Ozonation Of Seawater Research Articles

Semicontinuous and batch ozonation combined with peroxymonosulfate for inactivation of microalgae in ballast water

The Ballast Water Management Convention (BWMC) establishes limits regarding the permissible number of viable organisms in discharged ballast water. Ozone as a ballast water treatment is interesting because it can be generated in-situ and has strong oxidant power. Additionally, some oxidants can be formed in reaction with seawater, especially brominated compounds, that assist in inactivating microorganisms. The objective of this study is to assess the efficacy of semicontinuous and batch ozonation as well as their combination with peroxymonosulfate salt (PMS) as methods to be used to ensure compliance with regulation D2 of the BWMC using Tetraselmis suecica as a standard microorganism. Growth modeling method was employed to determine the inactivation achieved by the treatments. The results show that ozone is an effective treatment for accomplishing the D2 of the BWMC. Batch ozonation is more efficient than semicontinuous ozonation probably because of the brominated compounds formed during the ozone saturation of the water. The oxidants that are developed during the ozonation of seawater prolong the residual effect of the treatment throughout the days of storage with practically no presence of them in the ballast tanks at 72 h. The addition of the PMS increases the inactivation in the semicontinuous ozonation, but a threshold concentration of ozone is needed to observe the synergistic effect of both oxidants. No increase is associated with the combination of O3 and PMS in the case of batch ozonation.

Comparison of the bacterial viability assessments for the disinfected quarantined water along with an effect of total residual oxidants.

The water discarded from the quarantine station inspecting aquatic products can be served as an influx channel of invasive microorganisms to our own ecosystem. This study thus compared the viability of three different pathogenic bacteria (Escherichia coli, Vibrio harveyi, and Enterococcus faecalis) in either seawater or freshwater after their disinfection. For that, they were treated by ozonation (2.08mM of ozone), ultraviolet irradiation (UVC-254), or thermal treatment (90℃) for 10min, during which their resultant viability was monitored using colorimetric ATP assay, colony counting, and real-time quantitative RT-PCR. From this, ATP measurement and real-time quantitative RT-PCR have proved to be a much stronger correlation built in the fraction of each of their assays versus the colony counting, although they differed in the type of disinfection implemented. Especially, ATP assay was the most sensitively influenced by high levels of total residual oxidants(TRO) undesirably produced during the ozonation of V. harveyi and E. faecalis in seawater, although easily and shortly measured within 1h, with higher accuracy. Aside from that, the real-time quantitative RT-PCR had a stronger correlation versus either that of seawater ozonation or thermal treatment. It is decided referring to measurement time and convenience in the field that ATP assay can be more reliably used in bacterial cell viability measurement in the quarantine after the ozonation in seawater to specifically allow the bacterial deactivation, not to overwhelmingly produce TRO due to the residual ozone provided.

해수 오존처리시 브로민 생성과 소독효과

Pathogenic and/or invasive organisms are problematic in ballast water, desalination plants and aquaculture systems for both ecological and economic reasons. In a desalination plant, the presence of microorganisms can lead to biofouling of the ultrafiltration and seawater reverse osmosis membrane equipment. Meanwhile, in the aquaculture industry, some pathogenic organisms cause serious fish diseases, which can result in mass die-offs. Various disinfection techniques such as ozonation, ultraviolet irradiation, electrolysis and chlorination, have been applied to remove pathogenic organisms from seawater environments. The purpose of this study was to develop a kinetic model for the prediction of residual ozone and bromine concentrations in seawater following ozonation, taking into consideration the ozone dose, water salinity, and pH. Ozone chemistry in saltwater is considerably different from that in fresh water because saltwater contains much higher concentrations of dissolved anions and cations (e.g., chloride, bromide, magnesium, sulfate) than fresh water. Salinity greatly affects the formation of residual ozone and bromine during saltwater ozonation. Unlike freshwater ozonation, there is no hydroxyl radical formation in seawater ozonation because ozone decomposition is considerably faster in water containing bromide. Therefore, seawater ozonation involves the initial unstable oxidant (ozone) and a secondary, more stable oxidant (bromine) for disinfection. This study also aimed to evaluate the performance of ozone and bromine disinfection using E. coli. The log inactivation of E. coli with ozone and bromine was 2.5 and 4 log, respectively. The log inactivation of E. coli with seawater ozonation was 5.8 log.

