Total Residual Oxidant Research Articles

Enhancing the efficacy of electrolytic chlorination for ballast water treatment by adding carbon dioxide

We examined the synergistic effects of CO2 injection on electro-chlorination in disinfection of plankton and bacteria in simulated ballast water. Chlorination was performed at dosages of 4 and 6ppm with and without CO2 injection on electro-chlorination. Testing was performed in both seawater and brackish water quality as defined by IMO G8 guidelines. CO2 injection notably decreased from the control the number of Artemia franciscana, a brine shrimp, surviving during a 5-day post-treatment incubation (1.8 and 2.3 log10 reduction in seawater and brackish water, respectively at 6ppm TRO+CO2) compared with water electro-chlorinated only (1.2 and 1.3 log10 reduction in seawater and brackish water, respectively at 6ppm TRO). The phytoplankton Tetraselmis suecica, was completely disinfected with no live cell found at >4ppm TRO with and without CO2 addition. The effects of CO2 addition on heterotrophic bacterial growth was not different from electro-chlorination only. Total residual oxidant concentration (TRO) more rapidly declined in electro-chlorination of both marine and brackish waters compared to chlorine+CO2 treated waters, with significantly higher amount of TRO being left in waters treated with the CO2 addition. Total concentration of trihalomethanes (THMs) and haloacetic acids (HAAs) measured at day 0 in brackish water test were found to be 2- to 3-fold higher in 6ppm TRO+CO2-treated water than in 6ppm TRO treated water. The addition of CO2 to electro-chlorination may improve the efficiency of this sterilizing treatment of ballast water, yet the increased production of some disinfection byproducts needs further study.

Application of electrochemically treated seawater as basic culture media for mass cultivation of Tetraselmis suecica

Microalgae have increased in demand as raw materials for functional biomolecules and biodiesel production. Various physiological and technological approaches have been investigated for maximizing productivity of microalgae. In the present study, we investigated the optimal condition of electrolysis-based water treatment system (EWTS) applicable to mass culture of marine microalgae. The first step was an electrolysis-based chlorination process of seawater for the on-site generation of biocide solution, and the initial total residual oxidants (TROs) of 20 mg/L was sufficient to completely eliminate contaminating aquatic organisms regardless incoming seawater quality such as high total organic carbon within 24 h. The second step was neutralization of residual TRO to prevent toxicity against microalgae culture, and sodium thiosulfate of 36 mg/L was optimum against the highest estimate of TRO 20 mg/L. Tetraselmis suecica cultured in seawater from neutralized EWTS showed similar growth curve with autoclaved seawater both in laboratory and outdoor culture conditions, which suggested that EWTS could be applied as an effective tool for the generation of basic media for biomass production of microalgae in outdoor culture system.

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.

Ecotoxicological effects of ballast water effluent teated by an electrolytic method on marine environment

Ballast water effluent treated by an electrolytic method contains reactive chlorine species and disinfection by-products (DBPs). In this study, we conducted whole effluent toxicity (WET) testing and ecological risk assessment (ERA) to investigate its ecotoxicological effects on marine environment. WET testing was carried out for three marine pelagic organisms, i.e., diatom Skeletonema costatum, rotifer Brachionus plicatilis and fish Paralichthys olivaceus. The biological toxicity test revealed that S. costatum was the only organism that showed apparent toxicity to the effluent; it showed no observed effect concentration (NOEC), lowest observable effect concentration (LOEC) and effect concentration of 50% (EC50) values of 12.5%, 25.0% and 83.3%, respectively, at brackish water condition. In contrast, it showed insignificant toxicity at seawater condition. B. plicatilis and P. olivaceus also showed no toxicities to the effluent at the both salinity conditions. Meanwhile, chemical analysis revealed that the ballast water effluent contained total residual oxidants (TROs) below 0.03 μg/L and a total of 20 DBPs including bromate, volatile halogenated organic compounds (VOCs), halogenated acetonitriles (HANs), halogenated acetic acids (HAAs) and chloropicrin. Based on ERA, the 20 DBPs were not considered to have persistency, bioaccumulation and toxicity (PBT) properties. Except monobromoacetic acid, the ratio of predicted environmental concentration (PEC) to predicted no effect concentration (PNEC) of the other 19 DBPs did not exceed 1. Thus, our results of WET testing and ERA indicated that the ballast water effluent treated by electrolysis and subsequently neutralization was considered to have no adverse impacts on marine environment.

