Conservation strategies create new challenges for wastewater systems
Eco-friendly products and services with a focus on conserving our natural resources are an emerging trend across the world. The water and wastewater industries are no exception to this global trend.
Conservations strategies that have been implemented to protect vital groundwater reservoir supplies have proven beneficial, however, they are not without their challenges. The old joke – “the solution to pollution is dilution” actually helps to explain what is happening. Reduced flow results in increased holding time in the collection system. This leads to increased microbial action, and therefore enhances corrosive activity.
High-performance protective coatings rise to the challenge
As a cost-effective solution to water and wastewater rehabilitation, high-performance, spray applied coating systems were developed. A long-held belief was that these coatings, although affordable, could not hold up to the severe environment of wastewater collection systems. As a result of advancements in technology along with extensive research and testing, that belief has proven to be outdated and inaccurate.
For example, OBIC’s spray applied protective coatings have not only proven to withstand the challenges of corrosive wastewater systems, they are also environmentally friendly, cost-effective solutions for everything from manhole coatings to pump station rehabilitation. We say this with confidence, because we put our products through extensive third-party testing using newly developed methods that have been proven to effectively simulate exposure in a wastewater headspace environment.
Out with the old and in with the new Severe Wastewater Analysis Test
Two widely used test methods for corrosion evaluation of coatings and linings for use in wastewater applications are the Los Angeles County Sanitation District “pickle jar test,” historically referred to as the “Redner Test,” and the University of Houston Center for Innovative Grouting Materials and Technology (CIGMAT) test. Both of these test protocols consist of immersing coating samples in sulfuric acid concentrations of 3% to 30%.
These tests are limited to evaluating resistance to chemical immersion and do not include the effect of biological activity. Microbes in the wastewater stream, through various chemical reactions, form hydrogen sulfide which is further metabolized to produce sulfuric acid. All of this microbial/chemical activity occurs in the headspace above the water line.
A new test method has been developed that more accurately replicates the effect of hydrogen sulfide in the headspace above the wastewater. This test – The Severe Wastewater Analysis Test (S.W.A.T.) – utilizes a test chamber to rapidly evaluate a particular coating/lining resistance to permeation by hydrogen sulfide and sulfuric acid. This method is described by ASTM G210-13, “Standard Practice for Operating the Severe Wastewater Analysis Testing Apparatus.”
The test simulates exposure in a wastewater headspace environment with intermittent wetting. Samples are continuously exposed to a methane/carbon dioxide/hydrogen sulfide gas at 150⁰F for 28 days. Additionally, samples are immersed for 15 minutes in 10% sulfuric acid three times each day. Following the 28-day test period, samples are evaluated for blistering or cracking, as well as adhesion, tensile strength, and compression or flexural properties.
OBIC products meet the most demanding performance requirements
Performance requirements for wastewater coatings and linings have become more demanding. Accordingly, the testing protocol requires improvement to more accurately reflect real-world conditions. The S.W.A.T. test (ASTM G210-13) affords owners and engineers increased assurance that the coating system being used meets or exceeds their expectations.
OBIC products have been successfully tested by the S.W.A.T. protocol and the complete third-party test data report is available for review. If you are not using OBIC products, it is probably time to ask your approved product suppliers for a copy of their S.W.A.T. test results.