Publications by authors named "Athanasia G Tekerlekopoulou"

18 Publications

  • Page 1 of 1

The Antimicrobial Properties of Modified Pharmaceutical Bentonite with Zinc and Copper.

Pharmaceutics 2021 Aug 2;13(8). Epub 2021 Aug 2.

Department of Geology, University of Patras, 26504 Patras, Greece.

Pharmaceutical grade bentonite, containing a high amount of montmorillonite, enriched with zinc (Zn) or copper (Cu) (ZnBent and CuBent, respectively) was used as the main component for the creation of formulations for cutaneous use and tested for their antimicrobial capacity. Bentonite (Bent) with added phenoxyethanol (PH) as a preservative and unmodified bentonite were used as control groups. The mineralogical composition, structural state, and physical or chemical properties, before and after the modification of the samples, were characterized utilizing X-ray Diffraction Analysis (XRD), Fourier-Transform Infrared Spectroscopy (FTIR) and X-ray Fluorescence (XRF) techniques, and Scanning Electron Microscope-Energy Dispersive Spectroscopy (SEM, SEM-EDS) analyses. In addition, the profile of zinc and copper concentration from two types of surfaces ZnBent and CuBent, and into Phosphate-Buffered Saline (PBS) are discussed. Finally, the formulations in the form of basic pastes were challenged against bacteria, molds, and yeasts, and their performance was evaluated based on the European Pharmacopeia criteria. The Cu-modified bentonite performed excellently against bacteria and yeasts, while the Zn-modified bentonite only showed great results against yeasts. Therefore, Cu-modified bentonite formulations could offer antimicrobial protection without the use of preservatives.
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http://dx.doi.org/10.3390/pharmaceutics13081190DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8399475PMC
August 2021

Nitrate removal from groundwater using a batch and continuous flow hybrid Fe-electrocoagulation and electrooxidation system.

J Environ Manage 2021 Nov 28;297:113387. Epub 2021 Jul 28.

Department of Chemical Engineering, University of Patras, Rio, GR-26504, Patras, Greece; Institute of Chemical Engineering Sciences (ICE-HT), Stadiou Str., Platani, GR-26504, Patras, Greece.

During the last two decades nitrate contaminated groundwater has become an extensive worldwide problem with wide-reaching negative effects on human health and the environment. In this study, a combination of electrocoagulation (EC) and electrooxidation (EO) was studied as a denitrification process to efficiently remove nitrates and ammonium (a by-product produced during EC) from real polluted groundwater. Initially, EC experiments under batch operating mode were performed using iron electrodes at different applied current density values (20-40 mA cm). Nitrate percentage removal of 100 % was recorded, however high ammonium concentrations were performed (4.5-6.5 mg NH-Ν L). Therefore, a continuous flow system was examined for the complete removal of both nitrates and EC-generated ammonium cations. The system comprised an EC reactor, a settling tank and an EO reactor. The applied current densities to the EC process were the same as those in the batch experiments, while the volumetric flow rates were 4, 6 and 8 mL min. Regarding the current density of the EO process was kept constant at the value of 75 mA cm. The percentage nitrate removal recorded during the EC process ranged between 52.0 and 100 %, while the NH-N concentration at the outlet of the EO reduced significantly (53-100 %) depending on the applied current density and the volumetric flow rate. Also, the dissolved iron concentration in the treated water was always below the legislated limit of 0.2 mg L (up to 0.027 mg L). These results indicate that the proposed hybrid system is capable of denitrifying real nitrate contaminated groundwater without generating toxic by-products, therefore making the water suitable for human consumption.
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http://dx.doi.org/10.1016/j.jenvman.2021.113387DOI Listing
November 2021

Evaluation of the Antimicrobial Protection of Pharmaceutical Kaolin and Talc Modified with Copper and Zinc.

Materials (Basel) 2021 Mar 2;14(5). Epub 2021 Mar 2.

Department of Geology, University of Patras, 26504 Patras, Greece.

