DWSD Wastewater System

Daniel Schechter, P.E.

Detroit Water and Sewerage Department

International Joint Commission

March 26, 2011

Wastewater Treatment Plant

• Discharges to Detroit River

• 930 MGD Secondary Capacity

• 1,700 MGD Peak Capacity (Wet Weather)

• Average Daily Flow 550 MGD

• Constructed 1940

• One of the largest WWTPs in US

Service Area Statistics • 3 million people

• 78 communities

• 900 square miles

(35% Combined)

City of Detroit • 3,500 miles of combined sewers

• 78 outfalls

• 3 major interceptors

• 140 square miles (100% combined)

Greater Detroit Regional Sewer System

Macomb County

Oakland County

Wayne County

In addition to our Wastewater Treatment Plant, our 9 newly

constructed CSO facilities provide treatment and disinfection

prior to discharge

Convey Discharge Treat Collect

WWTP Major Treatment Processes

• Primary Treatment – Remove heavy solids, and

floatables

• Secondary Treatment - Aeration (pure oxygen),

remove organic matter both suspended & dissolved

• Solids Processing – Dewatering heavy primary solids

and organic secondary solids

• Disinfection and Dechlorination prior to discharge

Wastewater is treated in an 8 step process; DWSD has had

historic issues with dewatering and disposal

Grit and scum

removal

Primary

treatment

Secondary

treatment

Settling tanks

and clarifiers

Disinfection /

Dechlorination

Discharge Disposal

Dewatering

Sludge

extraction

Convey Discharge Treat Collect

Water Solids

WWTP – Primary Clarifiers

WWTP – Secondary Clarifiers

Pre-1995 CSO Discharges in Detroit

• 76 permitted outfalls

(33 to Rouge River and 43 to Detroit River)

• ~ 50 discharge events/year (average);

• ~ 20 billion gallons discharged/year;

• Major impact on Rouge River water quality:

Dissolved Oxygen depletion

Bacteria exceedances

Sediment deposits and bank erosion

• Lesser impacts on Detroit River:

Bacteria exceedances

Focus of CSO Control Requirements

Rouge River Flow = 20 - 5,000 cfs

Sanitary Trash

Bacteria Kill

Minimize Toxic Impacts

Dissolved Oxygen

WWTP

Detroit River Flow = 190,000 cfs

Sanitary Trash

Bacteria Kill

Minimize Toxic Impacts

Detroit’s CSO Facilities (as of 2008)

CSO Project Costs (Construction Start )

• Hubbell-Southfield Basin (1994): $ 58.9 M

• Puritan-Fenkell Basin (1995) $ 18.1 M

• 7 Mile Basin (1996): $ 14.9 M

• Task 1 In System Storage (1996): $ 3.4 M

• St. Aubin S&D Facility (1999): $ 19.8 M

• Leib S&D Facility (1999): $ 33.4 M

• WWTP Expansion (2000): $ 101.2 M

• Conner Creek CSO Basin (2001) $ 201.4 M

• In-System Storage Devices (2002): $ 30.8M

• Baby Creek S&D Facility (2003): $ 76.1 M

• Belle Isle CSO Basin (2005): $ 16.1 M

• Oakwood Basin & P. Sta. (2007) $ 168.7 M

• Oakwood Sewer Improvements (2008) $ 15.0 M

$ 757 M

Benefits of CSO Control Program

What is Innovative?

• Compliance with Permit

• Reduced Metals, Industrial Loading

• More Treated and Captured CSO Volumes

• Land Application of Biosolids

• Green Infrastructure

• Technology of Collecting Data Real-Time

• Doing More with Less

Innovative CSO Control Technologies

• First Flush Capture Basins for Oxygen Demanding

Substances Removal

• Disposable Nets for Sanitary Trash Removal

• In-Sewer Disinfection for Bacterial Kill

Wastewater System (2009/10)

Collection System Treatment System

Treated Combined

Sewage Overflow

8 Facilities

Untreated Combined

Sewage Overflow

63 CSO Outfalls

1,991 MG

1,698.5 MG

165,000 Tons (Solids)

237,250 M Gallons (treated)

Co

mb

ined

Sew

age

Green Infrastructure Techniques

• Tree Planting

• Demolition and greening vacant property

• Downspout disconnection

• Green infrastructure along roadways

• Green infrastructure at municipal facilities

17 Detroit Water & Sewerage Department

Implementation Strategy

• Reduce inflow to combined sewers 10% - 20%

Goals include volume reduction, as well as quality of life

issues.

• Works towards City goals of removing abandoned

homes and dealing with urban blight

• Coordinating with Detroit Works efforts

18 Detroit Water & Sewerage Department

Implementation Strategy (continued)

• Original Pilot Areas • Two pilot areas focusing on

techniques consistent with stabilization efforts

• Grandmont/Rosedale

• Rouge/Cody

• Large Scale Greening Pilot:

Brightmoor

19 Detroit Water & Sewerage Department

Questions?

Detroit Water and Sewerage Department

www.dwsd.org

Daniel Schechter, P.E.

Superintendent of Engineering – Wastewater

9300 W Jefferson Ave.

Detroit MI 48209

dschecht@dwsd.org

Extra Slides

Disposable Net Operations

• Inspected after

each event

• Changed when

50% Full

Net Installation

• Boom Truck

• Lifting Basket

• 6-mm Mesh Nets with

• Plastic Frame

• Net Size –

• 2.5’Wx4.0’Hx8.0’L

Courtesy Fresh Creek Technology

Disposable Net

Removal

Courtesy Fresh Creek Technology

In-Sewer Disinfection System

• Centralized chemical storage

and feed facility for multiple

outfalls

• Dedicated variable speed

pumps & double-walled feed

lines per outfall

• Chemical feed rate adjusted

based on existing flow signal

• Simple pipe diffuser, no

mechanical mixers

• No additional storage, contact

time achieved in existing

sewers

• Feed lines (1”-3.5” Diameter)

are flushed after every event

Disposable Net Facility

Interceptor

Existing flow signal for total outfall flow

Central

Disinfection

Facility

Chemical Feed Pumps

River

Capital Cost Comparisons

• Rouge River Controls:

• Conventional $850 Million

• First Flush/Nets/

In-Sewer Disinfection $415 Million

• Detroit River Controls:

• Conventional $1,000 Million

• Nets/In-Sewer Disinfection $200 Million

The Wastewater Operations Group collects, conveys, treats and

discharges wastewater in accordance with NPDES regulatory

permits

Treated

Combined

Sewage

Overflow

8 Facilities

Untreated

Combined

Sewage

Overflow

76 CSO

Outfalls

~ 2 B

Gallons/yr

~ 1.7 B

Gallons/yr

165,000 Tons

(Solids)

~ 237 B

Gallons /yr

(treated)

Co

mb

ined

Sew

age

Detroit

and Rouge

Rivers

Convey Discharge Treat Collect

Regional Sewer System Tributary to DWSD

Wastewater Treatment Plant

Convey Discharge Treat Collect

Total Service Area Statistics

▪ 3.5 million people

▪ 78 communities

▪ 900 square miles

(35% combined)

City of Detroit Statistics

▪ 3,500 miles of combined

sewers

▪ 78 outfalls

▪ 3 major interceptors

▪ 140 square miles (100%

combined)