Inactivation of dinoflagellate Scripsiella trochoidea in synthetic ballast water by advanced oxidation processes

Ship-borne ballast water contributes significantly to the transfer of non-indigenous species across aquatic environments. To reduce the risk of bio-invasion, ballast water should be treated before discharge. In this study, the efficiencies of several conventional and advanced oxidation processes were investigated for potential ballast water treatment, using a marine dinoflagellate species, Scripsiella trochoidea, as the indicator organism. A stable and consistent culture was obtained and treated by ultraviolet (UV) light, ozone (O3), hydrogen peroxide (H2O2), and their various combinations. UV apparently inactivated the cells after only 10 s of irradiation, but subsequently photo-reactivation of the cells was observed for all methods involving UV. O3 exhibited 100% inactivation efficiency after 5 min treatment, while H2O2 only achieved maximum 80% inactivation in the same duration. Combined methods, e.g. UV/O3 and UV/H2O2, were found to inhibit photo-reactivation and improve treatment efficiency to some degree, indicating the effectiveness of using combined treatment processes. The total residual oxidant (TRO) levels of the methods were determined, and the results indicated that UV and O3 generated the lowest and highest TRO, respectively. The synergic effect of combined processes on TRO generation was found to be insignificant, and thus UV/O3 was recommended as a potentially suitable treatment process for ballast water.

선박평형수 처리를 위한 전기화학 반응에서 음극의 영향

Abstract In this study, we examined the effect of cathode from electrolysis reactor for treating ballast water. We are going to select a suitable cathode for seawater electrolysis after considering the effect on the generation of the oxidant of cathode and the electrode deposition materials adhering to the surface of cathode. Anode is Ru-Ti-Pd electrode and cathode are Ti, Pt, JP520 (Ni-Pt-Ce) electrodes. Using the cathode of the three types, experiments were conducted to examine the effects of TRO (total residual oxidants) generation concentration and RNO (N, N-Dimethyl-4-nitrosoaniline, indicator of the generation of OH radical) degradation concentration (in 1, 35 psu), ohmic drop, FESEM(field emission scanning electron microscope) observation of cathode surface and EDX (energy dispersive X-ray spectroscopy) measurements of attached fouling material. The results showed that TRO generation concentration and RNO degradation concentration in according to each type of cathode are not different. The attached fouling materials were observed on the surface of Ti and the JP520 electrode by the observation of SEM after electrolysis for two hours, but it was not observed on the surface of Pt electrode. When considering the surface ohmic drop of cathode and the attached fouling materials, Pt electrode was judged as the excellent cathode.

Evaluation of disinfection efficacy and chemical formation using MPUV ballast water treatment system (GloEn-PatrolTM)

This study was undertaken to evaluate the efficacy of inactivation of several indigenous marine species and the formation of oxidants and other by-products using medium-pressure ultraviolet (MPUV) ballast water treatment. The ballast water treatment system (BWTS) used in this study was composed of filtration modules as a pretreatment process, followed by a UV irradiation process equipped with a polychromatic MPUV lamp. The experiments were performed on seawater (Busan,>32 PSU) and brackish water (Nakdong River, 20–22 PSU) with flow rates of 50 and 250 m3/h. The disinfection efficacy of the system was evaluated using indigenous species (>50 μ m and 10–50 μ m) and surrogate microorganisms (E. coli and Enterococci group). The test results successfully met the D-2 regulation of the IMO (International Marine Organization). In addition, oxidants, such as H2O2, total residual oxidants (TRO) and OH radicals, and potential halogenated by-products, such as haloacetic acids, trihalomethanes and total organic halides, that had potentially formed after MPUV treatment, were measured. In conclusion, the ballast water treatment system employing the MPUV physical process not only effectively eliminated indigenous species in ballast water but also generated no harmful by-products.

선박평형수 처리장치의 활성물질 농도에 관한 고찰

국제해사기구(IMO)는 선박평형수를 통한 수중생물의 이동을 막기 위해, 2004년 선박 평형수와 침전물 통제 및 관리를 위한 국제협약을 채택하였다. 34개 선박평형수 처리장치가 IMO 활성물질 승인을 받았고, 이 가운데 20개 처리장치가 최종승인을 받았다. 본 논문에서는 IMO 활성물질 승인을 받은 처리장치에 대한 작용 원리와 총잔류산화제(TRO) 농도를 고찰하였다. TRO 최대 허용 배출 농도는 중화장치를 통해 낮추어 대부분 0.2 ppm 이하의 농도를 보였으나, 최대 처리 허용 농도는 장치별로 1-15 ppm으로 큰 차이를 나타내었다. 처리장치 별로 TRO 처리 허용 농도의 차이는 처리장치의 특성 및 필터의 유무와 종류 등과의 연관성 보다는 생물 사멸시험 시 생물종 특성과 수온, 탁도 등 수질 특성에 기인하는 바가 크다고 판단된다.

