J Water SRT - Aqua 51 (2002) 307-318

Effects of chlorine and ozone on algal cell properties and removal of algae by coagulation

Jeanine D. Plummer and James K. Edzwald

Department of Civil and Environmental Engineering, 100 Institute Road, Worcester Polytechnic Institute, Worcester, MA 01609, USA Phone: 508-831-5142 Fax: 508-831-5808 E-mail: jplummer@wpi.edu

Department of Civil and Environmental Engineering, 18 Marston Hall, University of Massachusetts at Amherst, Amherst, MA 01003, USA

The effects of ozone and chlorine on algae were examined with respect to cell surface characteristics, lysis and coagulation ability. Two algae were studied: a green alga (Scenedesmus quadricauda) and a diatom (Cyclotella sp.). Cell properties were characterized using scanning electron micrographs, particle size distributions and electrophoretic mobility measurements. Jar tests were used to evaluate the coagulation of the algal suspensions with a polyaluminium chloride (PACl). The results showed that changes in the characteristics of the algal cells from ozone or chlorine yielded an improvement in removal of Scenedesmus through a combination of lysis and improved coagulation ability with PACl. Cyclotella removal was not enhanced by preoxidation. Additionally, preoxidation increased the organic carbon concentration of the settled water, which could lead to increased tastes and odours and production of disinfection by-products.

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