Six pharmaceutical pastes were prepared using chemically modified kaolin and talc powders. Tests were conducted to determine their structural and chemical characteristics as well as their antimicrobial protection, thus rendering them suitable for cosmetic and pharmaceutical uses. Kaolin and talc were treated chemically via the cation exchange method to load the clay particles with copper and zinc ions, two cations well known for their antimicrobial properties. Mineralogical analyses were conducted by using X-ray diffraction (XRD) before and after the modification, confirming the mineralogical purity of the samples. Scanning electron microscopy was also used in conjunction with energy dispersed spectroscopy (SEM-EDS) to obtain chemical mapping images, revealing the dispersion of the added metals upon the clay minerals surfaces. Moreover, chemical analysis has been performed (XRF) to validate the enrichment of the clays with each metal utilizing the cation exchange capacity. All modified samples showed the expected elevated concentration in copper or zinc in comparison to their unmodified versions. From the X-ray photoelectron spectroscopy (XPS), the chemical state of the samples' surfaces was investigated, revealing the presence of salt compounds and indicating the oxidation state of adsorbed metals. Finally, the resistance of pastes in microbial growth when challenged with bacteria, molds, and yeasts was assessed. The evaluation is based on the European Pharmacopeia (EP) criteria.
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http://dx.doi.org/10.3390/ma14051173DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7958952PMC
March 2021

Combined electrocoagulation and electrochemical oxidation treatment for groundwater denitrification.

J Environ Manage 2021 May 10;285:112068. Epub 2021 Feb 10.

Department of Chemical Engineering, University of Patras, Rio, GR-26504, Patras, Greece; Institute of Chemical Engineering Sciences (ICE-HT), Stadiou Str., Platani, GR-26504, Patras, Greece. Electronic address:

Electrocoagulation (EC) with an aluminum electrode arrangement as anode-cathode was applied to denitrify groundwater and electrooxidation (EO) was examined as a post-treatment step to remove the produced by-products. Initially, EC experiments were performed under batch operating mode using artificially-polluted tap water to investigate the effects of initial pH (5.5, 7.5, 8.5), initial NO-N concentration (25, 35, 45, 55 mg L) and applied current density (10, 20 mA cm) on process efficiency. The effect of initial solution pH on ammonium cation concentration was also investigated as their generation (as a by-product) is the main drawback preventing wide-scale application of these treatment processes. Experimental results revealed high nitrate removal percentages (up to 96.3%) for initial pH 7.5 and all initial concentrations and current densities, while the final ammonium concentrations ranged between 5.3 and 9.2 mg NH-N L (for initial NO-N of 25 mg L). Therefore, EO was examined to oxidize the ammonium cations to nitrogen gas on iridium oxide coated titanium electrodes (IrO/Ti) anode surface. The effects of cathode material (aluminum, stainless steel), total current density and anode surface area (3.3-30 mA cm and 12-36 cm, respectively) were investigated, and lead to NH-N percentage removals of between 25% (10 mA cm, 12 cm) and 100% (30 mA cm, 24 cm) for an initial NH-N concentration of 10 mg L. The optimum EC (20 mA cm, natural initial pH 7.5-7.8) and EO parameters (30 mA cm, 24 cm surface area anode, Al cathode) were combined into a hybrid system to treat two real nitrate-polluted groundwaters with initial NO-N concentrations of 25 and 75 mg L. Results revealed that the proposed hybrid treatment system can be used to efficiently remove nitrate from groundwaters.
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http://dx.doi.org/10.1016/j.jenvman.2021.112068DOI Listing
May 2021

Two-step treatment of brewery wastewater using electrocoagulation and cyanobacteria-based cultivation.

J Environ Manage 2020 Jul 8;265:110543. Epub 2020 Apr 8.

Department of Chemical Engineering, University of Patras, Rio, GR-26504, Patras, Greece; Institute of Chemical Engineering Sciences (ICE-HT), Stadiou Str., Platani, GR-26504, Patras, Greece.

This study combines electrocoagulation (EC) and cyanobacteria-based cultivation for the two-step treatment of brewery wastewater (BW), with the aim to develop a viable alternative to conventional activated sludge technology. The first step applied EC as a pretreatment method, using different electrode materials (aluminum and iron), to remove color and some pollutant load from the BW. After 30 min of EC treatment, decolorization of BW exceeded 80% for both electrode materials and a 100% reduction of total suspended solids was achieved. In the second step, the electrochemically pretreated BW was used as substrate for a cyanobacteria-based cultivation. After 15 days of cultivation total biomass concentrations (containing up to 50% carbohydrates) reached 525.0 mg L and 740.0 mg L, for aluminum- and iron-pretreated BW, respectively. Moreover, the cyanobacterial community assimilated most of the residual aluminum and iron produced by the EC process, therefore verifying its bioremediation abilities. The combined process also proved effective at pollutant removal (89.1%, 100%, 89.4%, 98.5% and 91.6% of nitrate, ammonium, total Kjeldahl nitrogen, total phosphorus and chemical oxygen demand, respectively). The two-stage treatment method proposed could offer a promising alternative to conventional BW treatment technologies as it combines both efficiency and sustainability.
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http://dx.doi.org/10.1016/j.jenvman.2020.110543DOI Listing
July 2020

A hybrid system for groundwater denitrification using electrocoagulation and adsorption.

