicator of sewage pollution. Tests of water samples detected that levels of faecal coliform bacteria at several locations were not in compliance with international standards (e.g. World Health Organization). That was back in 1982.
The ”1995 state of The Environment Report", published by the Environmental Management Authority, identified sewage pollution as a major factor in the degradation of Tobago's natural environment. The report identified sixteen sewage treatment plants in Tobago and, of these, only three were classified as functioning adequately.
More recently, between September of 1997 and January 1999, Environment TOBAGO, with the assistance of secondary school students and community volunteers, conducted a programme of coastal water quality monitoring at several locations around Tobago. Water samples from the sea, rivers, storm drains and canals were analyzed.
The findings of this survey indicated that sewage pollution is significant. The levels of faecal coliform bacteria detected were in many instances much higher than the maximum levels considered safe by the World Health Organization. Other studies of Tobago's water quality have been done and the findings are similar.
A reasonable conclusion that one can make is that Tobago has a serious sewage disposal problem.
To fix this problem however, one must understand its causes. A good starting point is to determine the sources of the sewage that is polluting our waterways and sea. The sources of sewage pollution can be classified as (a) domestic and (b) industrial/commercial. Domestic sources of sewage are basically households. These households generate black water containing faeces and urine and gray water from kitchen sinks and bathrooms. More than ninety percent (90%) of the households of Tobago use pit latrines or septic tanks and soakage pits (soakaways) for the disposal of blackwater sewage. Latrines and septic tanks/soak aways can work effectively if properly constructed. However, if they are constructed in areas where the water table is high, they do not function effectively. Also, soakage pits constructed in clay soils do not drain properly. The clay prevents the water from draining out of the soakage pit, causing sewage to overflow from the soakage pit and on to the surface to the nearest drain, canal or stream. A good indication of a soakage pit that is not functioning properly is black, smelly water flowing out of its top.
Another problem that occurs with septic tanks is the accumulation of sludge. The breakdown of sewage in the septic tank creates a sludge deposit that will eventually fill the septic tank and stop it from functioning properly. The sludge may even flow over to the soakage pit and clog the pores causing the filtration process to stop. Sludge accumulation is a major cause of the malfunction of septic tanks and soakage pits in this island. Domestic gray water sewage from kitchen sinks, washing machines, washtubs and bathrooms generally undergoes no treatment. This water usually flows from households to the closest drain or canal.
In the Scarborough area, some households have recently been connected to the sewer mains that take sewage to the Smithfield's sewage treatment plant. Both black water and grey water sewage are treated at this facility which has the capacity to handle all of the sewage generated in Scarborough. However, the majority of households in Scarborough still utilize septic tanks/soakage pits and latrines.
At the Milford Court and Buccoo Housing Estates, the homes are connected to sewage treatment plants. In both instances these plants are not functioning properly. This situation has existed for several years and the sewage treatment plants have been identified as being major contributors to the pollution of the Bon Accord Lagoon and Buccoo Reef. An exception exists at the Bon Accord Integrated Development where the households are linked to a sewage treatment system that provides a high level of treatment.
Commercial/Industrial (non-domestic) sources of sewage in Tobago include pig farms, hotels, schools, guests houses, restaurants, dancehalls, offices, banks, stores etc. These establishments generally produce large volumes of sewage on a regular basis. Most pig farms do not utilize any type of treatment for sewage effluent resulting in severe contamination of waterways. The large hotels use package treatment plants for treating their sewage effluent. Most of these package plants only provide primary treatment of sewage. This means that the sewage undergoes decomposition and chlorinating before it is released into the surrounding environment. Most of these package plants malfunction from time to time due to overloading or poor maintenance.
Most small hotels and guesthouses utilize the septictanks/soakage pit method for sewage disposal and tend to experience problems of over loading during peak visitor periods. Like most households, these small hotels and restaurants release grey water that has received little or no treatment. Most schools in Tobago utilize septic tanks/soakage pits to treat sewage effluent and also face the problem of overloading resulting in poorly treated effluent being released.
Restaurants, including fast food outlets, pose a particular problem because of the large amounts of oils, fats and food remains that they release. A quick survey of the canals and drains in downtown Scarborough will illustrate this particular problem of gray water effluent. Putrefying oil and fat is a major contributor to the stench that comes from these drains and canals in lower Scarborough, especially during the dry season when there is less water to flush these oils and fats out to sea.
