Full Article: Coating Issues In Wastewater Treatment Collection And Treatment Systems

Collections. Drains. Sewer Lines. By whatever name they are called, they and their associated treatment plants present unique protection and maintenance challenges. Imagine being asked to put a coating on concrete that is saturated with water, covered with grease and a nasty biofilm, heavily attacked by sulfuric acid and contaminated with anaerobic bacteria. Imagine too that surface preparation techniques at best remove degradated concrete and surface contaminants but have no effect upon the level of moisture in the substrate nor the degree of subsurface microbial colonization. Suppose your coating had to cure at cool temperatures in an environment that is at more than 90% RH and filled with hydrogen sulfide. That is enough to make even hardened coating applicators nervous and the best coating formulator sweat. Yet, those are precisely the conditions found in wastewater collection and treatment systems. A system that is out of sight, out of mind, and often out of order. To say there are "coating issues" in wastewater treatment systems is a classic understatement. Contributing to those issues are two underlying factors – a basic lack of understanding of the cause of deterioration on the part of the industry and its specification writers and an all too common material specification for the concrete that demonstrates the combined effects of ignorance and inertia. This paper highlights these issues, outlines the corrosion mechanisms involved, discusses substrate specifications, and coating selection including properties and chemistry.

Reprinted from JPCL (October 2004)
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