Total Residual Oxidant Research Articles

The efficacy of ozonated seawater for surface disinfection of haddock (Melanogrammus aeglefinus) eggs against piscine nodavirus

Piscine nodavirus, also known as viral nervous necrosis (VNN), is a lethal, vertically transmitted virus that causes severe mortality in fish. It affects primarily marine species, including cultured haddock (Melanogrammus aeglefinus). Ozone has been used successfully to disinfect Atlantic halibut (Hippoglossus hippoglossus) eggs against nodavirus. Fertilized eggs from different species of fish can tolerate varying levels of dissolved ozone, so specific exposure levels need to be determined for individual species. The objectives of this study were to investigate the tolerance of newly fertilized haddock eggs to dissolved ozone and to determine if this exposure is sufficient to disinfect against piscine nodavirus. Eggs were exposed to an ozone concentration of 3.0(±0.3)mg/l of total residual oxidants (TRO) of Cl2 for CT units (TRO×duration of exposure in min, mg/l/min) of 0, 5, 10, 15, 20, 25, 30, 40 and 50. A decrease in survival was observed when the exposure exceeded 30CT units. Following this, other fertilized haddock eggs were submerged in nodavirus suspensions with densities of 102.5 and 103.5/0.1ml TCID50 units for 30min, followed by exposure to ozonated seawater at a concentration of 3.0mg/l for CT units of 0, 10, 20 and 50. Viable VNN was detected by cell culture using striped snakehead (SSN-1) cell lines. The positive controls (exposed to 0CT units) all tested positive for nodavirus, while all but one of 24 egg samples exposed to ozonated seawater tested negative. This indicates that ozone can be successfully used to disinfect haddock eggs against nodavirus at a concentration of 3(±0.3)mg/l TRO as Cl2 for 3.3–6.7min.

High resistance of fish pathogenic viruses to UV irradiation and ozonated seawater

Important fish pathogenic viruses, including infectious pancreatic necrosis virus (IPNV), Atlantic halibut nodavirus (AHNV) and infectious salmon anaemia virus (ISAV), were exposed to ultraviolet (UV) irradiation or ozonated seawater in a laboratory model system. Inactivation curves were obtained, and the occurrence of oxidants and ozonation by-products (OBP), including their removal by granular activated carbon (GAC) filtration, was studied. In ISAV, 99.9% inactivation was obtained by an UV dose of 7.7mJ/cm2. The corresponding figures for AHNV and IPNV were 105 and 246mJ/cm2, respectively. In ozonated seawater, total residual oxidants (TRO) were assayed by the DPD colorimetric method. The CT value (the product of TRO concentration and contact time) was calculated from the average TRO concentration (as mg Cl2/l) during the respective contact time (s). 90% reductions in virus titers were obtained by CT values of 1.4(mgs)/l for ISAV, 1000(mgs)/l for AHNV and 1944(mgs)/l for IPNV. The results of this study demonstrate a wide span in UV and TRO resistance among the viruses tested. ISAV was sensitive to both methods, while high resistance in AHNV and IPNV was experienced. The TRO resistance in IPNV and AHNV contradict earlier published results and suggests reconsideration of existing ozonation practise to inactivate these viruses in seawater. Considerably higher CT values than previously reported seem to be required. These discrepancies in results between studies clearly demonstrate the need for development of a standard procedure to conduct inactivation experiments and to develop improved analytical techniques to determine individual oxidants in seawater. Of the detected carcinogenic OBPs, bromate was found in concentrations of 50 and 70μg/l after a contact time of 20 and 80min, respectively, at a TRO concentration of 0.9mg/l. Bromoform was the only trihalomethane (THM) found in significant amount. The bromoform concentration of 16.4μg/l measured after 80min contact time was reduced to 1.6μg/l by GAC filtration with an empty bed contact time (EBCT) of 4.2min. TRO and bromate was reduced below the detection limit after GAC filtration. However, long-term filtration experiments were not conducted. Such experiments should be conducted to determine the adsorptive capacity of GAC for bromate- and THM-removal in ozonated seawater.

