Agriculture Reference
In-Depth Information
consumers to promote 'safer vegetables for healthier cities'. This was
prompted because tourists were suffering from outbreaks of gastrointestinal
disorders after consuming vegetables in urban areas.
Another potential health risk derives from the use of pesticides, although
this is beneficial in decreasing crop loss both before and after harvest (Clarke
et al, 1997). Despite the recognition of urban agriculture (UA) as a source of
urban food security, concerns are growing among city authorities on the
indiscriminate use of pesticides. Insu
cient data exist, however, on the actual
gravity of the problem. These would provide guidance on appropriate
interventions or policy formulation.
Hence research into other risk-reduction options is required for regions or
countries where wastewater treatment is not a realistic option. Therefore, this
study was designed to explore the contamination and decontamination of
wastewater-irrigated crops. The structure of this chapter first outlines the
concepts, objectives and hypotheses, then describes the research methods
followed by results, a discussion of impacts and finally some recommendations.
K
EY
C
ONCEPTS
Wastewater
Wastewater is the liquid portion of waste. It may be defined as a combination
of liquid or water-carried wastes that are removed from residences and
institutions, as well as commercial and industrial establishments. In addition,
a combination of groundwater, surface water and storm water may be present
(Metcalf and Eddy, 1995). In this section, it is assumed that urban wastewater
may be a combination of some or all of the following:
.
Municipal wastewater consists of domestic e
uent made up of black water
(excreta, urine and associated sludge) and grey water (kitchen and bathroom
wastewater). It may also include water from commercial establishments and
institutions, including hospitals.
Industrial euent is water polluted by industrial processes and containing high
levels of heavy metals or other chemical or organic constituents. Industrial
euent does not normally contain high levels of microbiological pollution
unless it emanates from slaughterhouses or food-processing plants.
.
Storm water is run-off precipitation that finds its way across surfaces into
receiving waters. Urban storm run-off is collected and transported in
storm or combined sewers. The composition of storm water reflects the
composition of precipitation and the surfaces with which it is in contact
(Environment Canada, 2006).
.
Other terms
.
Marginal-quality water: water whose quality might pose a threat to
sustainable agriculture and/or human health, but which can be used safely
