Evaluation of Algicides and Algistats Intended for Use in Swimming Pools or Industrial Water Cooling Systems using Pure Culture Technique

Purpose of Test

In order to determine the effectiveness of an algicide or algistat designed to control algae in swimming pools or industrial water cooling systems, the U.S. EPA recommends a laboratory test be performed followed by a simulated in-use test to confirm efficacy. The laboratory test requirement for these claims can be satisfied using the Pure Culture Technique method.

Summary of Test

In this method, a series of product samples are spiked with a suspension of pure culture algae. The flasks are incubated under conditions designed to promote algal growth and are subsequently subcultured to detect surviving algae. After three weeks of incubation, the flasks are visually examined, rated for growth and compared with untreated control flasks. An effective algistat must demonstrate 70% control of algae in the primary cultures for 3 weeks. An effective algicide must demonstrate 70% control of algae in the primary cultures for 3 weeks and also demonstrate no visible sign of algae growth in any of the subcultures. Representative algal species that are tested may include Chlorella vulgaris, Scenedesmus obliquus, Euglena gracilis, Phormidium inundatum and Phormidium faveolarum.