EFFECTS OF VERY LOW pH SULFURIC ACID EXPOSURE ON COMMON SEWER PIPE LININGS
Abstract:For many decades American Cast Iron Pipe Company (AMERICAN) has conducted and also collaborated with others in research involving pipe linings for many services. AMERICAN has also worked as a notable supplier of lined piping materials used predominantly in the water and wastewater but also other sectors. This paper discusses a specific research program started on February 4, 1999 (and with some continuing to date) in AMERICAN laboratories to evaluate the effects of long-term, soaking exposure of commonly supplied sewer pipe linings to very low pH sulfuric acid. Many other researchers have shown that very low pH (1 or even less) sulfuric acid is in fact created above the flow line by microbial (or biogenic) action related to the presence of hydrogen sulfide and other factors in some gravity and also in locations of some pressure sewers. Of course, many utilities are also well aware of the devastating structural, sociological, and economic damages sometimes created by these effects.
The most commonly specified linings for ductile iron wastewater pipes, Portland cement (mortar), novolac epoxy with ceramic filler, composite fusion bonded epoxy (FBE) primer/heat-fused polyethylene, and 100% calcium aluminate cement were exposed to sulfuric acid solutions with a pH from 1-4 in this testing program. An effort was made in this testing program to simulate possible effects of “surcharge events”, or high/low periodic flowing cycles. This procedure also allowed best possible periodic examination of lining conditions as the solutions were emptied, the samples were gently rinsed with fresh water for inspection, and then the exposure solutions were carefully refreshed. The results of this testing program indicate only the novolac epoxy with ceramic filler and composite fusion bonded epoxy (FBE) primer/heat-fused polyethylene linings have shown significant resistance to such sulfuric acid exposure in the pH 1-2 range. The best available acid-resistance exemplified in these tests is from the composite FBE primer/heat-fused polyethylene lining, which has exhibited no ill effects in exposure to pH 1 solution sulfuric acid of more than 700 days (16,800 hr).
Document Type: Research Article
Publication date: January 1, 2001
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