ACID PHASE DIGESTION – FOR FREE

A survey was conducted of raw sludge pipeline installations to identify the number in use, and how much information was developed on the operation of the pipeline, with emphasis on its characteristics as a biological reactor. Fourteen installations were identified, including a number in areas of the United States where warmer sewages (greater than 15°C) prevail even if only a few months of the year. However few if any of the owners of these facilities obtain monitoring information for parameters reflecting a potential role for raw sludge pipelines as anaerobic biological reactors. Nonetheless it was evident from the survey that pipelines with a hydraulic residence time (HRT) greater than two days will serve as acid phase digesters, and at warmer sewage temperatures and HRTs greater than two days will change the characteristics of the raw sludges after transit, making thickening and odor control more challenging, and reducing the volatile solids supplied to the anaerobic digesters.