Aquaculture Water Quality and the Affect of Ozone
(To obtain more information on recirculating aquaculture systems, a complete set of tables, figures and references shown on this and related pages please refer
to the book "Recirculating Aquaculture Systems, 2nd Edition", M. B. Timmons, et al, 2002, Cayuga Aqua Ventures, Ithaca, NY. You can obtain a copy of the
publication from Cayuga Aqua Ventures by visiting their website at www.c-a-v.net.)
Dissolved Organic Matter
Dissolved organic carbon (DOC) is, by convention, defined as total organic carbon (TOC) after filtration through a 0.45
m membrane filter. In freshwater supplies, humic substances originating from the terrestrial environment are often the
most significant contributor to the DOC, conferring a brownish-yellow color on the water. In wastewater, proteins,
carbohydrates, lipids, and organic amines will elevate the concentration of DOC. Oxidizing disinfectants like ozone will
lose bactericidal strength through reaction with organic matter. The reaction products will generally have weak or no
bactericidal activity. Hoigne (1988) has shown that aqueous ozone reactivity can be ascribed to two mechanisms: direct
reactions involving molecular ozone and reactions of active hydroxyl-radical intermediates produced by ozone
decomposition.
Humic substances of natural waters are relatively resistant to ozonation. Sufficient contact time will produce small
amounts of acetic, oxalic, formic and terephthalic acids, phenolic compounds and carbon dioxide. Generally, ozonated
organic matter is more biodegradable than the original compounds. The instantaneous ozone demand of surface waters
with DOC content of 2.5–3.5 mg/L has been reported to be in the range of 0.50–0.75 mg/L (Roustan et al. 1998).
Surface water ozone demands of 0.4–0.5 mg ozone/mg DOC after 5 min of exposure at pH 7.5 was found by Graham
(1999). The ozonolysis of carbon-carbon double bonds in organic molecules is an example of an ozone-demanding
reaction.
Inorganic Compounds
Oxidizing disinfectants will react with inorganic compounds in accordance with their oxidation potential. Ozone will be
involved in several redox reactions due to its high oxidation potential. Metal and heavy metal ions are oxidized to form
stable compounds with low solubility. Ferrous and manganeous ions will react to ferric and manganic ions, respectively,
which in turn will react with OH- to form an insoluble precipitate. Bromide will be oxidized to bromate through several
intermediary steps, while the reaction with chloride is limited by poor kinetics. The conversion of ammonia to nitrite is a
slow, pH-dependent, first order reaction, while the nitrite is rapidly oxidized to nitrate. The latter reaction may have a
significant effect on ozone disinfection capacity in wastewater treatment systems with incomplete nitrification. Venosa
(1983) reports that as much as 2 mg/L ozone was required to oxidize 1 mg/L of nitrite-N.
pH
Extreme pH values may inactivate microorganisms, or limit their growth. The activity of many disinfectants depends on
pH. Small changes in the hydrogen ion concentration may influence the disinfection performance. The pH dependence
of the biocidal activity of ozone is not clear. Reduced effect at high pH towards poliovirus and rotavirus as well as the
cysts of the parasite Naegleria gruberi has been observed (Vaughn et al. 1987; Wickramanayake et al. 1991). However,
the opposite relation was evident for Giardia muris cysts, which were more sensitive at pH 9 than at pH 5 and 7
(Wickramanayake et al. 1991). Changes in pH have little to no impact upon UV effectiveness.
Temperature
In general, the microbial inactivation rate by chemical disinfectants will increase with increasing temperature. Farooq et
al. (1977) found a higher degree of ozone inactivation of Mycobacterium fortuitum at elevated temperatures. On the
other hand, UV inactivation seems relatively insensitive to temperature. Negligible effects were observed in the range 5–
35C when pure cultures of E. coli, Candida parapsilosis and bacterial virus f2 were exposed to UV light in batch
reactors (Severine et al. 1983).
Additional information on ozone chemical reactions can found by following the link embedded in this line. The following
links on color removal and iron and manganese removal are primarily related to drinking water, but also provide general
information on ozone reactions for these materials.
(To obtain more information on recirculating aquaculture systems, a complete set of tables, figures and references shown on this and related pages please refer
to the book "Recirculating Aquaculture Systems, 2nd Edition", M. B. Timmons, et al, 2002, Cayuga Aqua Ventures, Ithaca, NY. You can obtain a copy of the
publication from Cayuga Aqua Ventures by visiting their website at www.c-a-v.net.)
