Formal Technical Report

(Podolec)

SENECA COLLEGE SCHOOL OF APPLIED ARTS AND TECHNOLOGY

Update of the Ashbridges Bay Wastewater Treatment Plant To Tertiary Conditions

TECHNICAL REPORT

Julian Tersigni ENVIRONMENTAL TECHNOLOGY

4/7/2011

Writing Advisor: Peter Rethazy Technical Advisor: Nadia Kelton

Update of the Ashbridges Bay Wastewater Treatment

Plant To Tertiary Conditions

Prepared By: Julian Tersigni

Student Number: 028 606 085

Environmental Technology: EMT

Engineering Technical Report II: ETR 592 BD

Prepared For: Nadia Kelton, April 7 2011

Peter Rethazy, April 7 2011

Acknowledgments

I would like to thank my advisor Nadia Kelton, for her time and guidance in the

completion of this report.

Abstract

Lake Ontario faces numerous water quality issues due to industries and population growth surrounding it. Wastewater treatment facilities in the city of Toronto are currently designed to release secondarily treated effluent into the lake. If nutrient concentrations in effluent were lowered, this could contribute to the lakes recovery. This could be achieved by upgrading the plant to tertiary conditions with a focus on removing specific pollutants: nitrogen, and phosphorus. Numerous technologies are available for tertiary treatment. The denitrifying filter process best suits Ashbridges Bay as it requires a relatively small area to function and it provides a high removal rate of nitrogen and phosphorus. Reducing nutrient concentrations at Ashbridges Bay alone may not have a significant impact. However, if all WWTP’s discharging into the lake implement a tertiary system, the reduction of nutrient loadings would be significant. In order for this to proceed the Maximum Allowable Concentrations on each plant’s Certificate of Approval would have to be lowered and each facility would need adequate surface area to implement tertiary treatment.

Table of Contents

Acknowledgments ii

Abstract iii

List of Illustrations vi

1.0 Introduction 1

1.1 Purpose 1

1.2 Scope 1

2.0 Water Quality of Lake Ontario 2

2.1 Historical Conditions 2

2.2 Current Conditions 3

3.0 Operations at Ashbridges Bay WWTP 4

3.1 Influent Quality 4

3.2 Preliminary Treatment 5

3.3 Primary Treatment 5

3.4 Secondary Treatment 6

3.5 Final Effluent 7

4.0 Comparison of Technologies Available 7

4.1 Denitrifying Filters with Chemical Removal 8

4.2 Tertiary Clarification with Filtration 9

4.3 Membrane Filtration Technologies (Dynasand D2 Advanced Filtration System) 9

4.4 Suitable Process 10

5.0 Impact Assessment 11

5.1 Nutrient Reduction at Ashbridges Bay WWTP 11

5.2 Nutrient Reduction for all WWTP Discharging to Lake 12

5.3 Environmental Impacts 13

6.0 Feasibility 13

6.1 Lowering MAC’s 13

6.2 Design Footprint 14

7.0 Conclusion 15

Work Cited 16

Work Consulted 17

Glossary 18

List of Illustrations

Figures

Figure 1 Historical Nutrient Concentrations for Lake Ontario 2

Figure 2 Total Phosphorus Concentrations in the Great Lakes 3

Figure 3 General Processes at the Ashbridges Bay WWTP 4

Figure 4 Denitrifying Filter Process 8

Figure 5 Denitrifying Filter Makeup 9

Figure 6 Dynasand D2 Advanced Filtration System 10

Figure 7 Proposed Site Location and Footprint 14

Tables

Table 1 Influent Parameters 5

Table 2 Primary Treatment Effluent Parameters 6

Table 3 Secondary Treatment Effluent Parameters 6

Table 4 Final Effluent Parameters 7

1.0 Introduction

Wastewater treatment facilities in the city of Toronto are currently designed to release secondarily

treated effluent. Lake Ontario, the plants discharge point, has suffered greatly from effluent containing

low water quality from various sources. This report analyzes the environmental benefits of creating

tertiary treatment conditions at the plant. This topic is applicable as an update to an already existing

treatment plant. The plant is required to meet various water quality parameters under a Certificate of

Approval (C of A) provided by the province. These parameters include meeting Maximum Allowable

Concentrations (MAC) of nutrients such as nitrogen and phosphorus. The effect of lowering

concentrations of these nutrients has been analyzed.

