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Meeting the recent biological standards established by the Ballast Water Management Convention requires the application of ballast water treatment systems; ultraviolet irradiation is a frequently used option. However, organisms can repair the damage caused by ultraviolet irradiation primarily with photo-repair mechanisms that are dependent on the availability of light. The objective of this study is to quantify the impact of dark storage following ultraviolet irradiation on the viability of the microalgae Tetraselmis suecica. Results showed that one day of dark storage after ultraviolet irradiation enhanced the inactivation rate by 50% with respect to the absence of dark storage and increased up to the 84% with five days of dark storage. These results are consistent with photorepair, mostly in the first two days, prevented in the dark. The dose required to inactivate a determined ratio of organisms was correlated with the length of the dark post-treatment according to an inverse proportional function. This correlation may help to optimize the operation of ultraviolet ballast water treatment systems. Further, the results show that growth assays can detect organisms that are capable of repair after treatment with UV., This work was supported by the Spanish Ministry of Economy and Competitiveness-FEDER through the R+D AVANTE Project [CTM2014-52116-R].

Seawater treatment is increasingly required due to industrial activities that use substantial volumes of seawater in their processes. The shipping industry and the associated management of a ship's ballast water are currently considered a global challenge for the seas. Related to that, the suitability of an Electrochemical Advanced Oxidation Process (EAOP) with Boron Doped Diamond (BDD) electrodes has been assessed on a laboratory scale for the disinfection of seawater. This technology can produce both reactive oxygen species and chlorine species (especially in seawater) that are responsible for inactivation. The EAOP was applied in a continuous-flow regime with real seawater. Natural marine heterotrophic bacteria (MHB) were used as an indicator of disinfection efficiency. A biphasic inactivation kinetic model was fitted on experimental points, achieving 4-Log reductions at 0.019 Ah L−1. By assessing regrowth after treatment, results suggest that higher bacterial damages result from the EAOP when it is compared to chlorination. Furthermore, several issues lacking fundamental understanding were investigated such as recolonization capacity or bacterial community dynamics. It was concluded that, despite disinfection processes being effective, there is not only a possibility for regrowth after treatment but also a change on bacterial population diversity produced by the treatment. Finally, energy consumption was estimated and indicated that 0.264 kWh·m−3 are needed for 4.8-Log reductions of MHB; otherwise, with 0.035 kWh·m−3, less disinfection efficiency can be obtained (2.2-Log red). However, with a residual oxidant in the solution, total inactivation can be achieved in three days.

Shrimp (Litopenaeus vannamei) farming is an important economic activity in several countries. Pathogens in shrimp farms and its effluents pose a potential hazard for both humans and shrimps. Wild strains of bacteria were characterized in a shrimp farm, and Klebsiella pneumoniae was chosen as a good indicator due to its presence in the pond and the effluent and its resistance to antibiotics. Different photochemical processes (UV/H2O2, UV/H2O2/Fe3+) were tested for inactivation of wild isolated K. pneumoniae and compared to UV-C radiation. By kinetic modelling, a kmax equal to 0.43 s−1 was obtained for UV-C treatment. After optimizing the cited processes, ranging [H2O2]: 10–30 mg·l−1; an optimal [H2O2] of 10 mg·l−1 was found, increasing kmax on 13.63% compared to UV-C. This optimal concentration was tested for UV/H2O2/Fe3+ process; ranging [Fe3+]: 2–20 mg·l−1. The highest yield was obtained by a [H2O2]:[Fe3+] = 10:2, which leads to 4-Log reduction in 12.88 s of treatment. Moreover, resistance of K. pneumoniae was compared to Escherichia coli. The latter proved to be more sensitive despite its similar cellular structure. Results suggested that the photochemical processes could enhance disinfection efficiency, especially for photo-assisted Fenton-like process in most resistant bacteria.

The importance of seawater treatment in order to avoid microbiological pollution related to aquaculture or ballast water management has increased during the last few years. Bacterial indicators used for the evaluation of different disinfection treatments are usually related with both waste and drinking water, these standards are not usual microorganisms found in seawater. Thus, it is thought necessary to study the behavior of different marine-specific organisms in regard to improve the disinfection processes in seawater. In this study, three different bacteria have been selected among major groups of bacterial community from marine waters: two water-associated, Roseobacter sp. and Pseudomonas litoralis, and one sediment-associated, Kocuria rhizophila. A kinetic inactivation model together with a post-treatment growth tendency has been obtained after the application of UV-C and UV/H2O2 processes. According to the first kinetic rate constant, different responses were obtained for the different bacterial groups. Once the treatment was applied, modeling of growth curves revealed high recover within the first 3 days after treatment, even when UV/H2O2 was applied. This study introduces a sensitivity index, in which results show different levels of resistance for both treatments, being Roseobacter sp. the most sensitive bacteria, followed by P. litoralis and K. rhizophila.

