Background:
The province of Prince Edward Island is relatively unique in that it derives all of its potable water from relatively shallow, Sandstone Bedrock aquifers.
Conventional sewage disposal systems can have negative impacts on valuable groundwater resources. Pollutants in septic tank effluent can travel downward to shallow groundwater systems causing nutrient and bacterial contamination.
In the case of many high density coastal developments, groundwater is extracted from aquifers, converted into sewage and the effluent discharged to the ocean where it is not available to recharge the local groundwater system.
The methods used to manage human wastes at Greenwich avoid both of these potential environmental concerns.
Blackwastes:
The Clivus Multrum Composting Toilet system has been designed for an average of 300 visitors (uses) per day and a peak of 600 uses per day.
95% of the toilet wastes are converted into water vapour and carbon dioxide. 5% remains as the safe, stabilized end product we call "compost". It will take several years before the nitrogen-rich solids arrive in the finished compost area.
Urine entering the toilets and urinals is biochemically transformed as it passes through the compost pile. By the time it reaches the finished compost area the liquid is stable, and odourless. It is high in nitrogen, potassium and phosphorus and makes an excellent fertilizer when diluted with ten parts water.
At an average rate of 300 uses per day, approximately 0.10 cubic metres of compost will eventually be produced per season. The total amount of liquid end-product generated is estimated at 5000 liters per season.
Greywater:
Potable water will be consumed and greywater will be produced from the outdoor showers and hand basins at an average rate of approximately 13 liters per person per day - half of what the water requirement would have been if conventional toilets had been used.
A shallow trench disposal field will be used to disperse the greywater into the uppermost, biologically active soil layer which is home to soil bacteria, earthworms, centipedes and sow bugs. This diverse soil ecosystem will naturally consume any organic matter, bacteria or pathogens in the greywater. Water and nutrients will naturally be taken up by the roots of plants through the process of evapotranspiration. Any excess water will infiltrate downward to recharge the bedrock aquifer which underlies the site.
ETC recognized for introducing naturally composting toilets at Greenwich National Park
Composting toilets in use at Greenwich dunes "Green building" day use facilities.
ETC provided consulting services for management of human wastes at the Greenwich Day-use Area in the PEI National Park. The Day-use Area is a model for sustainable development and the project was chosen by Natural Resources Canada to form part of the Canadian poster presentation at the International Green Building Challenge 2000.