1.1 Purpose

This report analyzes how reducing nutrient concentrations in the plant’s effluent affects Lake

Ontario’s water quality. Lake Ontario has suffered from numerous water quality issues in the

past due to industries and population growth surrounding it. 95 waste water treatment plants

(WWTPs) discharge into the lake having similar effluent water quality constraints as Ashbridges

Bay, these constraints are outlined in a Certificate of Approval issued by the province (Toronto

Water). If all WWTPs discharging into the lake reduced effluent nutrient concentrations the

reduction in loading could be significant. This report analyzes the effects derived from reducing

nutrient concentrations in effluent from Ashbridges Bay as well as surrounding WWTPs

discharging into the lake. It focuses on water quality statistics for Lake Ontario, the plant’s

current operations, tertiary technologies, environmental impacts, and feasibility. Treatment

plants must constantly undergo improvements meeting higher water quality constraints, this

ensures environmental impacts are minimized.

1.2 Scope

This report is specifically applicable at the Ashbridges Bay Waste Water Treatment Plant in the

city of Toronto. It is one of four major wastewater plants in the city. It is applicable as an update

to an already existing treatment plant. The design and methods used at the plant are similar to

wastewater facilities across Ontario, therefore data from this report can be applied to other

WWTPs in the province.

2.0 Water Quality of Lake Ontario

Lake Ontario has faced, and still faces, a variety of water quality issues derived from industrial chemicals,

agricultural fertilizers, untreated sewage and detergents (“Lake Ontario”). These issues have led to the

lakes increased eutrophication. Lake Ontario is one of five great lakes in North America with populous

cities, industries and agriculture surrounding it. These land uses have changed the lake’s water

chemistry and ecological communities into what is seen today. Effects have been seen both socially and

economically. For example, frequent beach closing due to poor water quality (specifically high bacterial

counts) has given residents a negative outlook on the lake leading to reduced recreational use.

Furthermore, as water quality degrades the costs for treating drinking water increases significantly.

2.1 Historical Conditions

During the early 70’s lax laws on industries and municipalities led to increased pollution in the

lake. Addition of substances such as nitrates and phosphates caused negative water quality

effects (eutrophication). Sources of these substances were found mainly from fertilizers or

detergents in sewage water. The result was excessive plant growth (i.e. frequent algal blooms)

Once the nutrient supply was exhausted, algal populations died on mass and the resulting decay

brought about a severe drop in dissolved oxygen, which caused fish deaths (United States E.P.A).

High concentration of nutrients through this time period is seen in Figure 1 at approximately

22.5 ug/L. Since then environmental stresses led to tighter environmental regulations and

constraints on industries and municipalities. Higher restrictions on waste water treatment plants

and de-industrialization surrounding the lake assisted in restoring water quality (“Lake

Ontario”).

Figure 1 Historical Nutrient Concentrations for Lake Ontario (“Ecological Indicators”)

2.2 Current Conditions

Although water quality has improved since previous years, eutrophication is still an issue (United

States E.P.A). Drinking water has received scrutiny over taste and odour problems and these

problems have been linked to naturally occurring chemicals such as geosmin, produced by blue-

green algae and bacteria. Drinking water treatment costs increase as more resources are

needed to purify lake water to acceptable levels. Localized beach closings surrounding the lake

have occurred due to increased levels of E. Coli, which thrive under low oxygen, eutrophic

conditions (United States E.P.A). This poses a health risk when levels exceed 100 organisms/100

ml. Aesthetic reasons such as dead fish and algae blooms have also been involved in closures.

