The Municipal Wastewater Treatment Plant in Hatfield, PA, uses an 8000-standard-cubic feet-per-minute (scfm) regenerative thermal oxidizer (RTO) to control volatile organic compound emmissions from its multiple-hearth sludge incinerator.

Since its 1994 startup, the RTO consistently has met all regulatory emissions limits with a significant margin of safety. However, after approximately a year of operation, the pressure drop across the ceramic saddles in the heat-recovery canisters had increased to a level that compromised the induced-draft (ID) fan capacity.

Washing the saddles initially restored the pressure profile, but required frequency of washing increased with operation. The washing procedure required an 18-hour shutdown of all processing operations. Heat recovery diminished over time, causing fuel gas costs to skyrocket.

In consultation with Stan Chilson of Harrisburg, PA-based CET Engineering Services, plant operators experimented with ceramic multilayer media (MLM) supplied by Lantec Products, Agoura Hills, Calif. These media use parallel-flow channels to provide high heat capacity without high pressure drop. Hatfield decided initially to try the media in only one of the three heat-recovery canisters. Eight feet of 1-inch saddles were replaced with 4 feet of MLM.