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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

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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]