AWWA ACE65192

Within the first 17 months of operation, the pressure filters at a 1.8 MGD (78.9 l/s) water treatment plant began having trouble. The operator first observed problems by a shortening of the filter run. When one of the hatches blew out, the operator had his first look at what was going on inside of his filters. He saw an orange slime coating the interior walls. Further inspection of all the filters showed an accumulation of fine sediment on the top of the media and mud balls, in addition to the orange film. In spite of corrective actions by its second year the plant was reduced to half the design capacity, well below its operating efficiency and required extensive maintenance. Review by the manufacturer and engineer recommended media replacement, as they attributed the plant's poor performance to damaged media. The cause of the crushing was unclear. In the absence of a directed investigation it was probable that media failure would recur. This study was performed as an academic research project and incorporated analytical evaluation and physical testing, adapted from conventional gravity systems for pressure filtration. Working together with the local water department and manufacturers, the authors conducted this independent plant study with the support of Northeastern University's College of Engineering. It has enabled effective identification of equipment shortcomings, implemented structural corrections, improved plant productivity and increased media life. Includes 10 references, tables, figures.