Over the years, industrial activities that generate high salinity effluents have been intensifying; this has relevant potential for causing organic and microbiological pollution which damages both human and ocean health. The development of new regulations, such as ballast water convention, encourage the development of treatment systems that can be feasible for treating seawater effluents. Accordingly, an approach based on the UV activation of persulfate salts has been assessed. In this scenario, two different persulfate sources (S2O82− and HSO5−) were evaluated under UV-C irradiation for disinfection purposes. An optimization process was performed with low chemical doses ( E. coli > E. faecalis ≈ Marine Heterotrophic Bacteria. With an evaluation of regrowth after treatment, greater cell damage was detected with the addition of persulfate salts. The major ability of regrowth for marine bacteria encourages the use of a residual disinfectant after disinfection processes.

Due to the increasing number of ecosystem invasions with the introduction of exogenous species via ballast water, the International Maritime Organization adopted the Ballast Water Convention (BWMC). The BWMC establishes standards for the concentration of viable organisms in a ballast water discharge. Ultraviolet (UV) irradiation is commonly used for treating ballast water; however, regrowth after UV irradiation and other drawbacks have been reported. In this study, improvement in UV treatment with the addition of hydrogen peroxide or peroxymonosulfate salt was investigated using the microalgae Tetraselmis suecica as the target organism. Results reported that each of these reagents added in a concentration of 10 ppm reduced the concentration of initial cells by more than 96%, increased the UV inactivation rate, and enabled reaching greater level of inactivation with the treatment. These improvements imply a reduction of the UV doses required for a consistent compliance with the BWMC standards., This work has been co-funded by the 2014–2020 ERDF Operational Programme and by the Department of Economy, Knowledge, Business and University of the Regional Government of Andalusia (Spain). Projects Ref.: FEDER-UCA18 - 108023 and FEDER-UCA18-105151.

The development of technologically advanced recirculation aquaculture systems (RAS) implies the reuse of water in a high recirculation rate (>90%). One of the most important phases for water management in RAS involves water disinfection in order to avoid proliferation of potential pathogens and related fish diseases. Accordingly, different approaches have been assessed in this study by performing a comparison of photolytic (UV-LEDs) at different wavelengths (λ= 262, 268 and 262+268 nm), photochemical (UV-LEDs/H2O2, UV-LEDs/HSO5- and UV-LEDs/S2O82-) and photocatalytic (TiO2/SiO2/UV-LEDs and ZnO/SiO2/UV-LEDs) processes for the disinfection of water in RAS streams. Different laboratory tests were performed in batch scale with real RAS stream water and naturally occurring bacteria (Aeromonas hydrophyla and Citrobacter gillenii) as target microorganisms. Regarding photolytic processes, higher inactivation rates were obtained by combining λ262+268 in front of single wavelengths. Photochemical processes showed higher efficiencies by comparison with a single UV-C process, especially at 10 mg·L-1 of initial oxidant dose. The inactivation kinetic rate constant was improved in the range of 15-38%, with major efficiency for UV/H2O2 ~ UV/HSO5- > UV/S2O82-. According to photocatalytic tests, higher efficiencies were obtained by improving the inactivation kinetic rate constant up to 55% in comparison with a single UV-C process. Preliminary cost estimation was conducted for all tested disinfection methods. Those results suggest the potential application of UV-LEDs as promoter of different photochemical and photocatalytic processes, which are able to enhance disinfection in particular cases, such as the aquaculture industry. Post-print / Final draft

The development of advanced photochemical processes has experienced the emergence of a promising alternative for water disinfection, different from traditional methods. The applicability has primarily been investigated in drinking and wastewater; however, new challenges related to microbiological control in marine waters necessitate evaluating the applicability of this process in such water matrices. In this study, the efficacy of persulfate (PDS) activated with UV-light against E. faecalis has been tested on the bench scale. Firstly, optimization of the different PDS concentrations (1–10 mM) and exposure times (0–5 min) was performed in distilled water. 1 mM of PDS was selected as the best dosage within the range tested. Secondly, in order to evaluate the effects of different inorganic compounds usually found in natural waters, the efficiency of the UV/PDS system was tested in three different matrices: mineral water, saltwater, and marine saltwater. Finally, different bacteria were evaluated in consortium (E. coli + E. faecalis), suggesting the same inactivation level independently on the bacterial groups and structures. The results suggest that PDS is an attractive alternative to other photochemical processes currently in use for seawater treatment and this application deserved further research.

