Farm Intake Water Treatment (FIWT) project

FRDC 2017/231 – start July 2018

‘Water treatment to control influent water biosecurity risk on Australian

prawn farms. Effectiveness and impacts on production ponds.’

David Mann Co-invest. Paul Palmer Tom Gallagher

Stephen Wesche

Bribie Island Research Centre DAF

Project context

Enhancing farm biosecurity

• Intake water is a significant potential vector

• 2018/19 farms in the Logan River Region operating in

the white spot control zone

Filtration to remove disease vectors is a common biosecurity measure

• alone or in combination with a following disinfection step

• rotating drum filters – best tech. for high flow volume

Project context

“From a biosecurity standpoint, WSSV risk decreases with screen size.”

Responsible Aquaculture Foundation / World Bank. 2013. Case Study…Mozambique and Madagascar: Impacts and Management Recommendations.

Intake water filtration

• Farms now screen pond inflow water

• This project is about the next level of protection

• requires large farm investment

• Need to optimise the cost:benefit

• Fine filtration (sub-100µm) as well as water disinfection

will impact plankton bloom dynamics

• Need to manage adverse impacts

Project results

Part 1. Farm monitoring

• Performance of commercially operated rotating drum

filtration system

• Impact of filtration on downstream plankton composition

Part 2. Filter mesh size tests

• Direct comparison of different filter sizes (20-150µm)

Outcomes

• What do the results mean for farm biosecurity and

operations

Results: Part 1. Farm monitoring

Gold Coast Marine Aquaculture

Hosted project monitoring activities over the whole

2018/19 production season

Operating parameters

• two filters in parallel at start, third installed later

• nominal 80µm mesh

• estimated 5 ML/h flow rate

Results: Part 1. Farm monitoring

Farm intake water filtration What it did do…

1. removed large quantities of small crustaceans

• in raw water and backwash water - not in filtrate

• amphipods, shrimp, crab and other decapod larvae

• filter feeders, scavengers, predators

• large proportion of these in the 0.3 to 4mm range

2. potentially obstructed entry by Penaeid prawns

• very few non-P. monodon prawns within the farm

• different from previous years

Small crustaceans in filter backwash

Results: Part 1. Farm monitoring

Farm intake water filtration

What it didn’t do…

1. Did not greatly affect the copepod population

2. Did not stop glass shrimp (Acetes sp) from colonising

the farm

• passage of larval stages?

3. Did not stop barnacles

• heavy colonisation occurred within first few weeks

Barnacles on pond linerGlass shrimpCopepods

Copepods at different points within the farm

• no statistically significant differences

Results: Part 1. Farm monitoringn

um

ber

/ m

3 • Adult copepods of the four groups present

• Some larger adults restricted - Calanoids

Results: Part 1. Farm monitoring

Nauplii at different points within the farm

• no statistical differences within water supply system

nu

mb

er /

m3

• Nauplii not affected by filtration

• No difference in body size pre- and post-filter

Plankton much larger than the

80µm nominal mesh size pass

through the filters

• copepods over 200µm width

• almost all nauplii (to 340µm)

HOW?

1. Plankton tend to be bendy,

squishy and variably shaped

2. Filter mesh actual pore size and

shape

Results: Part 1. Farm monitoring

Acartia sp. copepod

Barnacle nauplii

Nominal 80µm mesh – [absolute 125µm]

Results: Part 1. Farm monitoring

Plain weave

Weft Warp

167µm167µm

166µm 250µm

Location

Results: Part 2. Mesh size tests

Pumicestone Passage

Bullock Creek Prawn Farm

Mesh size comparison...

1. Tested range (20, 40, 80,150µm), nominal pore size

greatly affects copepod population

• 20µm retains virtually all copepods and nauplii

• 150µm retains around half of copepods and nauplii

2. All copepod groups pass through 40µm & above

3. Copepods and nauplii passing through 40µm are viable

4. Rotifers can pass through 20µm

• small species? ; eggs?

Results: Part 2. Mesh size tests

Testing set-up

• Inshore estuarine water • prawn farm standard

• Scaled down drum filter • Reparator Pty. Ltd

(manuf. by Adriyatic)

• Stainless woven mesh• 20, 40, 80, 150µm, (raw)

• 80µm same weave as GCMA

• 21 tank array• plankton mesocosms to

assess animal viability

Results: Part 2. Mesh size tests

Results: Part 2. Mesh size tests

Copepod density post-filter

Initial

# / m3

Day 14

# / m3

• Comparatively large restriction step from 150 to 80 µm • Copepod size did not follow same pattern as abundance

Results: Part 2. Mesh size tests

All nauplii density post-filter

Initial# / m3

Day 14# / m3

• 150µm mesh restricts 50% of nauplii, 40µm 25%• Average body size of filtrate nauplii same for all mesh sizes

1. Logan River plankton and glass shrimp samples WSSV

negative (intake and in farm; over the season).

2. Drum filtration at nominal 80µm effectively excludes higher

WSSV risk organisms at practical flow rates.

3. Nominal 80µm stainless filter has a low impact on pond bloom.

• time to peak copepod density delayed but main groups

present to form normal productive pond bloom

4. To prohibit barnacle entry need 40µm or less filter mesh.

• larval stages of crustaceans still enter (lower risk?)

5. Nominal 40µm stainless filter would allow some copepod entry

but retard pond population development.

6. Filtration alone lowers probability of vector intrusion.

• chemical disinfection – high protection

Outcomes

This project

• sampling completed

• final report will have more detailed analyses

What next…

What next…

Future work on water biosecurity…

1. Continue farm monitoring and testing

• performance and impacts of the re-developed systems

being implemented on farms this season

– ‘Growing together’ theme – sharing information

2. Optimise chemical disinfection for high water biosecurity

• options – oxidants, eg ozone, other oxidants; trichlorfon

• conditioning of disinfected water important

3. Creating healthy pond systems

• water/pond biome management

• adapting overseas innovations to the Australian context

• FRDC and DAF funded the project

• Gold Coast Marine Aquaculture opened their Logan River

farm to regular sampling and assisted on farm activities

• Frank Coman and Julian Uribe Palomino (CSIRO) assisted

pond sampling method development and conducted training

of DAF staff in zooplankton identification

• Bullock Creek Prawn Farm allowed use of hatchery and

intake facility and assisted in systems set-up

• Reparator Pty. Ltd supplied the fully equipped drum filter

and different size mesh screen replacements for tests

Acknowledgements

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