Sue Lawrence:

Day 1, Session 6Russell Reed

Sue Lawrence

City of La Center WA MBR vs SBRThe Path to Lower OPEX

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Location

HISTORY

Built in 1967

Upgraded 9 times

Limited room for expansion!

Existing facility borders:

Commercial Area

Bridge entrance to the City

La Center Bottoms Wetland

Public Park and Amphitheater



2010 MBR Constructed

DESIGN INFORMATION

Current – $11.7 Mill 0.69 MGD Max Month (Membranes – 0.84 MGD)1.29 Peak Day (Membranes – 1.68 MGD Peak Day)

Phase 1B – $1.95 Mill, 1.04 MGD Max Month (Membranes – 1.68 MGD) 1.94 MGD Peak Day (Membranes – 3.36 MGD Peak Day)

Phase 2 would be for solids and it is estimated at $3.9 MillionPhase 3 – est $8.7 Million

2.25 MGD Max Month (Membranes – 3.36 MGD)4.20 MGD Peak Day (Membranes – 6.72 MGD Peak Day

Small Foot Print20 year at 8.7% growthReliability & FlexibilityKennedy/Jenks Consultants, Portland, OR

Preselection of MBR – Enviroquip/Kubota Flat Plate Currently OVIVOwater



Click here to insert a picture

Upgrades

TOP 5 UPGRADES

The plant was built to be energy efficient

Raised headworks for gravity flow into the plant

Phased the expansion by only filling two MBR basins

Utility water converted from Potable water

Combined old and new SCADA into one system

New Headworks - Two Rotary Drum Screens - 6.0 MGD 3 mm

Pump Assisted Gravity

Phased Expansion

Utility Water System

SCADA System


LA CENTER PROCESS SCHEMATIC – EXISTING AND FUTURE

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T h e L a C e n t e r w a s t e w a t e r T r e a t m e n t P l a n t



Influent Quality

COMPARING SBR TO MBR

The Plant Flows and Loads were similar during the evaluation for both the Sequencing Batch Reactor and the all four years as an Membrane Bioreactor

The SBR was started in 2004, so it was less than 3 years old at the time of this study




Challenges

TOP 5 CHALLENGES

Growth dropped from 8.7 % to less than 1%

City Council requested a 10% reduction in expenditures

Casino Resort not constructed (0.5 MGD)

Programming was not flexible

Could not reduce volume of system

Growth Rate Reduced

Dewatered Solids

Energy Usage

Programming

Valve Placement Reduced Flexibility




Optimization

TOP 5 OPTIMIZATION STRATEGIES

Couldn’t take one process train completely offline without removing one MBR Basin

Forced only one MBR to run during regular flows. Higher flows required both

Worked With OVIVO to have someone look at the programming to make it more efficient

Take Equipment Out of Service

Only Operate at Medium or High Flow Rates

Tune Control Loops

Program in Flexibility

Inspect and Clean Diffusers



Effluent Quality

DISCHARGE CHARACTERISTICS

When we changed from the SBR to the MBR we realized

a 92 % reduction in the pounds of Total Suspended

Solids and 57 % reduction in the pounds of BOD

discharged to the receiving stream.

The Biosolids production dropped dramatically. We

produce 32% fewer pounds with the MBR than we could

with the SBR.



Actual Expenses

OPEXs

Two year average of Operation and Maintenance

expenses Not including labor expenses

Before optimization - MBR was over 13% less to

operate

In 2013-2014,we increased the savings to 19%

compared to the SBR


The standard flow-based control equation for permeate set point: – Fout = (Fin x Rf) x [Fm + (0.3 x Fc) x (Li-Le)/(Lh-Ll)]

• Fout = process train calculated flow set point• Fin = time averaged influent flow divided by number of online trains• Rf = [(Relax Freq – Relax Duration ) / Relax Freq ] -1• Fm = meter correction factor, 0.85 to 2.0• Fc = gain for level correction, 0.85 to 2.0• Li = average or individual controlling basin level• Le = desired equilibrium level• Lh = high flow level set point• Ll = low flow level set point

This was not intuitive to figure out how changes in the settings would affect the flow settings.


HOW IT WORKS


Program ChangeLooks at incoming flow and at the difference in the basin level.

• If Li <= Lw, then dflow = ((Li - Le)* Vpa)/10• If Li > Lw, then dflow = (((Lw - Le)* Vpa) + ((Li - Lw) * Vtot)/10 min)

= ( +(dflow*0.3))*

Fout Calculated permeate flow set point in gpmFin Time averaged influent flow in gpm Rf [(Relax freq – Relax duration) / Relax freq ] – 1 (1.11)Li Average or individual controlling basin level, ftLe Target Level, ft (Set by Operator)Lw Weir Level, ft (Set by Operator)Vpa Volume Aerated basins, gal/ft (Set by Operator)

Vtot Volume Aerated basins, gal/ft (Set by Operator)




Areas of Usage

Evaluated 5 sections of electrical use

2011 – 2012Baseline for MBR - $65,731 2014 – Current - $58,781

2015 – Goal - $54,660

MBR Electrical Use



Flux Rate

Current Minimum Flow Rate is 160 gpm/header

Increasing the minimum flow rate to 180 gpm and increasing the maximum level in the process basins can increase the plant efficiency

MAXIMUM INSTANTANEOUS AND AVERAGE DAILY FLUX RATES



MBR Air Scour Electrical costs

Baseline 2011-2012

Optimized 2013-2014

Goal 2015

MBR Air Scour Electrical CostBaseline, Current and Goal for MBR Air Scour electrical


Conclusions

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Thank you!

Sue Lawrence:

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