Sep 20, 2001

Editorial Emphasis: Wastewater Treatment

The Port Burwell Sewage Treatment Plant sits on the shore of Big Otter
Creek near Lake Erie in Bayham, Ontario

Hal Gillette


The Port
Burwell Sewage Treatment Plant sits on the shore of Big Otter Creek near Lake
Erie in Bayham, Ontario. The population in the surrounding area is growing
steadily, creating a need for additional wastewater treatment to accommodate
the growth. After a review of the possibilities, the experts decided that the
most efficient option was to connect the surrounding communities to the area’s
Port Burwell Sewage Treatment Plant.


however, presented a challenge to community government officials charged with
protecting the lake environment, while providing for future growth and

In December
1998, engineers were hired to evaluate the expansion options for the facility.
The resulting conceptual design report for the plant was based on adding the
projected future populations for Eden, Straffordville, and Vienna. The report
determined that the treatment capacity of the existing Port Burwell plant would
have to be expanded from 528 m3 per day to 1060 m3 per day in order to handle
the future demand.


Prepared by
Acres & Associated Environmental Limited of Niagara Falls, Ontario, the
report presented three options for the expansion of the facility. Any of these
three options would enable the treatment of the additional sewage flows
generated due to the connection of Eden, Straffordville, and Vienna to the
existing treatment plant in Port Burwell.


The first
option was to construct a duplicate of the existing extended aeration plant.
Another possibility presented was to construct a second facility capable of
treating the additional sewage flows using new treatment technologies such as
sequencing batch reactors (SBR). The third was to retrofit the existing
extended aeration facility with new treatment technology (SBRs) and
Infiltrator® High Capacity H-20 distribution chambers to treat total flows
generated by both the existing and newly connected populations.


With any of
these three options, the expanded plant needed upgrading to provide sludge
digestion and storage facilities to replace the existing sludge-holding tank.
This was necessary to allow for the continued application of processed
biosolids to the land in compliance with Ontario Ministry of the Environment
(MOE) policy. MOE policy also included a provision for 180 days of sludge
storage so that biosolids are not land-applied on frozen or snow-covered


Based on
the evaluation carried out in the report, engineers from Acres & Associated
Environmental Limited recommended that the existing plant be retrofitted with
SBRs to expand the treatment capacity of the plant to 1060 m3 per day. The MOE
approved the modified installation with the stipulation that an upgraded
outfall structure that would not discharge directly into the mouth of Big Otter
Creek be included as part of the expansion. This stipulation was in response to
the limitations of the existing outfall structure, comprised of a gravity sewer
discharging to a pump station approximately 30 meters west of the harbor wall.
The pump station then pumps the effluent directly into the mouth of Big Otter


original late 1970s concept for the Port Burwell plant was to include an
outfall pipe extending out into Lake Erie with a multi-port diffuser. This
facility was not part of the construction when the plant was built in 1984. In
its place, a two-port diffuser was installed at the mouth of Big Otter Creek
and it was subsequently upgraded to a pumped discharge,” commented Geoff Burn,
Manager of the Municipal Infrastructure Division at Acres & Associated and
Port Burwell project manager.


Burn added
that construction of a new outfall into the lake would be expensive because of
the uncertain nature of the lake bottom around the mouth of the river. A
submerged pipe would have to be placed deep into the lake bottom to provide
protection against the migration of sand. Because the water is shallow for some
considerable distance into the lake, the practicality of effluent dispersion
from a multi-port diffuser was also unclear unless the diffuser could be
located in an area where the depth exceeded 8 to 10 meters. It was determined
that both of these factors would add considerably to the project cost.


detailed investigation and discussions with the London office of the Ontario
Ministry of the Environment, Acres and Associated recommended that the outfall
from the treatment plant be converted to an exfiltration gallery. This gallery
would provide sufficient capacity to discharge the effluent from the SBRs on a
sequential basis including a 25 percent surcharge.


benefit of providing effluent filtration at a treatment plant is the typical
reduction in effluent phosphorous levels. Where filters have been used,
effluent levels can be achieved to less than 0.3mg/l. At Port Burwell,
additional phosphorous will be removed from the effluent through the filtering
action provided by the natural sand found on the beach beside the plant,” Burn
said. The exfiltration gallery will allow for absorption of the suspended
solids in the effluent. This will contain the phosphorous in the sand, thereby
removing its impact from the lake water. The proposed effluent discharge method
will provide some environmental benefits over the traditional multi-port lake


exfiltration gallery at Port Burwell includes approximately 220 meters of
Infiltrator High Capacity H-20 distribution chambers and uses bottomless
culverts over a 2000 m2 area. The gallery will be located in the existing plant
outfall easement adjacent to the treatment facility. As proposed, the
exfiltration gallery will have capacity to contain one full discharge from one
SBR including a 25 percent surcharge. It is proposed to divide the bed into two
sections, one for each SBR, with interconnections so that one bed

can be used
by both SBRs if desired. The design will include inspection ports and manholes
so the bed can be physically inspected.


construction of the bed includes 300 mm of clear stone as a base. The chambers
are installed on top of the stone and are covered with filter fabric followed
by native sand, topsoil, and vegetation that are slightly mounded over the bed.
The entire bed area is excavated to a depth of approximately 1.2 meters.


As the
groundwater level fluctuates, it is possible that the bed will become
submerged. In this scenario, the hydraulics of the plant will ensure that the
plant effluent will enter the bed and filter into the groundwater. Depending on
the level of the groundwater, a surface breakout of the bed may be possible. If
this ever occurs, it would be very infrequent. Given the quality of the plant
effluent and the fact that ultraviolet disinfection will take place, this is
not considered a major concern. In the case of such a surface breakout, the
effluent would be sampled and tested for contaminants. The existing outfall
will be maintained for emergency purposes only and requires manual operation of
interconnecting valves. It could be used whenever there may be an occurrence of
breakout in the exfiltration system.


for the plant expansion were Stone Town Construction of St. Marys, Ontario. The
Infiltrator chambers used in the project were provided by C. J. Pink Ltd., of
London, Ontario.

About the author

For more information, contact Infiltrator Systems Inc. at 800-221-4436.