Implications of hydrogen peroxide on bromate depression during seawater ozonation

The presence of hydrogen peroxide (H2O2) in ozonation process can resist the formation of carcinogenic bromate (BrO3¯) efficiently, and the bromate depression is closely related with background water qualities, especially in high bromide-containing seawater. In this study, the freshwater and seawater were selected to investigate the effects of H2O2 on ozone (O3) decomposition kinetics, bromide transformation and bromate depression, and the evolutions of BrO3¯ under different scavengers were explored to speculate the primary bromate formation pathways. The results showed that the initial O3 half-live period (t1/2-O3) in seawater was only one-sixth of that in freshwater, and its attenuation rate increased analogously with the increase of H2O2 concentration in both freshwater and seawater. The H2O2 could promote the formation of BrO3¯ via hydroxyl radical (•OH) based bromate pathways, nevertheless higher concentration of H2O2 facilitated the reduction of HOBr/OBr¯ back to Br¯, resulting in 87.0% and 73.2% of BrO3¯ retardment in freshwater and seawater, respectively. The suppression ratios of BrO3¯ were up to 48.4% and 35.3% in freshwater with the addition of •OH and •O2¯ scavengers, and the corresponding depressions in seawater decreased to 35.3% and 12.7%, indicating that •OH was dominant on bromate formation when the concentration of residual ozone was adequate to generate some bromine intermediates, meanwhile H2O2 and •O2¯ functioned as the key reductants for bromate depression. Based on these results, the Br¯ transformation mechanisms via O3, •OH, H2O2, and •O2¯ reactions were speculated, and the feasibility of H2O2-ozonation was verified for the treatment of high Br¯-containing seawater.

Oxidation of Florfenicol and Oxolinic Acid in Seawater by Ozonation

There has been an increase in the use of antibiotics by the aquaculture industry in marine aquaculture for the prevention of diseases in fish. Antibiotics in the water discharged into the sea without treatment can cause disturbances to the marine ecosystem. Therefore, there is a need for research on how the removal of antibiotics used in aquaculture can be achieved. In this study, the removal of two types of antibiotics (florfenicol, FF, and oxolinic acid, OA) used in the aquaculture industry, by ozonation, was evaluated. Currently, there is a lack of research studies on FF and OA removal from seawater by ozonation. Seawater ozonation shows a significantly different oxidation mechanism as compared to that of freshwater. The high amount of Br− in seawater (60 mg/L) allows for a rapid reaction with ozone to produce bromine (HOBr/OBr−) at a rate of 160 M−1s−1. To predict the removal efficiency of antibiotics by ozone and bromine, the species-specific rate constants for the reaction of FF and OA with ozone and bromine were determined. The predicted removal efficiencies of FF and OA using measured rate constants were verified by the ozonation process in water containing bromide ions in similar concentrations as in seawater. The result for FF indicated less than 10% removal during 20 min, with the rate constants of FF with ozone and bromine being 3.2 M−1s−1 and 3.5 M−1s−1, respectively. However, the removal of OA using ozonation was approximately 99% or higher within 90 s. In the presence of bromide ions, approximately 60% of OA was removed by trace ozone within 15 s, and approximately 30% of OA was removed by the generated bromine after 15 s. Comparing the removability of FF and OA used in aquaculture by ozone, it was observed that FF was more difficult to remove because of its low reaction rate constant. Meanwhile, the reaction rates of OA with ozone and bromine were 2.4 × 103 M−1s−1 and 4.0 × 102 M−1s−1, respectively. At the beginning of the reaction, OA was removed by the trace ozone. Subsequently, OA was removed by the generated bromine after the ozone was decomposed.

