This study proposes a novel electrolytic method for simultaneous removal of trace estrogens and regeneration of electrolytic cells for long-term wastewater treatment. Continuous treatments of estrogens estrone (E1), 17β-estradiol (E2) and 17α-ethinyl estradiol (EE2) were theoretically and experimentally studied using an electrolytic reactor equipped with a multi-packed granular glassy carbon electrode reactor. Experimental results demonstrated that E1, E2 and EE2 were effectively removed through electro-polymerization on the granular glassy carbon (and Pt/Ti) anode counter. Polymer formed during continuous treatment was quickly decomposed and electrodes were regenerated completely by OH radicals produced through the reduction of ozone. Calculated overall energy consumptions were less than 10Wh/m3, demonstrating extremely low energy consumptions. In addition, a mathematical model developed based on the limiting mass transfer rate and post-regeneration could represent general trends in time series data observed in experiments.

This study proposes a novel electrolytic method for simultaneous removal of trace estrogens and regeneration of electrolytic cells for long-term wastewater treatment. Continuous treatments of estrogens estrone (El), 17 beta-estradiol (E2) and 17 alpha-ethinyl estradiol (EE2) were theoretically and experimentally studied using an electrolytic reactor equipped with a multi-packed granular glassy carbon electrode reactor. Experimental results demonstrated that El, E2 and EE2 were effectively removed through electro-polymerization on the granular glassy carbon (and Pt/Ti) anode counter. Polymer formed during continuous treatment was quickly decomposed and electrodes were regenerated completely by (OH)-O-center dot radicals produced through the reduction of ozone. Calculated overall energy consumptions were less than 10 Wh/m(3), demonstrating extremely low energy consumptions. In addition, a mathematical model developed based on the limiting mass transfer rate and post-regeneration could represent general trends in time series data observed in experiments. (C) 2014 Elsevier B.V. All rights reserved.

Treatments of estrogens such as Estrone (E1), Estradiol (E2) and Ethinylestradiol (EE2) were conducted using an electrolytic reactor equipped with multi-packed granular glassy carbon electrodes. Experimental results showed that E1, E2 and EE2 were oxidized in the range of 0.45-0.85 V and were removed through electro-polymerization. Observed data from continuous experiments were in good agreement with calculated results by a mathematical model constructed based on mass transfer limitation. In continuous treatment of trace estrogens (1 mu g/L), 98% of E1, E2 and EE2 were stably removed. At high loading rate (100 mu g/L), removal efficiency of E1 was kept around 74%-88% for 21 days, but removal efficiency reduced due to passivation of electrodes. However, removal efficiency was recovered after electrochemical regeneration of electrodes in presence of ozone. Electric energy consumption was observed in the range of 1-2 Wh/m(3). From these results, we concluded that the present electrochemical process would be an alternative removal of estrogens.

Electrochemical removals of natural and synthetic estrogens, Estrone (E1), 17 beta-Estradiol (E2) and Ethynylestradiol (EE2), were experimentally studied using granular electrolytic reactor in combination with a cyclic voltammetric technique. Experimental results showed that by an application of electric current, the estrogens were oxidized at 600-800 mV (vs. Ag/AgCl reference electrode) on the surface of anode and then removed through polymerization of estrogens. Moreover, the electrochemical removal of the estrogens could be reasonably well simulated by a mathematical model developed assuming the external liquid-film mass transfer as a rate-limiting step. Furthermore, it was found that E1 was produced and then removed during the treatment of E2. Further study will be needed to quantify and control the electro-polymerization of estrogens.

:Treatments of estrogens such as Estrone (E1), Estradiol (E2) and Ethinylestradiol (EE2) were conducted using an electrolytic reactor equipped with multi-packed granular glassy carbon electrodes. Experimental results showed that E1, E2 and EE2 were oxidized in the range of 0.45-0.85 V and were removed through electro-polymerization. Observed data from continuous experiments were in good agreement with calculated results by a mathematical model constructed based on mass transfer limitation. In continuous treatment of trace estrogens (1 μg/L), 98% of E1, E2 and EE2 were stably removed. At high loading rate (100 μg/L), removal efficiency of E1 was kept around 74%-88% for 21 days, but removal efficiency reduced due to passivation of electrodes. However, removal efficiency was recovered after electrochemical regeneration of electrodes in presence of ozone. Electric energy consumption was observed in the range of 1-2 Wh/m(3). From these results, we concluded that the present electrochemical process would be an alternative removal of estrogens.