Nitrates and phosphates are considered nutrients and do not bio-accumulate, however, at

elevated concentrations, nitrates can have toxic implications. This has resulted in reduced

fishery levels and negative effects on humans (United States E.P.A). The lake has a volume of

1638 km3 and a residence time of approximately 8 years. Figure 1 shows that TP concentrations

have levelled at 10 ug/L from previous years, this converts to 0.01 mg/L. Figure 2 spatially

illustrates total phosphorus (TP) concentrations across all of the Great Lakes. Lake Ontario and

Erie are most affected by eutrophication.

Figure 2 Total Phosphorus Concentrations in the Great Lakes (Environment Canada)

3.0 Operations at Ashbridges Bay WWTP

Wastewater plants in the city of Toronto are required to meet various water quality parameters under a

Certificate of Approval provided by the province. A revision of the maximum allowable quantities for

each parameter is done annually. In 2009, Ashbridges Bay continued to generate a high quality effluent

which met requirements of the plant’s Certificate of Approval. It provides secondary treatment for

wastewater which includes the removal of suspended solids and dissolved organics. The plant also

provides effluent disinfection and disposal of biosolids. Figure 3 illustrates major treatment processes

including screening and grit removal, primary and secondary treatment, effluent disinfection, waste

activated sludge thickening, anaerobic digestion, biosolids dewatering and biosolids management

(Toronto Water).

Figure 3 General Processes at the Ashbridges Bay WWTP (Toronto Water)

3.1 Influent Quality

Upon entering the plant, wastewater is gravity fed throughout the plants processes. Influent

received at the plant includes sludge flows coming from the Humber treatment Plant and the

North Toronto treatment Plant. Ashbridges Bay received 40.4 dry tonnes/day of liquid biosolids

and 15.0 dry tonnes/day of waste activated sludge, on average, from the Humber Treatment

Plant via the Mid-Toronto Interceptor. The North Toronto Treatment Plant transferred an

average of 4.4 dry tonnes/day of biosolids to Ashbridges Bay via the Coxwell Sanitary Trunk

Sewer. This totalled 59.8 dry tonnes/day of solids received in 2009 coming from these two

sources. Ashbridges Bay experienced an increase of 7% for influent flows from 2008 to 2009. A

summary of annual flow and influent parameter concentrations for 2008/2009 is included in

Table 1. Influent Total Phosphorus is considerably high and must be lowered to reduce

environmental impacts. If influent concentrations were not lowered Lake Ontario would suffer

from harmful effects (Toronto Water).

Table 1 Influent Parameters (Toronto Water)

3.2 Preliminary Treatment

The process starts with wastewater entering one of three Grit and Screening Buildings which

provides preliminary treatment. In total, there are six chain and bucket type grit channels, each

rated for 145,340 m3/day. There are ten aerated grit channels (clam shell bucket type), each

rated for 313,390 m3/day, for removing grit and inorganic material from wastewater flow. There

are 14 automatic bar screens, with bars spaced at 1.25 centimetres apart. These mechanical

screening machines remove rags and large pieces of debris from the wastewater. Grit and used

screenings are hauled to a sanitary landfill site. Grit and screenings removed by the aerated grit

channels and mechanical bar screens averaged approximately 9.67 tonnes/day in 2009, being a

12% increase from 2008 (Toronto Water). Preliminary processes significantly reduce TP by

removing sediments and debris from wastewater.

