July 5, 1999
To:Works Committee
From:Barry H. Gutteridge, Commissioner, Works and Emergency Services
Subject:High Rate Treatment Technology Demonstration Projects for
Combined Sewer Overflows and Stormwater (Wards 1 and 2)
Purpose:
To obtain authorization to enter into an agreement with the Federal Department of Environment, Burlington Environmental
Technology Office (BETO) to continue with Phase III of High Rate Treatment Technology Demonstration Projects for
combined sewer overflow (CSO) treatment process in the North Toronto CSO Detention Tank and stormwater treatment
using a pilot scale facility within District 2 (Etobicoke).
Funding Sources, Financial Implications and Impact Statement:
Funding in the amount of $175,000.00 has been approved in the 1999 Capital Works Program, Water and Wastewater
Services, under District Stormwater Management, Project No. WP953-S25020, to undertake stormwater management
initiatives including the High Rate Treatment Technology Demonstration Projects at the North Toronto CSO Detention
Tank and for stormwater treatment in District 2 (Etobicoke).
Recommendations:
It is recommended that:
- Authority be granted to enter into an agreement with the Federal Department of Environment, Burlington
Environmental Technology Office, to jointly fund and undertake the Demonstration Projects for treatment of combined
sewer overflows at the North Toronto Detention Tank and for stormwater treatment in Etobicoke; and the City's
contribution of $175,000 toward the project is subject to equal funding of $175,000.00 being provided by Environment
Canada and $60,000.00 being provided by the Ontario Ministry of the Environment.
- The appropriate City Officials be authorized and directed to take the necessary action to give effect thereto.
Council Reference/Background/History:
The environmental impacts of stormwater runoff and combined sewer overflow discharges on area watercourses and the
waterfront are well documented. The impact of these non-point sources of pollution has contributed to Toronto's
designation as one of forty-two Areas of Concern in the Great Lakes basin by the International Joint Commission.
Environmental impacts attributed to wet weather pollution include: posting of recreational beach areas due to bacterial
contamination; nuisance algal growth as a result of nutrient enrichment; degraded water clarity attributed to algal growth
and suspended solids; elevated contaminant levels in lake sediments; and stressed aquatic communities in areas close to
sewer outfalls. A Remedial Action Plan has been developed to restore beneficial uses within the area. The Remedial Action
Plan has identified and includes recommendations to abate the impacts of these discharges through implementation of
source controls, in-system or conveyance control measures and implementation of downstream storage and/or treatment
systems. These downstream control measures typically consist of storage facilities to detain combined sewer overflows
(CSOs) for subsequent treatment at a wastewater treatment plant and to provide treatment of stormwater flows through
sedimentation prior to discharge to a receiving water body. These options, however, are expensive and unable to intercept
flows from large storm events.
Satellite high-rate treatment facilities may provide a significnatly more cost-effective alternative, if demonstrated to
provide treatment satisfying the requirements of the Ontario Ministry of the Environment. The Assessment of Advanced
Physical-Chemical Treatment Options For Combined Sewer Overflows Study undertaken by CH2M Hill Engineering Ltd.
for the City of Toronto estimated savings of more than $40,000,000.00, could be derived on the Don Sewer System alone,
by implementing the high rate satellite treatment instead of conventional CSO control methods.
Subsequently, an investigation of high-rate treatment technology for combined sewer overflows and stormwater was
initiated as a multi-agency initiative between Environment Canada, the Ontario Ministry of the Environment and the
former Cities of Metropolitan Toronto, Scarborough, Toronto and Etobicoke. To date, the former municipalites contributed
$973,000 towards this $2.593M initiative as follows:
- 1994, City of Scarborough - $250,000
- 1995, Metropolitan Toronto - $250,000
- 1996, Metropolitan Toronto- $333,000
- 1997, City of Toronto- $100,000
- 1997, City of Etobicoke- $ 40,000
In 1994, Phase I of the Pharmacy Pilot-Scale High Rate CSO Treatment Demonstration Project was established to
investigate new technologies for high-rate treatment of CSO. The project was a multi-agency initiative consisting of the
former municipalities of Metropolitan Toronto and the City of Scarborough, Environment Canada, and the Ontario
Ministry of the Environment.
The initial objective of the project was to examine the performance of a vortex separator and ultraviolet irradiation, in
conjunction with small storage. The performance of the vortex separator was limited by the fine suspended solids
characteristic to CSOs and would only meet the treatment objectives at low loading rates. In addition, acceptable
disinfection levels could not be achieved due to the high residual suspended solids in the effluent. Alternative treatment
options and chemical coagulants were examined subsequently in Phases II and III of the project during the 1995, 1996 and
1997 operating seasons.
