BIOLOGICAL TREATMENT CHECKLIST –
ATTACHED GROWTH – TRICKLING
FILTER, ROTATING BIOLOGICAL
CONTACTOR (RBC)
Water Quality
Water/Wastewater/#5.11, August 2001
Wastewater Technical Review and Guidance
FACILITY NAME DATE
CONSULTING ENGINEER SITE INSPECTION (DATE & INSPECTOR)
PLANNING OR DESIGN PHASE
TRICKLING FILTER GENERAL
Trickling filters may be used for treatment of wastewater amenable to treatment by aerobic
biological processes. Trickling filters must be preceded by effective clarifiers equipped with
scum and grease removal devices and other suitable preliminary facilities. If primary
clarifiers are bypassed, effective screening devices must be employed.
Influent Characteristics
A) Hydraulic load (MGD) AWW:
PHWW:
PIWW:
B) Organic load (#CBOD/day)
(for strong industrial waste, use 8-16
hour average strength).
C) Amenable to biological treatment.
D) Must receive primary treatment to
Contents: remove settleable solids, scum and
grease.
Trickling Filter …….1
RBC………………..7 HYDRAULICS
A) Uniform distribution should be
provided.
wq-wwtp5-11
Minnesota Pollution Control Agency, 520 Lafayette Road North, St. Paul, Minnesota 55155-4194
(651) 296-6300, toll-free (800) 657-3864, TTY (651) 282-5332 or (800) 657-3864
This material can be made available in alternative formats for people with disabilities.
Printed on recycled paper containing at least 20 percent fibers from paper recycled by consumers.
BIOLOGICAL TREATMENT CHECKLIST –
ATTACHED GROWTH – TRICKLING
FILTER, ROTATING BIOLOGICAL
CONTACTOR (RBC)
Water Quality
Water/Wastewater/#5.11, August 2001
Wastewater Technical Review and Guidance
Flow must be evenly applied at a rate that keeps the
filter unclogged. Uneven application of flow and
insufficient flow rates for adequate flushing will result
in poor performance. For uniform distribution over
the area of the filter, the flow rate per unit of length
should be proportional to the radius from the center
(Wastewater Engineering, Metcalf & Eddy (M&E),
1991, page 620).
C) Deviation from a calculated uniformly distributed
volume/ft2 of filter service shall not exceed + 10
percent at any point.
For reaction type distributors, 24” minimum head
between low water level in siphon chamber and center
of arms shall be allowed.
Switches for turning off motor driven distributor arms
should be located so that the arms can be stopped
quickly.
Allow 12” minimum clearance between media and
distributor arms.
Turnbuckles on guy rods must have sufficient thread
length to make necessary adjustments.
Design piping system (including dosing and
distributor) to provide capacity for peak hourly flow
Contents: rate, including recirculation.
Trickling Filter …….1 Application of wastewater over the media should be
RBC………………..7 practically continuous. Galvanized, PVC, or
aluminum distributors should be considered to
minimize maintenance and reduce weight. To avoid
arm stoppage during low flow conditions, it may be
necessary to provide four (4) arms with only two (2)
arms used during low flow conditions.
wq-wwtp5-11
MEDIA
Minnesota Pollution Control Agency, 520 Lafayette Road North, St. Paul, Minnesota 55155-4194
(651) 296-6300, toll-free (800) 657-3864, TTY (651) 282-5332 or (800) 657-3864
This material can be made available in alternative formats for people with disabilities.
Printed on recycled paper containing at least 20 percent fibers from paper recycled by consumers.
BIOLOGICAL TREATMENT CHECKLIST –
ATTACHED GROWTH – TRICKLING
FILTER, ROTATING BIOLOGICAL
CONTACTOR (RBC)
Water Quality
Water/Wastewater/#5.11, August 2001
Wastewater Technical Review and Guidance
A) Type (rock, slag, plastic, etc.) should be resistant
to spalling, flaking, etc.
B) Slag media should be iron-free.
