ADVANCED SCRUBBER TECHNOLOGY GIVES NEW LIFE TO AN OLD FURNACE

Facing aging equipment, odor complaints and the inability to meet emission standards the East Norriton, Plymouth, Whitpain Joint Sewer Authority (ENPWJSA) entered into a Consent Order and Agreement (CO&A) with the Pennsylvania Department of Environmental Protection (DEP) to modify solids handling practices at their 8.0 MGD Wastewater Treatment Facility.Preservation of reasonable costs and the control of odors associated with biosolids handling prompted a study of solids handling alternatives. The study evaluated continued use of an Existing Multiple Hearth Furnace (MHF) with three add-on emission control systems. A comparison to other solids handling options including alkaline stabilization processes was also made. A Present Worth Analysis demonstrated the economic viability of improvements to, and continued use of, the MHF. The select alternative included replacement of the existing high-energy scrubber with a more efficient post cooler multi-venturi wet scrubber followed by a recuperative heat exchanger and afterburner.Conversion to this patented post scrubbing afterburner process configuration was completed in less than one year. The modification required only one extended (25 consecutive day) shutdown of the furnace and only 15 days of off-site biosolids disposal costs.EPA (1993) estimated there were approximately 343 active biosolids incinerators in the U.S. Of these, 277 were MHF, while the remaining were Fluid Bed Combustors (FBC). The present worth analysis for ENPWJSA clearly identified the economic advantages to add-on modifications to the existing MHF compared to replacement costs. The process configuration utilized in ENPWJSA also demonstrated the capability of the MHF to meet conflicting priorities of NOx and CO at reasonable fuel demands.