This study proposes a new treatment method to decompose persistent chemicals such as pentachlorophenol (PCP) in water, utilizing hydrogen peroxide present in aquatic plants to proceed the biological Fenton reaction. PCP was not effectively removed by aquatic plants. However, by adding 2.8 mM of Fe2+, there was a rapid removal of PCP while at the same time consumption of endogenous hydrogen peroxide occurred. It was observed the increase of chloride ions formation in water-confirming the complete degradation of PCP. These results demonstrated that PCP was oxidized through a biological Fenton reaction, and hydrogen peroxide in aquatic plants was a key endogenous substance in treatment of refractory toxic pollutants.

Continuous experiments for phosphate removal and recovery from a synthetic wastewater containing calcium phosphate were carried out using an electrolytic reactor equipped with a multi-electrode system. Experimental results demonstrated that phosphate was removed by deposition of aggregates in reactor. In addition, it was found that removal rates and recovery rates of phosphate increased and, after reaching their maximum values, decreased with an increment of applied electric current. Deposit in reactor was recovered and was identified as hydroxyapatite (HAP) from XRD analysis. Furthermore, from comparisons of observed and calculated ions fluxes, it was shown that removal rates of phosphate had a maximum value at a certain electric current density and were controlled by either electrolytic production of hydroxyl ion or mass transfer of hydrogen phosphate ion depending on applied electric current density. Moreover, it was considered that the removal and recovery performance could be enhanced by using working electrodes having larger specific surface area.

Field surveys were conducted to obtain fundamental information on the removal of endocrine disrupting chemicals (EDCs) and pharmaceutical residues (PRs) with conventional water quality parameters in wastewater treatment plants (WWTPs) in Thailand. Oxidation ponds and constructed wetlands were focused on because these systems are adapted in about 60% of municipalities. In the field surveys, water samples including the influent and effluent as well as water at the middle part of plants were taken from 6 WWTPs receiving municipal sewage or hospital wastewater. Totally 11 EDCs and PRs which have been detected frequently in public water body in Thailand were measured by LC-MS/MS. It was found that the EDCs and PRs were present in the range of 0.001 to 10² μg/L and 0.001 to 1 μg/L in the influents and effluents of WWTPs, respectively. Every pollutant was removed by WWTPs in different manner. More than 80% of naproxen and 70% of estrone were removed, while those of other pollutants such as p-acetaminophen, ibuprofen, DEET, and gemfibrozil were different among WWTPs. It was shown that oxidation ponds and constructed wetlands are effective to remove EDCs and PRs concurrently. However, a further study will be needed to evaluate precise removal performances and relations to design and operation parameters.

 In order to clarify the removal performances of estrogens by aquatic plants, experimental studies were conducted using four species of aquatic plants (Ceratophyllum demersum, Riccia fluitans, Spirodela polyrhiza and Limnobium laevigatum) and six enzymes (soluble peroxidase, ionicaly cell wall-bound proxidase, covalently cell wall-bound peroxidase, laccase, polyphenol peroxidase and glutathione-S-transferase) extracted from the plants. Estrone (E1), 17β-estradiol (E2) and 17α-ethinyl estradiol (EE2) were target compounds. It was found that estrogens were efficiently removed by plants as well as by peroxidase and hydrogen peroxide inside plants. Compared with a mathematical model developed based on an assumption of mass transfer diffusion limitation, removal rates of estrogens by aquatic plants were considered to be governed by mass transfer rates of estrogens in liquid film.

