CLAY FLOCCULATION WITH A NATURAL POLYELECTOLYTE

Abstract

The flocculation performance by using biological flocculants (BFs) extracted from Moroccan cactus pads of Opuntia Ficus Indica (OFI) for turbidity removal was investigated. The results showed that BFs were able to eliminate turbidity from natural clay solution over a wide dosage range (initial turbidity about 1000 Nephelometric Turbidity Unit (NTU)). The removal efficiency with BFs reached 98.6 % on average at pH 12.4 adjusted with lime, higher than 62 % with a new Chelating-Soluble extract (CP) from cladode also. For bioflocculants, bridging flocculation other than charge neutralization should be responsible for turbidity removal. The combined applications of CP with H2SO4 increased overall turbidity up to -238 %; from an initial turbidity of about 76 NTU to 257 NTU. It was also shown that combination of BFs and H2SO4 was effective for removing turbidity from raw water and can achieve 94% with a residual turbidity about 10 NTU at pH 2.0. This study provides a proof-in-concept demonstration of BFs for water purification, which can in part reduce operational costs in flocculation treatment, as well, effectively reduce the concentration of residual metallic elements (e.g. aluminum) used as coagulant.