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Presidential Green Chemistry Challenge: 1997 Designing Greener Chemicals Award

Albright & Wilson Americas (now Rhodia, a member of the Solvay Group)


THPS Biocides: A New Class of Antimicrobial Chemistry


Innovation and Benefits: Albright & Wilson discovered the antimicrobial properties of THPS and developed it into a safer biocide that can be used to control the growth of bacteria and algae in industrial water systems. THPS, or tetrakis(hydroxymethyl)phosphonium sulfate, offers many advantages over other, traditional biocides because, for example, it is significantly less toxic to nontarget organisms, is effective at much lower concentrations, and is more biodegradable than other biocides.

Summary of Technology: Conventional biocides used to control the growth of bacteria, algae, and fungi in industrial cooling systems, oil fields, and process applications are highly toxic to humans and aquatic life and often persist in the environment, leading to long-term damage. To address this problem, a new and relatively benign class of biocides, tetrakis(hydroxymethyl)phosphonium sulfate (THPS), has been discovered by Albright & Wilson Americas. THPS biocides represent a completely new class of antimicrobial chemistry that combines superior antimicrobial activity with a relatively benign toxicology profile. THPS's benefits include low toxicity, low recommended treatment level, rapid breakdown in the environment, and no bioaccumulation. When substituted for more toxic biocides, THPS biocides provide reduced risks to both human health and the environment.

THPS is so effective as a biocide that, in most cases, the recommended treatment level is below that which would be toxic to fish. In addition, THPS rapidly breaks down in the environment through hydrolysis, oxidation, photodegradation, and biodegradation. In many cases, it has already substantially broken down before the treated water enters the environment. The degradation products have been shown to possess a relatively benign toxicology profile. Furthermore, THPS does not bioaccumulate and, therefore, offers a much-reduced risk to higher life forms.

THPS biocides are aqueous solutions and do not contain volatile organic compounds (VOCs). Because THPS is halogen-free, it does not contribute to the formation of dioxin or absorbable organic halides (AOX). Because of its low overall toxicity and easier handling compared to alternative products, THPS provides an opportunity to reduce the risk of health and safety incidents.

THPS has been applied to a range of industrial water systems for the successful control of microorganisms. The U.S. industrial water treatment market for nonoxidizing biocides alone is 42 million pounds per year and growing at 6–8 percent annually. There are over 500,000 individual user sites in this industry category. Because of its excellent environmental profile, THPS has already been approved for use in environmentally sensitive areas around the world and is being used as a replacement for higher risk alternatives.

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