New Cobar Water Treatment Plant

Nyngan Cobar Water Supply Scheme

Cobar Water Treatment

Macquarie River

Bogan River

Nyngan Weir & PS

Cobar Water

Board Storage

Town reticulation

Cobar - 3 hr drive from Dubbo

Existing Water Treatment Plant (WTP)

• 4 ML/d

• Built in early 1960s

• Horizontal flow clarifier + sand filtration

Issues

• Limited capacity

• Process deficiencies

• Signs of structural deterioration

• Some WHS issues

• Manual operation

• Investigation revealed refurbishment not economical

A new Water Treatment Plant

• Council decided to build a new WTP

• $8M grant received from government

• Sought help from Public Works Advisory (PWA)

• PWA commenced investigation

• Number of challenges encountered

New WTP – Required Level of Service

• Increased capacity - 8 ML/d

• Minimum: Australian Drinking Water Guidelines

• Capable of treating mixed water from different sources

• Capable of handling up to 450 NTU

Key Challenge 1: Raw Water Source and Treatability

Macquarie River Bogan River

Algae

Cobar bulk

storage

High turbidity

Key Challenge 1 cont’d

Key Challenges cont’d

• Anaerobic conditions in the rising main causing taste & odour

• Iron; manganese

• Lack of representative raw water samples for lab trials

Solution

Blending Unit

with Instruments

SCADA

Telemetry

RW Balance

Tank

(existing)

Settling

• Selective Withdrawal

• Variable Speed Drives (VSDs)

Floatation (DAF)

+ Filters Clear Water

Reservoir

(existing) VSDs for

Nyngan pumps

MF/Tu

MF/Tu

Tu

Agreed Design

Raw Water

Reservoir

PAC

Contact

Tank

Flocculation

Chambers

Lamella

Clarifier DAFF

Re-

Flocculation

Zone

UV

unit Clear Water

Storage Tank Treated

Water Pumps

Million

Gallon Tank

(MGT) Retic

PAC KMnO4

Sludge Lagoons

(x2)

Supernatant

Return PS

Cobar Water

Storage

Blending

Unit From

Nyngan

Raw Water

Transfer Pumps

New work

Existing facilities

Cl2

Fluoride/

Soda ash Coag/

Poly

Main process unit

Site layout

Need a new site

Key Challenge 2

• Close to open cut mine

• Area around existing WTP is not

suitable

Main selection criteria of new site

• Close to existing raw water / clearwater reservoirs

• Hydraulics

• Environmental issues

• Land ownership

• Construction difficulties

• Road access

• Above 100 year flood line

Key Challenge 2 cont’d

Key Challenge 2 cont’d

Construction Difficulties

• Shallow rock

Selected Site

Location 3A

• 9 sites were investigated

• Land exchange with mine

• About 700m from the

existing raw water /

clearwater reservoirs

• All expected criteria met

except shallow rock

Clearwater

Reservoir

(MGT )

Existing WTP

Key Challenge 3: Skills of Operational Staff

• High turnover of permanent operational staff

• New WTP process will be different to existing process

Solution

• New staff including Water and Wastewater Engineer

• Operator training in the contract – 3 programs in 12 months

• Fluoride course/DPI Water Operator TC

Key Challenge 4: Funding

• PWA’s revised concept

• Concept agreed with Council/stakeholders

• New estimate $15.5M

• Only $8M in hand

Funding Solution

• Decided to seek additional funding

• PWA assisted with the funding application

• Council/PWA/DPI Water discussions with Funding Authorities/INSW

• Secured additional $7.5M (total $15.5M)

Tender

• A Design and Construct open tender

• Mandatory Pre-tender site meeting

• 15 companies attended with six WTP contractors

• Three tenders received

Conclusion

• Holistic approach

• Addressed all major concerns

• Robust process

• Tender was awarded in June 2017

• Total project cost within the estimate

• Due for completion in June 2018

Acknowledgements

• Staff of Cobar Shire Council, special thanks to Stephen Taylor, Director of Engineering Services

• Infrastructure NSW

• Staff of DPI Water, special thanks to Bill Ho, Manager Water & Sewerage

• My colleagues - the great bunch of supporters:

Glenn Fernandes - Senior Process Engineer

Mounir Tayyar – Senior Process Engineer

Graham Attenborough – Director, Infrastructure Services

Hendrik van Rhijn – Director Engineering, Water & Wastewater

Janet Moule - Project Officer

Glen Edgtton – Manager Business Process

Kim Nguyen – Process Engineer

David Watson & staff of PWA Dubbo Office

Thank you

Jay Ariyawanse Senior Process Engineer

Public Works Advisory | Department of Finance, Services and Innovation p 02 9372 7893 e Jay.Ariyawanse@finance.nsw.gov.au | www.publicworksadvisory.nsw.gov.au Level 13, McKell Building, 2-24 Rawson Place Sydney NSW 2000