3.3 Primary Treatment

The following step in the treatment process is called Primary Settling or Sedimentation. Here,

flow enters large tanks where its velocity is reduced, this allows heavier solids in the wastewater

to settle to the bottom. Sludge collectors in the tank sweep and remove the settled sludge into

sludge hoppers located at the bottom of the tank at one end, where it is pumped to the

anaerobic digestion tanks. This process removes some phosphorus by physically removing

Parameter 2009 2008

Influent Flow (ML/day) 697.6 653.2

Total Annual Flow (ML) 254,609 239,045

Influent SS (mg/L) 255.5 274.3

Influent CBOD5 (mg/L) 121.1 101.0

Influent TP (mg/L) 6.2 6.0

settled sludge and sediments. Twelve Primary Clarifiers exist, six tanks with dimensions of 61 m

x 19.5 m X 4.5 m and rated at 142,900 m3/day, three tanks with dimensions of 76.2 m x 32.04 m

X 4.5 m and rated at 308,400 m3/day, and an additional three tanks with dimensions of 91.4 m x

35.05 m X 4.88 m rated at 385,500 m3/day. This totals to an installed capacity of 2,939,100

m3/day. Table 2 is a summary of primary treatment effluent parameter concentrations over

2008/2009 (Toronto Water).

Table 2 Primary Treatment Effluent Parameters (Toronto Water)

Parameter 2009 2008

Primary SS (mg/L) 319.1 257.7

Primary CBOD5 (mg/L) 113.5 96.9

3.4 Secondary Treatment

In the activated sludge process, effluent from the Primary Clarifiers is mixed with Return

Activated Sludge from the Final Clarifiers and aerated. This sludge is made up of naturally

occurring bacteria and other micro-organisms. The micro-organisms use oxygen and dissolved

organics in the wastewater for their metabolic functions which help purify wastewater. There

are eleven rectangular Aeration Tanks, these have dimensions of 161.5 m x 6.17 m x 4.6 m and

rated at 91,000 m3/day. These tanks employ a step-feed aeration process with four passes per

aeration tank and are equipped with coarse air bubble diffusers. Mixed liquor from the Aeration

Tanks flows to large Final Clarifiers where Activated Sludge is allowed to settle. A controlled

amount of this sludge is returned to the Aeration Tanks to repeat the treatment process. Any

excess is removed as Waste Activated Sludge and directed to the Primary Clarifiers, or the

Flotation process for thickening, and then pumped to the Digestion Tanks. There are eleven

Final Clarifiers, each with dimensions of 124.4 m x 24 m x 5.3 m and rated for 91,000 m3/day

(Toronto Water). A summary of key aeration parameters for the previous two years is seen in

Table 3.

Table 3 Secondary Treatment Process Parameters (Toronto Water)

Parameters 2009 2008

Aeration Loading (kg CBOD5/day) 0.65 0.53

Mixed Liquor Suspended Solids (mg/L) 2215 2014

3.5 Final Effluent

Before being discharged into Lake Ontario, chlorine is used to disinfect final effluent. The final

effluent conduit is equipped with several diffusers and extends 1000 m into the lake from the

shore. The Ashbridges Bay Treatment Plant produced a high quality effluent which met

requirements of the plant’s Certificate of Approval in 2009. This certificate outlines maximum

allowable concentrations of various water quality parameters. A summary of key final effluent

parameters for the previous two years is shown in Table 4. TP concentrations in final effluent

are recorded at 0.7 mg/L and meets allowable concentrations. That concentration limit provided

by the Certificate of Approval is based on minimizing effects on receiving waters and

ecosystems. Although the limit is sufficient for not causing major harmful effects on discharge

points, it could further be improved to almost eliminating any negative impacts caused by

excessive nutrients.

Table 4 Final Effluent Parameters (Toronto Water)

Parameter Certificate of Approval

2009 Removal Efficiency

2008 Removal Efficiency

Final SS (mg/L) 25 8.7 97% 9.4 97%

Final CBOD5 (mg/L) 25 4.7 95% 3.6 96%

Final TP (mg/L) 1 0.7 89% 0.7 88%

Final E-coli (CFU/100ml) 200 1.9 - 2 -

Final SS Loading Rate (kg/day)

20,450 6,041 - 6,128 -

Final CBOD5 Loading Rate (kg/day)

20,450 3,239 - 2,347 -

Final TP Loading Rate (kg/day)

818 482 - 464 -

4.0 Comparison of Technologies Available

To achieve tertiary conditions at the plant the focus is on removing specific pollutants: nitrogen, and

phosphorus. Different processes are available for the removal of these pollutants. These processes are

described and compared based on benefits/limitations and ease of application to existing conditions.

