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The Impact of Artificial Monolayers on Water Quality: Data from Tank and Field Trials Pam Pittaway (NCEA, USQ)

Evaporation Loss

Science Forum, 19-20 June 2012

Urban Water Security Research Alliance

BENCHMARK IMPACT OF NATURAL MICROLAYERS, PRIOR TO MONOLAYER Concentration of hydrophobic organic matter 1.Reduces surface tension (>surface pressure) 2.Increases microbial activity (enrichment) 3. Modifies oxygen and heat transfer across air/water interface 4.Modifies light penetration & photodegradation

MICROALGAE AS A NATURAL SOURCE OF ORGANIC MATTER IN MICROLAYERS

1=C18, 2 to 5= increasing ratios of collagen to C18, 5=collagen (Gladyshev 2002)

5 10 15 20 25 30 35 40

21/7/09 5/8/09 19/8/09 2/9/09 2/10/09 14/10/09 27/10/09 11/11/09 25/11/09 8/12/09 23/12/09 6/1/10 20/1/10 3/2/10 19/2/10 10/3/10 24/3/10 7/4/10 20/4/10 5/5/10 19/5/10 2/6/10 17/6/10 30/6/10 14/7/10 28/7/10 12/8/10 25/8/10 22/9/10 5/10/10 20/10/10 3/11/10 16/11/10 1/12/10 15/12/10 30/12/10 20/1/11 2/2/11 18/2/11 2/3/11 16/3/11 30/3/11 13/4/11 20/4/11 27/4/11

Surface pressure (mN/m) 20 40 60 80 100 120 Phytoplankton (mm3/L) SE micro NW micro Biovolume

IMPACT OF ALGAE ON SURFACE PRESSURE AT LOGAN’S PRE MONOLAYER

Maximum reading for surface pressure is 36 mN/m

SEASONAL CHANGE IN DEPTH & AQUATIC HUMIC SUBSTANCES AT LOGAN’S

blue arrows are water pumped in

WATER INPUTS AND OUTPUTS AT LOGAN’S

POTENTIAL ADVERSE IMPACT OF A CONDENSED MONOLAYER

• 1. Increase in surface pressure
• 2. Increase in surface water temperature
• 3. Reduction in dissolved oxygen concentration?
• 4. Increase in concentration of organic carbon in

microlayer?

• 5. Increase in microbial activity in microlayer?

IMPACT OF A MICROLAYER ON THE LIQUID THERMAL BOUNDARY LAYER (LTBL)

LTBL modified by microlayers AND monolayers

N Floating energy balance platform & thermistor chain Dead tree Scintillometer path Sump boundary Thermistor chain and depth sensor Rainfall, wind speed & direction, temperature, humidity and pressure Scintillometer transmitter/reciever, temperature profile, net radiation Pump station, flow meters (x5) and communication base Crest of dam wall Piezometer transect (leakage detection) 50 100 150m

32 mN 14

21 >34 >34 14 17 18 17 18 18 18

Surface pressure <1hr of product application (8 am 2/2/2011) shown in boxes. Surface pressure <4 mN across entire storage 48 hrs after application (6 am 2/2/2011).

Purple arrows indicate wind

LIMITATIONS OF MONOLAYER STUDY

IMPACT OF C18 OH ON MICROLAYER DYNAMICS IN COVERED TANK TRIALS

• x3 10m diam. 0.7 m deep tanks
• x2 covered, with x1 continuous twice

weekly C18 OH application for 4 months

• x1 uncovered control
• Black cover wind & light-impervious, white

cover more wind turbulence and greater light penetration

HOURLY SURFACE TEMPERATURE DEVIATION C18 OH IN COVERED TANKS

72 hrs with wind <6 m sec-1 no/light rain (LTBL dominant)

HOURLY SURFACE DEVIATION TEMPERATURE DIFFERENCE AT LOGAN’S

72 hrs with wind <6 m sec-1 no/light rain (LTBL dominant)

Tcair-Tcw,0.5 (0C)

• 10

10 20 30 40 DT clean - DT monolayer (0C)

• 2

2 4 6 8 Black covers White covers

TEMPERATURE BUFFERING EFFECT OF MONOLAYER RELATIVE TO CLEAN WATER

72 hrs with wind <6 m sec-1 no/light rain (LTBL dominant)

MONOLAYER IMPACT ON MICROBIAL ACTIVITY (log scale)

Sampling date MPN SE shore TOC SE shore MPN NW shore TOC NW shore 11/12/10 4 1 0.5 1.3 20/1/11 10 1 0.03 1.3 2/2/11 1 0.9 0.5 0.9 30/3/11 1 1.3 0.3 0.8 20/4/11 1 1.3 3.6 0.9 11/5/11 1 0.9 2.6 1.1

MICROLAYER ENRICHMENT DURING LOGAN’S MONOLAYER APPLICATION

MONOLAYER IMPACT ON TOTAL ORGANIC C

Sampling date Biochemical Oxygen Demand (mg mL-1) MPN Phenol-degrading bacteria (CFU 100 mL-1) Tank 1 covered Tank 2 cover +C18OH Tank 3 uncovered Tank 1 covered Tank 2 cover +C18OH Tank 3 (uncovered) 19/1/’10 Black

4 4 3 2 1 9

23/2/’10 White

2 2 6 2 2 2

25/3/’10 Black& white

4 2 2 12 9 12

15/4/’10

2 2 10 12 9 12

C18 OH IMPACT ON BOD AND MONOLAYER- DEGRADING BACTERIAL POPULATIONS

ADVERSE IMPACT OF MONOLAYERS ON WATER QUALITY?

• Monolayers affect molecular diffusion

within LTBL, under low wind speed and light or no rain

• Monolayers buffer heat exchange within

the LTBL (< heat loss with a negative air to water temp., < heat gain with a positive air to water temp.)

• Low application rates minimise change in

water chemistry and biology

Urban Water Security Research Alliance THANK YOU www.urbanwateralliance.org.au

Acknowledgements:

Co-authors - V. Martinez-Alvarez, B. Gallego-Elvira and N. Hancock