Continuous treatments of chlorinated compounds such as 2,4-Dichlbrophenol (2,4-DCP) and Pentachlorophenol (PCP) were conducted using different aquatic plants. Experimental results showed that efficient treatment was achieved for 2,4-DCP but not for PCP. Enzymatic assays indicated that primal enzymes involved in 2,4-DCP removal were peroxidises (POs) that catalyze the following reaction; 2,4-DCP + H2O2 -> Products + H2O. Endogenous H2O2 levels in plants were in the range of 0.1 to 1mmol/kg-F.W. Based on this relatively high H2O2 levels, experimental trials were conducted to decompose PCP by adding Fe2+ ions, demonstrating that PCP could be removed quickly in parallel with the decrease in H2O2 concentration and the production of chloride ions. In addition, OH radical formation was detected by Electron Spin Resonance (ESR) Analysis. These results demonstrate the occurrence of a biological Fenton reaction (i.e. Bio-Fenton Process), which may be used for further treatments of other refractory pollutants.

Endocrine Disturbing Chemicals (EDCs) and pharmaceuticals from human beings and livestock origin are excreted via urine. These substances exist in the levels of mg/l in urine and μg/l or less in aquatic environment, respectively. Their effects are of great concern to public health as well as reproductions of aquatic lives. In this study, we investigated the possibility and performance of electrolytic oxidation treatment of 17βestradiol (E2) and tetracycline (TC) in artificially prepared urine (AU) and human urine. In the batch experiments, it was shown that E2 and TC were removed both in AU and human urine. However, removal rates of E2 and TC were smaller than those observed in an AU solution containing only E2 and TC, where these contaminants were almost removed within an hour. Furthermore, removal efficiency of E2 and TC at 1mA was higher than at 0.1mA. These results indicated that if uric acid was removed by a proper treatment with sufficient electric current, E2 and TC in urine could be efficiently removed by the present electrolytic process.

Continuous treatments of dissolved endocline disrupting chemicals (EDCs) were conducted using a 3-dimensinal electrolytic cells process and treatment performances under different operating conditions were analyzed. Experimental results demonstrated that phenolic EDCs (bisphnol-A, nonyle phenol, 4t-octyle phenol, and 17β-estradiol) were removed efficiently and stably by the process and removal rates were fairly in good agreement with calculation results of a mathematical kinetic model constructed based on mass transfer limitation on liquid film on the surface of electrode. Division of electrolytic cells was considerd effective for enhancing the removal performance.

The wide pollution of Endocrine Disrupting Chemicals (EDCs) in the aquatic environment is of great concern to aquatic organisms and human health. Previous researches indicated that the main sources of the EDCs were sewage treatment plants (STPs). In this paper, we reported treatment results of synthetic wastewater containing several EDCs by a three-dimensional electrode system. Pt/Ti granular electrodes were used to enlarge the effective surface area of the anode. Concentrations of EDCs were prepared in the range of 1-1000 mu g/l. In batch and continuous treatments, EDCs were successfully removed by the present system. Electric current and recycling flow rate played important roles for removal efficiency and reactor design. Energy consumptions were in the range of 0.1-10 Wh/m(3). Furthermore, a selective removal of EDCs was demonstrated. From these results, we concluded that electrochemical oxidation process using the system has a potential for the treatment of trace EDCs.

In this study, the treatment characteristics of nitrate and toxic pesticide by a combined bioelectrochemical reactor (BER)/adsorption process was investigated. Experimental results showed that the disappearance of NO3- in BER was in accordance with the applied current. NO2- was not detected in the effluent, but the production of NO was increased with increasing IPT loading. In the presence of IPT, up to 30% of the nitrate nitrogen consumed was converted to N2O, while more than 95% converted to N-2 in the absence of IPT. In adsorption column, IPT was efficiently removed onto either granular activated carbon or silicone resin so as to meet the guideline value (40 mug/l) and to reduce the N2O accumulation. A simplified kinetic model that considers the sequential reduction of nitrate and inhibition of the N2O reduction step by pesticide as well as Langmuir adsorption isotherm was developed and used to evaluate the process performance. Theoretically predicted effluent concentrations were in good agreement with the observed results for nitrate, nitrite, N2O, N-2 and IPT. It was considered that high removal performance of nitrate and pesticide by the combined process is attributable to high affinity of adsorbates for IPT in comparison with relatively large inhibition constant (K-i). (C) 2002 Elsevier Science Ltd. All rights reserved.