J Environ Manage 2019 Nov 6;249:109355. Epub 2019 Sep 6.

Department of Chemical Engineering, University of Patras, Caratheodory 1, University Campus, GR-26504, Patras, Greece; Institute of Chemical Engineering Sciences, Foundation for Research and Technology, PO Box 1414, GR-26504, Patras, Greece. Electronic address:

The treatment of nitrate-contaminated groundwater was studied using a hybrid system comprising an electrocoagulation unit and a zeolite adsorption reactor. In the electrocoagulation (EC) process, aluminum alloy electrodes were used in an undivided cell. Experiments in the laboratory-scale reactor were carried out in unregulated temperature conditions to treat synthetic groundwater solutions containing initial nitrate concentrations of 10-100 mg NO-N·L in batch mode and without using additional pH buffers. Various operating variables, such as applied current density (about 20 mA cm to 80 mA cm), concentration of NaCl electrolyte (0.0-1.0 g L) and treatment time (up to 120 min), were tested for their effects on nitrate removal. Results showed that initial NO-N concentration, current density and electrolyte concentration, play important roles in EC. For all initial NO-N concentrations and current densities tested, the highest NO-N removal rates (up to 2.374 g L·d) were achieved without additional electrolyte and/or with the lowest electrolyte concentration of 0.1 g L. In these experiments, EC reduced NO-N to below the standard limit of 10 mg L after 10-60 min of electrolysis. A significant quantity of by-products, ammonium and dissolved aluminum, formed during the process, however these were successfully removed by zeolite adsorption in the post-treatment step. The electrochemical reactor using the specific anode/cathode combination and an environmentally-friendly post-treatment step such as zeolite adsorption, can be used to efficiently remove nitrate from groundwaters because of its high efficiency.
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http://dx.doi.org/10.1016/j.jenvman.2019.109355DOI Listing
November 2019

Treatment of printing ink wastewater using electrocoagulation.

J Environ Manage 2019 May 27;237:442-448. Epub 2019 Feb 27.

Department of Chemical Engineering, University of Patras, Rio, GR-26504, Patras, Greece; Institute of Chemical Engineering Sciences (ICE-HT), Stadiou Str., Platani, GR-26504, Patras, Greece. Electronic address:

The present study investigates the treatment of real printing ink wastewater by using the electrocoagulation (EC) process. Effects of initial chemical oxygen demand (COD) concentrations, electrode materials and current densities were examined to determine the maximum COD and color removal from the wastewater. In parallel, raw and treated printing ink wastewater toxic potential was further estimated via the application of toxicity tests using the freshwater crustacean Thamnocephalus platyurus for assessing EC process efficiency. According to the results, it was observed that the EC is efficient under most of the operating conditions used, as COD and color removal ranged between 72.03 to 85.81% and 98.7-100%, respectively. The total cost of the EC process, considering the treatment time, applied current, applied voltage and the total anode electrode mass consumption was also estimated. The Fe electrode proved to be of lower cost than the Al electrode, however the use of Al electrode produced better decolorization results in the solutions. Moreover, toxicity tests currently performed with the use of larvae of the fairy shrimp Thamnocephalus platyurus revealed a substantial decrease in the toxic potential of printing ink wastewater, thus indicating the efficiency of the proposed EC process.
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http://dx.doi.org/10.1016/j.jenvman.2019.02.080DOI Listing
May 2019

Fish farm effluents are suitable growth media for , a polyunsaturated fatty acid producing microalga.

Eng Life Sci 2018 Nov 4;18(11):851-860. Epub 2018 Sep 4.

Division of Genetics, Cell & Developmental Biology Department of Biology University of Patras Patras Greece.