Cruise ship wastewater discharges are pollution sources towards the marine environment that are poorly characterized. In this study, wastewater samples from cruise ships have been obtained during repair works in a shipyard. Different organic pollutants have been analyzed and their concentrations were similar to those in urban wastewaters for pharmaceuticals and fragrances, but higher for UV filters and PAHs. For the first time, cypermethrin, a pesticide highly toxic towards aquatic species, was found at relevant concentrations (>1 µg L^-1). The faecal microorganisms were for all parameters higher than 10^4 CFU 100 mL^-1, which together with the presence of antibiotic compounds in wastewater (e.g., triclosan), could potentially lead to the generation of antibiotic resistance bacteria (ARB). The historical position of cruise ships, determined from the Automatic Identification System (AIS), were used to define the time ships were underway, at port, or in repair. From ship's passenger and crew load, and from estimates of discharges the total volume of wastewater produced by these ships (371,000 m^3 year^-1) and the average flow (0.15 ± 0.03 m^3crew^-1 day^-1) were calculated.

Organisms carried with ballast water can find a way that enables them to spread into a new habitat, becoming invasive species. This can generate large impacts threatening the ecosystem and human activities. The effectiveness of microbiological disinfection by UV/H2O2 treatment on Enterococcus faecalis has been evaluated in this study at laboratory scale, in both buffered distilled water (DW) and saltwater (SW). A Collimated Beam Reactor was used to determine optimal H2O2 concentration with DW and a Continuous Flow Reactor was tested with DW and SW. The optimal concentration of hydrogen peroxide found was 5 mg/L. The improvement of adding H2O2 increased efficacy by 28.9% in SW compared with UV alone; while results indicated that water salinity did not induce strong interference in treatment. In addition, re-growth of surviving bacteria was prevented 24 h after the treatment; even an additional one-log inactivation was obtained. The results suggest that the addition of small concentrations of H2O2 leads to an improvement in UV treatment. Finally, the operational costs were estimated for typical cargo vessels; UV/H2O2 treatment was considered to be competitive for ballast water treatment, since it could improve the effectiveness of the process with similar costs per 1000 m3 of treated water: 14 € for UV treatment and 16 € for UV/H2O2 treatment.

Biofouling is a complex and important problem in cooling systems using water from natural sources such as lakes, rivers and sea. The first stage of biofilm formation is the colonization and uncontrolled microbial growth on surfaces. The aim of this study was to evaluate and to compare the effectiveness of different antifouling treatments in a heat exchanger cooled by seawater. Two types of experiments were carried out. Firstly, by employing a pilot plant simulating an industrial heat exchanger, chlorination and its combination with other treatments (UV and copper ions) were tested and the formed fouling was monitored and quantified. Then, the disinfection effectiveness of biocides employed was checked on two marine bacteria in order to identify the antifouling action mechanism. The combination of chlorine and copper was the most effective strategy for mitigation of fouling growth. After 60 days of testing, the thermal resistance showed no significant increase and the total solids accumulated inside the test tube were reduced by 70% compared to control treatment. The effectiveness of chlorine–copper treatment against fouling is probably due to a combination of their synergic inactivation mechanisms under prolonged exposure times, such as those of fouling experiments (60 days). The effectiveness of antifouling treatment was not only affected by the concentration of chlorine in the cooling water, but also by the dosage pattern. A chlorine peak of 0.4 mg L−1 for 1 h a day over the concentration of control (0.12 mg L−1) was able to reduce the increment in Rf and the accumulation of solids by approximately 50%. The combined use of chlorine and copper as antifouling treatment can be recommended in specific cooling systems that use seawater.

Industries located in coastal areas and maritime transport are economic activities that use large amounts of seawater. In most cases, this water requires disinfection treatment to avoid fouling problems in industrial facilities or to prevent environmental impacts after used seawater is released. This study proposes the photocatalysis with immobilized TiO 2 as a disinfection treatment for seawater and evaluate its efficacy by comparing with UV 254 radiation treatment. The experiments were carried out employing artificial seawater and using an annular UV reactor in the laboratory scale tests. Two species of marine bacteria were used as microbial indicators of the treatment efficacy: Alteromonas sp and Corynebacterium stationis . The photocatalytic treatment had faster disinfection kinetics than that using UV 254 light for both bacteria species, being necessary between 30 and 33% less UV dose to achieve the same level of disinfection. The catalyst used for photocatalytic treatment showed a progressive decay of activity until its complete inactivation after 215 h of treatment, due to factors such as fouling or catalyst loss.

The aim of this work was to study in depth the behavior and optimization of a novel process, called advanced thermal hydrolysis (ATH), to determine its utility as a pretreatment (sludge solubilization) or postreatment (organic matter removal) for anaerobic digestion (AD) in the sludge line of wastewater treatment plants (WWTPs). ATH is based on a thermal hydrolysis (TH) process plus hydrogen peroxide (H(2)O(2)) addition and takes advantage of a peroxidation/direct steam injection synergistic effect. On the basis of the response surface methodology (RSM) and a modified Doehlert design, an empirical second-order polynomial model was developed for the total yield of: (a) disintegration degree [DD (%)] (solubilization), (b) filtration constant [F(c) (cm(2)/min)] (dewaterability), and (c) organic matter removal (%). The variables considered were operation time (t), temperature reached after initial heating (T), and oxidant coefficient (n = oxygen(supplied)/oxygen(stoichiometric)). As the model predicts, in the case of the ATH process with high levels of oxidant, it is possible to achieve an organic matter removal of up to 92%, but the conditions required are prohibitive on an industrial scale. ATH operated at optimal conditions (oxygen amount 30% of stoichiometric, 115 °C and 24 min) gave promising results as a pretreatment, with similar solubilization and markedly better dewaterability levels in comparison to those obtained with TH at 170 °C. The empirical validation of the model was satisfactory.