Enhancement of ozonation of seawater-based wastewater containing pharmaceutical compounds by total residual oxidants: Salinity, ammonia, and organic matter

The ozonation process has recently been proposed as an effective treatment method for removing pharmaceutical compounds from seawater-based wastewater discharged from fish farms or hatcheries. Seawater ozonation can lead to the production of secondary stable oxidants such as bromine (HOBr/OBr−), which can be expressed as a total residual oxidants (TRO) owing to the high reaction rate constant with respect to ozone and bromide ion. TRO formation depends on water quality, in terms of aspects such as salinity, ammonia, and organic matter content; therefore, it is important to understand the variations in the ozone chemistry of bromide-containing water by considering the factors influencing TRO formation. In addition, the removal of pharmaceutical compounds in bromide-containing water should be evaluated owing to the different oxidation efficiency between TRO and pure aqueous ozone. This study aims to investigate the factors influencing the formation of TRO and the removal of pharmaceutical compounds during the ozonation of bromide-containing water. The results show that salinity increased the TRO formation rate by 6%, while ammonia and organic matter decreased the TRO formation rate by 51% and 39%, respectively. The removal efficiency of pharmaceutical compounds by TRO was higher compared with that by only ozone. Ammonia and organic matter inhibited the ozonation of bromide-containing water. These results indicate that TRO can be broadly used in the field of seawater ozonation; however, additional case studies on the removal of pharmaceutical compounds from seawater-based wastewater are needed to elucidate the oxidation mechanisms of various TRO.

Seawater ozonation: effects of seawater parameters on oxidant loading rates, residual toxicity, and total residual oxidants/by-products reduction during storage time

ABSTRACTThe efficacy of ozonation in different seawater conditions provides an improvement in the water quality and promotes the increment of dissolved oxygen. By-products (bromine, bromate, and bromoform) formation is directly proportional to the ozonation time. Ozone-produced oxidants remain toxic in both closed and dark containers for at least 4 days; however, during long storage period (35 days) in dark and cold conditions, these residual oxidants decrease slowly. These results have practical implications for both the installation of ozone systems on ships ballast water or for recirculating aquaculture system for inactivating undesirable organisms present in seawater.

Formation of Bromate and Chlorate during Ozonation and Electrolysis in Seawater for Ballast Water Treatment

Many effective technologies have been developed and approved for ballast water treatment, and the effectiveness of a process should be evaluated considering its environmental friendliness. The aim of this study was to evaluate the formation and formation mechanisms of bromate (BrO3−) and chlorate (ClO3−) in seawater during ozonation, electrolysis, and a combined (ozonation/electrolysis) process. In seawater ozonation, BrO3− was generated exceeding a 5 mg/L ozone dose despite the high Br− (65 mg/L). The formation of BrO3− and ClO3− by electrolysis depended on the electrode materials where two types of electrodes (IrO2/Ti and Pt/Ti) were used. The combined (ozonation/electrolysis) process generated much higher levels of BrO3− and ClO3− than either individual process. In ozonation or electrolysis, mixed oxidant including HOCl/OCl− and HOBr/OBr− is the main parameter for inactivation, which is called total residual oxidant, TRO. In this study, a predictive model for BrO3− and ClO3− was suggested in terms of TRO formation. This predictive model can recommend allowable TRO (generated by ozonation or electrolysis) for practical applications in seawater treatment.

