Current through Register Vol. 41, No. 3, September 23, 2024
A. Rotary drums.
The following rates of vacuum filtration, in pounds of dry solids per square
foot of drum filter area per hour, for various types of sludge, may be
considered conventional loading with proper prior sludge conditioning. A
variable speed drive shall be provided.
| Type of Treatment Process Producing Sludge Prior to
Stabilization |
Pounds of Dry Solids Per Square Foot Per Hour
Minimum - Maximum |
| a. Primary |
4 - 6 |
| b. Primary and Contact Reactor |
3 - 5 |
| c. Primary and Suspended Growth Reactor |
3 - 4 |
1. Unless
dual trains are provided, the following appurtenant equipment shall be provided
in duplicate with necessary connecting piping, and electrical controls to allow
equipment alternation. Spare filter fabric shall be provided except when metal
coils are utilized.
a. Feed pump.
b. Vacuum pump.
c. Filtrate pump.
2. Wetted parts should be constructed of
corrosion-resistant material. Drum and agitator assemblies shall be equipped
with variable speed drives and provisions for altering the liquid level shall
be made.
3. Vacuum pumps having a
capacity of at least 1.5 cfm per square foot for metal-covered drums should be
provided. Vacuum receivers are required with dry type vacuum pumps.
4. Each filter shall be fed by a separate
feed pump to ensure a proper feed rate. Filtrate pumps must be of adequate
capacity to pump the maximum amount of liquid to be removed from the
sludge.
5. Careful consideration to
filter washing and variable sludge pickup depth should be made.
B. Plate and frame presses. Actual
performance data developed from similar operational characteristics should be
utilized for design. The impact that anticipated sludge variability will have
on the design variables for the press as well as chemical conditioning shall be
addressed. Appropriate scale-up factors shall be utilized for full size designs
if pilot scale testing is done in lieu of full-scale testing.
1. The following appurtenant equipment shall
be considered for duplicate operation unless multiple units are provided:
a. Feed pump.
b. Air compressor.
c. Washwater booster pump.
2. The following spare
appurtenances shall be provided where multiple units are not installed:
a. At least one extra plate for every ten
required for startup, but a total of not less than two extra plates
required.
b. One complete filter
fabric set.
c. Closure drive
system.
d. Feed pump (when
duplicates are not provided).
e.
Air compressor (when duplicates are not provided).
f. Washwater booster pump (when duplicates
are not provided).
3.
Filter feed pumps shall be capable of a combination of initial high flow, low
pressure filling followed by sustained periods of operating at 100 to 225 psi.
An integral pressure vessel to produce this initial high volume flow should be
considered. Operating pressures less than 225 psi will be considered if actual
performance data using similar sludges is provided.
4. Provisions for cake breaking to protect or
enhance downline process shall be incorporated where necessary.
5. Crane or monorail services capable of
removing the plates should be considered. In some installations, the capability
to remove other press parts should also be considered.
6. Provision for a high pressure water or
acid wash system to clean the filter shall be considered. Booster pumping
should be addressed.
C.
Belt presses. Actual performance data developed from similar operational
characteristics should be utilized for design. The impact that anticipated
sludge variability will have on the design variables for the press as well as
chemical conditioning shall be addressed. A second belt filter press or an
approved backup method of dewatering shall be required whenever a single belt
press is operated 60 hours or more within any consecutive five day period or
the average daily flow received at the treatment works equals or exceeds four
mgd. Appropriate scale-up factors shall be utilized for full-size designs if
pilot plant testing is performed in lieu of full-scale testing.
1. The following appurtenant equipment shall
be considered for duplicate operation unless multiple units are provided:
a. Feed pump.
b. Washwater booster pump.
2. Requirements for spare
appurtenances should include the following:
a.
Complete set of belts.
b. One set
of bearings for each type of press bearing.
c. Tensioning and tracking sensors.
d. One set of wash nozzles.
e. Doctor blade.
f. Conditioning or flocculation drive
equipment if duplicate units are not provided.
3. A polymer selection methodology,
accounting for sludge variability and anticipated sludge loading to the press
shall be provided.
4. Sludge feed
shall be as constant as possible to eliminate difficulties in polymer addition
and press operation. The range in feed variability shall be identified and
equalization shall be provided as necessary. A method for uniform sludge
dispersion on the belt shall be provided. Grinders for the sludge feed to the
flocculation system shall be considered. Thickening of the feed sludge should
be an integral part of the design of the filter press. Separate thickening or
dual purpose thickening will be considered on a case-by-case basis.
5. The filter press design shall consider the
following:
a. Variable belt speed
mechanism.
b. Belt tracking and
belt tensioning equipment.
c. Belt
replacement availability based on evaluation of the belt equipment selection
especially if the weave, material, width, or thickness cannot be reasonably
duplicated.
6. Rollers
specified for the press design should provide:
a. Rubber coating or other protective
finish.
b. Maximum frame and roller
deflection and operating tension.
c. Roller bearings that are watertight and
rated for a B-10 life of 100,000 hours.
7. The washwater system should provide for:
a. High pressure washwater for each belt with
a specified operating pressure.
b.
Booster pumps if necessary.
c.
Spray wash systems designed to be cleaned without interference with the system
operation.
d. Particular care in
nozzle selections and optional nozzle cleaning systems when recycled wastewater
is used for belt washing.
e.
Replaceable spray nozzles.
f. Spray
curtains.
D.
Additional design features to be considered include:
a. Drip trays under the press and under the
thickener to readily remove filtrate if gravity belt thickening is
employed.
b. Adequate clearance to
the side and floor for maintenance and removal of the dewatered
sludge.
c. Location of all
electrical panels or other materials that are subject to corrosion out of the
area of the press.
d. Adjustable
doctor blade clearance.