Fish farm effluents may be used as culture media for marine microalgae, the cell mass of which constitute an excellent fish feed rich in bioactive compounds. In the current investigation different fish farm effluents were tested as culture media for strains. Among them, grew well on the effluent released from the sedimentation tank (EST), which is the final step of the wastewater treatment. Mono-algal but non-aseptic cultures were conducted in two types of photo-bioreactors, namely stirred tank reactor (STR) and open pond simulating reactor (OPSR) working under various photoperiods. grew well under full illumination mode on phosphate rich EST in the STR, producing 847.0 mg/L of dry cell mass containing 7.8%, w/w lipids, while when cultivated on phosphate limited EST, cell mass production was slightly lower but lipid biosynthesis was favored, with the lipid content reaching 24.7%, w/w in dry cell mass. In all trials, cell mass contained significant quantities of proteins and polysaccharides. Neutral lipids were predominant over polar lipids. Both glycolipid and phospholipid fractions were rich in polyunsaturated fatty acids, especially in eicosapentaenoic acid. We conclude that fish farm wastewaters can be re-used as microalgae growth media, which is of financial and environmental importance.
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http://dx.doi.org/10.1002/elsc.201800064DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6999461PMC
November 2018

A Leptolyngbya-based microbial consortium for agro-industrial wastewaters treatment and biodiesel production.

Environ Sci Pollut Res Int 2018 Jun 22;25(18):17957-17966. Epub 2018 Apr 22.

Institute of Chemical Engineering and High Temperature Chemical Processes (FORTH/ICE-HT), Stadiou Str., Platani, 265 04, Patras, Greece.

A mixed cyanobacterial-mixotrophic algal population, dominated by the filamentous cyanobacterium Leptolyngbya sp. and the microalga Ochromonas (which contributed to the total photosynthetic population with rates of less than 5%), was studied under non-aseptic conditions for its efficiency to remove organic and inorganic compounds from different types of wastes/wastewaters while simultaneously producing lipids. Second cheese whey, poplar sawdust, and grass hydrolysates were used in lab-scale experiments, in photobioreactors that operated under aerobic conditions with different initial nutrient (C, N and P) concentrations. Nutrient removal rates, biomass productivity, and the maximum oil production rates were determined. The highest lipid production was achieved using the biologically treated dairy effluent (up to 14.8% oil in dry biomass corresponding to 124 mg L) which also led to high nutrient removal rates (up to 94%). Lipids synthesized by the microbial consortium contained high percentages of saturated and mono-unsaturated fatty acids (up to 75% in total lipids) for all the substrates tested, which implies that the produced biomass may be harnessed as a source of biodiesel.
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http://dx.doi.org/10.1007/s11356-018-1989-zDOI Listing
June 2018

A novel horizontal subsurface flow constructed wetland: Reducing area requirements and clogging risk.

Chemosphere 2017 Nov 1;186:257-268. Epub 2017 Aug 1.

Department of Environmental and Natural Resources Management, University of Patras, Agrinio, Greece.

The use of Constructed Wetlands (CWs) has been nowadays expanded from municipal to industrial and agro-industrial wastewaters. The main limitations of CWs remain the relatively high area requirements compared to mechanical treatment technologies and the potential occurrence of the clogging phenomenon. This study presents the findings of an innovative CW design where novel materials were used. Four pilot-scale CW units were designed, built and operated for two years. Each unit consisted of two compartments, the first of which (two thirds of the total unit length) contained either fine gravel (in two units) or random type high density polyethylene (HDPE) (in the other two units). This plastic media type was tested in a CW system for the first time. The second compartment of all four units contained natural zeolite. Two units (one with fine gravel and one with HDPE) were planted with common reeds, while the other two were kept unplanted. Second cheese whey was introduced into the units, which were operated under hydraulic residence times (HRT) of 2 and 4 days. After a two-year operation and monitoring period, pollutant removal rates were approximately 80%, 75% and 90% for COD, ammonium and ortho-phosphate, respectively, while temperature and HRT had no significant effect on pollutant removal. CWs containing the plastic media achieved the same removal rates as those containing gravel, despite receiving three times higher hydraulic surface loads (0.08 m/d) and four times higher organic surface loads (620 g/m/d). This reveals that the use of HDPE plastic media could reduce CW surface area requirements by 75%.
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http://dx.doi.org/10.1016/j.chemosphere.2017.07.151DOI Listing
November 2017

Electrochemical treatment of biologically pre-treated dairy wastewater using dimensionally stable anodes.

