Richard Walker Climate Change Case Study Water Quality Implications Water Safety Conference 2010.

Richard Walker

Climate Change Case StudyWater Quality Implications

Water Safety Conference 2010

Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia

Impact of Climate Change

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variability

Climate Change and Water Safety Plans – Case Study


Supply Infrastructure •Surface water source•Dam capacity 1.7 GL•Commissioned 1994•Augmentation expected 20 plus years


Climate change/Drought•By early 2000’s supply became problematic•Pump back direct from River commenced•2002 = winter from hell



Case Study – Scheme Supply

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Volume abstracted fromPump back(cummulative/month)

Margaret River TownshipMonthly Demand

Storage volume in TenMile (average/month)

Maximum Storage in TenMile Brook

Minimum Safe Storage inTen Mile Brook

Figure 1. River pump back, demand and storage levels 2000 to 2009.

Water Safety Plan Development•2004 – WSP’s commenced•Town scheme was reviewed•Dam catchment

- Some private land- Cattle- L3 source

• River source characterised as high risk (unsuitable)- No source protection- High E Coli detected- High C&G risk- High turbidity- High colour

•No barrier to C&G


Water Safety Plan Action Plan


•Turbidity limits on pump back (immediate)

•PCP = 5NTU

•Relocate pump back pipe to back of dam

•UV on dam outlet (months)

•CCP = 40ms/cm2


Ten Mile Brook DamCap 1,690,810m3

TWL 121.27mAHDLevel 2 Source

TransferPS

Chlorine Disinfection

Chlorine Analyser

To Reticulation

a) Margaret River scheme 1994



Margaret RiverUnsuitable Source

Pump Back PS

TransferPS


Chlorine Analyser

To Reticulation

b) Margaret River scheme 2001




Pump Back PS

TransferPS


To Reticulation

UV DisinfectionPump back inlet pipe relocated to back of dam

c) Margaret River scheme with the addition of UV disinfection August 2004


Long Term Plan

The use of the high risk River pump back and reliance on a single UV barrier was a catalyst to commence planning to stabilise the long term water supply to the town.

This process was instrumental in establishing the water quality principles of the ADWG in the guidelines used by planners for selecting new sources. Relevant statements in the ADWG include:“the greatest risk to consumers of drinking water is pathogenic micro-organisms” (ADWG 1-1)

“prevention of contamination provides greater safety than removal of contaminants by treatment, so the most effective barrier is protection of source water to the maximum degree practical” (ADWG 1-2).


Long Term Plan

This resulted in the Corporation establishing a preference order for new sources based on pathogen risk as set out below

•Confined groundwater•Unconfined groundwater•Surface water (large dam)•Surface water (small dam)•Pump back only acceptable if dam not operated for min 30 days after pump back ceases

The long term planning for the town has subsequently recommended using a confined aquifer source.

2007 Winter


•Low runoff to Dam

•% River water> 50%

•Breached colour and turbidity PCPs on dam outlet

•Single barrier may be compromised

•Corporate incident declared

•Stopped pumpback

•Decision to install MF on dam outlet (8-10 MLD)

Action Plan


•$10M for dam outlet too expensive

•$5M for pump back only (4MLD)

•Upgrade UV treatment on dam outlet

•Bought the private catchment land and fenced

•New source due 2012







Auto shutoff when turbidity > 5 NTUTurbidity

Analyser




Pump Back PS

TransferPS


Auto shutoff when chlorine system fails

Turbidity & Chlorine

Analysers

Auto shutoff when

turbidity > 5 NTU

To Reticulation

UV Disinfection

d) Margaret River scheme with the addition of turbidity analysers and auto shutoff 2007

Auto shutoff when turbidity > 5 NTUTurbidity

Analyser




Pump Back PS

TransferPS

UV DisinfectionChlorine

Disinfection

Auto shutoff when UV or chlorine

systems fail


Analysers

Auto shutoff when

turbidity > 5 NTU

To Reticulation

e) Margaret River scheme with the upgrade of UV disinfection December 2007

Auto shutoff when turbidity > 0.3 NTU or Colour >10 TCU

Turbidity & Colour

Analysers




Pump Back PS

TransferPS

UV DisinfectionChlorine

Disinfection

Auto shutoff when UV or chlorine systems fail


Analysers

Auto shutoff when

turbidity > 5 NTU

To ReticulationMembrane

Filter

f) Margaret River scheme with the addition of membrane filtration September 2008


Current Situation

These actions have considerably reduced the water quality risks at the town while the long term solution is implemented (now expected in 2012).

All waters entering the dam are now considered “low risk” with respect to cryptosporidium and giardia. The UV on the outlet of the dam is a robust second line of defence for the treated water supply. The micro filtration and UV plants are both designed to “fail safe” which means failure to achieve PCP & CCP targets result in the supply shutting down automatically.


Lessons Learnt

•Climate change/drought has seriously undermined system yield for many schemes

•New source development is expensive and takes many years

•There is pressure to use high risk sources (of unknown pedigree) to augment supply in the short term

•Application of WSP principles should be applied to those temporary sources to

•Minimise risk to customers•Demonstrate due diligence

Richard Walker Climate Change Case Study Water Quality Implications Water Safety Conference 2010.

Documents

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hell water safety conference

years water safety conference

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malaysia slide

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