Abstract
Both mesophilic and thermophilic anaerobic digesters are currently being utilized to treat sludge derived from more than typical municipal sewerage sources. Wastewater treatment plants are accepting septage and sludge from food waste and industrial contributors routinely today. Receiving these other sources of waste which are extremely high in volatile solids is a source of significant income for the utilities. However, high volatile solids loading into the digesters can cause out-of-balance biochemical conditions in the digesters. High volatile fatty acid to alkalinity ratios and low methane production are but a few of the repercussions of these imbalanced conditions. These process upsets result in high acetic, propionic and other intermediate fatty acids. These exposures, when sufficiently prolonged, can cause degradation to the polymers in some protective coating systems commonly used successfully in the past.
This paper will present evidence of this type of attack based on both field experience and laboratory testing data. Recommendations will be made for future material selection criteria and testing to avoid premature lining failures in anaerobic digesters in the future.