The process most suitable for the plant depends on target effluent quality and influent quality. These

processes are either an extension of usual secondary biological treatment or are physical and chemical

separation techniques (United States E.P.A.). A decision on which process would be best suited for the

plant has been made after comparison.

4.1 Denitrifying Filters with Chemical Removal

Denitrification is the process involved in converting nitrate to nitrogen gas. This process is

placed after secondary treatment. Besides providing nitrogen and phosphorus removal, it also

acts as an effluent filter. Denitrifying filters require a small area compared to other add-on

denitrification processes. Because it is carrying out denitrification, a carbon source, like

methanol, must be supplied for it to function. For the process to achieve a low concentration of

phosphorus, chemical addition such as ferric chloride (FeCl3) may be considered. Filters are used

to capture phosphorus as floc. These filters may use various materials in its design including:

sand, gravel, or anthracite. Denitrifying filters operate in an upflow mode, meaning water is sent

up through filtration materials. Through this, nitrogen gas created becomes trapped between

the grains which are then released through pumping. These types of denitrification filters have

a removal rate of 1 to 2 mg/L nitrate-nitrogen and are known to release effluent containing 0.1

to 0.3mg/L of TP (United States E.P.A.). A process flow diagram implementing the denitrifying

filter process is depicted in Figure 4. The denitrifying filter makeup is depicted in Figure 5.

Figure 4 Denitrifying Filter Process (United States E.P.A.)

Figure 5 Denitrifying Filter Makeup (“Astrasand”)

4.2 Tertiary Clarification with Filtration

This process involves the addition of a tertiary clarifier upstream of filters. This process would be

of benefit as it can achieve extremely low solids concentrations and in turn low phosphorus

levels. Different versions of tertiary clarifiers exist including solids contact clarifiers, up flow

buoyant-media clarifiers, tube clarifiers, plate clarifiers, and another set of secondary clarifiers.

Coagulants such as ferric chloride (FeCl3) or alum (KAl(SO4)2.12H2O) may be considered to

further improve the performance of the system. Secondary effluent undergoes heavy mixing in

this process with coagulants and previously settled solids creating a larger floc, thereafter

moving towards the settling zone where heavier solids move downwards and purified water

exits the unit. After this process, a filter further removes solids that pass through the clarifier.

For tertiary clarification to work, velocity through the system must be low enough to allow solids

to settle to the bottom. Case studies have shown that implementing tertiary clarification can

reduce effluent concentrations of TP to 0.05 mg/L (United States E.P.A.).

____________________________________________________

4.3 Membrane Filtration Technologies (Dynasand D2 Advanced Filtration System)

This process involves the use of a membrane filter either externally or internally. It is built into

the activated sludge process as a Membrane Bio Reactor. The system uses a suspended growth

biological reactor where effluent passes through a membrane filter. Through this process

suspended solids are effectively taken out. Micro-organisms then take up phosphates that

remain in the reactor. In most cases, this membrane is associated with the final aerobic step. A

lower level of TP concentration can then be achieved through the use of chemical precipitation

for any solids not taken up by these micro-organisms. Case studies have shown to achieve an

annual average of 0.027 mg/l of TP. Figure 6 depicts the process of the Dynasand D2 Advanced

Filtration System process being one of many membrane filtration technologies (United States

E.P.A.).

Figure 6 Dynasand D2 Advanced Filtration System (United States E.P.A.)

4.4 Suitable Process

The above descriptions assisted in the decision of implementing the denitrifying filter process at

the plant. The process takes up a relatively small area compared to other existing processes. In

addition to providing a high removal rate of nitrogen/phosphorus the system also acts as a filter

for all effluent coming out of the plant. Minimum retrofitting is needed to implement the

process in comparison to other technologies. Case studies have shown that the technology can

release effluent with low total nitrogen and TP concentrations. Although Tertiary Clarification

has a high capability of producing very low TP concentrations, it needs a large surface area to

implement. Ashbridges Bay has low space availability for further technologies and any upgrades

must have a low footprint associated with it. Various membrane filtration technologies available

may also produce low concentrations of TP, however the costs of these specialty filtration

systems do not make them feasible.

