Abstract |
A two year study was conducted at 4 locations in Pennsylvania to test the effect of various alkalies and filter aids on rotary vacuum precoat filtration for dewatering of lime neutralization sludge. The process consisted of neutralization, aeration, sedimentation and filtration. Alkalies investigated were limestone, limestone with hydrated lime, calcined magnesite, partially and fully calcined dolomite, and hydrated lime. Filter aids tested included Hyflo, Super-Cel, and Celite 501, 503, and 545. Results from the first three locations indicated limestone and hydrated lime were preferred alkalies and Celite 501 the preferred filter aid. At the 4th site a 27 run factorial experiment investigating the effect of flow rate, limestone feed level, aeration level, and sludge recirculation level on equipment operation and process cost was conducted. Sludge solids content, filtration rate, and sludge recirculation were found to be significant variables affecting process cost. Estimated operating costs for a 1.5 MGD treatment plant using lime neutralization were $1.16/1000 gallons treated or $8.02 per 100 lbs of acidity treated. |