Inactivation of Amphidinium sp. in ballast waters using UV/Ag-TiO2 + O3 advanced oxidation treatment

Ballast water poses a biological threat to the world’s waterways by transferring aquatic species from one body of water to another. This study investigates the use of combined ultraviolet (UV)/Ag-TiO2+ozone (O3) processes for treating ballast water using Amphidinium sp. as an indicator microorganism. Sufficient Amphidinium sp. cells in ballast waters can be inactivated using O3 alone, UV irradiation alone (with or without an Ag-TiO2 coating), and combined treatments. For the low inactivation ratio (<40%) regime, the effects of ozonation and photocatalysis were observed to be cumulative. The combined UV/Ag-TiO2+O3 treatment produced excess hydroxyl radicals and total residual oxidants (TROs), and readily damaged cell membranes to release intracellular substances. The comparison tests revealed that the combined treatments synergistically inactivate Escherichia coli in ballast waters. However, the combined process did not synergistically inactivate Amphidinium sp. cells. Inactivating different aqua species in ballast waters needs distinct treatment methods and dosages.

Inactivation of Escherichia coli using UV/AgTiO2/O3‐mediated advanced oxidation: application to ballast water disinfection

AbstractBACKGROUND: Ballast water discharge from ships is regarded as one of the four major risk factors that threaten global marine environmental safety, and ballast water treatment is vital to prevent the introduction of potentially invasive species. The UV/AgTiO2/O3 process has been investigated for its potential use for ballast water treatment using Escherichia coli (E. coli) as an indicator bacterium. Inactivation curves were obtained, and the occurrence of oxidants was studied.RESULTS: Compared with individual unit processes with ozone or UV/AgTiO2, the inactivation of E. coli by the combined UV/AgTiO2/O3 process was enhanced, and the inactivation efficiency was improved with increasing ultraviolet intensity and ozone dose. The initial total residual oxidant (TRO) concentration was positively correlated with ozone dose, and resulted in faster decay rate for lower initial concentration. Persistence of TRO resulted in a cumulative bacteria mortality in the effluent.CONCLUSION: The UV/AgTiO2/O3 process was found to be efficient for E. coli inactivation in simulated ballast water. Copyright © 2011 Society of Chemical Industry

Characteristics of discharged sea water generated by underwater plasma system

Discharge to sea water is very hard and require considerable high voltage. But specially designed electrode can support plasma discharge to saline water with relatively low voltage. The round-shaped ceramic electrode having a lot of pinhole combined with metallic one was developed. Different types of electrodes were tested by changing number of hole and diameter of hole. The operating conditions of power generator are 5 kV voltages, 10 kHz frequency, 3 micro second pulse width and 5 kW power at 4th generation plasma reactor (4G). During discharge in water, Temperature is increasing and pH decreased lineally. It was obtained that 0.36 decrease of pH and 16 °C increase of temperature by 4.5 MJ energy supply at 30 L water vessel. In this plasma condition, the nucleus and electrons are separated and new kinds of components are resynthesized by the intensive movement of the components. Especially chlorine ions can be separated and recombined to residual free chlorine like HOCl, OCl -. In this experiment, generation of chlorine was observed. It was obtained that 50 mg generation of total residual oxidant by 4.5 MJ energy supply. It was measured by several times repetitions that 0.52 mg-Cl 2/L could disinfect E. coli till 99.9%. Another unconfirmed radical and oxidants for example, OH and H 2O 2 can have an effect on microorganism of course

Effects of UV/Ag-TiO 2/O 3 advanced oxidation on unicellular green alga Dunaliella salina: Implications for removal of invasive species from ballast water

The UV/Ag-TiO 2/O 3 process was investigated for ballast water treatment using Dunaliella salina as an indicator. Inactivation curves were obtained, and the toxicity of effluent was determined. Compared with individual unit processes using ozone or UV/Ag-TiO 2, the inactivation efficiency of D. salina by the combined UV/Ag-TiO 2/O 3 process was enhanced. The presence of ozone caused an immediate decrease in chlorophyll a (chl- a) concentration. Inactivation efficiency and chl- a removal efficiency were positively correlated with ozone dose and ultraviolet intensity. The initial total residual oxidant (TRO) concentration of effluent increased with increasing ozone dose, and persistence of TRO resulted in an extended period of toxicity. The results suggest that UV/Ag-TiO 2/O 3 has potential for ballast water treatment.

