|Abstract or Summary
- The influence of media size upon the effective removal
of organic waste from a liquid substrate was studied by the
use of three experimental trickling filters under a set
of uniform operating conditions. The range of experiments
involved hydraulic loadings of increasing magnitude and
of constant organic strength.
The trickling filter columns consisted of three 18-foot,
5.8-inch diameter pipes with ports cut at various levels
to permit the taking of samples and observation of conditions
existing within the media mass.
The media selected for the analysis were 9/16-, 7/8- and 1-1/4-inch diameter marbles which were placed in the
columns in such numbers that the surface areas were related
in the ratio of the inverse diameter of the marbles.
The data collected for a basis of analysis were COD,
BOD, film quantity, pH, ORP and temperature at influent,
1-, 2-, 4-, 8-, 12- and 18-foot or effluent levels. The
other variable introduced intentionally was the hydraulic
loading rate which started at 15 mgad and was increased to
75 mgad in 15 mgad steps between data test runs. A data
test run consisted of five consecutive tests at each sampling
point for each of the items selected as data basis.
The performance of the three filter columns was measured
in terms of BOD and COD removals. These performance data
were subjected to an analysis of variance to detect
significant differences between columns. There were
observable differences in Columns II and III, but at the
90 percent significance level the analysis of variance
showed a similarity in treatment capacity at each level and
each rate applied between these filter units.
Failure to pass hydraulic loads above 45 mgad put
Column I out of the test series. This left Columns II and
III for comparison at the 60 and 75 mgad rates.
The performance of the filter columns showed that the
9/16-inch marbles were not a practical size media for use
in a trickling filter, as clogging and ponding made the
filter very hard to maintain and operate. COD and BOD
removals became less and less, and the filter failed to
function satisfactorily above the 45 mgad rate.
The 7/8- and 1-1/4-inch media both maintained treatment
capacity at the maximum rates applied. The measurable
conditions indicated a much greater removal of organic load
in total organic material removed at the higher rates than
at the lower rates even though effluent quality deteriorated.
The high rates of application favor the creation of a
healthy environment for bacterial growth in providing
better ORP and pH conditions.
The media size and thus surface area is shown to be
of great influence in the establishing of optimum treatment
conditions. The media size should be small enough to
provide for a large amount of surface area per unit volume
of media yet large enough to provide for a pore space
giving adequate reaeration and fluid passing channels.
The smallest media tested does not meet these requirements,
while the larger size media tested appeared to meet
them better at the higher rates of application.