Measurement of dissolved ozone in sea water: A comparison of methods

Dissolved ozone levels in sea water can be quantified using various iodometric methods, the colourmetric N, N-diethyl- p-phenylenediamine (DPD) method, or by measuring oxidation/reduction potential (ORP). Dissolved ozone concentrations in sea water can be expressed in mg/l of total residual oxidants (TRO), ozone produced oxidants (OPO), residual ozone concentration (ROC) and ozone. This study compared commonly cited methods of ozone measurement for their ability to measure dissolved ozone and the ease with which they can be applied on-site in an aquaculture facility. The different units for expressing dissolved ozone concentrations were also examined. It is recommended that under non-laboratory (i.e., hatchery) conditions, a DPD ‘total chlorine test’ be used to measure dissolved ozone levels, and that the results be reported in TRO in terms mg/l of Cl 2.

Effectiveness of the sulfur(IV) compound, sodium bisulfite, in reducing chlorine, chlorine dioxide, and chlorite toxicity to Daphnia magna in well water and pond water

Flow-through toxicity tests were conducted with Daphnia magna to determine the residual toxicity of chlorine, chlorine dioxide, and chlorite after treatment with the sulfur(IV) compound sodium bisulfite. Daphnids were exposed separately to 0.5-mg/L concentrations of each of the three compounds without the addition of sodium bisulfite, with a low stoichiometric dose of sodium bisulfite, and with a high stoichiometric dose of sodium bisulfite. Tests were performed in well water with a low total organic carbon (TOC) content and pond water with a high TOC content. Analysis of results indicated that sodium bisulfite did not eliminate the toxicity of chlorine dioxide or chlorite to D. magna. Total residual oxidant (TRO) concentrations were reduced and survival times were extended, but acute toxicity persisted even with a S(IV) concentration 10.0 times the stoichiometric ratio of oxidant. Mortality occurred in chlorine dioxide treatments in which no TRO was detected, indicating that standard analytical (amperometric) techniques may be inadequate to detect toxicity. Sodium bisulfite did succeed in eliminating chlorine toxicity except in pond water receiving a low (3.0x) sodium bisulfite dose. Oxidant reactions with organic substrates may have produced chlorinated residuals that were resistant to S(IV) dechlorination.

Effect of Ozone Treatment on Cultures of Nannochloropsis oculata, Isochrysis galbana, and Chaetoceros gracilis

AbstractThis research evaluated ozone treatment of three unicellular algal species commonly used in the culture of marine larvae. Isochrvsis galbana and Nannochloropsis oculata were found to be resistant to total residual oxidants (TRO); whereas, Chaetoceros gracilis was relatively sensitive to TRO. Isochrvsis galbana remained in log‐phase growth after treatment with 0.05 mg/L to 0.50 mg/L TRO, and N. oculata exhibited strong growth after being exposed to TRO levels up to 0.67 mg/L. Only TRO levels of 0.92 mg/L and 0.90 tng/L reduced cell counts of N. oculata and I. galbana, respectively. Furthermore, algal cultures having higher concentrations at the time of ozone treatment may respond more favorably to the treatment. Initially, C. gracilis was reduced in cell count at TRO levels above 0.06 mg/L, but log‐phase growth was resumed 2 d after exposure to TRO levels as high as 0.31 mg/L. It is concluded that I. galbana and N. oculata can be successfully treated with ozone in the mass production stages without hampering the timely production of concentrated cultures. Although C. gracilis was found to be relatively sensitive, ozone treatment of starter cultures can be performed routinely with this species. We have demonstrated that ozone treatment of algal cultures is a feasible technique, but studies need to be conducted on ozone treatment of other species of unicellular algae and on ozone treatment of varying concentrations of algae in order to enhance the applications of this technique. Also, in order to determine the extent of disinfection of algal cultures, bacterial and viral composition of the cultures should be evaluated in future studies.

