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City of Allegan. Conversion of Lime Softening to Reverse Osmosis Softening. Background.

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City of allegan

City of Allegan

Conversion of Lime Softening to Reverse Osmosis Softening



The existing lime softening plant was constructed in the early 1970’s to service the City and local industries with high quality softened groundwater from a well water source along the Kalamazoo River in the City of Allegan (100 – 150 mg/l hardness)

Existing plant facts

Existing Plant Facts

  • Two upflow clarifiers, two rapid sand filters, originally rated at 3 mgd.

  • 1977 and 1999 modifications were made to the clarifiers to improve performance

Existing plant schematic

Existing Plant Schematic

Existing problems

Existing Problems

  • No standby power at treatment plant

  • Remote well can directly pump to system but with no treatment

Existing problems1

Existing Problems

  • Site along Kalamazoo River in the floodplain, frequently floods which restricts access and requires sandbags around the wells

  • Lime delivery can be problematic

Existing problems2

Existing Problems

  • All of the equipment is original to the plant and has outlived its useful life.

  • Building and HV systems are old and in need of replacement

Study phase

Study Phase

  • Examined upgrading lime plant versus retrofitting to RO treatment

  • Study concluded that retrofit to RO was most cost effective

  • Proceeded with Pilot study of RO technology on existing well water in 2006

Study phase1

Study Phase

  • Pilot Study

    • Conducted in 2006 for treatment performance

    • 2nd study conducted in 2009 to determine characteristics of concentrate for NPDES permit

    • Spiral wound Film Tec BW30LE-440 Membranes used in both studies

Study phase2

Study Phase

  • Pilot Study Conclusions

    • No significant scaling

    • Flux Rate 14 gfd

    • 70%+ Recovery for membranes

    • Minimal fouling

    • Iron remained in soluble form – no pretreatment required prior to membranes

    • Concentrate stream did have detectable phosphorus, even with low P antiscalant

Project plan phase

Project Plan Phase

  • Stimulus funding available in 2009

  • Reexamined issues – new plant on existing site or new plant elsewhere due to flooding concerns

  • Completed DWRF Project Plan while simultaneously designed plant in Spring/Summer 2009

  • New plant on existing site was the most cost-effective alternative

Permitting phase

Permitting Phase

  • Wetlands/Floodplain permit application

    • HEC analysis of Kalamazoo River

    • Cut back existing lime sludge lagoons for compensating cut for new fill on site

    • Raised new plant above 500 year flood level

Permitting phase1

Permitting Phase

  • NPDES permit application for RO concentrate discharge

    • Potable water, high in TDS and measurable Phosphorus

    • TMDL on Kalamazoo River for Phosphorus

    • Reallocated portion of City’s WWTP Phosphorus allocation to WTP

Plant design features

Plant Design Features

  • Cartridge Filters

    • 5 micron

  • Reverse Osmosis Treatment Skids

    • Permeate Quality = 0 mg/l Hardness

    • Total capacity = 3.45 mgd when blended at 100 mg/l Hardness (3 skids)

    • 2 Stage RO

    • Interstage boost system

Plant design features1

Plant Design Features

  • Raw Water Feed Test Panel

    • pH, SDI, Temp, Pressure, Conductivity

  • Membrane Clean-in-Place system

    • Immersion heater

Plant design features2

Plant Design Features

  • Three Iron Removal Filters

    • Air/Water simultaneous backwash

    • Automatic control backwash system

  • Automatic RO Permeate/Iron Filter Water blend control system

  • Air stripper for pH adjustment for RO permeate

Plant design features3

Plant Design Features

  • High Service Pumping

    • Five, horizontal split case high service pumps (2 pressure districts)

    • Total firm pumping capacity = 4.8 mgd

  • 500,000 gallon on site storage tank

Plant design features4

Plant Design Features

  • Three on-site wells

    • One new well (abandon existing well)

    • Retrofit two existing wells with submersible pumps (VFD control)

    • Total firm pumping capacity = 3.0 mgd

Plant design features5

Plant Design Features

  • Chemical feed

    • On site mixed oxidant generation (iron oxidation, disinfectant)

    • Fluoride (dental)

    • Antiscalant (membrane feed)

    • Phosphate (corrosion control)

    • Caustic soda (pH adjustment)

Plant design features6

Plant Design Features

  • Membrane Solar panels incorporated into metal roof

  • Camera/intrusion security system

  • Automatic sampling system for concentrate discharge to Kalamazoo River

Plant design features7

Plant Design Features

  • SCADA system for automatic control of entire plant, 24/7

  • Complete Laboratory

  • Water meter testing area



  • Final Project Funding

    • $3,744,000 EDA Grant

    • $3,744,000 DWRF Low Interest Loan

    • $2,501,000 Stimulus Loan Forgiveness

    • Total project cost $9,989,000

  • Grant = 63% of total project cost

Construction phase

Construction Phase

  • Began construction in February, 2010

  • Scheduled to begin operation of new plant in early 2011

  • Construction to be completed by Fall, 2011

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