J Environ Manage 2017 Nov 20;202(Pt 1):217-224. Epub 2017 Jul 20.

Department of Chemical Engineering, University of Patras, Caratheodory 1, GR-26504 Patras, Greece; Institute of Chemical Engineering Sciences, Foundation for Research and Technology, PO Box 1414, GR-26504 Patras, Greece.

In this work, electrochemical oxidation of aerobically pre-treated dairy wastewaters using IrO-Pt coated dimensionally stable anodes was investigated. It was found that IrO/Ti electrode outperforming Pt/Ti and IrO-Pt/Ti at lower current densities, while Pt/Ti achieved better efficiency at higher current density. Among the different parameters which were studied, the current density was the most crucial for the efficiency of the process. A current density of 100 mA/cm led to almost complete removal of 3700 mg/L COD after 360 min of treatment using IrO/Ti electrode and 0.2 M of sodium chloride while complete decolorization was achieved in less than 60 min. Electrolytes also found to significantly affect the process. More specific, the use of sodium chloride instead of sodium sulfate enhanced both COD and color removal due to the formation of active chlorine species. The effect of temperature was relative low; the process was favourable at elevated temperatures while increasing COD loading resulted in a decrease of COD and color removal.
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http://dx.doi.org/10.1016/j.jenvman.2017.07.046DOI Listing
November 2017

Treatment of table olive washing water using trickling filters, constructed wetlands and electrooxidation.

Environ Sci Pollut Res Int 2017 Jan 13;24(2):1085-1092. Epub 2016 Jun 13.

Department of Chemical Engineering, University of Patras, Caratheodory 1, University Campus, GR-26504, Patras, Greece.

The production of table olives is a significant economic activity in Mediterranean countries. Table olive processing generates large volumes of rinsing water that are characterized by high organic matter and phenol contents. Due to these characteristics, a combination of more than one technology is imperative to ensure efficient treatment with low operational cost. Previously, biological filters were combined with electrooxidation to treat table olive washing water. Although this combination was successful in reducing pollutant loads, its cost could be further reduced. Constructed wetlands could be an eligible treatment method for integrated table olive washing water treatment as they have proved tolerant to high organic matter and phenol loads. Two pilot-scale horizontal subsurface constructed wetlands, one planted and one unplanted, were combined with a biological filter and electrooxidation over a boron-doped diamond anode to treat table olive washing water. In the biological filter inlet, chemical oxygen demand (COD) concentrations ranged from 5500 to 15,000 mg/L, while mean COD influent concentration in the constructed wetlands was 2800 mg/L. The wetlands proved to be an efficient intermediate treatment stage, since COD removal levels for the planted unit reached 99 % (mean 70 %), while the unplanted unit presented removal rates of around 65 %. Moreover, the concentration of phenols in the effluent was typically below 100 mg/L. The integrated trickling filter-constructed wetland-electrooxidation treatment system examined here could mineralize and decolorize table olive washing water and fully remove its phenolic content.
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http://dx.doi.org/10.1007/s11356-016-7058-6DOI Listing
January 2017

Mathematical modeling of olive mill waste composting process.

Waste Manag 2015 Sep 11;43:61-71. Epub 2015 Jul 11.

Institute of Chemical Engineering Sciences, FORTH, Stadiou Str., Platani, GR-26504 Patras, Greece; Department of Chemical Engineering, University of Patras, GR-26504 Patras, Greece.

The present study aimed at developing an integrated mathematical model for the composting process of olive mill waste. The multi-component model was developed to simulate the composting of three-phase olive mill solid waste with olive leaves and different materials as bulking agents. The modeling system included heat transfer, organic substrate degradation, oxygen consumption, carbon dioxide production, water content change, and biological processes. First-order kinetics were used to describe the hydrolysis of insoluble organic matter, followed by formation of biomass. Microbial biomass growth was modeled with a double-substrate limitation by hydrolyzed available organic substrate and oxygen using Monod kinetics. The inhibitory factors of temperature and moisture content were included in the system. The production and consumption of nitrogen and phosphorous were also included in the model. In order to evaluate the kinetic parameters, and to validate the model, six pilot-scale composting experiments in controlled laboratory conditions were used. Low values of hydrolysis rates were observed (0.002841/d) coinciding with the high cellulose and lignin content of the composting materials used. Model simulations were in good agreement with the experimental results. Sensitivity analysis was performed and the modeling efficiency was determined to further evaluate the model predictions. Results revealed that oxygen simulations were more sensitive on the input parameters of the model compared to those of water, temperature and insoluble organic matter. Finally, the Nash and Sutcliff index (E), showed that the experimental data of insoluble organic matter (E>0.909) and temperature (E>0.678) were better simulated than those of water.
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http://dx.doi.org/10.1016/j.wasman.2015.06.038DOI Listing
September 2015

Integrated Cr(VI) removal using constructed wetlands and composting.