Effects of intermittent halogenation on settlement, survival and growth of the zebra mussel, Dreissena polymorpha

The effect of intermittent (2–4 h/day) treatments with chlorine or bromine at levels of 0.5 and 1.0 mg/L (total residual oxidant) upon settling and growth of veliger larvae of the zebra mussel, Dreissena polymorpha, was examined in two successive flow-through studies. The work was conducted in a field laboratory which received a constant supply of water from western Lake Erie. Veliger densities in the water at the field site peaked at 530/L, while mussel densities on settling monitors reached 147,100/m2 over the course of the two studies (early July to late September 1991). In Study 1, a 2-h daily treatment with 1.0 mg/L chlorine reduced mussel settling by 91% as compared with controls, although mussel densities of up to 6,000/m2 still occurred. Treatment with 0.5 mg/L chlorine for 4 h/day produced a similar reduction in mussel settling during the second study. Bromine was less effective than chlorine at reducing settling of veligers. Mussels which remained settled in the treatment tanks had growth rates similar to controls, reaching 2–4 mm in length over a 30-day period. The intermittent halogen treatments similarly had no effect on whole body glycogen levels or growth of adult D. polymorpha. The intermittent chlorination regime used may therefore delay, but would not prevent a mussel fouling problem.

The effect of ultraviolet irradiation, heat, pH, ozone, salinity and chemical disinfectants on the infectivity of white spot syndrome baculovirus

The virucidal effects of ultraviolet (UV) irradiation, heat, pH, ozone, salinity and some chemical disinfectants on white spot syndrome baculovirus (WSBV) were investigated by infectivity assay using juvenile black tiger prawn, Penaeus monodon. WSBV became completely non-infectious after 60 min UV irradiation (9×10 5 μW s/cm 2). WSBV was rendered non-infectious by 55°C and 70°C heat treatment within 90 min and 5 min, respectively. WSBV was also completely inactivated by high acidity, pH 1 for 10 min, pH 3 for 1 h and by high alkalinity, pH 12 for 10 min at RT (25°C). The effective concentration for ozone to reduce WSBVs infectivity to zero was 0.5 μg/ml as a total residual oxidant for 10 min at RT. WSBV was inactivated by contact for 10 min at RT with a final concentration of 100 ppm of sodium hypochlorite and povidone iodine and 75 ppm of benzalkonium chloride. Sodium chloride in concentrations ranging from 0–10% had no virucidal effect on the infectivity of WSBV.

海藻（スサビノリ殻胞子）を用いた生物検定による都市下水の塩素代替消毒処理水の毒性比較

Chlorination of secondary effluents produce strong toxic substance such as monochloramine or oxidant on growth of aquatic organisms. Therefore, alternative disinfection methods to chlorination should be considered. However, the effect of effluents disinfected with the alternatives on seaweed has not been clarified. In this study, the toxicity of secondary effluents disinfected with chlorine (NaOCl), chlorine dioxide (ClO2), ozone (O3), and ultraviolet rays (UV) were investigated by bioassay using Porphyra yezoensis conchospores. Secondary effluents used in this study were disinfected with disinfectants or rays which inactivated coliform groups in secondary effluents of 99.9%. Lowest-observed-effect concentrations (LOECs) of secondary effluents disinfected with NaOCl, ClO2, and O3 for germination ratio of conchospores were 1.0, 10, and 100% of effluent concentration, respectively. The toxicity of effluents disinfected with NaOCl and ClO2 were very strong. In contrast, the effluents disinfected with UV rays did not affect the germination of conchospores. The toxicity of effluents disinfected with NaOCl, ClO2, and O3 were considered to depend on initial total residual oxidant (TRO). Dechlorination with Na2SO3 of effluents disinfected with NaOCl or ClO2 did not affect the germination of conchospores, even in 100% of effluent concentration.

Tolerance of the rotifer Brachionus plicatilis to ozone and total oxidative residuals

