AWWA ACE58299

In 1997, the City selected Boyle Engineering Corporation (Boyle) to investigate treatment methods to reduce the color and the hydrogen sulfide in the water from Well 37. In addition, arsenic reduction treatment was desired if possible. Based on previous pilot testing of Hanford's water for arsenic reduction using oxidation, precipitation, and a proprietary filtration process, a pilot program utilizing two manufacturers (Filtronics, Inc. and Pureflow Filtration Division) was recommended. The proprietary filtration process (PFP) utilizes a proprietary multimedia within an enclosed pressure vessel. In general, raw water is pretreated in a reaction vessel using chlorine, sodium bisulfite, and possibly ferric chloride prior to filtration. In these treatment systems iron, manganese, hydrogen sulfide, and arsenic are oxidized. The hydrogen sulfide is oxidized to sulfate. The iron and manganese are precipitated as hydroxides, adsorbing the arsenic. The addition of ferric chloride assists in further reducing the arsenic. The arsenic is removed in the media-filled pressure vessel as an iron/arsenic or manganese/arsenic precipitate. The filter media requires no regeneration but must be backwashed periodically like a conventional sand filter. The backwash water is directed to a settling tank where the backwash water can be decanted and recycled to the head of the plant. The resulting sludge (and sometimes the entire backwash water) can be disposed of to a sewer or to on-site sludge-drying beds. Multiple pilot tests were performed at Well 37 by both Filtronics and Pureflow during 1997 and 1998. The purpose of these tests was to demonstrate the treatment capabilities to meet two-phased treatment objectives. The two-phased treatment objective unique to Hanford's operational goals, water quality standard compliance, and budget is discussed in this paper. Includes tables, figures.