A novel multi-electrode system is proposed for electrolytic and biological water treatments. The multi-electrode system is comprised of multiple working electrodes and their counter electrode, where electric current or potential applied to each electrode is controlled independently. Experimental result for different electrolyte solutions showed that electric charge in the system was efficiently carried by dissociative electrolytes such as carbonate ions. This transfer mechanism is regarded as being effective both in keeping pH level around neutrality and in passing certain amounts of electric current especially in dilute solutions such as groundwater and surface water. A long-term (over 500 days) experiment also showed the enhanced and stable denitrification performance of biofilm-electrode reactor (BER) equipped with the multi-electrode system, comparing to former BERs. This superior performance was thought to be attributable to large effective surface area of electrode, the charge transfer mechanism by dissociative electrolyte, and the formation of highly reducing (or oxidizing) zones. From these results, we conclude that the multi-electrode system is useful for electrolytic and biological treatments of groundwater and surface water.

In this study, a novel multi-cathode biofilm-electrode reactor (BER) combined with micro-filtration (MF) was investigated using a laboratory-scaled experimental apparatus for on-site, remediation of nitrate-contaminated groundwater. In BER, autotrophic denitrification takes place by applying electric current. Extended surface area of multi-electrodes enables BER to operate at high electric currents with low current densities. MF membranes with plate modules and pore size of 0.2 mum were chosen for the final rejection of suspended solids (SS) escaping from BER. Experimental results demonstrated that it was possible to operate the multi-cathode BER with high denitrification rates and low hydraulic retention time. (HRT = 20 min). The overall performance was enhanced by 10 to 60 times in comparison with those in former studies. MF membranes successfully rejected bacteria escaping from BER, so that effluent concentration of SS was below 1 mg-SS/L throughout the experiment. The present BER/MF process is considered applicable for on-site remediation of nitrate-polluted groundwater.

The feasibility of an in situ autotrophic denitrification process was investigated under oligotrophic conditions. Electrodes were embedded in laboratory-scale sandy aquifers and H-2, gas was produced through the electrolysis of water for enhancing autotrophic denitrification. In experiment, a groundwater containing about 20 mg-N/L of NaNO3, and no electron donor was fed continuously, while trace nutrients such as phosphate were not injected. Experimental results showed that, when carbon electrodes were embedded in a direction perpendicular to groundwater flow, the complete and stable denitrification was achieved over one year without clogging problem. Denitrification rate varied depending on applied current. Electric power requirement was in the range of 0.03 similar to 0.09 kWh/g-N. This energy requirement corresponded to about 8 % of total energy obtained from a wind or solar power generation at some places in Japan.

Microbial denitrification and the occurrence of neutralization in a denitrifying biofilm-electrode reactor (BER) using an amorphous carbon anode has been experimentally demonstrated. In this study, the BER was operated over one year and measurements of influent and effluent ionic species were made at different electric currents to evaluate the predominant electrochemical and biological reactions. The ionic species measured were NO3-, NO2-, SO42--, Cl-, PO43-, NH4+, Na+, K+, Ca2+ and Mg2+, most of which are common constituents of surface water or groundwater, Concentrations of Na+, K+, SO42- and Cl- were almost the same in the influent and effluent. Removal efficiency of nitrate (NOS) varied in the range of about 0 to 100%, depending on the electric current. Complete denitrification to Nz gas was readily achieved without accumulation of NO2-, N2O and NH4+. The concentration of Ca2+ and Mg2+ decreased due to deposition onto the surface of the electrode, but the calculation result from the solubility equilibrium of CaCO3, MgCO3 and CaMg(CO3)(2) using the saturation index (SI) showed that the deposition could be hampered by the electrochemical neutralization in the reactor. Furthermore, the deposited calcium and magnesium could be redissolved immediately by changing the polarity of electrodes. From these results, it is concluded that a highly selective reduction of nitrate is operationally possible in the present BER, hence this process is a feasible alternative for the treatment of various nitrate-contaminated water. (C) 1998 Elsevier Science Ltd. All rights reserved.