5.0 Impact Assessment

With the update of the plant to tertiary conditions, the further purified effluent is capable of impacting

water quality and aquatic life in Lake Ontario. Nitrogen and phosphorus are the main source of

eutrophication in surface waters. This eutrophication directly impacts the amount of algae blooms that

occur in a water body. Impacts of this eutrophication include low dissolved oxygen, death of fish, murky

water and the depletion of desirable flora and fauna (United States E.P.A.). The reduction of nutrient

loading has been examined for Ashbridges Bay with the addition of tertiary treatment. The magnitude of

impact the addition has had is based on the reduction of phosphorus, as TP is limiting in freshwater

(“Lake Ontario”). This impact is based on target TP effluent concentrations.

5.1 Nutrient Reduction at Ashbridges Bay WWTP

To examine impact, it is assumed that the system is capable of producing a final TP

concentration of 0.2 mg/l. This is based on removal rates from the denitrifying filter process.

Currently, final TP concentrations at the plant equals 0.7 mg/L, using effluent flow rate of 689

ML/day this gives a final TP loading rate of 483 kg/day (Toronto Water). Final nitrogen

concentrations are not of concern as it does not affect lake quality unless TP is in excess. The

filtration process in place removes nitrogen by converting it to a gas which is then released into

the atmosphere.

Current TP loading Over 1 Year: 0.7 mg/L X 689 ML/Day = 482 kg/day

482 Kg/day X 365 Days = 175,930 kg/year

Lake Volume: 1638 km3 X (1 X 10^12L) = 1.638 X 10^15L

Current TP In Lake: 0.01 mg/L X (1.638 X 10^15L) = 1.638 X 10^13 mg/L

= 1.638 X 10^7 kg/L

Proportion of TP from

Ashbridges Bay: 175,930 kg / 1.638 X 10^7 kg/L = 0.01

= 1%

Reduced Effluent

Concentrations to 0.2 mg/L: 0.2 mg/L X 690 ML/Day = 138 kg/day

138 kg/day X 365 days = 50,370 kg/year

50,370 kg / 1.638 X 10^7 kg/L = 0.003

= 0.3 %

5.2 Nutrient Reduction for all WWTP Discharging to Lake

Calculations show that reducing TP concentrations to 0.2 mg/L only accounts for 0.3% of the

total mass of TP in the Lake. Thus, if the lake is mixing, this has limited impact on water quality.

However, 95 WWTP’s currently discharge into the lake and thus, if all facilities converted to

tertiary treatment, the impact may become significant. Total effluent flow rate coming from

these sources equal to 6,846 ML/day (“Lake Ontario”) It is assumed that these plants currently

release effluent containing the same concentration of TP as Ashbridges Bay.

TP Loading for all WWTP

(Effluent TP-0.7 mg/L): 0.7 mg/L X 6,846 ML/day = 4,792.2 kg/day

4,792.2 kg/day X 365 days = 1,749,153 kg/year

TP Loading Percentage

Per Lake Volume: 1,749,153 kg / (1.638 X 10^7 kg/L) = 0.107

= 10.7 %

TP Loading for all WWTP

(Effluent TP-0.2 mg/L): 0.2 mg/L X 6,846 ML/Day = 1,369.2 kg/day

1,369.2 kg/day X 365 days = 499,758 kg/year

TP Loading Percentage

Per Lake Volume: 88,147.5 kg/year X 90 WWTP’s = 7,933,275 kg/year

499,758 kg / (1.638 X 10^7 kg/L) = 0.031

= 3.1%

5.3 Environmental Impacts

Reducing final TP concentrations at Ashbridges Bay WWTP alone may not have a significant

impact on TP levels in Lake Ontario. The large volume of water in the lake dilutes TP

concentrations coming out of the plant. However, calculations have shown that if all WWTP’s

discharging into the lake implemented a tertiary system, the total TP loading may be reduced by

7.6 %. Reduced TP concentrations will have a positive impact on the lake’s recovery.

