Laboratory investigation of the phosphorus removal (SRP and TP) from eutrophic lake water treated with aluminium

Mechanisms involved in phosphorus (P) removal from eutrophic lake water with aluminium (Al) were assessed by jar tests. For this purpose, eutrophic lake water enriched with soluble reactive phosphorus (SRP), algae or sediments in order to mimic the various conditions found in shallow eutrophic lakes was studied. Total phosphorus (TP) removal was reached after floc settling, the maximal TP removal efficiency (90–95%) was obtained for an Al concentration ranging from 2 to 5 mg L−1, depending on the organic matter (OM) origin (algae or sediments). Algae appeared to limit macro-floc formation (those able to settle). In contrast, in the presence of sediments, macro-floc formation was favoured at low Al dose (2–3 mg L−1 Al). High SRP removal was obtained with the lowest Al dose (1 mg L−1 Al) and remained greater than 60% for an SRP concentration up to 350 μg L−1. SRP removal was not influenced by the OM origin. The experimental data and literature were used to suggest a hypothetical model for floc formation and P removal with Al under the conditions observed in treated lakes.