| dc.description.abstract | The objective of this study was to determine the heavy metal content of the Gaborone
secondary effluent in Botswana before its discharged to the Notwane river. Secondary
effluent water was sampled every month for one year, from a breather pipe on the pivot
irrigation system at the Botswana College of Agriculture, Notwane Farm, Gaborone,
using USEPA procedures and guidelines. The results showed that the heavy metals of
most widespread concern to human health Hg, Cd, Pb and As were below detectable
limits, 5.75, 4.83 and 5.7 parts per billion (pgL1), respectively, and were below
concentrations that could pose pollution of the environment and were within the
recommended limits for irrigation water by FAO and the Botswana guidelines for
irrigation water. The other trace elements Be, Ti, V, Cr, Co, Cu, Ga, Ge, Se, Sr, Ba, Ce,
Bi, Al, Li, Mn, Mo and Fe were all below the recommended limits for irrigation water by
FAO and the Botswana guidelines for irrigation water. Most of the trace elements were in
concentrations of parts per billion. The current results suggest that the Gaborone
secondary effluent is suitable for unrestricted irrigation of field, fodder and horticultural
crops. However, heavy metal levels should be monitored continuously either by the
Gaborone City Council or any other government institution in order to make sure the
treated secondary sewage effluent meets the recommendations for irrigation water, and
prevent environmental pollution and reduce health hazards that may be caused by
pollutants to the end users of this scarce resource. | en_US |
