Protecting human health and the environment against siloxanes: The role and effectiveness of wastewater treatment technologies

Since they were first synthesized in 1940, siloxanes have been widely exploited by the cosmetic, construction, pharmaceutical, and food industries. Global siloxane production has grown steadily throughout the decades and now exceeds 10 million tons per year. This production growth has resulted in greater environmental spillover, whose adverse impacts are still being studied. Yet, a growing body of reports, government policies, and scientific investigations agree that volatile organic silicon compounds are some of the most noxious forms of siloxane chemistry. Environmental remediation of siloxanes is challenging; therefore, it is strategically advantageous to intercept and treat siloxanes before they reach the environment. Wastewater treatment plants are a primary collection point for siloxanes that originate from the residential sector, where siloxane products are consumed and rinsed away in copious quantities (e.g. cosmetics and personal care products). However, conventional wastewater treatment often cannot entirely remove siloxanes, which means a substantial portion still reaches the environment. There are advanced treatment technologies that target siloxanes (e.g. physical/chemical absorption and membrane separation); however, these technologies substantially increase the treatment cost. Therefore, researchers are pursuing other siloxane treatment strategies, including new biological approaches. This review provides a fresh look at the history, societal importance, and environmental impacts of siloxanes and the methods used to treat them. The review calls upon a wide array of research to compare and critically evaluate these treatment strategies – old and new – using basic concepts of sustainability as criteria.