In the Scarborough area some commercial enterprises and the hospital have been connected to the centralized sewage treatment system and this has led to some improvement in the sewage effluent problem over the last few years. However, the majority of establishments still have to be connected to the system, which is functioning well below capacity.
The increasing numbers of yachts that visit Tobago annually are another source of sewage effluent. Some yachts have holding tanks to store the effluent from their toilet systems whilst others do not with the result that this effluent is released directly into the sea. Because of the absence of sewage pump-out facilities in Tobago, the yachts that have holding tanks must release the sewage into the sea when the holding tanks are full. Very few yachts have on-board treatment systems.
The conclusion that we can make from this examination of the sewage disposal situation here in Tobago is that a serious problem exists. If this situation is not properly addressed it is to be expected that it will worsen with the anticipated increases in both local and visitor populations.
This has quite serious implications for the health of our human population and also the state of the natural environment.
(3) Sewage Pollution: A Threat to Human Health and Biological Diversity
In it's "1995 State Of The Environment Report: Trinidad and Tobago", the Environment Management Authority identified untreated or poorly treated sewage as a major source of coastal pollution. The report went on to describe South West Tobago as a coastal and marine "hot spot" characterized by the high levels of pollution.
The fact that the coastal waters of Tobago are being increasingly polluted with sewage is something that must concern all of us. The effects of sewage pollution can be divided into two broad categories. These are: (a) threats to human health and (b) threats to marine biodiversity.
The threats to human health from sewage pollution of rivers and coastal waters are not imaginary. These threats are real. At present no hard data has been gathered in Tobago from epimediological studies to establish a relationship between sewage pollution and human illness. Studies done in the U. S. A. and England have established that such a relationship exists. In 1995 the Santa Monica Bay Restoration Project conducted a large-scale epidemiological study at Santa Monica Bay, California, to investigate the possible adverse health effects associated with swimming in ocean waters contaminated by urban runoff. The study sought to establish if there was any relationship between illnesses experienced by bathers and levels of sewage pollution.
In this study more than thirteen thousand sea bathers were monitored for illnesses after bathing at Santa Monica Bay. At the same time water samples were taken from the Bay and analyzed for faecal coliform bacteria and enteric viruses. The basic idea was to find out if changes in the levels of certain illnesses reflected changes in the levels of sewage pollution. The illnesses monitored were fever, chills, ear discharge, vomiting, coughing, gastroenteritis and respiratory diseases.
The findings of this study included the following;
· There is an increased risk of illness associated with swimming near flowing storm drains.
· There is an increased risk of illness associated with swimming in areas with high densities of bacterial indicators.
· Illnesses were reported more often on day when samples were positives for enteric viruses.
The conclusions of the Santa Monica study are quite clear. There are serious health risks associated with bathing in areas with levels of bacterial and viral contamination, resulting from sewage pollution.
Studies done in the United Kingdom between 1973 and 1990 have isolated from sewage polluted coastal waters a variety of bacteria and viruses that have the potential to cause illness. These illness includes wound infections, ear infection, gastroenteritis, meningitis, dysentery, cholera, thrust, hepatitis and conjunctivitis. Investigations were also done on the die off rate of bacteria and viruses of seawater. Faecal coliform and faecal streptococci bacteria were found to survive for more than five days. Enteroviruses and the Hepatitis A virus survived for more than 50 days.
In addition to the health risks associated with bathing in sewage contaminated waters, there are also risks from the consumption of contaminated seafood. Since the coastal waters around Tobago are being exploited daily of seafood, any increases in sewage pollution have corresponding increased risks of disease transmission, particularly from seafood that is eaten raw.
Our dependence upon the plants and animals in the seas around our island also means that we should be seriously concerned about the impacts that sewage pollution is having on marine biodiversity. During the past two decades many biological studies have been done on identifying and controlling the negative impacts of human activity on the marine biodiversity of Tobago. Some of the research done, particularly in Southwest Tobago, has shown that sewage pollution is impacting negatively upon marine biodiversity especially the Buccoo Reef complex.
Increases in levels of nitrates and phosphates from increases in sewerage pollution have been held responsible for decreases in the growth of sea grasses and the death of corals. High levels of phosphate and nitrates in the sea contribute to increases in the growth or algae (algal blooming). This eventually leads to corals and sea grasses being deprived of sunlight. Also, when the algae die and decompose the level of oxygen in the water is reduced significantly. This in turn leads to the death of fishes and other oxygen dependent organisms (eutrophication).
