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Water Decontamination Technology Today and Tomorrow
Walter Wohanka Geisenheim Research Center Germany Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
Disinfection of Irrigation Water part of an adequate phytosanitary water management
● Pasteurization (heat) ● UVc-Irradiation ● Filtration ● Chemical Treatments
Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
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Pasteurization = Heating
95 to 97 °C for 30 sec
lower temperature (85-95 °C) longer exposition time (3 min)
heat exchanger Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
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Pasteurization = Heating Pros & Cons
☺
Most effective Reliable Easy to handle
High investment High energy input For small volumes only
Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
Solar Heating a "new" low-cost perspective?
http://upload.wikimedia.org/wikipedia/commons/thumb/6/67/Indonesia-sodis-gross.jpg/220px-Indonesia-sodis-gross.jpg Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
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Solar Heating Panels ? Low capacity! e.g. 1 m2
R&D for treating irrigation water required !
Image: http://ideastoenlighten.files.wordpress.com/2010/02/solar_heater1.jpg Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
50 L/day
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UVc – Irradiation ●
Highest microbicidal activity at 254 nm
●
Emitted by low- or high-pressure mercury vapor lamps
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Pathogens and their various structures differ in their sensitivity 1000 to 2500 J/m2 (= 100 to 250 mJ/cm2) recommended!
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Affected by the quality of the irrigation water (turbidity, color, organic content, iron etc.) – measured as T10-value (% UVc transmission)
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UV-sensor to check the intensity (cleaning or replacing the radiators)
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Pre-Filtration essential (preferably < 20 micron)
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Modular Design e.g.: 200 W-radiator at 1.25 m3/h and T10 = 50 % producing 2000 J/m2 Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
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UVc – Irradiation Pros & Cons
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Highly efficient against relevant pathogens Wide range capacities Easy to install, to handle and to maintain
Efficiency drops with low transmission and bulb age Interaction with micro-nutrients (Fe-Chelates!) Medium to high cost Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
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UV-Photocatalytic Water Disinfection
UVA+B-radiation
Photocatalytic oxidation (mineralization) of organic compounds including pathogens on the surface of titanium dioxide nanoparticles.
(300-400 nm)
www.taguig.com/saferpinasproductpicinfo/photocatalytic.jpg Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
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Natural UV-source (sun-light)
http://static.materialsgate.de/thumb/u/xka4.jpg Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
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Artificial UV-Source (UVA+B-radiator)
R&D for treating irrigation water required !
stationary
mobile
Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected] Fortos by ourtesy of B. Alsanius
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Filtration ● "pre-filtration" Essential pre-requisite for all water decontamination technologies! Screen, disc, centrifugal, media filters
● Pathogen removal Membrane filtration Slow- or Bio-Filtration screen filter to remove coarse particles (e.g. peat) Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
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Slow- or Bio-Filtration
Supernatant
Filter Layer 80 to 120 cm filter sand (0 - 2 mm) or rock wool granulate
Drainage System
● water passes very slowly through the filter bed ● 10 to 30 cm/h filtration rate: 100 - 300 L/m2h ● mechanisms mechanical physico-chemical biological “Schmutzdecke” Schmutzdecke (filter skin or biofilm)
3 layers of graded gravel 5 µm Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
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Slow Sand Filtration in Practice
Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
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Slow Sand Filtration in Practice
Foto: Ufer et al. 2008 Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
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Slow Sand Filtration in Practice
Any water reservoir can completely or partially be converted into a slow sand filter.
Foto: Ufer et al. 2008 Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
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Cleaning after Clogging ● No back flush! ● Removal of the top layer (1 - 2 cm) ● Raking
Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
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Slow- or Biofiltration Pros & Cons
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Low cost Low energy Construction simple
(considering site-specific requirements)
"Bio"-Technique
Not sufficient against viruses and nematodes Area consumption Risk of clogging
Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
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Point of Action (e.g. for ebb and flow)
chemical treatments CAUTION !
all methods Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
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Chemical Water Decontamination ● Ozone ● Hydrogen Peroxide ● Chlorine Dioxid
Oxidants
● Chlorine ● Other chemicals (Cu, Cu Ag, Br, Zn etc.)
Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
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Chlorination Gaseous Chlorine (Cl2) Calcium Hypochlorite (Ca(OCl)2 Sodium Hypochlorite (NaOCl)
Hypochlorous Acid
HOCl "active" or "free" chlorine Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
ECA-Water (electrochemically activated water) EO-Water (electrolyzed oxidized water) membrane electrolysis -
+
Catholyte
Anolyte NaOH
HOCl
H2O2 H2 and other
Cathode
O3 O2 H2O2 ClO2 Cl2 HCl HClO3
and other
(ECA-water)
Anode
membrane
Water
Water + NaCl or KCl (saturated brine solution)
Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
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ECA-Water in Practice
e.g.: 4.5 g/l "active chlorine" (HOCl) KCl
Photo: www.brinkman.nl/ecaunit/Ecaunit.jpg Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
Dosing of Chlorine has to consider the "active chlorine" ● No "standard" concentration often 2 to 4 ppm "active chlorine" is effective against bacteria and many fungal spores phytotoxicity can occur at 3 ppm already; No damage on woody plants up to 50 ppm
● Efficiency reduced by Short exposure time High pH (HOCl
ClO-)
Organic material (chlorine demand) Due to the chlorine demand a higher concentration must be provided at the inlet (e.g. 5 ppm to get 2 ppm = 3 ppm demand)
● Concentration at the point of action (e.g. water outlet) has to be monitored !
Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
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Chlorination Pros & Cons
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Low cost Suitable for small and big volumes Easy to fit into an existing irrigation system Residual effects Selective efficacy Affected by organics (chlorine demand) and pH Time dependent Risk of phytotoxicity Risk of toxic by-products
(trihalomethanes; e.g. chloroform)
Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
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Chlorine Dioxide (ClO2)
Cl O
O
● Chlorine dioxide is not "Chlorine" ● Water soluble gas (not transformed to HOCl) ● Strong oxidant ● Effective concentration: < 1 ppm (bacteria and sensitive fungal spores)
● Short exposure time (90%
1h
2h
4h
24 h
Ralstonia solanacearum
2 4
97 96
100 100
100 100
100 100
Erwinia carotovora
2 4
96 97
100 100
100 100
100 100
Clavibacter michig. ssp. michig.
2 4
54 65
91 94
98 98
100 100
Xanthomonas hort. pv. pelargonii
1 2 4
46 3 13
65 97 100
68 100 100
Agrobacterium tumefaciens
1 2 4
14 2 54
26 48 89
51 76 100
35 100 100
Fusarium oxysp. f.sp. cyclaminis conidia
1 2 4
16 28 65
30 54 84
56 78 92
58 82 94
** ** **
**) not tested Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
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Efficacy of Copper Phytophthora on Gerbera (Ebb and Flow System) 100 90 80
dead plants (%)
70 60
0.07 ppm Cu
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0.28 ppm Cu
40 30 20 10 0 FeSO4
FeHEEDDTA
Data from: Toppe & Thinggaard, 1998 Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
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Cu-Ionization Pros & Cons
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Low cost technique Easy to install, handle and maintain Low and very big volumes possible Residual effects
Selective efficacy Long reaction times Limited scientific proof in practical use Phytotoxicity at higher concentrations and long term application unclear
Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
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Economy not easy to compare - dependent on conditions at the production site
● Pasteurization ● UV-Irradiation ● Slow Filtration ● Chem. Treatm.
ca. 1.60 €/m3 ca. 1.40 €/m3 ca. 0.20 €/m3 < 0.10 €/m3
1 € ≈ 1.3 $
Data from: Jordbruksverket; Jordbruksinformation 4-2007, Sweden and various providers Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
The Best Treatment ?
Pasteurization UV-Irradiation Slow Filtration Chemical Treatments
Dependent on: ● Crop and Target Organism ● Cultivation and Irrigation System ● Size and Distribution of Cultivation Areas ● Water Consumption and Storage Capacity ● Water Quality ● Economic Aspects
There is no "Best Treatment", however a "Best Solution" for a certain Production Site
Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]
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Questions, Comments … ?
Walter Wohanka Geisenheim Research Center Germany
[email protected]
Prof. Dr. Walter Wohanka, Geisenheim Research Center, e-mail:
[email protected]