Dissolved Organic Matter
Dissolved organic carbon (DOC) is, by convention, defined as total organic carbon (TOC) after filtration through a 0.45
m membrane filter. In freshwater supplies, humic substances originating from the terrestrial environment are often the
most significant contributor to the DOC, conferring a brownish-yellow color on the water. In wastewater, proteins,
carbohydrates, lipids, and organic amines will elevate the concentration of DOC. Oxidizing disinfectants like ozone will
lose bactericidal strength through reaction with organic matter. The reaction products will generally have weak or no
bactericidal activity. Hoigne (1988) has shown that aqueous ozone reactivity can be ascribed to two mechanisms: direct
reactions involving molecular ozone and reactions of active hydroxyl-radical intermediates produced by ozone
decomposition.
Humic substances of natural waters are relatively resistant to ozonation. Sufficient contact time will produce small
amounts of acetic, oxalic, formic and terephthalic acids, phenolic compounds and carbon dioxide. Generally, ozonated
organic matter is more biodegradable than the original compounds. The instantaneous ozone demand of surface waters
with DOC content of 2.5–3.5 mg/L has been reported to be in the range of 0.50–0.75 mg/L (Roustan et al. 1998).
Surface water ozone demands of 0.4–0.5 mg ozone/mg DOC after 5 min of exposure at pH 7.5 was found by Graham
(1999). The ozonolysis of carbon-carbon double bonds in organic molecules is an example of an ozone-demanding
reaction.
Inorganic Compounds
Oxidizing disinfectants will react with inorganic compounds in accordance with their oxidation potential. Ozone will be
involved in several redox reactions due to its high oxidation potential. Metal and heavy metal ions are oxidized to form
stable compounds with low solubility. Ferrous and manganeous ions will react to ferric and manganic ions, respectively,
which in turn will react with OH- to form an insoluble precipitate. Bromide will be oxidized to bromate through several
intermediary steps, while the reaction with chloride is limited by poor kinetics. The conversion of ammonia to nitrite is a
slow, pH-dependent, first order reaction, while the nitrite is rapidly oxidized to nitrate. The latter reaction may have a
significant effect on ozone disinfection capacity in wastewater treatment systems with incomplete nitrification. Venosa
(1983) reports that as much as 2 mg/L ozone was required to oxidize 1 mg/L of nitrite-N.
pH
Extreme pH values may inactivate microorganisms, or limit their growth. The activity of many disinfectants depends on
pH. Small changes in the hydrogen ion concentration may influence the disinfection performance. The pH dependence
of the biocidal activity of ozone is not clear. Reduced effect at high pH towards poliovirus and rotavirus as well as the
cysts of the parasite Naegleria gruberi has been observed (Vaughn et al. 1987; Wickramanayake et al. 1991). However,
the opposite relation was evident for Giardia muris cysts, which were more sensitive at pH 9 than at pH 5 and 7
(Wickramanayake et al. 1991). Changes in pH have little to no impact upon UV effectiveness.
Temperature
In general, the microbial inactivation rate by chemical disinfectants will increase with increasing temperature. Farooq et
al. (1977) found a higher degree of ozone inactivation of Mycobacterium fortuitum at elevated temperatures. On the
other hand, UV inactivation seems relatively insensitive to temperature. Negligible effects were observed in the range 5–
35C when pure cultures of E. coli, Candida parapsilosis and bacterial virus f2 were exposed to UV light in batch
reactors (Severine et al. 1983).
Additional information on ozone chemical reactions can found by following the link embedded in this line. The following
links on color removal and iron and manganese removal are primarily related to drinking water, but also provide general
information on ozone reactions for these materials.
Spartan Environmental Technologies
Air and Water Treatment
Air and Water Treatment
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Spartan Environmental
Technologies, L.L.C.
7383 Lauren J Dr
Mentor, OH 44060
USA
Phone: 800-492-1252
Fax: 440-368-3569
E-mail: info@
spartanwatertreatment.com
Technologies, L.L.C.
7383 Lauren J Dr
Mentor, OH 44060
USA
Phone: 800-492-1252
Fax: 440-368-3569
E-mail: info@
spartanwatertreatment.com