오존발생기와 저온 유전체장벽 플라즈마를 이용한 오존 발생 및 살균력

Ozone concentrations in water and air, and resulting disinfective properties, were measured following generation by either an ozone generator or a low-temperature dielectric barrier discharge plasma generator. In freshwater, ozone concentrations of 0.81 and 0.48 mg/L were observed after the ozone and plasma generators had been operated for five minutes, respectively. Higher levels of dissolved were attained more easily with the ozone generator. In seawater, both systems were capable of creating concentrations greater than 3.00 mg/L after 5minutes of operation. Higher ozone levels were attained more easily in seawater than in freshwater. Rates of bacterial sterilization in seawater after three minutes were 96% and 88%, using the plasma and ozone generators, respectively. In freshwater, higher concentrations of ozone were released into the atmosphere by the ozone generator than by the plasma generator. In creating equivalent levels of dissolved ozone in freshwater, the plasma generator released 4.5 times more ozone into the atmosphere than did the ozone generator. This shows that ozone generators are more effective than plasma generators for creating ozonated water. For the same concentration of dissolved ozone in seawater, more ozone was released into the atmosphere using the ozone generator than using the plasma generator. Therefore, with regard to air pollution, plasma generators seem to be less expensive than ozone generators.

Inactivation characteristics of ozone and electrolysis process for ballast water treatment using B. subtilis spores as a probe

Since ballast water affects the ocean ecosystem, the International Maritime Organization (IMO) sets a standard for ballast water management and might impose much tighter regulations in the future. The aim of this study is to evaluate the inactivation efficiency of ozonation, electrolysis, and an ozonation–electrolysis combined process, using B. subtilis spores. In seawater ozonation, HOBr is the key active substance for inactivation, because of rapid reactivity of ozone with Br− in seawater. In seawater electrolysis, it is also HOBr, but not HOCl, because of the rapid reaction of HOCl with Br−, which has not been recognized carefully, even though many electrolysis technologies have been approved by the IMO. Inactivation pattern was different in ozonation and electrolysis, which has some limitations with the tailing or lag-phase, respectively. However, each deficiency can be overcome with a combined process, which is most effective as a sequential application of ozonation followed by electrolysis.

Disinfection of Seawater: Application of UV and Ozone

Ozone and ultraviolet technologies are proposed as potential disinfecting agents for seawater. Ozone doses were applied in the range 0.38 to 4.89 mg O3 L−1. They permit to observe a complete disinfection as well as UV doses superior to 320 J L−1. Impacts of both processes on organic matter were also studied. UV absorbances were reduced in both cases but in higher proportion using ozone (up to 50% removal). Total organic carbon was slightly reduced by UV radiation, and ozonation achieves up to 10% mineralization. Ozone reaction proceeds with biochemical oxygen demand increase. Seawater ozonation, in addition, leads to the formation of residual oxidants that show an inhibitory effect on autochthonous microorganisms.

Formation of haloacetic acids, halonitromethanes, bromate and iodate during chlorination and ozonation of seawater and saltwater of marine aquaria systems

This manuscript addresses identification, analysis, formation and occurrence of key disinfection byproducts (DBPs) formed during chlorination and/or ozonation of both natural seawater (NSW), and synthetic high- and low-bromide saltwater (HBSW and LBSW, respectively). In this study, several groups of water disinfection byproducts were studied, including haloacetic acids (HAAs), halonitromethanes (HNMs), bromate and iodate. Three different water systems were studied including filtered natural seawater (NSW, ca. 64.9mgL−1 Br−), a high-bromide (Br−) saltwater (HBSW, ca. 24.8mgL−1 Br), and low-Br− saltwater (LBSW, ca. 4.3mgL−1Br). Because ozone reacts with Cl− to form free chlorine in seawater and salt water systems, similar DBP patterns were observed for both chlorine and ozone oxidants. The results revealed that some HAAs and HNMs are formed at greater than 100μgL−1 concentrations and are greatly affected by water constituents and formulations when treated with chlorine and ozone. The results showed that in low-Br− water salt water, chlorinated HAAs and HNMs predominated, while much greater concentrations of brominated HAAs and HNMs were produced in both natural and synthetic higher Br− saltwater. Concentrations of bromate and iodate were strongly impacted by factors other than Br− and I− concentrations including whether the system was open or closed.

