BIOSOLIDS ENHANCEMENTS AT THE DOS RIOS WRC – SLUDGE BLEND TANKS AND CENTRIFUGESGarrett Kehoe, P.E.

September 21, 2018

© Arcadis 2017

Agenda

• Background

• Issues

• Phased Solution Approach

o Phase I – Sludge Blend Tank Improvements

o Phase II – Thickening Centrifuges

• Lessons Learned and Implemented

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• 1984/85 – Dissolved Air Flotation Thickening

• 2006- Gravity Belt Thickeners 1 & 2

• 2009 – Gravity Belt Thickeners 3 & 4

• Dos Rios WRC Sludge consists of:

o Excess Activated Sludge (WAS)

o Dos Rios Primary Sludge

o Leon Creek Sludge (Primary + WAS)

Background

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The issues

(Prior to Upgrades)

Inconsistent Feed Rate

Inconsistent Thickness

Lack of Automation

Lack of Redundancy

Capacity Limitations

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Existing SystemPrimary Sludge

DIGESTERS

DIGESTERS

DIGESTERS

EAS

EAS

EAS

Leon

Primary

Sludge

Leon

Blended

Thickened

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“The Issues”Primary Sludge

DIGESTERS

DIGESTERS

DIGESTERS

EAS

EAS

EAS

Leon

Primary

Sludge

Leon

Blended

Thickened

Centrifugal Pumps

(Inconsistent Flow)

Not Being Thickened

In Pipe Sludge Blending

(Inconsistent Thickness)

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Phase I – Sludge Blending Tank

• Fix consistency of flow and thickness

• Increase operational flexibility

Phase II – Centrifuges

• Add redundancy

• Add capacity

• Automation

• Reduce Operational Costs

Phased Approach

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New Gravity Belt Thickeners Feed Pump Station

New Recirculation Pump Station

New Blending Tank

Overflow Protection

Bypasses for Operational Flexibility

Phase I – Sludge Blend Tank

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Primary Sludge

DIGESTERS

DIGESTERS

DIGESTERS

EAS

EAS

EASLeon

Primary

Sludge

Leon

Blended

Thickened

Proposed System

New Feed Pump Station

(Improved Flow Rate Control)

New Blending Tank

(Improved Consistency)

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Completion Pictures

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• Two new Centrifuges

• New Polymer System

• New Centrate Pump Stations

• Automation

• Facilities for Future Centrifuges

Phase II

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• Solids Loading Capacity vs Flow Capacity

• Thickening equipment needs to be evaluated for both

Capacity Evaluation

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Phase II – Sludge Flows

GBT’s @ 750 gpm each

0

500

1000

1500

2000

2500

3000

3500

2014 2016 2018 2020 2022 2024 2026 2028 2030 2032

Slu

dge F

low

(gpm

)

Year

2% Growth Sludge Flow

Average Flow (gpm) 3 Operating GBT 4 Operating GBT

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Phase II - Solids Thickening Needs

GBT’s @ 3750 lb/hr | Centrifuge @ 6500 lb/hr

0

100000

200000

300000

400000

500000

600000

700000

800000

2014 2016 2018 2020 2022 2024 2026 2028 2030 2032

Dry

Solid

s (

ppd)

Year

2% Growth Solids Handling Capabilities

Average Flow Loading Rate (ppd) 3 Operating GBT 4 Operating GBT One Additional Centrifuge Two Additional Centrifuge

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Phase II

New Feed Pumps

New Polymer Building

New Electrical Building

New Centrate Pumps

New Centrifuges Future Centrifuges

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Ongoing Construction

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Ongoing Construction

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Scoping/Procurement Differences

General Contractor

Centrifuge

Backwash Pump

Thickened Sludge Pump

Polymer System

TYPICAL

Centrifuge

General Contractor

Backwash Pump

Thickened Sludge Pump

Polymer System

DOS RIOS THICKENING

Lessons Learned

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• Available underground space extremely limited

• Exposed piping can be your friend

Lessons Learned

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• I&C Workshops, I&C Workshops, I&C Workshops…

• 3 Instrumentation and controls workshops during design

• 1 Network workshop during construction

• 1 Control panel workshop during construction

• 1 Graphics workshop during construction

Lessons Learned

Record drawings are not always right!

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• Thickened sludge pumping is an art.

• Non Newtonian fluid.

• Highly recommend viscosity testing sludge for >5% solids.

Lessons Learned

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Lessons Learned – Control Maps

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Housekeeping and Safety By Design

Confined Space, no access provided

Tapered edge to prevent storm water entry

Grating above entire centrifuge area to clear spilled sludge easily

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Questions?