Severe Wastewater Analysis Test (S.W.A.T.)

Background

The Severe Wastewater Analysis Test (S.W.A.T.) is used to determine the performance of protective coatings and other materials under conditions simulating the headspace environments in municipal waste water collections systems (municipal sewers and pumping stations). The Severe Wastewater Analysis Test overcomes the limitations of simple chemical testing.

SWAT test cabinet with coated panels
Figure 1. SWAT test cabinet with coated
panels

Sanitary sewer wastewater headspace environments are very corrosive due to the presence of sewer gases (containing hydrogen sulfide and carbon dioxide), air (which contains oxygen), and high concentrations of sulfuric acid (generated during biogenic sulfide corrosion processes). Recent design changes in waste handling facilities have significantly increased the corrosivity, requiring the development and evaluation of new protective coating systems.

Clients for this testing service are Protective Coatings Manufacturers, Sewer Authorities, Specifying Engineers, and Industry Testing Agencies active in the municipal wastewater collection industry.

Description

Tensile bars and dog bones in SWAT test
Figure 2. Tensile bars and dog bones
in SWAT test

The S.W.A.T test consists of a test cabinet and procedure designed specifically to simulate the pertinent aggressive chemical conditions of head space environments. Test specimens (e.g., coated steel, ductile iron, concrete panels, or free films) are positioned on a carousel and placed inside the airtight test chamber. The chamber contains a prescribed aqueous solution (sulfuric acid with sodium chloride) and concentrated sewer gas. The test specimens are immersed in the aqueous solution for 15 minutes three times a day. For the balance of the time, the specimens are exposed to the sewer gas above the liquid. The cyclic exposure continues for a period of 28 days. An elevated test temperature such as 65°C accelerates the conditions and reaction rates. The chemical solution (liquid phase) and sewer gas concentrations can be adjusted to test specific industrial wastewater environments.

The tested coatings and materials are evaluated for performance based on: visual changes, such as development of blisters, cracking, swelling, and chemical attack; loss of adhesion; changes in mechanical properties such as tensile strength and elongation; and loss of barrier properties as determined by electrochemical impedance spectroscopy analysis (EIS). The results obtained by this test serve as a means for estimating the protective barrier qualities of a protective coating or lining for use in severe sewer conditions.

Awards

Assessing Coatings and Linings for Wastewater: Accelerated Test Evaluates Resistance to Severe Exposures was a winner of the NACE Materials Performance Readers’ Choice Corrosion Innovation of the Year Award. 2012

ASTM Standard Practice is under development
Standard Practice for Operating the Severe Wastewater Analysis Testing Apparatus
ASTM Work Group WK33537. Ballot process initiated 2012

Related Publications

Testing Permeation Resistance in Coatings for Wastewater Service, Vaughn O’Dea, et al, Journal of Protective Coatings & Linings, September 2010, pp. 16-28.

Severe Wastewater Testing Program for Rapid Evaluation of Coatings and Linings: Testing Procedure. Vaughn O’Dea, Remi Briand, and Linda G. S. Gray. PACE, January 27 – 30, 2008. Los Angeles, CA

Assessing Coatings and Linings for Waste Water: Accelerated Test Evaluates Resistance to Severe Exposures. Vaughn O’Dea, Remi Briand, and Linda G.S. Gray. Journal of Protective Coatings and Linings, April 2008, p 44.