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UNIT 5: THE SUSTAINABLE SITING, DESIGN AND CONSTRUCTION OF TOURISM FACILITIES
Alternative Sewage Treatments
These systems are designed to mimic natural wetland ecosystems. The wastewater
is passed through a series of plants and micro-organisms to remove solids,
bacteria and pathogens present in the sewage. Traditionally such systems required
a fair amount of land, but modern technology enables the wastewater to pass
through a series of ponds and tanks where plants, invertebrates, fish and sunlight
are used to clean it.
Examples of Good Practice
A successful wetland wastewater treatment system, the Splash Carnivore,
has been constructed on the edge of Nairobi National Park, Kenya. The
construction of the wetland was completed in mid-1994, and its performance
has continuously improved with the biological maturity of the wetland.
The wastewater first passes into a settling pond where the solid particles are
allowed to settle to the bottom. The water then passes through beds of gravel
where bacteria and aquatic plants such as bulrushes, sedges and reeds act
together to break down sewage. The water then passes through a series of
terraced ponds where other plants further purify the water. The water is now
clear and odourless and when it reaches the subsequent open ponds the sun’s
UV-C rays effectively eliminate remaining pathogens. The sewage nutrient-rich
bacteria falls prey to small crustaceans. Green algae and the absorption of
oxygen from the surrounding air also play important roles in purifying the
water.
This mini-ecosystem is now attracting numerous species of birds and other
aquatic wildlife.
The only maintenance required is to consistently clear away the excess
vegetation, for vegetation falling and rotting in the waterways increases the
nutrient levels in the water, and this interferes with the effectiveness of the
natural water purification process. The removed vegetation is composted or laid
on access footpaths to buffer the impact of foot traffic.
The Carnivore Restaurant actively participates in the project by channelling its
wastewater to the wetland for treatment. At first, the high level of fat in the
restaurant wastewater caused problems. This has now been rectified through
the separate collection of waste oils and fats, the fitting of grease traps to the
kitchen’s wastewater outlets and the introduction of selectively bred bacteria in
the gravel beds. The restaurant further ensures that all cleaning materials are
free from phosphates and chlorine.
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Composting Toilets
Composting toilets allow for the composting of waste in the toilet structure itself
and do not require water for flushing. As with all composting practices, bulking
material (hay, sawdust, wood shavings etc.) need to be added as regularly as the
toilet is used to maintain the carbon and nitrogen balance, and the pile needs to
be turned regularly. In cold climates, the toilet chamber needs to be insulated and
heated.
The heat generated from the composting process causes the moisture from the
waste to evaporate. Therefore the toilet needs to be aerated through a vent and/or
mechanical aerator. If the pile is well maintained, no odours will arise.