KemFlo’s Kempac plastic random packing is used in numerous applications where a
combination of surface area and open space are required. KemFlo manufactures three
different styles of plastic random media including the Tri-Pack, Pall Ring and Saddle Style, each
with distinct physical properties in regards to geometric surface area and void space. One of
the more common applications for plastic random media are trickling filters.

Trickling filters are one of the oldest water treatment processes in the United States and
around the world. The first trickling filter was built in Europe in the late 1800’s. In general, the
trickling filter is an aerobic treatment system which utilizes microorganisms attached to plastic
random packing or some other media to remove organic matter from wastewater that passes
over it. This is also referred to as an attached growth process. Trickling filters remove ammonia
nitrogen by oxidizing it to nitrate nitrogen. This process is known as nitrification. Nitrification is
a process in which ammonia nitrogen in wastewater is oxidized first to nitrite nitrogen and then
to nitrate nitrogen by autotrophic bacteria.

A trickling filter consist of media made from rock or plastic random packing, over which
wastewater is distributed and trickles through the media. These media beds of plastic random
packing media range in size and can be as large as 200 feet in diameter and three to eight feet
deep. Rotating distribution of wastewater over the media bed is preferred and is the standard
distribution method. A trickling filter design also includes an under drain system that collects
the filtrate and solids. The under drain also services as a source of air for the microorganisms in
the filter media. The treated wastewater and solids are piped to a settling tank where the
solids are separated. Some of the filtered liquid is recirculated over the plastic random packing
in order to keep the media wet and to maximize the system’s efficiency. Ventilation openings
located at the bottom of the system provide essential air flow. It is important that the plastic
random packing media had sufficient open area in order to accommodate the air flow
throughout the filter bed. The organic material in the wastewater is absorbed by the
microorganisms that attach to the plastic random packing as a biological film or slime layer.

As with any process there are advantages and disadvantages to consider. Advantages of
trickling filters include: Trickling filter are a simple and reliable process that are ideal in areas
where large tracks of land are not available for a treatment system. They may qualify for
equivalent secondary discharge standards. Trickling filters are effective in treating high
concentrations of organics depending on the type of plastic random packing used. Appropriate
for small to medium sized communities. High degree of performance reliability. Durability of
process elements. Low power requirements. Moderate level of technical expertise required to
manager the system. Disadvantages of trickling filters include: Depending on discharge
standards additional treatment may be needed. They generate sludge that must be treated and disposed of. Regular operator attention is needed. High incidence of clogging may occur.
Limited flexibility and control. There is a potential for odor problems.

There are a variety of factors that affect the nitrification performance of a system including
availability of oxygen, level of CBOD, ammonia nitrogen concentration, media configuration,
temperature and pH. In general trickling filters are very reliable but there are still a few
operational problems that may occur such as odor control, ponding on filter media, attracting
insects and rodents and icing in colder regions. When considering all of the positive and
negatives involved in a trickling filter process it is still a very reliable and efficient method for
treating wastewater.

Kempac plastic random media is an excellent option for trickling filter media beds and is
available in multiple configurations, sizes and materials. The Tri-Pack is available in 1”, 2” and
3.5”. The Pall Ring is available in 1”, 2” and 3.5”. The Plastic Saddle style packing is available in
1”, 2” and 3”. For more information on the kempac plastic random packing product line please