Live prey items, such as the rotifer Brachionus plicatilis, are an essential component of many marine larval production systems. However, in intensive larval rearing systems live food items are also a potential source of pathogens which could adversely affect survival of the larvae. Consequently, it would be advantageous to reduce or eliminate potential pathogens associated with rotifers and their culture water prior to feeding. Ozone is a strong oxidizing agent which can be utilized as a disinfectant. Ozone is utilized extensively by commercial operators for disinfection and treatment of culture water, but there is limited data on tolerance of rotifers to ozone, residual oxidants associated with using ozone in seawater and the efficacy of an ozone wash. This study sought to evaluate the effects of exposing rotifers to ozone and/or residual oxidants associated with the use of ozone in seawater. Under the described conditions, the rotifer was found to be sensitive to ozonated seawater, both as total residual oxidants (TRO) consisting of ozone, chloramines and bromamines and residual oxidants (RO) excluding ozone. A “no observable effect concentration” (NOEC) of 0.22 mg/L TRO was determined for maximum survival of the rotifers. High levels of ozone (≥ 1.63 mg/L) were found to inactivate rotifer eggs. Based on published values of the inactivation of bacterial and viral pathogens, a NOEC of 0.22 mg/L TRO would appear to be sufficient to inactivate a variety of surficial potential pathogens. Consequently, the utilization of an ozone bath is suitable for the surficial disinfection of rotifers prior to feeding and hence may help reduce the vertical transmission of potential pathogens. Although RO did not appear as toxic as TRO, rotifers were sensitive to RO remaining in seawater after the dissipation of ozone. A NOEC of 0.3 mg/L for a 1 min exposure or 0.5 mg/L for a 5 or 10 min exposure time was observed for RO. Due to potential adverse effects of RO, it is recommended that RO be neutralized if ozone‐treated water is to be used to culture rotifers.

人工海水中における低濃度オキシダントの魚類病原微生物に対する殺菌・不活化効果

The disinfectant effects of total residual oxidants (TROs) produced by ozonization of artificial seawater on fish pathogenic bacteria and viruses were investigated. A dose of0.1mg TROs/l was not stable in natural seawate, but was stable in artificial seawater with a bromine compound (sodium bromide). By the treatment with TROs of 0.1mg/l for 30 to 120 seconds, more than 99.9% of viable cells of Vibrio anguillarum, Aeromonas salmonicida, A. caviae, A. hydrophila, and Escherichia coli were killed, and 99.9% of infectivity of hirame rhabdovirus (HIRRV), infectious hematopoietic necrosis virus (IHNV), infectious pancreatic necrosis virus (IPNV), and yellowtail ascites virus (YAV) were inactivated. HIRRV was more than 99.7% inactivated by a treatment with a dose of 3.5g/m3 of ozone gas bubbles for 1 min.

Dechlorination Equipment Development for Shipboard Pollution Prevention

ABSTRACTBiological fouling (biofouling) of ship seawater cooling system components has been a persistent problem at several Navy homeport locations. Dockside electrolytic chlorination for biofouling control in ship seawater cooling systems is being utilized at Submarine Base (SUBASE) and Shipyard Pearl Harbor, Hawaii. However, the discharge of chlorine into Pearl Harbor is regulated by the Environmental Protection Agency (EPA) and the State of Hawaii under the National Pollutant Discharge Elimination System (NPDES). Current State of Hawaii discharge standards of 0.1 mg/L chlorine as total residual oxidant (TRO) for two hours a day is, along with its upstream concentration, not wholly effective in controlling biofouling in seawater cooling system components. In addition, more stringent regulation of chlorine point‐source discharge into marine waters by the EPA and state environmental protection agencies is anticipated. In response to these requirements, the Navy has developed a portable dechlorination unit for use shipboard. This unit injects a sulfur‐based dechlorination chemical that mixes with, and chemically binds the chlorine, making the resulting TRO discharge acceptable under current regulations.A team of scientists from the Naval Research Laboratory (NRL) and CHEM‐corr Consultants conducted a concept ship evaluation (SHIPEVAL) of a prototype dechlorination unit aboard the USS Indianapolis (SSN 697) during the period 12–23 September 1994 at SUBASE Pearl Harbor, Hawaii. Results indicate that sodium bisulfite injection downstream of SSN 697 auxiliary sea water (ASW) system heat exchanger components, at an approximate treatment ratio of 2.5:1 was fully effective in dechlorinating 0.1 mg/L TRO to zero prior to system discharge. Lessons learned from the SHIPEVAL will be utilized to develop a fleet‐ready, portable dechlorination unit for use at various Navy homeport locations.