Preliminary investigations were also initiated on the effectiveness of a cross-flow plate separator and a rotary screen in the
treatment of CSO. Initial results indicate that these unit processes provide treatment levels similar to the vortex separator.
The results of Phase II and Phase III work demonstrated the variability and relatively poor settleability of CSO solids
suspensions without chemical coagulation. With polymer coagulation in conjunction with the high-rate treatment process,
the study demonstrated the potential for effective solid/liquid separation, mostly by floatation, resulting in an effluent
amenable to ultraviolet disinfection. Initial analysis suggested that the technology could comply with the requirements of
the Ministry of the Environment's Procedure F-5-5.
In 1997, the former City of Etobicoke expressed an interest in the applicability of the high-rate treatment technology for the
treatment of stormwater discharges. The conventional approach to downstream stormwater control using facilities such as
ponds, filter berms and infiltration systems is reasonably effective but can be expensive because of the land requirements.
The use of a high-rate treatment device may be a more cost-effective approach.
Due to the uncertainty about the universality of the process, particularly when applied to locations with hydraulic
conditions and wastewater characteristics which may be appreciably different than those used in the pilot-scale project,
full-scale and pilot-scale testing at other sites was initiated in 1998. A full scale demonstration project was initiated at the
existing CSO storage tank facility at the North Toronto Treatment Plant site. The primary objective of the project was to
test the effectiveness of the polymer coagulant at a full-scale facility with a wastewater of potentially different
characteristics than those experienced at the Pharmacy pilot-scale site. In addition, pilot scale testing of a cross-flow plate
clarifier was initiated at a storm sewer, located south of Lakeshore Boulevard, west of Kipling Avenue, within the former
City of Etobicoke.
Comments and/or Discussion and/or Justification:
The lack of rainfall events in 1998 and the difficulty with the initial setup of monitoring, sampling and chemical feed
system resulted in limited performance data for the full-scale demonstration project at the North Toronto site . Although
this limited data did indicate that the objectives of the Ministry of the Environment's Procedure F-5-5 for CSO control can
be achieved, there is insufficient data to establish operational parameters.
The full-scale CSO demonstration project at the North Toronto site should be continued for the 1999 season to establish
optimal polymer dosages, a polymer mixing regime, process performance curves and the characteristics of the float and
sludge material and disposal options. This information is necessary to provide sizing criteria and assess the applicability of
this technology at other sites across the City through the development of the Wet Weather Flow Management Master Plan
and ultimately to seek Ministry of Environment approval to apply this technology.
Limited rainfall events and initial set-up difficulties of the pilot-scale stormwater demonstration facility in Etobicoke
provided limited operational data. The preliminary data suggests substandard performance as a stand-alone technology,
similar to the pilot scale testing results previously obtained for CSO treatment. Difficulties in obtaining the Certificate of
Approval for coagulant use at the site precluded an assessment of the technology with polymer coagulant. The testing
should be continued through 1999 and approval should be sought from the Ministry of the Environment to permit testing of
the cross-flow plate clarifier with polymer coagulation at the pilot-scale stormwater demonstration facility in Etobicoke.
The cost of conducting this testing is estimated to be $400,000. The City's contribution of $175,000 would be matched
with an additional $175,000 from Environment Canada and $50,000 from the Ontario Ministry of the Environment.
Conclusions:
Satellite High Rate treatment facilities at CSO locations may be practical cost-effective alternatives for CSO control which
have the potential to comply with the treatment requirements of the Ministry of the Environment's Procedure F-5-5 for
CSO control. The technology may also prove to be a viable downstream treatment option for stormwater. The data
obtained from the 1999 field tests is necessary to provide sizing criteria and assess the applicability of this technology at
other sites across the City through the development of the Wet Weather Flow Management Master Plan.
If the treatment efficiency of these innovative technologies are proven to be acceptable they may be an effective means of
limiting the environmental impacts of CSOs and stormwater discharges.
Contact Name:
Mr. M. D'Andrea, P.Eng.
Manager, Infrastructure Asset Management
Quality Control and System Planning
Telephone: (416) 397-4631
Fax: (416) 392-2974
e-mail: michael_d'andrea@metrodesk.metrotor.on.ca
Michael A. Price, P.Eng., FICEBarry H. Gutteridge
General ManagerCommissioner
Water and Wastewater ServicesWorks and Emergency Services
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