The enhancement of biological denitrification using a biofilm-electrode reactor (BER) is demonstrated. Removal efficiencies greater than 98% can be achieved. At electric currents in excess of 20 mA, the rate of denitrification within the BER is reduced due to hydrogen inhibition. A detailed steady-state biofilm model is developed taking into account hydrogen inhibition kinetics, the diffusion of neutral and ionic species, the effects of the applied current on the diffusion of ions, gas production within the biofilm, and the presence of a phosphate buffer and a mass transfer boundary layer. The biofilm model is coupled to a model of a completely stirred tank reactor (CSTR). The models are in excellent agreement with the experimental results when the applied electric current is between 0 and 20 mA. The results of the reactor model qualitatively predict the performance of the BER at currents greater than 20 mA using a hydrogen inhibition constant of 10(-4) M.

An electrochemical method for measuring mass transfer coefficients using dilute electrolyte solutions is described. Oxidation-reduction potential measurements are used to determine the limiting current density. A mathematical model taking into account the diffusion and migration of the various electrolyte species was developed to evaluate the mass transfer coefficient. The range of the Sherwood numbers obtained with the present method were of the same order of magnitude as those obtained from classical mass transfer studies. The proposed method and the analytical procedure is applicable to electrochemical bioreactors where the use of excess electrolytes is not recommended.

Denitrifying microorganisms were immobilized with a sodium alginate gel on a cathode electrode, and electric current was applied using a carbon electrode as the anode. Biological reductions of nitrate through the use of H-2 at the cathode and formations of inorganic carbons at the anode were observed. Experimental results showed that oxidation of carbon electrode to CO2 was favorable for developing anoxic conditions and to neutralize alkalinity formed during denitrification. Several volts of potential was needed to operate the reactor.

The effectiveness of a denitrification process which is driven and controlled by an electric current is demonstrated. Denitrifying microorganisms were immobilized on a carbon electrode and hydrogen was produced through the electrolysis of water. The hydrogen was utilized for the reduction of nitrate to N2. The denitrification rate was a linear function of the electric current, and it was shown that about 1 mol of electron reduces 0.2 mol of nitrate to N2 gas. These results exhibit that the proposed process is simple and feasible, especially for the treatment of low-strength nitrate solutions. (C) 1993 John Wiley & Sons, Inc.

Excessive growth of Phormidium tenue and musty odor due to it have been observedrecent years in lake Kusaki located in Gunma, Japan. Variations of the algal growth and water qualities in the lake were observed for two years, and investigated a possibility of forecasting the excessive growth from a simple ecological model with known parameters which were generally reported in former studies. The field surveys showed that distributions of temperature and nutrient concentrationswere significant in the vertical direction but not in horizontal, therefore, a vertical one-dimmensional mathematical model consisted of the heat and mass balance equations was used. The model fairly evaluated the seasonal changes in water qualities of TN, TP, TOC, and Chl. a as well as the thermal stratification and turnovers. Although some modifications of the model should be necessary to evaluatethe P.tenue population exactly. the growth pattern which had two peaks in earlyand late summer in 1990 were estimated reasonably well by assuming a maximum specific growth rate of 2.5 d^-1.

COD removal performance in an anaerobic fixed bed reactor(AAFBR), which treats soluble organic matter, was investigated theoretically by using a simplified biofilm model. The COD removal rate was assumed to be controlled by the decomposition rates of volatile fatty acids such as acetate, propionate and butyrate. The simplified biofilm model took into consideration the effects of intrabiofilm and interbiofilm substrate diffusion rates on substrate biodegradation rates. The COD removal rates in AAFBR were evaluated for various operating conditions by using known kinetic parameters. The calculated results show that the COD removal rates are not affected by adhered biomass provided that the biomass is more than about 4 mg-C/cm2, and vary with temperature, bulk liquid substrate concentrations and the bulk liquid flow rates which are in the range 0.01 approximately 1 m/hr. Relations between allowable COD loading rates and packing diameters were shown schematically for different bulk liquid flow rates.