Very small
extended aeration package plants, many of which are located throughout
West Virginia, have always been faced with the challenge of economical
sludge wasting. DEP Inspector Larry Robertson has developed a
simple, inexpensive sludge bagger for use on package plants. The
Robertson Sludge Bagger (RSB) is a non-mechanical device made from
readily available materials; costing about $125 to build and uses
ordinary burlap sacks to accumulate wasted solids. The RSB unit
connects directly to the sludge return line and uses an RV waste valve
to divert RAS flow into three bags set directly on the plant grating.
Materials for a
three bag RSB Unit:
|
25 feet of 3"
schedule 40 PVC pipe* |
$12.34/10’ |
|
1 - 3” RV waste
valve |
$18.00 |
|
4 - 3” PVC "L" (90°)
connectors |
$2.00 ea. |
|
5 - 3” PVC “T”
connectors |
$2.00 ea. |
|
3 - 3” Closet
flanges |
$4.00 ea. |
|
1 - 3” Flex coupling |
$5.00 ea. |
|
Feed bags (~34”
long)** |
$0.40 ea. |
|
PVC cement and
primer |
$2.00 ea. |
|
Total: |
$125.00 |
* Piping may
vary based on connection to different package plants.
**
Traditional burlap bags were used initially but, despite being highly
biodegradable, tore easily. Nylon feed bags purchased locally ($0.63
ea.) were also used because of their higher strength.
The RSB unit
was installed on the Cedar Lakes package plant adjacent to the ETC in
2002 where it has been in could be evaluated and has been in continuous
operation since then. Sludge is wasted to the unit approximately
2-3 times weekly with an average RAS of ~8,000 mg/L. After 1 month, the
bags are removed and can contain anywhere from 10-30% solids by weight.
Bags are then allowed to dry before disposal.
After
evaluation of the unit's solids removal at the ETC, the RSB unit could
be a viable solids wasting option for small extended aeration package
plants. Construction is very inexpensive, retrofitting to any
existing plant is feasible. and operation is very simple.
Therefore, the installation of the RSB unit at additional small extended
aeration plants would provide an economical method to effectively remove
solids from the treatment process.
Pictures:
(click on a thumbnail to
view the larger image)
 |
The complete
Robertson Sludge Bagger in use at Cedar Lakes. |
 |
The RSB unit
piping connects directly the package plant's RAS line. |
 |
A three inch RV
waste valve diverts RAS flow to the collection bags. |
 |
Closet flanges
for collection bag attachment. |
 |
Sequential
filling of collection bags on the RSB unit. |
 |
Nylon feed bags
allow efficient drainage of excess water while retaining
wasted solids. |
