Critical Elements to Ensure Methanol Safety on Site
Authors:
- Sarah Lothman, P.E., Laurissa Cubbage, P.E., Dennis Phelps
Wastewater treatment plants in Virginia that are significant dischargers to the Chesapeake Bay watershed are required to meet stringent effluent limits for total nitrogen (TN). In order to do so, enhanced nutrient removal is often required and methanol is commonly added to aeration basin anoxic zones and/or denitrification filters. Methanol, the most prevalent and historical low-cost carbon source option does, however, come with safety concerns. The objective of this paper is to identify critical safety elements required in a methanol facility and offer a comparison of nine Mid-Atlantic facility designs in order to identify equipment that is required and equipment, while not required by regulation, may be recommended for a specific installation. Specifically, fire suppression, tank safety, and gas monitoring equipment will be discussed. The paper will also discuss how safety concerns change if a facility seeks to feed various carbon sources.
Methanol is characterized by a low freezing point, low viscosity, sweet odor, and most importantly flammability. Methanol has an NFPA Hazard Index value of 3, indicating that methanol has a flash point below 100°F. Furthermore, when ignited, methanol burns with a colorless flame. A detailed discussion of these chemical properties and others will be provided along with an explanation of how these properties affect plant operations staff. Ultimately, POTWs choosing to use methanol must meet regulatory requirements for the storage and feed of a hazardous, flammable chemical and make protecting the health and safety of plant staff a top priority.
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