Article

Commissioning and optimization of an innovative system for electrolytic water disinfection in greenhouses

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Abstract

Tested in experimental scale, an innovative system for electrolytic water disinfection in greenhouses (SeWiG) was very efficient. It was developed by Humboldt-Universität zu Berlin and newtec Umwelttechnik GmbH. With scaling up this system for industrial greenhouses, the new technology will be tested, validated and optimized under practical conditions. The implemented technology will be incrementally scaled-up. After successful installation of the disinfection system within a separated part of an industrial greenhouse, two large-scaled greenhouses will use the on-site produced hypochlorite as a disinfectant for irrigation or drain water applied for vegetables and ornamental plants. The effects on plant growth, yield and product quality will be controlled and particular attention is paid to chlorate and perchlorate. Due to the first results, both pesticides are under the limits given by the European Commission. This can be related to the short dwell time of the disinfectant before dosing based on the on-demand production of fresh hypochlorite. Hypochlorite is dosed by the method of shock disinfection, which might decrease the accumulation of unwanted ingredients in plants. The special feature of the new system for electrolytic water disinfection is the functional superiority over common methods such as filtration, ultraviolet irradiation, heating, ozonation or chlorine dioxide. Worth highlighting is its high effectiveness against plant viruses and the reduced risk for users, plants and the environment while less energy is needed, compared to other disinfection systems. Besides a reduced formation of algae biofilm, a reduced application of fertilizers is expected. All parameters mentioned before will be monitored within this study.

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Technical Report
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Technical Report
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EU legislation, laid down in the Water Framework Directive, demands to minimize emissions of nitrogen, phosphate and crop protection products to achieve an excellent chemical and ecological quality in 2015. The aim is to force growers to a better water and disease management. Supply water of excellent chemical quality will have to be recirculated as long as possible, for which adequate disinfection equipment have to be used. Several sources of water are used as supply water. Rainwater is chemically best, followed by reverse osmosis water. However, the latter is rather expensive. Tap water and surface water often have a too high salinity, while well water may vary dramatically from place to place. Rainwater and surface water are potential risk factors for importing soil-borne pathogens. Disinfection of the recirculating nutrient solution can be done adequately by heat treatment and UV radiation. Membrane filtration performs well, but is mostly too costly. Chemical treatments as sodium hypochlorite, chlorine dioxide and copper silver ionization may partly solve the pathogen problem, but introduce a potential accumulation of other elements in closed systems. Hydrogen peroxide, chlorine dioxide and sodium hypochlorite perform better to clean pipe work instead of soil-borne pathogens.
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Microalgae have high potential to remove inorganic nutrients from wastewater and to produce biodiesel. Effects of nitrogen and phosphorus concentrations on growth, nutrient uptake, and lipid accumulation of a freshwater microalga Scenedesmus sp. LX1 were studied. Scenedesmus sp. LX1's growth was in accordance with the Monod model. The following Monod parameters were obtained: the N- and P-saturated maximum growth rate was 2.21 x 10(6) cells m L(-1)d(-1), and the half-saturation constants of N and P uptake were 12.1 mg L(-1) and 0.27 mg L(-1), respectively. In the nitrogen/phosphorus ratio of 5:1-12:1, 83-99% nitrogen and 99% phosphorus could be removed. In conditions of nitrogen (2.5 mg L(-1)) or phosphorus (0.1 mg L(-1)) limitation, Scenedesmus sp. LX1 could accumulate lipids to as high as 30% and 53%, respectively, of its algal biomass. The lipid productivity/unit volume of culture, however, was not enhanced. Further research should be made on how to enhance both lipid content and lipid productivity.
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Chemical control of Phytophthora cinnamomi in irrigation water
  • P Armitage
Armitage, P. (1993). Chemical control of Phytophthora cinnamomi in irrigation water. Aust. Hortic. 91, 30-36.
Treating irrigation systems with chlorine
  • G A Clark
  • A G Smajstrla
Clark, G.A., and Smajstrla, A.G. (1992). Treating irrigation systems with chlorine. Foliage Dig. 15, 3-5.
Characterization of Erwinia populations from nursery retention ponds and lakes infecting ornamental plants in Florida
  • D J Norman
  • J M F Yuen
  • R Resendiz
  • J Boswell
Norman, D.J., Yuen, J.M.F., Resendiz, R., and Boswell, J. (2003). Characterization of Erwinia populations from nursery retention ponds and lakes infecting ornamental plants in Florida. Plant Dis. 87 (2), 193-196 https://doi.org/10. 1094/PDIS.2003.87.2.193. PubMed
Control of several fungi in the recirculating hydroponic system by modified slow sand filtration
  • K W Park
  • G P Lee
  • M S Kim
  • S J Lee
  • M W Seo
Park, K.W., Lee, G.P., Kim, M.S., Lee, S.J., and Seo, M.W. (1998). Control of several fungi in the recirculating hydroponic system by modified slow sand filtration. Weonye Gwahag Gisulji 16, 347-349.
Managing Water in Plant Nurseries: a Guide to Irrigation, Drainage and Water Recycling in Containerised Plant Nurseries
  • C Rolfe
  • W Yiasoumi
  • E Keskula
Rolfe, C., Yiasoumi, W., and Keskula, E. (2000). Managing Water in Plant Nurseries: a Guide to Irrigation, Drainage and Water Recycling in Containerised Plant Nurseries, 2 nd edn (Orange: NSW Agriculture).
Information and External Relations Division of the United Nations Population Fund
  • Unfpa
UNFPA. (2011). State of World Population 2011. People and Possibilities in a World of 7 Billion (New York: Information and External Relations Division of the United Nations Population Fund), https://www.unfpa.org.