Articles
EFFECT OF PEAT-BASED SUBSTRATE AND IRRIGATION CYCLES ON THE RESIDUAL ACTIVITY OF SODIUM HYPOCHLORITE
Article number
891_29
Pages
241 – 248
Language
English
Abstract
Recycling of irrigation water increases water use efficiency, but can also increase the risk of disease transmission to crops.
Water sanitation systems are therefore required that combine filtration, sanitizing chemicals or other technologies such as UV light to reduce pathogen and organic load.
The objective of this study was to evaluate the persistence of the sanitizing chemical sodium hypochlorite (using Clorox® Regular-Bleach) during irrigation events, and in the presence of a peat-perlite substrate.
In Experiment 1, free chlorine concentration dropped within
30 min from 2 mgL-1 to near 0 mgL-1 following addition of 0.2 g (dry weight) of a (70% peat-30%perlite) substrate to 1 L of chlorinated water, and total chlorine dropped from 2 to 0.3 mgL-1. Initial solution ORP (730 mV) and pH (8.3) decreased with addition of increasing amounts of peat-perlite.
In Experiment 2, 500 ml of 2 or 4 mg.L-1 free chlorine solution was top-irrigated onto the peat-perlite substrate in 15-cm-diameter (1225 ml) azalea pots.
Free and total chlorine concentrations were measured close to zero in the 155 ml of leachate collected from the bottom of the pot.
In Experiment 3, chlorine solution was applied through sub-irrigation to 15-cm-diameter pots containing peat-perlite.
Approximately 25% of the irrigation solution was absorbed by pots, and the concentration in the collection tank dropped from an initial 2 to 1.2 mgL-1 free chlorine in the first sub-irrigation cycle, dropping to 0.3 mgL-1 with a second irrigation cycle.
With each sub-irrigation cycle, there was an increase in both chemical oxygen demand (14.4 to 45.7 mgL-1 from irrigation cycle 0 to 3) and total suspended solids (0 to 18.3 mgL-1). Results emphasize the rapid decrease in chlorine efficacy with increasing organic load, and the need for both filtration and real time monitoring of chlorine concentration or ORP.
Water sanitation systems are therefore required that combine filtration, sanitizing chemicals or other technologies such as UV light to reduce pathogen and organic load.
The objective of this study was to evaluate the persistence of the sanitizing chemical sodium hypochlorite (using Clorox® Regular-Bleach) during irrigation events, and in the presence of a peat-perlite substrate.
In Experiment 1, free chlorine concentration dropped within
30 min from 2 mgL-1 to near 0 mgL-1 following addition of 0.2 g (dry weight) of a (70% peat-30%perlite) substrate to 1 L of chlorinated water, and total chlorine dropped from 2 to 0.3 mgL-1. Initial solution ORP (730 mV) and pH (8.3) decreased with addition of increasing amounts of peat-perlite.
In Experiment 2, 500 ml of 2 or 4 mg.L-1 free chlorine solution was top-irrigated onto the peat-perlite substrate in 15-cm-diameter (1225 ml) azalea pots.
Free and total chlorine concentrations were measured close to zero in the 155 ml of leachate collected from the bottom of the pot.
In Experiment 3, chlorine solution was applied through sub-irrigation to 15-cm-diameter pots containing peat-perlite.
Approximately 25% of the irrigation solution was absorbed by pots, and the concentration in the collection tank dropped from an initial 2 to 1.2 mgL-1 free chlorine in the first sub-irrigation cycle, dropping to 0.3 mgL-1 with a second irrigation cycle.
With each sub-irrigation cycle, there was an increase in both chemical oxygen demand (14.4 to 45.7 mgL-1 from irrigation cycle 0 to 3) and total suspended solids (0 to 18.3 mgL-1). Results emphasize the rapid decrease in chlorine efficacy with increasing organic load, and the need for both filtration and real time monitoring of chlorine concentration or ORP.
Authors
Jinsheng Huang, D.P. Meador, D.B. Decio, P.R. Fisher
Keywords
chlorine, bleach, disinfestation, disinfection, ORP, Oxidation Reduction Potential, sanitation, suspended solids, water treatment
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