Seawater induced algal flocculation

Abstract

The effectiveness of the use of seawater in the removal of algae from oxidation pond effluents was investigated. Freshly collected samples of pond effluent were initially adjusted to pH levels of 9.0–11.5, then seawater in proportions of 0–20% (v/v) was added. The jar test technique was used to determine algal removal efficiencies. The effect of the process on alkalinity in the samples was studied. Test results indicated that the primary reactions responsible for the removal of algae were the formation and precipitation of CaCO 3 and Mg(OH) 2. These reactions were initiated at pH values of 9.5 and 11.0, respectively, in the absence of seawater. As seawater concentrations were increased, the reactions were initiated at lower pH values. Algal removals in excess of 80% were achieved at an initial pH of 10.5 and 5–10% seawater. Nearly complete removal (> 95%) was achieved at an initial pH of 11.0 and 10–15% seawater.