CATEGORY D - WATER RESOURCES
WASTEWATER TREATMENT FACILITY
JOHNSON, VERMONT
The final completion of the Village of Johnson’s Wastewater Treatment Facilities (WWTF) is the culmination of five years of planning, design and construction to bring the facility into compliance with 1992 State and Federal water pollution control regulations. When the original WWTF became operational in 1970, it was one of the first in the State to meet the new “secondary” level of treatment required at the time. Since 1970, the facility has served Johnson well. However, new State legislation in 1992 required much stricter discharge limits on phosphorous, ammonia and residual chlorine. At the same time, Johnson realized that it needed to increase the WWTF flow capacity and especially its ability to handle the high seasonal flows associated with storm events. Therefore, in 1992 the Village of Johnson began planning and engineering studies which led to the upgrade of their WWTF to the become first municipal Sequential Batch Reactor (SBR) facility in Vermont!
TREATMENT PROCESS DESCRIPTION
Raw wastewater enters the WWTF in the Pre-Treatment Area, where it flows through a manual bar screen to remove larger objects such as rags. Flow continues through a 30 foot long channel that allows heavier grit to settle out and the influent flow-rate is measured in a 3" wide parshall flume with ultrasonic level measurement. Next a sewage grinder grinds all of the solids into small pieces and the flow continues into the Influent Pump Station wetwell. From there, the dual-alternating variable speed centrifugal pumps pump the flow into one of the two SBR basins for biological and secondary treatment. The effluent from the SBR process continues via gravity to the two ultraviolet (UV) disinfection units and over a compound effluent flow measuring weir. The treated effluent discharges into the Gihon River.
SBR TREATMENT SYSTEM
The SBR treatment system is the core of the Johnson WWTF
treatment
process. As part of this upgrade, the two 1970 aeration tanks were
converted into the two SBR process basins. Both basins are
completely enclosed to minimize
the negative impact of the cold winter climate on the treatment process
while
allowing easy access for operations and maintenance. Each SBR basin
performs
three sequential treatment cycles as follows:
Fill/Aerate - Settle - Decant
.
During part of the fill cycle, air is added for mixing
and to encourage bacteriological growth. During the remainder
of the fill cycle, no air is added and the resulting
anaerobic zone aids in biological phosphorous removal. During the settle
cycle, the air remains off and the solids are allowed to settle
in a perfect
quiescent state. Finally, during the decant cycle,
the clarified wastewater is decanted from the basin by slowly lowering
the baffled decant trough.
When the first SBR basin begins the settle cycle, flow is shut off to
that basin and is directed to the opposite SBR basin to begin the
fill/aerate cycle. The two SBR basins continue to alternate in
timed sequences.
| WASTEWATER FLOW Design, Average Daily Flow (mgd) Design, Peak Flow (mgd) EFFLUENT LIMITS PRE-TREATMENT AREA INFLUENT PUMPING TREATMENT SYSTEM- |
0.270 0.980 30 1.0 200 to 600 2 |
PROCESS WATER STORAGE Capacity (gal) DISINFECTION DISCHARGE BIOSOLIDS SYSTEM PROCESS CONTROLS |
30,000
2 1.2 60
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| BOARD OF TRUSTEES Harlan Lumbra, Chairman (4/92 - 4/97) Chris Parker, Chairman (4/97 - present) Michael Dunham Steve Engel Gordon Smith |
OPERATORS Donald Garrett, Manager Roger Davis, Assistant VILLAGE CLERK |
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| ENGINEER
FORCIER ALDRICH & ASSOCIATES, INC. |
CONTRACTORS
CONTRACT NO.1 CONTRACT NO.2 |
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Photo and award plaque
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