Eutrophication will be reduced which will reduce the amount of algae blooms that occur in the

water body. Dissolved oxygen levels will not drop which will allow desirable fish to thrive. The

lake may become more desirable for recreational uses and drinking water treatment will require

fewer resources in creating potable water.

6.0 Feasibility

In order for municipalities to implement tertiary technology, Maximum Allowable Concentrations

(MACs) on the Certificate of Approval must be lowered. If any environmental benefits are to be seen all

WWTPs discharging to the lake must implement the denitrifying filtration process or another tertiary

technology capable of discharging nutrient concentrations of 0.2 mg/L or lower. These facilities must

have the physical space (land surface area) to implement tertiary treatment.

6.1 Lowering MACs

Ashbridges Bay currently operates under a Certificate of Approval No. 8319-7TTR62 issued by

the Ministry of the Environment. If all WWTPs discharging to the lake were to lower effluent TP

concentrations, MACs would have to be lowered on each plant’s Certificate of Approval. The

main purpose of these certificates in this context is to make sure that proposed works or

amendments are established or altered, in harmony with the Ministry’s requirements. These

certificates outline performance standards that protect human health and the environment by

preventing potential harmful effects. The Ministry may update a certificate based on site-

specific information or to support other environmental protection priorities at any time. A

process is taken in updating a Certificate of Approval for a facility. The Ministry of Environment

works with the facility manager throughout the process where the existing certificate is

presented with an application to amend current operations. During pre-application

consultation, the extent to which the Ministry may require new or amended requirements is

discussed for a certificate. In open dialogue, the ministry and the facility manager work together

to define environmental protection requirements of the project (new effluent requirements,

acceptability of proposed technology). An acknowledgment letter is sent to the facility manager

from the Ministry outlining their intent on updating the certificate in harmony with the

established protocol. The proposed amendments are then subject to public comment for a

period of time as required by the Environmental Bill of Rights. Upon completion, the final

edition of the amended Certificate of Approval is issued (Ministry of the Environment).

6.2 Design Footprint

Calculations below (based on Ashbridges Bay) give a rough estimate on the area needed to

implement the denitrifying filter process. It outlines the proposed area needed including

available space for tank, piping, platform and buffer area sizes. Figure 7 displays proposed site

locations and illustrates area needed to implement the design. The tanks would be arranged in a

2 by 8 formation outlining 16 tanks in total. This is a typical formation for this system. Surface

area dimensions equal out to approximately 60 ft by 250 ft.

Surface Area of Individual Tank: pi X (16 ft)2 = 804.25 ft2

Surface Area of Design: 804.25 ft2 X 16 Tanks = 12868 ft2

= 0.1195 ha

= 0.2954 Acres

Proposed Area Needed: 60 ft X 250 ft = 15,000 ft2

Available Area for Piping, Etc: 15,000 ft2 - 12868 ft2 = 2000 ft2

Figure 7 Proposed Site Location and Footprint

N

7.0 Conclusion

Ashbridges Bay WWTP currently operates as a secondary treatment plant. Various nutrient reducing

technologies are available to upgrade a WWTP to tertiary conditions. The environmental benefits of

creating these conditions have been examined at Ashbridges Bay. If the denitrifying filter process is

implemented, TP concentrations in effluent would be reduced to 0.2 mg/L. This would reduce nutrient

loading on Lake Ontario. For benefits to be seen on the entire lake, all 95 WWTPs discharging to the lake

would have to reduce nutrient concentrations to 0.2 mg/L by upgrading to tertiary treatment. For this to

happen, MACs for TP on each plants Certificate of Approval would have to be lowered to that

concentration. The Ministry of Environment would have to proceed in an administrative process to

amend MAC’s on each plant’s Certificate of Approval. This could take a substantial amount of time and

money. If the denitrifying filter process is implemented at Ashbridges Bay it would need a relatively

small portion of land. Locations have been proposed as to where the system could operate.

