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Dannehl D.,Humboldt University of Berlin | Schuch I.,Humboldt University of Berlin | Gao Y.,newtec Umwelttechnik GmbH | Cordiner S.,The New Zealand Institute for Plant and Food Research Ltd | Schmidt U.,Humboldt University of Berlin
Gesunde Pflanzen | Year: 2015

Physical and chemical disinfection methods are used or are under investigation in greenhouse facilities to minimize the occurrence of pathogens and the application of pesticides in recirculating systems. Since the most of these methods differ in their effectiveness, more investigation is needed to produce healthy plants in a sustainable way. Therefore, the present study is focused on the identification of interactions between hypochlorite (ClO−) used as a disinfectant for a recirculating system and algae formation, spread of microorganisms, as well as plant development. As such, on-site produced potassium hypochlorite (1 % KClO) solution were supplemented using proportional injection control once a week for 90 min, as a disinfectant, into a recirculating tomato production system (NFT) until a free chlorine concentration of 1 mg L−1 (D I) and 2 mg L−1 (D II) were reached, respectively. The formation of the algae biofilm was reduced by 15 % (D I) and 48 % (D II). These treatments also suppressed cultivated microorganisms up to 100 %. Tomato plants exposed to the treatment D I showed a comparable plant height to the control plants after 7 weeks, whereas D II led to a significant increase in plant height of 12 cm. However, the formation of leaves was more pronounced by treatment D I. After a growing period of 7 weeks, a significant difference in leaf number up to 2.9 leaves per plant was calculated compared to the other treatments. The same treatment had the largest positively impact on the fruit yield and number of fruit, which were increased by 10 and 15 %, respectively, compared to the control plants. Under consideration of all results, the most promising effects of ClO− as a disinfectant for hydroponic systems were achieved with a free chlorine concentration of 1 mg L−1 (D I), where phytotoxic effects can be excluded. © 2015, Springer-Verlag Berlin Heidelberg. Source


Dannehl D.,Humboldt University of Berlin | Schuch I.,Humboldt University of Berlin | Gao Y.,newtec Umwelttechnik GmbH | Cordiner S.,The New Zealand Institute for Plant and Food Research Ltd | Schmidt U.,Humboldt University of Berlin
European Food Research and Technology | Year: 2015

Recently, official food surveillance discovered high residues of chlorate (ClO3−) and perchlorate (ClO4−) in different plant-based foods, which was the start of a big discussion in the EU Commission. There is currently no knowledge about possible ClO3− uptake quantities in vegetable, when hypochlorite (ClO−) is used as a disinfectant in plant production facilities. Therefore, the present study is focused on the identification of interactions between ClO− applications and ClO3− accumulations in fruit, as well as findings in terms of suitable concentrations of ClO− to ensure food safety. Primary and secondary metabolites were analyzed as well. As such, on-site produced potassium hypochlorite (1 % KClO) solution was supplemented using proportional injection control once a week for 90 min, as a disinfectant, into a recirculating tomato production system (NFT) until a free chlorine concentration of 1 mg L−1 (D I) and 2 mg L−1 (D II) was reached, respectively. The chlorate (ClO3−) content in fruit increased from 0.01 mg (Control) to 0.22 mg (D I) and 0.25 mg ClO3− kg−1 FW (D II). A critical assessment of these values is given in the discussion section. Contrary to the expectations, a co-occurrence of ClO3− and ClO4− in fruit was not found. Compared to the control, the fruit contents of lycopene were increased by 21.3 % (D I) and 33.5 % (D II) and those of ß-carotene by 9.2 % (D I) and 23.9 % (D II), when calculated on a fresh weight basis. These results changed slightly when these substances were calculated on a dry weight basis. Furthermore, ClO3− induced stress in fruit. In this context, a significant correlation (r) and a significantly increased slope (m) compared to zero were found between ClO3− and lycopene (r = 0.74; m = 0.10), as well as ß-carotene (r = 0.70; m = 0.01). The content of soluble solids and that of titratable acids remained unaffected. © 2015 Springer-Verlag Berlin Heidelberg Source


Wagner M.,DVGW Technologiezentrum Wasser TZW | Burandt B.,Institute For Luft Und Kaltetechnik Dresden | Fischer M.,DVGW Technologiezentrum Wasser TZW | Petzoldt H.,DVGW Technologiezentrum Wasser TZW | And 2 more authors.
GWF, Wasser - Abwasser | Year: 2012

This work describes the potential of a decentralized multi effect desalination unit. The focus laid in the long term determination of the desalination efficiency, the elimination of organic algal toxins and the control of microbiological water parameters. For disinfection an inline-electrolysis unit was used the first time. The desalination of the water was working with high efficiency over the whole control period. The elimination of sea water algal toxins was sufficient. Without disinfection no clear reduction of biological contamination of the water was obtained. On the other hand, the pre-disinfection by inline chlorination decreased the colony numbers at 22°C and 36°C very efficiently. In conclusion, the reliability of the technique could be demonstrated. For permanently and safe production of drinking water by this equipment further research and development is necessary to achieve the marketability of the process. Source

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