Each row of pools represented one water pollution treatment
for water hyacinth. The treatments used in the pools’ artificial
solution were, sulphates (MgSO4) with Cu, Fe, Mn, and Zn.
Although the different sulphate concentrations used in this trial
were similar to concentrations spanning those measured in local
water-bodies such as the Vaal River near the AngloGold Ashanti
mining sites at Orkney (North West Province) in receipt of acid
mine drainage and effluents from the local settlement, the heavy
metals were above the average concentrations found in surface
waters in South Africa (Newete, 2014). Nevertheless, high concentrations
of heavy metals were chosen for this trial to match those
used in other studies, e.g. Kay and Haller (1986). Nitrogen and
phosphorus nutrients from a technical grade fertilizer, and the
heavy metal treatments were added at the same dose across all
pools, whereas the SO4
2 treatment was added as MgSO4 to the
pools at three different concentrations, one in each row (low, medium
and high). The extended sulphate dose treatments in this
experiment were designed to account for the increase in sulphate
concentrations in surface waters such as the Vaal River, which
receives a constant influx of effluents from the local settlements
near Kennan in the North West Province through its tributaries
the Schoonspruit and the Koekemoerspruit in addition to the
AMD (DWAF, 2009).