Risks of seawater ozonation in recirculation aquaculture – Effects of oxidative stress on animal welfare of juvenile turbot ( Psetta maxima, L.)

Ozone is frequently used for water treatment and disinfection in recirculating aquaculture systems. However, due to the fragmentary data on chronic toxicity of ozone produced oxidants (OPO) and its safe concentrations, the daily application of ozone in aquaculture is challenging. To evaluate the chronic effects of sublethal OPO concentrations, juvenile turbot ( Psetta maxima, L.) were exposed to OPO concentrations of 0.06, 0.10 and 0.15 mg/l for 21 days. Gills were analysed for histopathological alterations and mRNA expression of heat shock protein 70 (hsp70), hsp90 as well as glutathione-S-transferase (gst) were determined in the gills and the liver after 1 d, 7 d and 21 d. Histopathologic findings confirmed adverse effects at 0.10–0.15 mg/l, but these (necrosis, lamellar clubbing, hypertrophy, hyperplasia) could only be observed after an extended exposure (mostly 21 d), and were considered as irreversible tissue damage. Hsp70 expression in the gills was only significantly increased at the highest OPO concentration (0.15 mg/l) on 1 d and 7 d, and returned to basic levels until day 21. Hsp90 mRNA was already increased at 0.10 mg/l after 1 and 7 days of exposure, and again was comparable to the control group on day 21. In contrast, elevated gst mRNA expression was only observed on day 7 at 0.10 mg and 0.15 mg/l. Although similar trends were observed in the liver for all markers, differences were only significant in exceptional cases due to the high individual variation observed. Thus, mRNA expression in the gills rather than in the liver is recommended as a marker to characterize OPO-induced oxidative stress in turbot. It has to be noted that mRNA expression returned to basic levels on day 21 regardless the actual OPO concentration, suggesting a collapse of adaptive mechanisms as a possible explanation for the observed tissue damage.

Seawater ozonation and formalin disinfection for the larval culture of eastern rock lobster, Jasus ( Sagmariasus) verreauxi, phyllosoma

The effects of seawater disinfection with continuous ozonation or with daily formalin treatment during flow-through culture, on the survival, growth, bacteriology and histology of eastern rock lobster, Jasus ( Sagmariasus) verreauxi, phyllosoma were determined. Survival from hatch to Instar II was highest and bacterial abundance was least in low ozonated seawater (containing 5 ppb ionised bromine, Br). By contrast, at high ozonation (45 ppb Br) and medium ozonation (15 ppb Br), 77% and 69% of larvae, respectively, suffered deformities at the moult to Instar II and starved to death. Histological examination of phyllosoma showed no differences in cuticular epithelium thickness but the digestive gland tissue of moribund deformed phyllosoma had significantly thinner tubule epithelium, the lumen was dilated, B-cells were more abundant and there was greater separation between the cuticular epithelium and distal tip of digestive gland tubules. In unozonated (Control) water, 66% of larvae died during Instar II probably resulting from a possible Vibrio infection. In a second experiment, survival to Instar III was highest at low ozonation or no ozonation without addition of formalin (0 ppm). Bacterial numbers were lowest in low ozonation with 0 ppm formalin treatments, compared to daily treatment with formalin at 10 ppm or above. A concentration of 250 ppm formalin killed all larvae by Instar III. In a final experiment, larval survival between Instar III to VI in low ozonated seawater was approximately 80% at formalin levels of 0 to 80 ppm, whereas all larvae treated with 160 ppm formalin died shortly after Instar V. Disinfection improved survival by minimising bacterial disease for the culture of phyllosoma to Instar VI without interrupting growth and development. The present study established that the optimum treatment for the culture of phyllosoma to Instar VI appeared to be low ozonation (5 ppb Br) with 10 ppm formalin.