Degradation and Neutralization of Total Residual Oxidant (TRO) in the Treated Ballast Water by Ozonation

The aims of this study are to provide data on the ozone dosage control system and TRO sensor performance, to assess the performance of the degradation of total residual oxidant (TRO) neutralizer and to provide data on degradation rates of TRO in the ballast tanks, following treatment by the Ozone BWTS. This study includes the results of an evaluation of the TRO neutralizer, which was tested on the test barge. Accordingly, it has undertaken the evaluation of TRO degradation rates following treatment by the Ozone BWTS.

Shipboard trials of an ozone-based ballast water treatment system

Legislation introduced by the United Nations International Maritime Organization (IMO) has focused primarily on standards defining successful treatments designed to remove invasive species entrained in ballast water. An earlier shipboard study found that ozone introduced into salt water ballast resulted in the formation of bromine compounds, measured as total residual oxidants (TRO) that were toxic to both bacteria and plankton. However, the diffuser system employed to deliver ozone to the ballast water tanks resulted in patchiness in TRO distribution and toxicity to entrained organisms. In this follow-up study, the shipboard diffuser system was replaced by a single Venturi-type injection system designed to deliver a more homogeneous biocide distribution. Within-tank variability in TRO levels and associated toxicity to zooplankton, phytoplankton and marine bacteria was measured via a matrix of tubes deployed to sample different locations in treated and untreated (control) tanks. Three trials were conducted aboard the oil tanker S/T Prince William Sound in the Strait of Juan de Fuca off Port Angeles, Washington State, USA, between June and December 2007. Mortalities of plankton and bacteria and oxidant concentrations were recorded for treated and untreated ballast water up to 3days following treatment, and residual toxicity beyond this period was measured by bioassay of standard test organisms. Results indicated uniform compliance with current IMO standards, but only partial compliance with other existing and pending ballast water legislation.

Spectrophotometric Method for Determination of Total Residual Oxidants in Seawater

Spectrophotometric Method for Determination of Total Residual Oxidants in Seawater

Optimal Dose of Total Residual Oxidants for Hybrid Tilapia (Oreochromis mossambicus x O. niloticus) and Whiteleg Shrimp (Litopenaeus vannamei) in Ozone-Treated Sea Water

The purpose of this study was to use total residual oxidants (TRO) as an indicator for determining the optimal ozone dosage needed to control water quality and thereby enhance survival of cultivated aquatic organisms. When the TRO concentration was maintained at 0.16 mg/l for two hours, the total bacteria plate count dropped from 7.7 x 103 CFU/ml in the untreated sea water to less than 10 CFU/ml in the ozone-treated sea water. The TRO con- centration in the ozone-treated water was well below the 96-h LC50 for hybrid tilapia (Oreochromis mossambicus x O. niloticus) and whiteleg shrimp (Litopenaeus vannamei) determined in this study. Hence, adjust- ment of the ozone concentration in aquacultural sea water is a viable option that simultaneously kills the majority of harmful bacteria in the water and enhances survival of cultivated aquatic organisms.

Ozone treatment of ballast water on the oil tanker S/T Tonsina: chemistry, biology and toxicity

Worldwide transfer and introduction of non-indigenous species in ballast water causes significant environmental and economic impact. One way to address this problem is to remove or inactivate organisms that are found in ballast water. In this study, 3 experiments were conducted in Puget Sound, Washington, USA, using a prototype ozone treatment system installed on a commercial oil tanker, the S/T Tonsina. Treatment consisted of ozone gas diffused into a ballast tank for 5 and 10 h. Treatment and control tanks were sampled during the ozonation period for chemistry, cultur- able bacteria, phytoplankton and zooplankton. Selected fish and invertebrates were placed in cages deployed in the treatment and control tanks. Ozone introduced into seawater rapidly converts bro- mide (Br - ) to bromines (HOBr/OBr - ), compounds that are disinfectants. These were measured as total residual oxidant (TRO). Ozone treatment inactivated large portions of culturable bacteria, phyto- plankton and zooplankton. The highest reductions observed were 99.99% for the culturable bacteria, >99% for dinoflagellates and 96% for zooplankton. Caged animal results varied among taxa and locations in the ballast tank. Sheepshead minnows and mysid shrimp were most susceptible, shore crabs and amphipods the least. Distribution of ozone in the treatment tank was not homogenous during experiments, as suggested by the observed TRO concentrations and lower efficacies for inactivating the different taxa in selected ballast tank locations. Low concentrations of bromoform, a disinfection byproduct, were found in treated ballast water.

