Solving the sewage system

The Cayman Islands Government is trying to sell Grand Cayman’s wastewater system. Given the tough economic times it can be seen as a necessary revenue measure, but the sale may be what’s needed for more than just the budget’s sake.

The existing sewage system’s scope is limited. A report by Catherine Crabb of the Water Authority released in August 2009 indicated that only about 20 per cent of the wastewater generated in the Cayman Islands is collected and treated at the central wastewater treatment plant.

Poorly treated or untreated wastewater creates a health hazard and an environmental hazard.

Currently the wastewater system only serves properties along West Bay Road from Watler’s Road in the south to Raleigh Quay in the north, the exceptions being Canal Point, sections of Governor’s Harbour, and Snug Harbour.

As part of the sale, however, whoever takes it over will be responsible for improving and expanding the sewage system to serve George Town, West Bay and Bodden Town, Grand Cayman’s three most densely populated areas.

The situation today
The higher proportion of  Cayman’s sewage, 80percent,  is treated in onsite treatment systems comprised of approximately 13,500 septic tanks and 520 aerobic treatment units. In their 2009 report the Water Authority noted that

Septic tanks serve the majority of developments constructed prior to 1990 as well as smaller developments constructed since that time. Any new development that cannot be hooked up to the West Bay Beach Road Sewerage System requires a septic tank and a deep well as a minimum.

Aerobic treatment units are required at larger developments, to achieve a higher level of treatment, known as secondary treatment, a septic tank alone only provides primary treatment.

An aerobic treatment unit, or package plant as they are known, is required if a development generates over 1,800 gallons of wastewater per day.

Where it goes
The effluent from these aerobic plants and from the septic tanks is injected into disposal wells at a depth of 40 to 100 feet below the water table, depending on their location, to ensure injection is into brackish or saline, not fresh water.

The effluent then travels laterally, eventually reaching the sea. Water Authority director Gelia Frederick-van Genderen explains.

“The lateral path that groundwater takes in Cayman’s substrate serves two purposes: it prevents it from travelling upwards into freshwater that may overlay it, or up to the ground surface where people could come into contact with it; secondly, pathogens contained in effluent die off due to contact time (travel time) through the brackish water, preventing pathogen contact with bathers in the sea.”

However, she says that does not mean there is no contamination of the freshwater lenses with wastewater effluent. Many systems were already in existence before the establishment of the Water Authority’s legislation but focus has been on the newer developments.

“Given the rapid rate of development since that time, limited resources have focused on getting new developments – which now far outnumber the pre-existing – in line with current standards for effluent disposal,” she continued.

The Authority is also currently working with the well drilling industry, to tighten up the standardization of works using the knowledge gained regarding the vagaries of Cayman’s substrate.

Exceeding the parameters
Under the Water Authority Law and Regulations treated sewage discharged from private plants must meet two parameters. Often this standard is referred to as the 30/30 standard. Both parameters can be tested by the Water Authority’s Laboratory.

The two parameters are:

Biochemical Oxygen Demand to be 30 milligram per litre. This parameter is a general indicator of organic pollution.

Suspended Solids to be 30 milligram per litre. This parameter determines the amount of solids left in the water.

On 31 May 2009 our sister publication the Compass reported that sampling done by the Water Authority at 186 package plants throughout Grand Cayman between April 2008 and February 2009 revealed that 126 did not meet the legal requirements.

In June 2009 the Compass revealed the 18 worst waste management systems in private estates and retail sites in Cayman, including one site that was almost 275 times over the legal limit of total suspended solids.

The Water Authority report, released in August of 2009 found that overall, only thirteen percent of the systems it sampled met the limits for both Biological Oxygen Demand and Total Suspended Solids.

“The results ranged widely, often not only exceeding the “30/30” limits, but exceeding the industry standard for untreated domestic wastewater,” the report states.

Clearly, the current methods in are not working the way they should be, and indications from government suggest expansion of the piped sewage system may provide at least some part of the solution.

It’s a huge job, and Water Authority Board chairman Jonathan Piercy says that’s why a major overhaul and expansion of the wastewater management system is best undertaken as a public private partnership.

How it will work
Once sold, the wastewater system’s services will be part of a multi-year license issued by the Cayman Islands Government.

Furthermore, the physical job of building such a system needs to be accompanied by regulations governing its use and operation once the license is issued, another major undertaking.

Piercy thinks it is worth it.

“If we compare the amount of treated and untreated wastewater being released into the ground compared to what’s going into Mount Trashmore, our problem is at least three times greater.”

Why it matters
A UN report released last month revealed that more people die from polluted water every year than from all forms of violence, including war.

Typically extreme examples of health hazards happen after a natural disaster when wastewater is not treated increasing the risks of water-borne diseases such as cholera, dysentery and other gastro-intestinal diseases. The environment is also affected.  “The environmental consequence of poorly treated wastewater is that the natural environment is at risk of being degraded,” says Frederick-van Genderen.

The worry in Cayman is that wastewater might affect the fresh   groundwater supply. Cayman has three significant freshwater lenses, located in Lower Valley, East End and North Side.  “In the Cayman Islands the potential health effect of poorly treated wastewater is that it affects the fresh groundwater, a very limited resource which is still used for potable and non-potable purposes,” says Frederick-van Genderen.

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