The freshwater component of sewage is a significant factor in coral reef decline. Coral reefs require certain levels of salinity. The daily release of large volumes of sewage at specific locations can lead to declines in salinity and the subsequent death of corals. We need to appreciate that the corals are like the trees of the forests and that the increased loss of coral cover will ultimately lead to a decline in fish and shellfish populations.
Sewage pollution of the marine environment of Tobago must be addressed because of current and potential negative impacts. To ensure the long-term viability of our tourism and fishing sectors and to protect the health of sea bathers, it is necessary that a comprehensive programme for sewage management be developed for this island.
(4) Planning for Sewage Management in Tobago
At this point in time there should be no doubt that sewage pollution is a serious problem in Tobago. Water quality studies give clear indications that sewage effluent is having significant impacts upon fresh water and marine life and posing grave threats to human health.
Correcting the problem of sewage pollution will not be an easy task. A first step and probably the most difficult is that of accepting that a real problem exists and needs to be addressed. The ongoing debate about public access to the results of water quality monitoring is illustrative of the fact that some are not willing to accept that a serious problem exists and that others are aware of the problem but willing to hide its extent from the larger population. Once we have made the first step of accepting that there is a major problem with serious implications for Tourism and Fisheries development we may then be able to proceed to the next step of solving the problem.
This writer does not seek to provide the answers to the sewage pollution problem of Tobago. To do so will require extensive data collection and analysis with respect to sources of pollutants, specific environmental impacts and the appropriate methods of sewage treatment that can be applied. This does not however prevent the proposal of approaches based on the experience of water quality monitoring in specific areas, along with some attempts at source identification and the evaluation of treatment methods.
The basic approach that should be undertaken in sewage management is that it be done within a larger context of Integrated Coastal Zone Management. The management of sewage effluent must be integrated with the management of other human activities and impacts. A holistic approach towards sustainable development is critical to the effort of maintaining clean and safe waters.
Within an Integrated Coastal Zone Management Programme any efforts at the management of sewage effluent should first be informed by the results of an ongoing monitoring programme. Ongoing monitoring is necessary to determine the levels of sewage pollution, the sources of these pollutants and the impacts upon the natural environment. From a human health perspective, ongoing monitoring is important to protect the population from diseases that can be contracted through contact with contaminated water. Associated with this programme of monitoring should be some type of system to inform sea bathers of safe or unsafe bathing conditions.
The ongoing monitoring of sewage pollution will provide information about the extent of the problem but will not solve the problem itself. This basically requires the reduction of the volume of wastewater and the levels of specific pollutants to be treated and also the application of wastewater treatment methods that will prevent the release of harmful effluent into ground water, rivers and the sea. Measures that can be used to reduce the volumes of wastewater include low flush toilets and composting toilets. Low phosphate detergents and similar innovations can reduce the levels of specific pollutants. The appropriate methods to be applied in the treatment of wastewater will be determined by a number of factors including composition, volumes, capital and maintenance costs and the assimilative capacity of the environment.
In the application of treatment methods, a two-pronged approach will be necessary. Firstly, the upgrading of existing and poorly functioning sewage treatment systems will have to be done at both the domestic and industrial levels. Secondly, new systems must be thoroughly assessed and approved before construction and commissioning. The inspection and rehabilitation of existing sewage systems at the domestic level will be a massive undertaking that will require significant innovation if it is to be accomplished successfully. It is a daunting task but it has to be done. This needs to be accompanied by an ongoing programme of annual inspections to ensure that such systems are working properly.
In some areas it may be feasible to pursue the option of large centralized sewage treatment plants. However, this option has a very high capital cost attached and will take several years to fully implement as the experience in Scarborough has taught us. At present, plans have been proposed for a large centralized sewage treatment plant for southwest Tobago. This plant will not address with the sewage pollution problem in coastal areas such as Roxborough, and Charlottville. Attention must be given to these areas if the situation as exists in south west Tobago is not to be replicated.
The problem of sewage pollution from yachts may be the easiest one to deal with. A requirement that all yachts have holding tasks and the provision of a sewage pump-out facility to service these yachts may prove to be quite effective in dealing with this problem. This approach has been used successfully in other areas.
The successful management of sewage pollution in Tobago can be achieved. It is not an impossible task but it will require significant input of human and financial resources. Where there is the will then a way can be found. Environment TOBAGO stands ready to work with all concerned in dealing with this problem.