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436 Gregory T. Kleinheinz and Phillip C Wright

Table 7
Microbial, pH, and Moisture Content Averages During the Pilot Study
Microbial pH of solid Solid-support
count support moisture content
July average 1.1 E8 CFU/g 6.2 35% (w/w)
August average 2.7 E5 CFU/g 6.6 30%
September average 2.9 E6 CFU/g 6.7 28%
Take down 3.4 E6 CFU/g 7.1 31%

Table 8
Airborne Chemicals Monitored During the Pilot Study
Parameter Overall removal Influent mean (ppm) Effluent mean (ppm)
VOCs 93.7% 16.33 (±5.39) 0.94 (±5.72)
H S 100% a 0.06 (±0.22) 0.00 (±0.00)
2
Ammonia 81.6% 19.67 (±6.50) 3.61 (±5.14)
a Very low concentrations of H S.
2

Table 9
Estimated and Actual Costs of the Two Air Treatment Systems

Chemical system Biofilter
Estimated capital cost $1,224,000 $941,000
Estimated annual O&M $194,000 $45,000
Actual capital Cost n/a $1,120,000 a
Actual O&M (First year) b n/a $45,000
a Includes all engineering, lava rock, and so forth.
b Unit has been operating for 1.5 yr.

A decision on mode of operating, such as upflow or downflow of the polluted air and
method of delivery of liquid/nutrients, would subsequently need to be decided.

5.2. General Odor Control at a Municipal Wastewater-Treatment Facility
The following is a case study of a successful biofilter application for odor control of
a low concentration but chemically diverse airstream. The case study describes the rea-
sons for an air treatment system, the cost comparisons for a competing technology, a
description of the decision-making process, and outcomes of the process. It should be
noted that there are numerous ways to go about choosing your treatment system and this
is one of many possible successful routes. However, this example does illustrate the great
potential cost savings of biofiltration technology. Additional information is presented in
Tables 7–10 and Fig. 4.
The Neenah–Menasha Sewerage Commission owns and operates a regional 13 mgd
waste-water treatment facility serving a population of 55,000 in northeast Wisconsin.
The plant serves the cities of Neenah and Menasha, Waverly Sanitary District, Town of