C) Installed media should be able to support a
person’s weight, or an access walkway should be
provided for distributor maintenance.
Depth of Media
Rock/slag media; 6’ – 10’ above underdrain.
Manufactured media: minimum of 6’ above
underdrain.
Sizing and Grading of Media
Rock/Slag: < five percent by weight pieces whose
longest dimension is three times the least dimension.
Should be free from thin and flat pieces, dust, clay,
sand or fines.
Passing 4 1/2” screen: 100 percent by weight
Retained on 3” screen: 95-100 percent
Passing 2” screen: 0-2 percent
Passing 1” screen: 0-1 percent
Contents:
Manufactured media: See manufacturer’s
recommendations.
Trickling Filter …….1
RBC………………..7
Media Handling and Placing
A) Store on clean, hard surface at site.
B) Rock/Slag: wash and re-screen or fork at site to
remove fines.
wq-wwtp5-11
C) Install first 12 inches by hand.
Minnesota Pollution Control Agency, 520 Lafayette Road North, St. Paul, Minnesota 55155-4194
(651) 296-6300, toll-free (800) 657-3864, TTY (651) 282-5332 or (800) 657-3864
This material can be made available in alternative formats for people with disabilities.
Printed on recycled paper containing at least 20 percent fibers from paper recycled by consumers.
BIOLOGICAL TREATMENT CHECKLIST –
ATTACHED GROWTH – TRICKLING
FILTER, ROTATING BIOLOGICAL
CONTACTOR (RBC)
Water Quality
Water/Wastewater/#5.11, August 2001
Wastewater Technical Review and Guidance
D) Rehandle at site; no material should be dumped
directly into filter.
E) Cutting of manufactured media not allowed in
filter to avoid clogging
UNDERDRAINAGE SYSTEM
A) System shall cover entire filter floor.
Contents:
Trickling Filter …….1
RBC………………..7
wq-wwtp5-11
Minnesota Pollution Control Agency, 520 Lafayette Road North, St. Paul, Minnesota 55155-4194
(651) 296-6300, toll-free (800) 657-3864, TTY (651) 282-5332 or (800) 657-3864
This material can be made available in alternative formats for people with disabilities.
Printed on recycled paper containing at least 20 percent fibers from paper recycled by consumers.
B) Inlet openings into underdrains shall have an
unsubmerged gross combined area of at least 15
percent of the filter surface area.
C) Minimum slope 1 percent
D) Minimum velocity in effluent channel 2 ft./sec. at
average daily rate.
E) 50 percent or less of the cross-sectional area of the
underdrain system shall be submerged under
design peak hydraulic load, including
recirculation, to supply adequate air.
F) A cover over the filter may be provided to avoid
cold temperature problems, in which case forced
ventilation should be provided.
Installation of vent stacks on the filter periphery,
extensions of underdrains through filter walls,
ventilating manholes, and discharge of filter effluent
to the subsequent settling tank in an open channel or
partly filled pipe are some methods of passive
ventilation (MOP-8, page 701).
Consideration shall be given to the use of forced
reversible ventilation, particularly for heavily loaded
filters, filters below grade and deep manufactured
media filters. Such design should provide for a
minimum airflow of 1 cubic foot per foot squared per
min of filter area in either direction (M&E, page 624).
It may be necessary during periods of extremely low
air temperature to restrict the flow of air through the
filter to keep it from freezing.
G) Provision shall be made for flushing the
underdrains (small filters can utilize peripheral
head channel and vertical vents).
When Plastic or wood media is used, filter underdrain
blocks are not required. Instead beams, column
supports or grating may be used.
SPECIAL FEATURES
A) Appropriate valves, sluice gates, etc., provided to
enable flooding of filters comprised of rock or
slag media for filter fly control.
B) A 4’ minimum freeboard should be provided for
tall, manufactured media filters to contain spray.
On covered filters provide 6’ headroom for
maintenance.
C) Distributor devices, underdrains, channels and
piping systems should be so designed as to
provide for proper maintenance, flushing, and
draining.
