The pH changed little with contact time for the lower solid loadings (0.5-2 grock mL -1 ) but gradually increased with higher solid loadings. The P concentrations (Figure ) mirrored the trend in pH: at lower solid loadings, the concentration did not change significantly with contact time but decreased with increasing contact time with higher solid loadings. Different trends were recorded for dissolved Ca (Figure ). After 15 min, the Ca concentration increased with low solid loadings but decreased with higher loadings. The Ca concentration then fluctuated with contact time, but with no significant changes at all but two data points (A decrease at 24 h and 48 h for the 2 g L -1 solid loading. The Mg concentrations (Figure ) changed only with higher loadings, decreasing significantly after 24 h.