J Hazard Mater 2015 Jan 7;281:106-113. Epub 2014 Jul 7.

Department of Environmental and Natural Resources Management, University of Patras, G. Seferi 2, GR-30100 Agrinio, Greece; Institute of Chemical Engineering Sciences, Stadiou Str., Platani, GR-26504 Patras, Greece.

The present work was conducted to study integrated chromium removal from aqueous solutions in horizontal subsurface (HSF) constructed wetlands. Two pilot-scale HSF constructed wetlands (CWs) units were built and operated. One unit was planted with common reeds (Phragmites australis) and one was kept unplanted. Influent concentrations of Cr(VI) ranged from 0.5 to 10mg/L. The effect of temperature and hydraulic residence time (8-0.5 days) on Cr(VI) removal were studied. Temperature was proved to affect Cr(VI) removal in both units. In the planted unit maximum Cr(VI) removal efficiencies of 100% were recorded at HRT's of 1 day with Cr(VI) concentrations of 5, 2.5 and 1mg/L, while a significantly lower removal rate was recorded in the unplanted unit. Harvested reed biomass from the CWs was co-composted with olive mill wastes. The final product had excellent physicochemical characteristics (C/N: 14.1-14.7, germination index (GI): 145-157%, Cr: 8-10mg/kg dry mass), fulfills EU requirements and can be used as a fertilizer in organic farming.
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http://dx.doi.org/10.1016/j.jhazmat.2014.06.046DOI Listing
January 2015

Molasses as an efficient low-cost carbon source for biological Cr(VI) removal.

J Hazard Mater 2015 Jan 13;281:95-105. Epub 2014 Aug 13.

Department of Environmental and Natural Resources Management, University of Patras, 2 G. Seferi Str., GR-30100 Agrinio, Greece; Institute of Chemical Engineering Sciences (FORTH/ICE-HT), Stadiou Str., Platani, P.O. Box 1414, GR-26504 Patras, Greece.

In the present study, indigenous microorganisms from industrial sludge were used to reduce the activity of Cr(VI). Molasses, a by-product of sugar processing, was selected as the carbon source (instead of sugar used in a previous work) as it is a low-cost energy source for bioprocesses. Initially, experiments were carried out in suspended growth batch reactors for Cr(VI) concentrations of 1.5-110 mg/L. The time required for complete Cr(VI) reduction increased with initial Cr(VI) concentration. Initial molasses concentration was also found to influence the Cr(VI) reduction rate. The optimal concentration for all initial Cr(VI) concentrations tested was 0.8 gC/L. Experiments were also carried out in packed-bed reactors. Three different operating modes were used to investigate the optimal performance and efficiency of the filter, i.e. batch, continuous and SBR with recirculation. The latter mode with a recirculation rate of 0.5L/min lead to significantly high Cr(VI) reduction rates (up to 135 g/m(2)d). The results of this work were compared with those of a similar work using sugar as the carbon source and indicate that molasses could prove a feasible technological solution to a serious environmental problem.
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http://dx.doi.org/10.1016/j.jhazmat.2014.08.004DOI Listing
January 2015

Biological Cr(VI) removal using bio-filters and constructed wetlands.

Water Sci Technol 2013 ;68(10):2228-33

Department of Environmental and Natural Resources Management, University of Patras, G. Seferi 2, GR-30100 Agrinio, Greece.