The production of secondary sewage sludge at urban wastewater treatment plants (WWTPs) is increasing and this, in turn, leads to significantly higher wastewater treatment costs. Thermal Hydrolysis (TH) and Advanced Oxidation Processes (AOPs), such as Wet Air Oxidation (WAO) or Fenton's peroxidation, have been widely studied in an effort to manage this type of waste. In this work, a new process named Advanced Thermal Hydrolysis (ATH) is introduced for the pre-treatment and/or treatment of secondary sewage sludge and the advantages in terms of performance and improvements have been evaluated. The ATH process employs the synergistic effect of peroxidation plus direct steam injection and it operates under mild conditions and without the addition of a catalyst. The dewaterability and solubilization of sludge processed by ATH were monitored and the results were compared with those obtained by TH. The organic matter elimination was also assessed, with satisfactory results obtained in most cases. A concise economic viability discussion is included in this paper and it was concluded that ATH is a promising technology.

Disinfection studies with two pure strains of Escherichia coli ATCC 11229 and ATCC 15597 and real municipal wastewater were carried out at laboratory scale with a 10 W low pressure ultraviolet lamp in an ultraviolet (UV) disinfection system with recirculation of the liquid. A double first order kinetic model was established to fit the ultraviolet disinfection curves for the two microorganisms. This model implies that there are two subpopulations within the study population, one of which is sensitive to ultraviolet and another that is radiation-resistant. The kinetic model depends on the applied UV dose and is directly related to the initial bacterial concentration (No). It was possible to establish relationships between the kinetic parameters of the equation and the initial concentration, and so to predict the disinfection curves. The kinetic model was successfully fitted to a real wastewater sample, with the final microbial disinfection predicted as a function of the UV dose and No.

Industrial wastes have a substantial impact on coastal environments. Therefore, to evaluate the impact of cooling water discharges from coastal power plants, we studied the kinetics of the degradative processes and the ecotoxicity of two antifouling products: (1) a classic antifouling product; sodium hypochlorite (NaClO) and (2) an alternative one; aliphatic amines (commercial under the registered trade mark Mexel432). To assess the persistence of both compounds the decay of sodium hypochlorite and the primary biodegradation rate of Mexel432 were determined in natural seawater at 20 degrees C. The results indicated a more rapid decay of NaClO than Mexel432. The degradation behavior of both chemicals was described following a logistic model, which permitted calculating kinetic parameters such as t(50) or t(90). The t(50) was 1h and 2d for NaClO and Mexel432, respectively. To evaluate the potential risks of the aforementioned treatments to marine organisms, the acute toxicity of both antifouling products was studied on the microalgae Isochrysis galbana and Dunaliella salina, and on the invertebrate Brachionus plicatilis, using growth inhibition and death tests as toxic response, respectively. For I. galbana, the 96-h EC(50) values were 2.91+/-0.15mg/L of NaClO and 4.55+/-0.11mg/L of Mexel432. D. salina showed values of 96-h EC(50) of 1.73+/-0.16mg/L of NaClO and 7.21+/-0.1mg/L of Mexel432. Brachionus plicatilis showed a 24-h LC(50) of 1.23+/-0.1mg/L of NaClO and 3.62+/-0.37mg/L of Mexel432. Acute toxicity was highly dependent on the chemical and species tested. NaClO presented more toxic effects than Mexel432, also B. plicatilis was the most sensitive species in both cases. The lowest NOECs obtained, 0.25mg/L for NaClO and 2.12mg/L for Mexel432, were similar to the theoretical residual concentrations of these biocides in cooling water discharges. Therefore, these discharges can cause undesirable negative effects upon the aquatic organisms present.