Histological and physiological alterations in juvenile turbot ( Psetta maxima, L.) exposed to sublethal concentrations of ozone-produced oxidants in ozonated seawater

Ozone is a powerful oxidizing agent and is widely used for disinfection and improvement of water quality in aquaculture plants. However, the generation of ozone-produced oxidants (OPO) during ozonation of seawater may lead to toxicity impacts. To determine adverse effects of continuous, sublethal OPO concentrations, juvenile turbot ( Psetta maxima, L.) were exposed to three different OPO concentrations (0.06, 0.10 and 0.15 mg/l) for up to 21 days. Fish were sampled after 1, 7 and 21 days of exposure to cover short-term, intermediate and long-term OPO effects. Gills were analyzed for morphological alterations, hemoglobin and hematocrit were quantified to assess loss in gill functionality. Plasma cortisol was measured as physiologic stress marker. Gill histology revealed significant histopathological alterations with increasing OPO concentration and prolonged times of exposure. However, hemoglobin concentrations were only elevated during short-term exposure at the highest OPO concentration. Hematocrit values did not show any differences between OPO-exposed specimens and the control group. At 0.15 mg/l, plasma cortisol was elevated after 24 h. The results demonstrate that sublethal OPO concentrations of 0.10 and 0.15 mg/l cause histological and physiological alterations in juvenile turbot, characterising ozone-produced oxidants as substantial stressor in recirculation systems. At an OPO concentration of 0.06 mg/l, just slight alterations in the tested parameters were observed suggesting concentrations of ≤ 0.06 mg/l as acceptable OPO levels for the rearing of juvenile turbot.

Recolonization by heterotrophic bacteria after UV irradiation or ozonation of seawater; a simulation of ballast water treatment

Transport of ballast water with ships represents a risk for introduction of foreign species. If ballast water is treated during uptake, there will be a recolonization of the ballast water by heterotrophic bacteria during transport. We investigated survival and succession of heterotrophic bacteria after disinfection of seawater in the laboratory, representing a model system of ballast water treatment and transport. The seawater was exposed to ultraviolet (UV) irradiation, ozone (2 doses) or no treatment, incubated for 16 days and examined with culture-dependent and -independent methods. The number of colony-forming units (CFU) was reduced below the detection level after disinfection with UV and high ozone dose (700 mV), and 1% of the initial level for the low ozone dose (400 mV). After less than 3 days, the CFU was back or above the starting point for the control, UV and low ozone treatment, whereas it took slightly more than 6 days for the high ozone treatment. Disinfection increased substrate availability and reduced cell densities. Lack of competition and predation induced the recolonization by opportunistic bacteria (r-strategists), with significant increase in bacterial numbers and a low diversity (based on DGGE band pattern). All cultures stabilized after the initial recolonization phase (except Oz700) where competition due to crowding and nutrient limitation favoured bacteria with high substrate affinity (K-strategists), resulting in higher species richness and diversity (based on DGGE band pattern). The bacterial community was significantly altered qualitatively and quantitatively and may have a higher potential as invaders in the recipient depending on disinfection method and the time of release. These results have implications for the treatment strategy used for ballast water.