Effect of chemical and physical treatments on the inactivation of striped jack nervous necrosis virus (SJNNV)

The effects of some chemical disinfectants, organic solvents, hydrogen ions, heat, ultraviolet (UV) irradiation and ozone on the inactivation of striped jack nervous necrosis virus (SJNNV) were investigated. SJNNV was inactivated by contact with a final concentration of 50 ppm of sodium hypochlorite, calcium hypochlorite, benzalkonium chloride and iodine for 10 min at 20 °C. Cresol concentrations of more than 10 000 ppm were required to inactivate SJNNV, and no inactivation of SJNNV by formalin was detected at any concentration tested. The effective concentrations of ethanol and methanol were 60% and 50%, respectively, but SJNNV was resistant to ether and chloroform. SJNNV was inactivated by high alkalinity, pH 12 for 10 min at 20 °C, and also inactivated by heat treatment at 60 °C for 30 min. Inactivation of SJNNV by UV irradiation was observed at an intensity of 410 μW cm −2 for 244 s. Ozone at 0.1 μg ml −1 as a total residual oxidant was required to inactivate SJNNV for 2.5 min. Washing fertilized eggs and the treatment of sea water with ozone decreased the rate of occurrence of VNN.

有害物質・障害生物の水環境への影響と制御 淡水産植物プランクトンの増殖阻害試験によるモノクロラミンと塩素殺菌下水処理水の毒性評価

Monochloramine (NH2Cl) which is a highly toxic pollutant is usually contained in chlorinated sewage effluents. Effects of NH2Cl and chlorinated sewage effluent on freshwater ecosystem were investigated by an algal growth test using a green alga Selenastrum capricornutum.Toxicity of NH2Cl for the alga was stronger than that of free chlorine, and NH2Cl was extremely stable in freshwater. Lowest-observed-effect concentration (LOEC) of NH2Cl after 96 hours exposure was 0.01 mg-Cl2l-1. Comparison of chlorinated effluents with non-chlorinated effluents, the algal growth was inhibited significantly in chlorinated effluents. The final chlorinated effluents collected from the sewage treatment plant also affected the growth of alga, and about 80% of total residual oxidants in the effluents was detected as NH2Cl. On the contrary, the algal growth was not inhibited in dechlorinated effuents with Na2SO3 because of disappearance of the residual oxidant. Judging from these results, it was clear that NH2Cl was the most important pollutant in chlorinated wastewater effluents for aquatic organisms.

Application of ozone disinfection to remove Enterococcus seriolicida, Pasteurella piscicida, and Vibrio anguillarum from seawater.

Survival of bacterial fish pathogens, including Enterococcus seriolicida, Vibrio anguillarum, and Pasteurella piscicida, in ozonated seawater was determined in a batch system. Bacterial counts of all fish pathogens decreased at more than 0.040 to 0.060 mg of total residual oxidants (TROs) per liter, whereas no decrease in viable counts was observed at less than 0.018 to 0.028 mg of TROs per liter. The 99% inactivation point was achieved at concentrations of 0.111 mg/liter for E. seriolicida, 0.063 mg/liter for P. piscicida, and 0.064 mg/liter for V. anguillarum within 1 min. Moreover, the mean 99 and 99.9% killing concentration-contact time (C.t) products were 0.123 and 0.186 mg.min/liter for E. seriolicida, 0.056 and 0.084 mg.min/liter for P. piscicida, and 0.081 and 0.123 mg.min/liter for V. anguillarum, respectively. However, the mean 99 and 99.9% C.t products for the mixed population in coastal seawater were 0.200 and 0.621 mg.min/liter. These results strongly suggest that ozone treatment at more than 1.0 mg of TROs per liter for several minutes is able to disinfect seawater for mariculture efficiently.

Effects of dechlorinated seawater on fish behavior

Behavioral responses to chemically dechlorinated seawater were studied using two species of marine fish associated with power plant discharge areas off Southern California. Opaleye ( Girella nigricans) neither avoided nor were attracted to chlorinated seawater containing 0·1 mg/liter total residual oxidants (TRO) which had been dechlorinated using equimolar or excess sodium thiosulfate. Blue-banded goby ( Lythrypnus dalli) did not avoid dechlorinated seawater initially containing 0·1 or 0·9–1·0 mg/liter TRO. Previously it has been shown that opaleye avoided chlorinated seawater with oxidant concentrations of 0·1 mg/liter and blue-banded gobies avoided 0·9–1·0 mg/liter TRO. Elimination of chlorine-produced oxidants by thiosulphate dechlorination resulted in 100% survival in both species. The toxicological implications of exposure to dechlorinated seawater are discussed.

