Urban Water Security Research Alliance 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
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)
IMPACT OF ALGAE ON SURFACE PRESSURE AT LOGAN’S PRE MONOLAYER 40 120 SE micro NW micro 35 Biovolume 100 30 Surface pressure (mN/m) Phytoplankton (mm3/L) 80 25 20 60 15 40 10 20 5 0 0 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 Maximum reading for surface pressure is 36 mN/m
SEASONAL CHANGE IN DEPTH & AQUATIC HUMIC SUBSTANCES AT LOGAN’S
WATER INPUTS AND OUTPUTS AT LOGAN’S blue arrows are water pumped in
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
0 50 100 150m N Surface pressure <1hr of product 14 1 4 application (8 am 21 >34 2/2/2011) shown in 32 >34 mN boxes. 18 18 18 17 17 Surface pressure 18 <4 mN across entire storage 48 hrs after Purple Dead tree application (6 am Scintillometer path arrows 2/2/2011). Sump boundary indicate Thermistor chain and depth sensor Crest of dam wall wind Piezometer transect (leakage detection) Floating energy balance platform & thermistor chain Pump station, flow meters (x5) and communication base Rainfall, wind speed & direction, temperature, humidity and pressure Scintillometer transmitter/reciever, temperature profile, net radiation
LIMITATIONS OF MONOLAYER STUDY
IMPACT OF C 18 OH ON MICROLAYER DYNAMICS IN COVERED TANK TRIALS • x3 10m diam. 0.7 m deep tanks • x2 covered, with x1 continuous twice weekly C 18 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 C 18 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)
TEMPERATURE BUFFERING EFFECT OF MONOLAYER RELATIVE TO CLEAN WATER 8 6 DT clean - DT monolayer ( 0 C) 4 2 0 Black covers White covers -2 -10 0 10 20 30 40 T cair -T cw,0.5 ( 0 C) 72 hrs with wind <6 m sec-1 no/light rain (LTBL dominant)
MONOLAYER IMPACT ON MICROBIAL ACTIVITY (log scale)
MICROLAYER ENRICHMENT DURING LOGAN’S MONOLAYER APPLICATION Sampling MPN TOC MPN TOC date SE SE NW NW shore shore shore 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
MONOLAYER IMPACT ON TOTAL ORGANIC C
C 18 OH IMPACT ON BOD AND MONOLAYER- DEGRADING BACTERIAL POPULATIONS Sampling Biochemical Oxygen MPN Phenol-degrading date Demand bacteria (mg mL -1 ) (CFU 100 mL -1 ) Tank 1 Tank 2 Tank 3 Tank 1 Tank 2 Tank 3 covered cover uncovered covered cover (uncovered) +C 18 OH +C 18 OH 19/1/’10 4 4 3 2 1 9 Black 23/2/’10 2 2 2 6 2 2 White 25/3/’10 2 9 4 2 12 12 Black& white 15/4/’10 2 2 10 12 9 12
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 Acknowledgements: Co-authors - V. Martinez-Alvarez, B. Gallego-Elvira and N. Hancock THANK YOU www.urbanwateralliance.org.au
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