city of allegan
DESCRIPTION
City of Allegan. Conversion of Lime Softening to Reverse Osmosis Softening. Background. - PowerPoint PPT PresentationTRANSCRIPT
City of Allegan
Conversion of Lime Softening to Reverse Osmosis Softening
Background
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
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 Problems
No standby power at treatment plant
Remote well can directly pump to system but with no treatment
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 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
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 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 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
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
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 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
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 Features
Raw Water Feed Test Panel pH, SDI, Temp, Pressure,
Conductivity
Membrane Clean-in-Place system Immersion heater
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 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 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 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 Features
Membrane Solar panels incorporated into metal roof
Camera/intrusion security system
Automatic sampling system for concentrate discharge to Kalamazoo River
Plant Design Features
SCADA system for automatic control of entire plant, 24/7
Complete Laboratory Water meter testing area
Funding
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
Began construction in February, 2010
Scheduled to begin operation of new plant in early 2011
Construction to be completed by Fall, 2011