What are the functions of trickling biofilters? Is there any substitute of trickling bio filters?
Answers
DESCRIPTION
Trickling filters (TFs) are used to remove organic
matter from wastewater. The TF is an aerobic
treatment system that utilizes microorganisms
attached to a medium to remove organic matter
from wastewater. This type of system is common
to a number of technologies such as rotating
biological contactors and packed bed reactors (bio-
towers). These systems are known as
attached-growth processes. In contrast, systems in
which microorganisms are sustained in a liquid are
known as suspended-growth processes.
APPLICABILITY
TFs enable organic material in the wastewater to be
adsorbed by a population of microorganisms
(aerobic, anaerobic, and facultative bacteria; fungi;
algae; and protozoa) attached to the medium as a
biological film or slime layer (approximately 0.1 to
0.2 mm thick). As the wastewater flows over the
medium, microorganisms already in the water
gradually attach themselves to the rock, slag, or
plastic surface and form a film. The organic
material is then degraded by the aerobic
microorganisms in the outer part of the slime layer.
As the layer thickens through microbial growth,
oxygen cannot penetrate the medium face, and
anaerobic organisms develop. As the biological
film continues to grow, the microorganisms near
the surface lose their ability to cling to the medium,
and a portion of the slime layer falls off the filter.
This process is known as sloughing. The sloughed
solids are picked up by the underdrain system and
transported to a clarifier for removal from the
wastewater.
ADVANTAGES AND DISADVANTAGES
Some advantages and disadvantages of TFs are
listed below.
Advantages
C Simple, reliable, biological process.
C Suitable in areas where large tracts of land
are not available for land intensive treatment
systems.
C May qualify for equivalent secondary
discharge standards.
C Effective in treating high concentrations of
organics depending on the type of medium
used.
C Appropriate for small- to medium-sized
communities.
C Rapidly reduce soluble BOD5
in applied
wastewater.
C Efficient nitrification units.
C Durable process elements.
C Low power requirements.
C Moderate level of skill and technical
expertise needed to manage and operate the
system.
Disadvantages
C Additional treatment may be needed to meet
more stringent discharge standards.
C Possible accumulation of excess biomass that
cannot retain an aerobic condition and can
impair TF performance (maximum biomass
thickness is controlled by hydraulic dosage
rate, type of media, type of organic matter,
temperature and nature of the biological
growth).
C Requires regular operator attention.
C Incidence of clogging is relatively high.
C Requires low loadings depending on the
medium.
C Flexibility and control are limited in
comparison with activated-sludge processes.
C Vector and odor problems.
C Snail problems.