Many Changes atKealakehe WWTP2015 Pacific Water Conference

Craig Lekven

Brown and Caldwell, Maui

• County of Hawaii Department of Environmental Management, Wastewater Division• Dora Beck, Division Chief

• Lyle Hirota, Deputy Division Chief

Acknowledgements

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• WWTP for Kailua-Kona

• 5.3 mgd ultimate capacity

• Constructed early 1990s

• Aerated lagoon system

• Current flows are about 2 mgd

Kealakehe WWTP

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• Lagoon sludge levels high• Sludge Removal Project

• Aeration system inefficient, near capacity, diffusers broken, not maintainable• Aeration Upgrade Project

• Growth, effluent disposal controversies• Master planning efforts

Problems/Solutions

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• Can’t upgrade aeration system without sludge removal

• Can’t remove sludge without aeration upgrades

• $14.7M low bid

• General contractor: Performance Systems Inc.

• 2-year project duration

Aeration Upgrade and Sludge Removal Project

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• Estimated 3,000 dry tons solids in Lagoons 1, 2, 3

• Performance-based specification

• Experience minimum qualifications

• Payment based on dry weight of solids disposed• Wet weight by landfill scale• Total solids testing by independent laboratory

• Harvesting by floating dredge

• Temporary mechanical dewatering – belt filter presses• Contractor anticipates 20 percent solids

• Covered truck transport

• Disposal at West Hawaii Landfill – tip fee included in price

Sludge Removal

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Floating Dredge

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• Subcontractor: Golden Enviro LLC

• $221,000 for mobilization/demobilization

• $1,220/dry ton disposed

Sludge Removal Costs

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• Siemens Turblex Blowers• 2 at 700 hp

• Yes, turbo blowers were considered

• Larger aeration piping• Sized for ultimate airflow capacity

• Better airflow control• Flow meters, DO probes

• Motorized control valves

• Master control panel

• Maintainable piping and diffusers• Parkson Biolac system

Aeration Upgrade

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Parkson Biolac Diffuser System

• Construction sequencing to maintain operations

• Endangered species

Project Challenges

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Construction Sequencing

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Endangered Species

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• Hawaiian Stilt – Ae`o

• Hawaiian Coot - `Alae kea

• Other protected migratory species

• Cooperation with USFWS and DLNR

• No “take” allowed

• Biological monitor: Scott Waddington (Kona Wildlife)

• Deterrent measures

Endangered Birds

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Hawaiian Stilt

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Hawaiian Coot

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Effluent Disposal Controversies

Subsequent Reuse Opportunities

• Lava fields – no soil

• High pipeline installation cost

• Recycled water salinity

• Lack of potential users close by

Reuse Challenges

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• R-1 treatment

• Buffer parcel irrigation

• Off site R-1 use

• Subsurface flow constructed wetlands – 12 acres

• Soil aquifer treatment system – 10 acres

Master Plan - Future Elements

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Future Schematic

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Master Plan

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• Covered lagoon for algae control

• Chemical addition

• Flocculation

• Filtration

• UV disinfection

• R-1 storage tank

• Pumping systems

• R-1 pipelines to off-site users

R-1 Treatment

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Modular Insulated Floating Cover

Reuse Plan

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Kealakehe Regional Park Master Plan

• Provides polishing treatment

• Denitrification

• Some P removal

• Metals removal

• Trace organics removal

Subsurface Flow Constructed Wetlands

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Master Plan

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Subsurface Flow Constructed Wetland

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Subsurface Flow Wetland on Molokai

• USEPA recognized form of land treatment

• Removal of:• BOD and TSS

• Pathogens

• Nutrients

• Trace organics

• Metals

• Endocrine disrupters

Soil Aquifer Treatment (SAT)

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SAT

A`a Lava

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SAT Concept – 10 Acres

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• Total project cost: $48M

• Benefits: • Water reuse

• 85% reduction of N and P mass loads to groundwater

• Recognized form of land application

Master Plan Cost & Benefits

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• Preliminary design efforts

• Environmental impact statement

Next Steps

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