9 pages, 5 figures, 2 tables, The time-course stress responses (0, 1, 2, and 7 d) was assessed in plasmatic, branchial and renal parameters of juveniles Solea senegalensis exposed to different concentrations of the antifouling sodium hypochlorite (0.1, 0.2, and 0.5 mg L-1). These stress responses were only assessed for the total length of exposure (7 d) at the lowest NaClO concentration due to the high toxicity of this chemical. In addition, the xenobiotic metabolism responses were evaluated by means of enzymatic activities of ethoxyresorufin O-deethylase (EROD), glutathione S-transferase (GST), glutathione reductase (GR), glutathione peroxidase (GPX), catalase (CAT), and carboxylesterase (CbE) in liver; as well as GST, GPX, CAT and acetylcholinesterase (AChE) in gill. Oxidative stress damage due to sodium hypochlorite exposure was measured by lipid peroxidation levels in liver and gill. Concentrations of 0.2 and 0.5 mg L-1 produced lethal effects after 1 d and 2 h of exposure, respectively. After 1 d of exposure to sublethal concentration of sodium hypochlorite (0.1 mg L-1) osmoregulatory (osmolality and chloride) and stress (cortisol, glucose and lactate) plasmatic parameters were enhanced to respect at control fish. However after 3 or 7 d these parameters returned to control values. No effects were observed on plasma protein and triglyceride levels or on gill and kidney Na+/K+-ATPase activities. Diverse gill pathologies such as hypertrophy, lamellar fusion and an increase in goblet cell number and size were observed after 7 d of exposure. Most biochemical parameters related to xenobiotic metabolism and oxidative stress were also significantly affected which suggests that seawater affected by sodium hypochlorite discharges from power plants, is able to alter the fish xenobiotic metabolism and generate oxidative stress, This work was partially funded by the Grants CTM2005-02658 and AGL2007-61211/ACU (Ministerio Educación y Ciencia of Spain) and Proyecto de Excelencia PO7-RNM-02843 (Consejería de Innovación, Ciencia y Empresa. Junta de Andalucía)

The aim of this work is to present the application of the hydrothermal oxidation in supercritical conditions, also named supercritical water oxidation (SCWO) to the treatment of two commercial cutting fluids: Biocut and Servol. Experiments were carried out in a continuous flow system at a constant pressure of 25 MPa, using pure oxygen as oxidant in excess, and different temperatures ranging from 673 to 773 K. Both semi-synthetic cutting fluids are a mixture of several compounds so the efficiency of the oxidation process was followed in terms of the reduction in chemical oxygen demand (COD) and total organic carbon (TOC). A comparison of the results obtained in the study showed that it is possible to apply successfully SCWO for both cutting fluids, obtaining more than 95% for both COD and TOC removal at 773 K. However, the results also show that different residence times are needed to obtain the same percentage of COD or TOC removal depending on the cutting fluid treated, being in all cases Servol easier to oxidize than Biocut. A kinetic model to predict COD and TOC conversion has been proposed for both cutting fluids. A two-parameter mathematical model involving two steps (a fast reaction followed by a slow reaction) was used to describe the Biocut SCWO kinetics and to calculate the kinetic constants.

Low molecular weight acids are common intermediate reaction compounds formed during the wet air oxidation (WAO) of aqueous waste streams, and frequently their oxidation is the rate-controlling step in the overall reaction. The WAO kinetics of aqueous solutions of butyric acid was studied in a stainless steel 316 autoclave over a temperature range of 200−320 °C with a total pressure of 15 MPa of synthetic air, which provides an excess of oxygen. Kinetic models were developed with respect to various concentrations of butyric acid and chemical oxygen demand (COD). Oxidation reactions always obeyed a pseudo-first-order kinetic, but two different activation energies were needed to represent the temperature dependence in two ranges, namely 200−275 and 275−320 °C. This finding can be explained by the competition between two main reaction pathways in the oxidation of the acid, since both pathways take place simultaneously. A mechanism in accordance with the results obtained is proposed.

The wet air oxidation of long-chain carboxylic acids has been studied. Caprylic acid and oleic acid were selected for the degradation studies. The effectiveness of the process has been followed in terms of the disappearance of carboxylic acids and in terms of COD removal. The oxidation process was studied in the temperature range 473–573 K with a total pressure of 15 MPa of synthetic air, which means an oxygen excess. The oxidation process was found to be pseudo-first order with respect to the carboxylic acid concentration and the activation energies were 55.5 kJ/mol for caprylic acid and 53.8 kJ/mol for oleic acid. Acetic acid was found to be the main intermediate in the oxidation process and, therefore, a generalized kinetic model based on the formation and elimination of acetic acid has also been applied to the experimental data.

Studies on the development and evolution of anaerobic digestion (AD) pretreatments are nowadays becoming widespread, due to the outstanding benefits that these processes could entail in the management of sewage sludge. Production of sewage sludge in wastewater treatment plants (WWTPs) is becoming an extremely important environmental issue. The work presented in this paper is a continuation of our previous studies with the aim of understanding and developing the advanced thermal hydrolysis (ATH) process. ATH is a novel AD pretreatment based on a thermal hydrolysis (TH) process plus hydrogen peroxide (H2O2) addition that takes advantage of a peroxidation/direct steam injection synergistic effect. The main goal of the present research was to compare the performance of TH and ATH, conducted at a wide range of operating conditions, as pretreatments of mesophilic AD with an emphasis on methane production enhancement as a key parameter and its connection with the sludge solubilization. Results showed that both TH and ATH patently improved methane production in subsequent mesophilic BMP (biochemical methane potential) tests in comparison with BMP control tests (raw secondary sewage sludge). Besides other interesting results and discussions, a promising result was obtained since ATH, operated at temperature (115 °C), pretreatment time (5 min) and pressure (1 bar) considerably below those typically used in TH (170 °C, 30 min, 8 bar), managed to enhance the methane production in subsequent mesophilic BMP tests [biodegradability factor (fB) = cumulative CH4production/cumulative CH4production (Control) = 1.51 ± 0.01] to quite similar levels than conventional TH pretreatment [fB = 1.52 ± 0.03].