Behavioural responses of selected marine fishes to chlorinated seawater

Behavioural responses to chlorinated seawater were studied in the laboratory using eight species of fish (topsmelt, Atherinops affinis [Ayres]; pile perch, Rhacochilus vacca [Girard]; señorita, Oxyjulis californica [Günther]; blacksmith, Chromis punctipinnis [Cooper]; northern anchovy, Engraulis mordax [Girard]; opaleye, Girella nigricans [Ayres]; bluebanded goby, Lythrypnus dalli [Gilbert] and mussel blenny, Hypsoblennius jenkinsi Jordan and Evermann) which occur near the Units 7 and 8 discharge of Southern California Edison's Redondo Beach Steam Generating Plant in King Harbor, California, USA. All species except Engraulis demonstrated prolonged avoidance of chlorinated quadrants of the behaviour chamber. The avoidance thresholds were species-specific and species totally avoided estimated total residual oxidant (TRO) concentrations from 0·094 to 0·456 mg/litre. Calculated significant avoidance thresholds averaged 0·066 mg/litre TRO; young Atherinops significantly avoided TRO concentrations as low as 0·028 mg/litre ( p < 0·001). The highest avoidance thresholds were exhibited by sedentary species and were modified by the presence of cover inside the behaviour chamber. The avoidance response protected against mortality in all species except Lythrypnus and Engraulis.

Physiological responses of a marine fish exposed to chlorinated seawater at concentrations near its avoidance threshold

To determine if avoidance of chlorinated seawater by fish resulted in physiological protection from toxicity, studies were carried out which assessed (a) changes in the routine oxygen consumption rate and (b) the ability of treated fish to successfully compete with untreated conspecifics for a limited food resource. Temperate marine damselfish, Chromis punctipinnis, were exposed to stepwise increasing levels of chlorinated seawater in a behaviour chamber and avoided total residual oxidant (TRO) levels greater than 0·15-0·16 mg/litre. Cumulative exposures ranged from the equivalent of 0·38-5·23 in at 1·0/litre TRO. One day after exposure, routine oxygen consumption rates were decreased by 25 to 45% from pre-exposure rates and were correlated with the cumulative oxidant exposure. One month post exposure, respiration rates returned to pre-treatment levels. This transient depression of the respiratory rate did not affect survival or growth of chlorine-treated fish which were forced to compete with untreated conspecifics for a restricted food supply.

Sea urchin sperm bioassay for sewage and chlorinated seawater and its relation to fish bioassays

Bioassays were conducted with sea urchin and sand dollar sperm to determine the toxicity of chlorinated and unchlorinated sewage effluent and chlorinated and brominated seawater. The sperm cells were exposed to seawater dilutions of each toxicant for 5–15 min. The fertilisation of eggs served as the indicators of sperm viability. The effective concentrations which reduced fertilisation success by 50% (EC50) averaged 2·2 and 4·8% chlorinated and unchlorinated sewage in seawater, respectively. The sperm cells were extremely sensitive to chlorinated seawater at concentrations from 0·002 to 0·020 mg/litre total residual oxidant (TRO). Brominated seawater proved toxic to sperm in one test at 0·015 mg/litre TRO. Results of the sperm bioassays are compared with previous acute and chronic bioassays with fish.

Chlorine speciation in seawater; a metastable equilibrium model for Cl I and Br I species

A thermodynamic model for the inorganic, fast-reacting fraction of the total residual oxidant produced by chlorination in marine waters reveals that Br I species are more stable than Cl I species. At typical amino-N levels, HOBr, NBr 3, and NHBr 2 predominate. Data on organic byproducts of chlorination generally support the model calculations.

Conditions D'Exploitation De La Méthode à La Diéthyl-P. Phénylénediamine Au Dosage Du Brome Libre Et/Ou Combiné En Milieu Marin

Abstract Free bromine and bromamine analysis by the diethyl-p. phenyl-lene-diamine (DPD) colorimetric method requires some care when chloride and bromide are present at seawater concentration. If no particular problem is encountered in mono and dibromamine determination, on the contrary the analysis of either free bromine or that of a free bromine and tribromamine mixture can induce errors of at least twenty per cent in the total residual oxidant concentration due to halogen loss. In order to prevent that phenomenon, iodide addition into the phosphate buffer and DPD mixture is necessary before the sample introduction. In these conditions the results are in good agreement with those of the phenol red method.