Wastewater Treatment Plant
The Winterport Wastewater
Treatment Facility is a 301(H) waiver primary treatment plant utilizing
unit processes of influent pumping, grit removal, clarification, and
disinfection for normal flow conditions and swirl concentrations (for
removable of readily settleable solids and floatables) and pumping for
high flow conditions. The Districts sanitary sewage collection system is
many decades old and in some areas is in poor condition. These areas are
subject to a wide range of seasonably variable non-sewage flows often
referred to as I & I. For the most part it is the high non-sewage flows,
which cause the most problems, which arise at the facility.
Overall design parameters are
reported in table 1-1 below.
|
Table 1-1 |
|
Design Influent Loading
Parameters |
| ITEM |
Average and
Standard Deviation |
| Annual |
|
|
|
|
|
0.140 ± |
.02 |
mgd |
|
|
260 ± |
110 |
lb/d |
|
|
200 ± |
80 |
lb/d |
|
|
79 ± |
|
lb/d |
|
|
270 ± |
|
lb/d |
| |
|
|
|
| Spring
Peak ( 5 day average ) |
|
|
|
|
|
0.350 |
|
mgd |
|
|
520 |
|
lb/d |
|
|
390 |
|
lb/d |
|
|
130 |
|
lb/d |
|
|
520 |
|
lb/d |
| |
|
|
|
| Peak
Instantaneous Flow Rate |
|
|
|
|
|
2,450 |
|
gpm ( 3.5 mgd ) |
|
|
2,000 |
|
gpm (2.9 mgd ) |
|
|
450 |
|
gpm ( 0.65 mgd ) |
Solids which are removed via
clarification accumulate in an Imhoff chamber below the clarifier for
storage and digestion. Periodically the digested sludge is withdrawn from
the chamber, dewatered and trucked to a sludge recycling facility.
The treatment plant is
intended to satisfy the state and federal issued wastewater discharge
license. The discharge license requires that monthly averages of the daily
mean effluent BOD5 and Total Suspended solids do not exceed the effluent
concentrations listed in table 1-2.
The treatment facility is
composed of the following components:
1.) Collection System
2.) Main Pumping Station
3.) Primary treatment
4.) Disinfection
5.) Sludge Removal
Sanitary sewage is transported
to the Main Pumping Station via 12-inch interceptor sewers. Influent
sewage entering the main pumping station passes through a trash rack and
two slide gates, which under normal conditions direct flow to a swirl
concentrator. Sewage is passed through an online disintegrator and is then
pumped via alternating heavy-duty sewage pumps with variable frequency
drives to the treatment plant.
The Main Pumping Station is
designed to handle a hydraulic flow of 2,450 gpm; however the primary
treatment process will only process a maximum flow rate of 450 gallons per
minute. Flow exceeding 450 gpm passes thru a swirl concentrator to the
high flow wetwell for primary solids removal prior to be pumped directly
to the outfall discharge manhole. Flows of 450 gpm or less which are
pumped to the primary treatment plant are first directed to an
automatically operated, flow controlled grit collector and removal
apparatus.
Grit is removed via airlift
and grit screw. Degritted sewage flows to an Imhoff digester which
consists of two stages; clarification with sludge storage and digestion.
Supernatant from the Imhoff digester flows to three parallel chlorine contact tanks
for disinfection; disinfected effluent passes through a Palmer-Bowlus
flume for flow measurement prior to discharge to the Penobscot River via
12-inch ductile iron sewer. A flow schematic of the Main Pumping Station
and primary treatment process is presented in Figure 1-1.
Figure 1-1