Place hose bibs at convenient locations for washing
down the filter and other maintenance jobs. Provide
access to filter such as roads for maintenance
equipment and walkways for personnel.
D) The recirculation rate shall be variable
E) The recirculation ratio should range from ) .5:1 up
to 4:1.
F) A minimum of two recirculation pumps shall be
provided.
G) A device to measure recirculation should be
provided. For less than 1 MGD flows, time lapse
meters and pump head recording devices are
adequate.
ROTARY DISTRIBUTOR SEALS
No mercury seals shall be permitted on rotary
distributor seals. In existing facilities mercury seals
shall be replaced. Provide proper access to seals for
maintenance.
UNIT SIZING
A) Based on pilot testing with particular wastewater
or use empirical design equations based on actual
experience.
In the absence of supporting data the following values
may be used for plants receiving hourly peak to
average daily organic load ratios less than 4:1.
Equalization facilities or other methods should be used
to reduce the peak to average load ratio to less than
4:1 to the trickling filter so the following table may
apply:
PERMISSIBLE CAPACITIES & LADINGS
Hydraulic Loading Organic Loading
(Gal/Day/Sq. Ft. ) (lbs. BOD/Day/1000 Cu. Ft.)
Standard Rate 25-90 5-25
High Rate 230-290 25-300
(Stone Media)
High Rate 350-2100* up to 300
(Plastic Media)
Roughing 1400-4200 100 plus
* Does not include recirculation.
Expected performance of filters packed with manufactured media
such as plastic redwood, etc., shall be determined and submitted from
documented full scale experience on similar installations through
actual use of a pilot plant on site.
Refer to MPCA Reliability guidelines to determine required
number of units.
A) Based on pilot testing with particular wastewater
Or emperical design equations and experience
B) Surface area of media.
C) Volume of media.
D) Type of loading rate (standard, high, etc.).
E) Hydraulic loading (Gal/Day/Ft2).
F) Organic loading (lbs BOD/day/1000 ft3).
G) Percent removal.
UPGRADING AN EXISTING FACILITY
When upgrading an existing facility, the distribution
system, underdrain system, and media shall be
Error: Reference source not found
inspected and evaluated.
Examples of problem areas: Rusted arms, missing
and/or broken nozzles, splash plates, and plates and
condition of bearings and bearing rate.
Trickling filters can readily be supplemented by
treatment process such as media filtration, ponds, and
activated sludge. These processes, together with the
conversion of single stage to two-stage filters and/or
chemical treatment, provide flexibility to upgrading
existing trickling filter facilities.
Rotating Biological Contactors
Influent
A) Flow (mgd)
B) Organic load (#BOD/day or mg/l)
C) Temperature (˚C)
D) Amenable to biological treatment
Pretreatment
Must be preceded by primary treatment, such as
settling tanks with scum and grease removal. Bar
screens and comminutors alone are not adequate.
Unit Sizing
A) Should be based on similar full-scale installations
or pilot testing with particular wastewater.
B) Percent of BOD to be removed.
C) Media arrangement:
1) Number of stages
2) Unit area per stage
3) Total surface area
D) Rotational velocity of media
E) Retention time within media tank
Error: Reference source not found
F) Percent of influent BOD which is soluble
G) Nitrification loading rate:
1) influent Kjeldahl nitrogen
2) pH
3) allowable effluent ammonia nitrogen
concentration
H) Hydraulic loading rate:
gpm/ft2
Hydraulics
To buffer load variations, it may be necessary to:
A) increase design surface area proportional to the
ammonia nitrogen diurnal peaking rates or;
B) provide flow equalization chambers
Operations
A) Enclosure of corrosion resistant material to
protect biological growth from cold temperatures.
B) Windows or equivalent should be provided for
ventilation.
C) Insulate and/or heat to minimize condensation.
D) Isolation of individual reactor banks possible.
E) Flow pattern flexibility series/parallel operation,
etc. Adequate access to allow removal of RBC
units for repair/replacement.