Work Cited

“Astrasand Continuous Backwash Filter.” Siemens Water Technologies. Siemens, Dec. 2007. Web. 12

Feb. 2011.

“Ecological Indicators and Sustainability of the Lake Ontario Ecosystem.” Sea Grant New York, November

2006. Web. 28 March 2011.

Environment Canada. "Nearshore Waters of the Great Lakes." Canadian Government, October 2006.

Web. 16 Feb. 2011.

“Lake Ontario.” International Lake Environment Committee. World Lakes Database, June 1992. Web. 12

Feb. 2011.

“Lake Ontario.” New World Encyclopedia. 2 April 2008. Web. 28 Mar. 2011.

Ministry of the Environment. "Protocol for Updating Certificates of Approval for Sewage Works." Govt.

of Canada, January 2005. Web. 28 Mar. 2011.

Podolec, Tom. Ashbridges Bay Wastewater Treatment. 2008. Tom Podolec Photostream, Toronto. Flickr.

Web. 28 Mar. 2011.

Toronto Water. "Ashbridges Bay Wastewater Treatment Plant 2009 Annual Report." City of Toronto, 31

March 2010. Web. 28 Oct. 2010.

United States E.P.A. "Biological Nutrient Removal Processes and Costs." United States Government,

June 2007. Web. 27 Nov. 2010.

United States E.P.A. "Municipal Nutrient Removal Technologies Reference Document." United States

Government, September 2008. Web. 30 Jan. 2011.

Work Consulted

Hammer, Mark J., and Mark J. Hammer Jr. Water and Wastewater Technology. 5th ed. New Jersey:

Pearson, 2004. Print.

United States E.P.A. "Primer for Municipal Wastewater Treatment Systems." United States Government,

June 2007. Web. 27 Nov. 2010.

United States E.P.A. "Human Health and the Great Lakes." United States Government, 29 April 2003.

Web. 27 Nov. 2010.

Glossary

Activated Sludge - System for treating sewage and industrial wastewater using air and biological floc

composed of bacteria and protozoans.

Anaerobic Digestion - A processes in which micro-organisms break down biodegradable material in the

lack of oxygen.

Bios Solids (Sludge) – Refers to the remaining semi-solid material left from industrial wastewater

treatment processes. It also is used as a generic term for solids separated from suspension in a liquid.

Certificate of Approval - A facility that releases emissions to the atmosphere, discharges contaminants

to surface waters, provides potable water or disposes of waste must have a Certificate of Approval to

operate under the law.

Coagulants (Colloids) - A colloidal sized particle is defined in diameter from 5-200 nanometers.

Denitrification – Process involved in converting nitrogen to nitrogen gas.

E. Coli - This bacteria is commonly found in recreational waters, and their presence indicates the

existence of faecal contamination.

Eutrophication - Process by which a body of water becomes supplemented in nutrients, which in turn

stimulates aquatic plant growth and death, resulting in the depletion of dissolved oxygen.

Fauna - Animal life in any particular region or time.

Flocculation (Floc) - Process by which fine particles are clumped together to form a larger substance

(floc) that can be more easily filtered.

Flora - Plant life existing in a defined region.

Geosmin - This substance is produced by cyanobacteria (blue-green algae) among other microbes and is

released when these microbes die. Drinking water derived from surface water can occasionally be

unpleasant-tasting when bacteria release geosmin into the local water supply.

Mega Liter (ML) – One million liters in the metric system.

Metabolic Functions - Chemical reactions that occur in living organisms to sustain life.

Precipitation - The creation of a solid in a solution or inside an additional solid through a chemical

reaction.

Residence Time - The average time that a particle spends in a particular system. This varies with the

amount of substance in the system.