Supercritical Water Oxidation (SCWO) has been proved to be a powerful technology to eliminate a wide range of wastes, but there are few references in the literature about the application of SCWO to oily wastes. Even though these industrial wastes are quite important due to their large volume and toxicity, no attempt to study the kinetics involved have been found in the literature. In this work, SCWO have been tested to treat cutting oil wastes in a continuous flow system operating at 400–500 °C. In order to simplify the kinetic study of a complex waste, a generalized kinetic model available in the literature has been proved to represent the evolution of the oxidation process in terms of TOC and acetic acid. A modification of that model is proposed here, considering carbon monoxide as the main refractory intermediate in the reaction scheme.

Wet air oxidation (WAO) and supercritical water oxidation (SCWO) processes have been studied by numerous researchers, proving their effectiveness to treat a wide variety of wastes and presenting the kinetics involved in each case. As a result, a substantial amount of kinetic information describing organic reactions in those environments has been accumulated. In most cases, predictions from kinetics models obtained below and above the critical point of water are completely different. Furthermore, predictions from kinetic expressions obtained in the same range of operating conditions vary considerably. Phenol is a model pollutant that has been the subject of numerous studies both in subcritical and supercritical conditions. In this work, both batch and continuous flow reactors have been used to compare the kinetics obtained for phenol oxidation at subcritical and supercritical conditions. Moreover, most of the rate expressions available in the literature have been compared in order to find the reasons for the discrepancies found. © 2001 Elsevier Science B.V. All rights reserved.

11 pages, 5 figures, 1 table, It now is widely recognised that the global temperature is rising, a phenomenon which could alter the effects of pollution on wildlife. In order to assess the role of temperature and exposure to chlorine due to cooling water discharges, a battery of metabolic, oxidative stress and histological parameters were evaluated in Mytilus galloprovincialis after 15 and 30 days at 15 °C and at two increased temperatures (+5 and + 10 °C). Diverse gill pathologies such as haemolymphatic sinus dilatation, an increased number of mucocytes and granulocytes as well as a lower number of cilia were observed after 30 days exposure at higher temperatures. Protein, amino acid, triglyceride and fatty acid levels decreased when the temperature increased, as a consequence of higher energetic demand. Similarly, acetylcholinesterase, catalase and glutathione S-transferase activities showed an inhibition at higher temperatures, although gill lipid peroxidation levels remained unaffected. Our results suggest that increased temperatures induce deterioration in the health status of themussels and in their defensive capacity against a polluted environment, This research work was funded by grant CTM2009-09527 and CSD2007-0055 to E.N.

Biofilm development in an open-pore sintered-glass material (SIRAN) was studied using a laboratory-scale, anaerobic fixed-film reactor under thermophilic conditions. The start-up and performance of this reactor, operating on distillery wastewater feed (vinasses), were also studied. Stepped organic loading during initial reactor start-up reduced the periods of adaptation in the colonisation process and micro-organism attachment, and biofilm formation was accelerated by the surface characteristics of the carrier. The results obtained by operating with stepped organic loading (3.81 kg COD/m3/day) over a period of 75 days suggest that a stable operation of the process (80% COD removal) and high density of biomass immobilised on the support (89.26 g VSatt/m3 SIRAN) was achieved. Epifluorescence microscopy demonstrated that, initially, attached growth developed in crevices where biomass was protected from shear forces and, finally, SIRAN was completely covered and biofilm developed on the entire SIRAN particles. The support, under anaerobic thermophilic conditions, due to its properties of low density, high porosity and specific area, is suitable for the immobilisation of slow-growing micro-organisms (e.g. anaerobic thermophilic organisms), and is especially adequate as a support for anaerobic fluidised beds for the treatment of high-rate organic loads.

10 pages, 4 figures, 3 tables, The sublethal effects of two antifoulants currently used in power plant cooling systems were assessed in the common mussel Mytilus galloprovincialis. The concentrations of sodium hypochlorite (NaClO) and an alkyl amine surfactant (Mexel®432) assayed, were within the range of those currently discharged by power plants into receiving waters. Enzymatic activities and oxidative stress responses were measured in digestive gland and gill of mussels after 1, 3, 7 and 14 days of exposure, as well as histopathology in gill tissue. Both antifoulants caused a pathological response in gills and the activities of the enzymes glutathione S-transferase, catalase, acetylcholinesterase and the lipid peroxidation levels were also affected. Exposure to NaClO caused a greater toxicological response than Mexel®432. In both treatments, gills appeared to be the most affected tissue, although Mexel®432 also significantly affected digestive gland parameters, This work was funded by grants: CTM2005-02658 to E.N. and AGL2007-61211/ACU (Ministerio Educación y Ciencia of Spain) and Proyecto de Excelencia PO7-RNM-02843 (Consejería de Innovación, Ciencia y Empresa. Junta de Andalucía) to J.M.M.

