Environmental Engineering Reference
In-Depth Information
Wa ste sludge
Cl 2 or NaOCl
Chlorine
contact tank
Primary
sedimentation
Grit
chamber
Trickling
filter
Settling
tank
Euent
Influent
Bar racks
Return euent
figure 7.2 Simplified flow diagram of trickling filter used for wastewa-
ter treatment.
the media material. The organisms aerobically decompose the solids,
producing more organisms and stable wastes, which either become part
of the slime or are discharged back into the wastewater flowing over the
media. This slime consists mainly of bacteria, but it may also include
algae, protozoa, worms, snails, fungi, and insect larvae. The accumulat-
ing slime occasionally sloughs off individual media materials (see Figure
7.4) that collect at the bottom of the filter, along with the treated waste-
water, and are passed on to the secondary settling tank for removal. The
overall performance of the trickling filter is dependent on hydraulic and
organic loading, temperature, and recirculation.
7.3.1 Trickling filter definitions
To clearly understand the correct operation of the trickling filter,
the operator must be familiar with certain terms. (Note that the follow-
ing list of terms applies to the trickling filter process. We assume that
other terms related to other units within the treatment system or plant
are already familiar to operators.)
Biological towers— A type of trickling filter that is very deep (10 to
20 ft). Filled with a lightweight synthetic media, these towers are
also know as oxidation or roughing towers or (because of their
extremely high hydraulic loading) super-high-rate trickling filters. .
Biomass— The total mass of organisms attached to the media. Similar
to the solids inventory in the activated sludge process, it is some-
times also referred to as zoogleal slime.
distributor arm— The device most widely used to apply wastewater
evenly over the entire surface of the media. In most cases, the force
of the wastewater being sprayed through the orifices moves the
arm.
filter underdrain— The open space provided under the media to col-
lect the liquid (wastewater and sloughings) and to allow air to enter
the filter. It has a sloped floor to direct the flow toward a central
channel for removal.
 
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