Mesocosm experiments for evaluating the biological efficacy of ozone treatment of marine ballast water

Ballast water is a major pathway for the transfer of non-indigenous species in aquatic environments. The objectives of this study were to determine the ability of ozone to reduce the numbers of a spectrum of marine organisms collected from Puget Sound, Washington in replicated mesocosm (280 l) experiments, and estimate the minimum ozone concentrations as measured by total residual oxidant (TRO) required to reduce organism densities. Ozone treatment was effective in removing bacteria, phytoplankton, and mesozooplankton with initial TRO concentrations of 2–5 mg l −1 as Br 2. Persistence of TRO resulted in an extended period of toxicity and cumulative mortality. TRO decay allowed bacteria populations to multiply when TRO levels fell below 0.5–1.0 mg l −1 as Br 2. Phytoplankton chlorophyll a concentrations were rapidly reduced by ozone treatment and did not increase in any treatments or controls because of lack of light. Overall mesozooplankton viability was rapidly reduced by 90–99% in treatment TRO levels above 1.85 mg l −1 as Br 2. Our study outlines novel protocols that can be used for testing different potential ballast water treatment systems in replicated and controlled mesocosm experiments.

Toxicity of ozonated seawater to marine organisms

Ballast water transport of nonindigenous species (NIS) is recognized as a significant contributor to biological invasions and a threat to coastal ecosystems. Recently, the use of ozone as an oxidant to eliminate NIS from ballast while ships are in transit has been considered. We determined the toxicity of ozone in artificial seawater (ASW) for five species of marine organisms in short-term (< or = 5 h) batch exposures. Larval topsmelt (Atherinops affinis) and juvenile sheepshead minnows (Cyprinodon variegatus) were the most sensitive to oxidant exposure, and the mysid shrimp (Americamysis bahia) was the most sensitive invertebrate. Conversely, benthic amphipods (Leptocheirus plumulosus and Rhepoxinius abronius) were the least sensitive of all species tested. Mortality from ozone exposure occurred quickly, with median lethal times ranging from 1 to 3 h for the most sensitive species, although additional mortality was observed 1 to 2 d following ozone exposure. Because ozone does not persist in seawater, toxicity likely resulted from bromide ion oxidation to bromine species (HOBr and OBr-), which persist as residual toxicants after at least 2 d of storage. Total residual oxidant (TRO; as Br2) formation resulting from ozone treatment was measured in ASW and four site-specific natural seawaters. The rate of TRO formation correlated with salinity, but dissolved organic carbon and total dissolved nitrogen did not affect TRO concentrations. Acute toxicity tests with each water over 48 h using mysid shrimp, topsmelt, and sheepshead minnows yielded results similar to those of batch exposure. Addition of sodium thiosulfate (Na2S2O3) to ozonated waters resulted in TRO elimination and survival of all organisms. Our results provide necessary information for the optimization of an efficacious ozone ballast water treatment system.

Ozonation of seawater from different locations: Formation and decay of total residual oxidant—implications for ballast water treatment

Ballast water is a likely cause for worldwide transfer of non-indigenous aquatic species because of the large volumes and frequency of possible inoculations. Ozone is one treatment option being considered for eliminating non-indigenous species in ballast water. When ozone is applied to seawater, secondary disinfectants are formed, commonly measured and expressed as total residual oxidant (TRO). The goal of this study was to determine those variables most likely to affect the rate of TRO increase during ozonation and the subsequent TRO decline that occurs over time. These parameters strongly influence the efficacy of ozone treatments aimed to eliminate organisms present in ballast water. Seawater was obtained from Puget Sound, Washington; Cape Fear, North Carolina; and San Francisco Bay. Results indicated that seawater characteristics, including the organic content and ammonia, affect the amount of ozone required to achieve a desired TRO level and rate of TRO decay, and therefore need to be considered in determining ozone requirements for ballast water treatment.