The bioreduction of hexavalent chromium from aqueous solution was carried out using suspended growth and packed-bed reactors under a draw-fill operating mode, and horizontal subsurface constructed wetlands. Reactors were inoculated with industrial sludge from the Hellenic Aerospace Industry using sugar as substrate. In the suspended growth reactors, the maximum Cr(VI) reduction rate (about 2 mg/L h) was achieved for an initial concentration of 12.85 mg/L, while in the attached growth reactors, a similar reduction rate was achieved even with high initial concentrations (109 mg/L), thus confirming the advantage of these systems. Two horizontal subsurface constructed wetlands (CWs) pilot-scale units were also built and operated. The units contained fine gravel. One unit was planted with common reeds and one was kept unplanted. The mean influent concentrations of Cr(VI) were 5.61 and 5.47 mg/L for the planted and unplanted units, respectively. The performance of the planted CW units was very effective as mean Cr(VI) removal efficiency was 85% and efficiency maximum reached 100%. On the contrary, the unplanted CW achieved very low Cr(VI) removal with a mean value of 26%. Both attached growth reactors and CWs proved efficient and viable means for Cr(VI) reduction.
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http://dx.doi.org/10.2166/wst.2013.480DOI Listing
March 2014

Modelling of biological Cr(VI) removal in draw-fill reactors using microorganisms in suspended and attached growth systems.

Water Res 2013 Feb 2;47(2):623-36. Epub 2012 Nov 2.

Department of Environmental and Natural Resources Management, University of Western Greece, 2 Seferi Str., 30100 Agrinio, Greece.

The kinetics of hexavalent chromium bio-reduction in draw-fill suspended and attached growth reactors was examined using sugar as substrate and indigenous microorganisms from the industrial sludge of the Hellenic Aerospace Industry. Initially, experiments in suspended growth batch reactors for Cr (VI) concentrations of 1.4-110 mg/l were carried out, to extensively study the behaviour of a mixed culture. The maximum Cr(VI) reduction rate of 2 mg/l h was achieved for initial concentration 12.85 mg/l with biomass production rate 4.1 mg biomass/l h. Analysis of the microbial structure in the batch reactor culture indicated that the dominant bacterial communities were constituted by bacterial members of Raoultella sp., Citrobacter sp., Klebsiella sp., Salmonella sp., Achromobacter sp. and Kerstersia sp. while the dominant fungal strain was that of Pichia jadinii. Experiments using the same mixed culture were also carried out in packed-bed reactors with plastic support media. High removal rates were achieved (2.0 mg/l h) even in high initial concentrations (109 mg/l). A combination of the model of Tsao and Hanson for growth enhancement and that of Aiba and Shoda for growth inhibition was used in order to describe and predict the process of Cr(VI) bio-reduction in suspended growth and packed-bed reactors. Kinetic constants of the equation obtained from both batch (or draw-fill) culture experiments. In the draw-fill experiments at the packed-bed reactor, hexavalent chromium inhibitory effects were minimized increasing the inhibitory constant value K(i)' at 148.5 mg/l, compared to suspended growth experiments which was K(i) = 8.219 mg/l. The model adequately predicts hexavalent chromium reduction in both batch reactors for all initial concentrations tested.
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http://dx.doi.org/10.1016/j.watres.2012.10.034DOI Listing
February 2013

The effect of carbon source on microbial community structure and Cr(VI) reduction rate.

Biotechnol Bioeng 2010 Oct;107(3):478-87

Department of Environmental and Natural Resources Management, University of Ioannina, 2 Seferi Street, Agrinio 30100, Greece.

In the present work, the effect of the carbon source on microbial community structure in batch cultures derived from industrial sludge and hexavalent chromium reduction was studied. Experiments in aerobic batch reactors were carried out by amending industrial sludge with two different carbon sources: sodium acetate and sucrose. In each of the experiments performed, four different initial Cr(VI) concentrations of: 6, 13, 30 and 115 mg/L were tested. The change of carbon source in the batch reactor from sodium acetate to sucrose led to a 1.3-2.1 fold increase in chromium reduction rate and to a 5- to 9.5-fold increase in biomass. Analysis of the microbial structure in the batch reactor showed that the dominant communities were bacterial species (Acinetobacter lwoffii, Defluvibacter lusatiensis, Pseudoxanthomonas japonensis, Mesorhizium chacoense, and Flavobacterium suncheonense) when sodium acetate was used as carbon source and fungal strains (Trichoderma viride and Pichia jadinii), when sodium acetate was replaced by sucrose. These results indicate that the carbon source is a key parameter for microbial dynamics and enhanced chromium reduction and should be taken into account for efficient bioreactor design.
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http://dx.doi.org/10.1002/bit.22837DOI Listing
October 2010
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