8 pages, 5 figures, 1 table, Mexel®432 is an anionic surfactant used as biocide in the cooling water system of power plants for biofouling reduction. Refrigeration waters from power plants do not usually follow, prior to their discharge to sea, any treatment aimed to eliminate biocides and this can have negative consequences on the aquatic fauna nearby. The effects of different concentrations of the antifoulant Mexel®432 (0.5, 1 and 2 mg L-1) on osmoregulation (osmolality and Na+/K+-ATPase activity) and stress parameters (cortisol, glucose, and lactate) were assessed in juveniles of the flatfish Solea senegalensis. Gill histopathology and alterations due to oxidative stress (increased lipid peroxidation, LPO, levels) at branchial and hepatic levels were also considered. Other parameters tested were the antioxidant enzymes (catalase, CAT; glutathione peroxidase, GPX; and glutathione reductase, GR), xenobiotic metabolism defenses involved in detoxification (carboxylesterase, CbE; 7-ethoxyresorufin O-deethylase, EROD; and glutathione S-transferase, GST) and the neurotransmitter acetylcholinesterase (AChE) activity. Significant variations in osmoregulatory parameters, histological lesions and decreased branchial Na+/K+-ATPase activity were observed in exposed fish. Other gill biomarkers presented little or no significant variations in relation to controls. In contrast, hepatic parameters, such as CAT activity, were inhibited while EROD activity was initially elevated but after longer exposures it recovered basal values. These results suggested that under our experimental protocol exists toxic associated to Mexel®432 exposures, This work was partially funded by the grants CTM2005-02658 to E.N. and AGL2007-61211/ACU (Ministerio Educación y Ciencia of Spain) and Proyecto de Excelencia PO7-RNM-02843 (Consejería de Innovación, Ciencia y Empresa. Junta de Andalucía) to J.M.M.

In an industrial seawater cooling system, the effects of three different antifouling treatments, viz. sodium hypochlorite (NaClO), aliphatic amines (Mexel1432) and UV radiation, on the characteristics of the fouling formed were evaluated. For this study a portable pilot plant, as a side-stream monitoring system and seawater cooling system, was employed. The pilot plant simulated a power plant steam condenser, having four titanium tubes under different treatment patterns, where fouling progression could be monitored. The nature of the fouling obtained was chiefly inorganic, showing a clear dependence on the antifouling treatment employed. After 72 days the tubes under treatment showed a reduction in the heat transfer resistance (R) of around 70% for NaClO, 48% for aliphatic amines and 55% for UV, with respect to the untreated tube. The use of a logistic model was very useful for predicting the fouling progression and the maximum asymptotic value of the increment in the heat transfer resistance (DRmax). The apparent thermal conductivity (l) of the fouling layer showed a direct relationship with the percentage of organic matter in the collected fouling. The characteristics and mode of action of the different treatments used led to fouling with diverse physicochemical properties.

Because of the lack of readily available information about the influence of temperature on microorganism reactivation processes subsequent to inactivation with UV radiation, a series of batch reactivation studies were performed at 5, 10, 15, 20, 25, and 30°C. A special effort was made to model the reactivation process to enable the effect of the temperature variable to be quantified. Because an earlier-proposed kinetic model (K. Kashimada, N. Kamiko, K. Yamamoto, and S. Ohgaki, Water Sci. Technol. 33:261-269, 1996), a first-order saturation type, does not adequately fit the data obtained in experiments of reactivation in conditions of light and darkness, a modification of that model is proposed. The new model, which actually coincides with the classical logistic equation, incorporates two kinetic parameters: the maximum survival ratio ( S m ) and the second-order reactivation rate constant ( k 2 ). In order to interpret correctly the reactivation occurring in conditions of darkness, a new term for the decay is added to the logistic equation. The new model accurately fits the data obtained in reactivation experiments, permitting the interpretation of the kinetic parameters S m , k 2 , and M (for only repair in darkness), where M is mortality, a zero-order decay rate constant, and their relationship with various environmental conditions, such as microbial type, light, and temperature. The parameters S m and k 2 (and M for reactivation in conditions of darkness) show exponential dependence on the reactivating temperature, and it is possible to predict their values and hence the reactivation curve from the equations proposed in this work.