Decay properties of ozone in seawater and its sterilization effects

Decay properties of ozone in seawater and its sterilization effects

Effects of seawater ozonation on biofilm development in aquaculture tanks

Microbial biofilms developing in aquaculture tanks represent a reservoir for opportunistic bacterial pathogens, and procedures to control formation and bacterial composition of biofilms are important for the development of commercially viable aquaculture industries. This study investigated the effects of seawater ozonation on biofilm development on microscope glass slides placed in small-scale aquaculture tanks containing the live feed organism Artemia. Fluorescence in situ hybridization (FISH) demonstrated that ozonation accelerated the biofilm formation cycle, while it delayed the establishment of filamentous bacteria. Gammaproteobacteria and Alphaproteobacteria were the most abundant bacterial groups in the biofilm for both water types, but ozonation influenced their dynamics. With ozonation, the bacterial community structure was relatively stable and dominated by Gammaproteobacteria throughout the experiment (21–66% of total bacteria). Without ozonation, the community showed larger fluctuations, and Alphaproteobacteria emerged as dominant after 18 days (up to 54% of total bacteria). Ozonation of seawater also affected the dynamics of less abundant populations in the biofilm such as Betaproteobacteria, Planctomycetales and the Cytophaga/Flavobacterium branch of phylum Bacteroidetes. The abundance of Thiothrix, a bacterial genus capable of filamentous growth and fouling of larvae, increased with time for both water types, while no temporal trend could be detected for the genus Vibrio. Denaturing gradient gel electrophoresis (DGGE) demonstrated temporal changes in the dominant bacterial populations for both water types. Sequencing of DGGE bands confirmed the FISH data, and sequences were related to bacterial groups commonly found in biofilms of aquaculture systems. Several populations were closely related to organisms involved in sulfur cycling. Improved Artemia survival rates in tanks receiving ozonated water suggested a positive effect of ozonation on animal health. Although the used ozonation protocol did not hinder biofilm formation, the results suggest ozonation as a promising approach for manipulation of bacterial populations in aquaculture systems, which can prove beneficial for cultured animals.

Modeling the effect of iodide distribution on ozone deposition to seawater surface

Spatial changes in the dry deposition of ozone to the sea surface associated with ozone uptake by the dissolved iodide ions were analyzed in the northwestern Gulf of Mexico using the Community Multiscale Air Quality Model (CMAQ). The dry deposition module in CMAQ was modified using a formula developed by Chang et al. [2004. Ozone deposition to the sea surface: chemical enhancement and wind speed dependence. Atmospheric Environment 38, 1053–1059], which accounts for chemical enhancement by iodide reacting with ozone in seawater. In addition, an attempt was made to incorporate iodide concentrations from the satellite-derived estimates of near-surface chlorophyll a concentrations into the CMAQ gridded fields. One-month CMAQ simulations conducted with the modified module including iodide reaction showed a significant increase in the dry deposition velocity of ozone onto the sea surface, especially Texas and Louisiana Coast corresponding to the area with high iodide concentrations. On average, about 70% enhancement of ozone dry deposition velocity over the seawater was attributed to the iodide effect alone and the rest is mostly due to the effects of wind. The enhanced deposition velocity by iodide effect led to the marked increase in dry deposition amounts mostly near the coast, resulting in some changes in ambient ozone concentration. Interestingly, a small decrease in deposition amounts was found just inland from the shoreline, indicating that the iodide interaction can also affect ozone concentration in the inland coastal area. An in-depth analysis of a 2-day simulation showed the iodide effects on changes in the spatiotemporal distributions of the ozone deposition and concentration, which are highly dependent on coastal winds.

Ozonation of seawater improves the survival of larval southern rock lobster, Jasus edwardsii, in culture from egg to juvenile

Phyllosoma larvae of the southern rock lobster, Jasus edwardsii, were cultured from egg to juvenile. For larvae reared from hatch to Stage III, survival was highest and bacterial contamination was lowest in seawater ozonated at low and moderate levels (400 and 500 mV oxidation–reduction potential, ORP). By contrast, at high ozonation (600 mV), all larvae suffered deformities at the moult to Stage II and terminally starved, while in unozonated water (about 300 mV), all larvae died at Stage III probably as a consequence of Vibrio bacteria proliferation. In a second experiment between Stages VI to VIII, larval survival was highest in ozonated water that had been filtered through activated charcoal and coral sand, compared to ozonated water with no filtration or filtered only through activated charcoal. Ozonated water with the combined filtration was used subsequently but there were ongoing deformities, so the level was progressively reduced from 400 mV at Stage VIII to 330 mV at Stage X, at which time ozonation was discontinued. Larvae were then cultured in unozonated water to metamorphosis of eight pueruli at 377 to 437 days after hatch, of which two survived to juvenile. Ozonation was thus effective up to Stage IX in improving culture water to minimise bacterial disease without problems of larval deformities.