Environmental Engineering Reference
In-Depth Information
For closures that are designed to prevent moisture entry into the wastepile, a vegeta-
tive cover on top of the impermeable barrier can assist in reducing dust generation. The
roots of the plants need to be short to avoid penetrating the waste that would inhibit their
growth. Biogases at active landills should be collected for energy recovery—as done, for
example, in the landill in the city of Montreal. Other gases generated in the wastepile
will need to be collected to avoid problems—as seen in the Love Canal problem discussed
previously.
Wastes are treated in many ways according to the regulations in the country where it
is generated. In many ways, unsorted MSWs can be treated as a resource containing dis-
carded bottles, paper, glass, and cans that can be recovered and recycled. Construction
wastes contain many items that are recyclable, for example, broken concrete elements
crushed and used as granular ill and scrap lumber and wood chips that can be converted
to particle board and paper into cardboard. Organic wastes can be converted via compost-
ing or anaerobic digestion. (Mulligan, 2002). One tonne of green waste produces 0.3 tonnes
of compost and 0.12 tonnes of biogas.
Mixed wastes can be very dificult to treat and thus may require incineration. However,
this reduces the weight of the waste to one third and the volume to one ifth of the original
volume. In addition, 1 tonne of household waste can produce an equivalent energy value
of 120 L of heating oil or 200 kg of coal (Genske, 2003). Despite these positive aspects,
wastes generated from incinerators include gaseous emissions (74%), bottom (23%) and ly
ashes (3%), and process water. These ashes must be stored and properly disposed of since
exposure to acidic solutions enhances metal leaching that will ind its way into aquifers or
surface water. If these ashes are recycled, the heavy metals must be immobilized. Volatile
substances such as dioxin are produced during incineration and can accumulate in ani-
mals, plants, and humans. Filtration and chemical methods are needed to reduce emis-
sions of dioxins and other hazardous components such as sulfur compounds that lead to
acid rain, and carbon and nitrogen oxides that can contribute to the greenhouse gas effect.
The caloriic value of the waste also must be suficient to run the incinerator in a sustain-
able manner.
Treatment of liquid wastes is by physical and chemical means. Deep underground injec-
tion and storage is a method that has been used. However, in addition to possible com-
paction and ground subsidence, groundwater contamination may also result. Modeling
and experimental investigations to predict the consequences of long-term storage are
required.
7.5.1.1 Fresh Kills Urban Dump, New York City, New York, USA
As an example of sustainable practice, we can take a brief look at the Fresh Kills urban
dump. Fresh Kills Landill is 7500 ha in area and was established in 1948 on Staten Island
for the disposal of waste for the 20 million people living in New York (Chamley, 2003).
Although more than 21,000 tonnes were dumped daily in the 1980s, this decreased to
13,000 tonnes per day by the 1990s, mainly due to sorting and recycling. The dump was
closed in 2001 with the exception of the waste from the rubble from the September 2001
World Trade Center disaster. As the site was originally a wood, meadow- and saline-
soil mixed coastal landscape, plans are underway to restore the site. Local vegetation
has been planted on a new 100-m hill, with an ultimate objective of transformation of
the site into a nature and leisure place. It will be an 890-hectare park that is three times
the area of Central Park and will emphasize sustainability and ecological restoration.
The irst part of the park (Schmul Park) was opened in October 2012 (City of New
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