Cutting oils are emulsionable fluids widely used in metalworking processes. Their composition is normally oil, water, and additives (fatty acids, surfactants, biocides, etc.) generating a toxic waste after a long use. Generally, it is a waste too dilute to be incinerated and it is difficult to treat biologically. Other conventional treatment methods currently used are not satisfactory from the environmental point of view. Wet air oxidation (WAO) and supercritical water oxidation (SCWO) are two forms of hydrothermal oxidation that have been proved to be effective processes to treat a wide variety of industrial wastes, but hardly tested for oily wastes. In the case of refractory wastes, WAO process is not efficient enough due to the moderate temperatures used. SCWO is a more powerful process since operating temperatures are usually around 600 degrees C, but the use of severe conditions leads to major disadvantages in the commercialization of the technology. In order to enhance WAO and SCWO efficiency at mild conditions, the use of free radical promoters has been studied in this work. Both normal and promoted hydrothermal oxidation have been tested to treat cutting oil wastes in a continuous flow system operating at 300-500 degrees C. Hydrogen peroxide has been used both as a source of oxygen and as a source of free radicals by introducing it into the reactor with or without previous thermal decomposition, respectively. Organic material is easily oxidized in both cases, obtaining more than 90% TOC reduction in less than 10s at 500 degrees C. At lower temperatures, the use of promoters clearly enhances the oxidation process. Activation energies have been estimated for normal and promoted oxidation processes.

The experimental conditions selected (addition to assay medium of micronutrients, macronutrients and pH control), the experimental design and the procedure for maximum acidogenic and methanogenic activity determination tests in thermophilic biomass, are presented. The proposed tests are highly reproducible and can be carried out in a short space of time. Specific tests are applied to measure the maximum acidogenic and methanogenic activities in lab-scale anaerobic reactors treating wine-distillery wastes in the thermophilic range (55°C).

Wine alcohol distilleries produce eight volumes of high-strength waste (known as vinasse) from every volume of ethanol. The waste has an acidic character and a high organic content. Three adequate microbiological treatments (aerobic, mesophilic anaerobic and thermophilic anaerobic) for the purification of vinasses were examined. When around 90% biodegradable chemical oxygen demand (COD) removals were achieved in every treatment, optimum operating conditions had been attained, resulting in an optimum hydraulic retention times (HRT) of 8 days for aerobic, 6 days for mesophilic anaerobic, and 4 days for thermophilic anaerobic processes. The experimental results were compared with those obtained from a substrate utilization kinetic model. The model accurately predicted the performance of these processes, except at HRTs shorter than minimum, since these systems work under transient conditions. A comparison between kinetic coefficients obtained from the model showed that a thermophilic anaerobic process was the more efficient, since the process reached the same purification level, could be energy self-maintaining and needed smaller process plants than the other two systems.

Supercritical Water Oxidation (SCWO) processes have been studied by numerous researchers. The effectiveness of this approach to treat a wide variety of wastes has been proved and the kinetics involved in some cases have been described. Phenol is commonly present in industrial wastewaters and it is extremely toxic. Hence, phenol is a model pollutant that has been the subject of numerous studies by SCWO on a laboratory scale. In this work, a pilot-scale SCWO system has been used to compare experimental and predicted conversions in the SCWO of phenol, using the reaction kinetic equations obtained at the laboratory scale. In this context, “PROSIM PLUS” software was employed to develop a simulator for the pilot plant facility, with the reaction kinetic parameters adjusted to represent the experimental data. In this study it was necessary to determine the thermal losses between the experimental reactor and its surroundings. These thermal losses were obtained from tests with pure water and oxidant streams in the absence of chemical reaction. An equation that predicted the effect of flow rate and temperature on the thermal losses was used. Experimental oxidation tests were conducted with initial temperature in the range 380 to 425 ºC, at 250 bar and phenol concentrations ranging from 1 to 12 g/l. Good agreement in the simulation was obtained by adjusting the kinetic parameters within their confidence range. This simulator was used to optimize the SCWO of phenol solutions in the pilot plant facility.

Under current legislations most oils used are considered hazardous wastes and its safe collection and disposal must be ensured. Since conventional treatment methods are often inefficient or environmentally unacceptable, the development and application of new technologies is highly necessary. Wet Air Oxidation (WAO) and Supercritical Water Oxidation (SCWO) are two forms of hydrothermal oxidation that have been proved to be effective processes to treat a wide variety of industrial wastes, but they have hardly been tested for oily wastes. In this work, the suitability of hydrothermal oxidation to the treatment of oily wastewaters is described by the results obtained with three different substrates: free fatty acids, cutting oils and bilge wastes. The efficiency of the treatment process is demonstrated for the three oily wastes tested. At temperatures below 350 °C and reaction times of 40 minutes, a 70--90 % of COD elimination is achieved, obtaining an effluent with low molecular weight compounds, mainly carboxylic acids. At 500 °C, a 99 % of COD removal is achieved in less than one minute. At this temperature the reaction seems to proceed mainly through total mineralization to carbon dioxide and water.