Apostolos Vlyssides

Electrochemical oxidation of a textile dye wastewater using a Pt/Ti electrode

Textile dye wastewater (TDW) from a reactive azo dyeing process was treated by an electrochemical oxidation method using Ti/Pt as anode and stainless steel 304 as cathode. Due to the strong oxidizing potential of the chemicals produced (chlorine, oxygen, hydroxyl radicals and other oxidants) when the wastewater was passed through the electrolytic cell the organic pollutants were oxidized to carbon dioxide and water. A number of experiments were run in a batch, laboratory-scale, pilot-plant, and the results are reported here according to residence time and initial addition of HCl in raw wastewater. When of 2 ml of HCl 36% were added and after 18 min of electrolysis at 0.89 A/cm(2), chemical oxygen demand (COD) was reduced by 86%, biochemical oxygen demand (BOD(5)) was reduced by 71%, ADMI color units were reduced by 100%, and TKN was reduced by 35%. The biodegradability of the wastewater was improved because the COD/BOD ratio decreased from 2.16 to 1.52. At the same time the efficiency of the electrode was about 170 g h(-1) A(-1) m(-2). and the mean energy consumption was 21 kW h/kg of COD. These results indicate that this electrolytic method could be used for effective TDW oxidation or as a feasible detoxification and color removal pretreatment stage for biological post treatment.

Olive oil wastewater treatment with the use of an electrolysis system

Olive oil wastewater (OOW), a toxic liquid associated with the production of olive oil, was treated by an electrochemical method using TiPt as anode and Stainless Steel 304 as cathode. In this technique, sodium chloride 4%(w/v) as an electrolyte was added to the wastewater and the mixture was passed through an electrolytic cell. Due to the strong oxidizing potential of the chemicals produced (chlorine, oxygen, hydroxyl radicals and other oxidants) the organic pollutants were wet oxidized to carbon dioxide and water. A number of experiments were run in a batch, laboratory-scale, pilot-plant, and the results are reported here. After 1 and 10 h of electrolysis at 0.26 A/cm2, total COD was reduced by 41 and 93%, respectively, total TOC was reduced by 20 and 80.4%, VSS were reduced by 1 and 98.7%, and total phenolic compounds were reduced by 50 and 99.4%, while the mean anode efficiency was 1960 g h−1 A−1 sq.m−1 and 340 g h−1 A−1 sq.m−1. Also, the mean energy consumption was 1.273 kwh per kg of COD removed and 12.3 kwh per kg of COD removed for 1 and 10 h, respectively. These results strongly indicate that this electrolytic method of total oxidation of OOW is not feasible. However, it could be used as an oxidation pretreatment stage for detoxification of the wastewater.

Thermal-alkaline solubilization of waste activated sludge as a pre-treatment stage for anaerobic digestion

This work studied the hydrolysis kinetics and the solubilization of waste activated sludge under a medium range temperature (50-90 degrees C) and pH in the alkaline region (8-11), as a pretreatment stage for anaerobic digestion. The hydrolysis rate for the solubilization of volatile suspended solids (VSS) followed a first-order rate. A linear polynomial hydrolysis model was derived from the experimental results leading to a satisfactory correlation between the hydrolysis rate coefficient, pH, and temperature. At pH 11 and a temperature of 90 degrees C the concentration of the VSS was 6.82%, the VSS reduction reached 45% within ten hours and at the same time the soluble COD was 70.000 mg/l and the total efficiency for methane production 0.28 l of CH4 per g of VSS loading.

Testing an electrochemical method for treatment of textile dye wastewater

Abstract Wastewater from total dyeing and finishing stages (TDFW) and wastewater only from dyeing stage (DW) from a Textile cellulosic reactive azo dyeing process were treated separately by an electrochemical method using Ti/Pt as anode and Stainless Steel 304 as cathode. In this technique, sodium chloride was used as an electrolyte and the mixture was passed through an electrolytic cell. Due to the strong oxidizing potential of the chemicals produced (chlorine, oxygen, hydroxyl radicals and other oxidants) the COD, BOD of the wastewaters were substantially decreased using this electrochemical technique. A number of experiments were run in a batch 5 litre apparatus and the results of the electrochemical treatment on the two kinds of wastewaters are reported here. The results indicate that the electrochemical method used is feasible for treatment of textile dyeing wastewaters.

Heavy metal uptake by natural zeolite and metals partitioning in sewage sludge compost

A major limitation of land application of sewage sludge compost is the potential high heavy metal content due to the metal content of the original sludge. Zeolites may be useful as metal scavengers in metal-rich sludges. The natural zeolite, clinoptilolite has the ability to take up heavy metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn). The aim of the reported work was to determine the metal forms most readily taken up by a natural zeolite when used as a bulking material during the composting process. Using a sequential extraction procedure in the raw sludge and in the final products after 150 days of maturity, the heavy metal content was associated with five fractions; the exchangeable, the carbonate, the reducible, the organic and the residual. It was found that a significant percentage of the metals not taken up by the zeolite was associated with the residual fraction, which is considered an inert form.

Integrated strategic approach for reusing olive oil extraction by-products

Abstract Olive oil production is generally connected to the generation of a number of adverse environmental problems. Integrated solutions using various clean technologies within the production processes and the development of new wastewater treatment technologies in connection with by-product utilization approaches can dramatically reduce these problems. In the present study, an integrated solution is presented, based upon results derived from a pilot-plant scale study. According to the results of this study, a 50% decrease in wastewater production from the 3-phase olive oil extraction process was achieved. In addition the implementation of a Fenton oxidation process led to wastewater detoxification with a possible parallel extraction of commercial-value anti-oxidant products. Furthermore, high-quality compost from the solid residues was produced and applied to the soil of the olive orchards.

Detoxification of tannery waste liquors with an electrolysis system

This paper describes an electrochemical treatment and detoxification of tannery waste liquors (TWL). In this technique, TWL was passed through an electrolytic cell using a Ti/Pt anode and a stainless steel 304 cathode. Owing to the strong oxidizing potential of the chemicals produced (chlorine, oxygen, hydroxyl radicals and other oxidants) the organic and inorganic pollutants (ammonia, sulfides and chromium) were wet oxidized to carbon dioxide, nitrogen oxides and sulfur dioxide. In addition, chromium was precipitated as Cr(2)(SO(4))(3). Experiments were run in a batch, laboratory-scale, pilot-plant, and the results are reported herein. After 30 min and 3 h of electrolysis at 0.26 A cm(-2), 45 degrees C and pH 9, total chemical oxygen demand (COD) was reduced by 52 and 83% and biochemical oxygen demand (BOD(5)) was reduced by 35 and 66%, respectively. Additionally, total suspended solids (TSS) were reduced by 8.6 and 26%, total phenolic compounds were reduced by 95.6 and 99.4%. Ammonia, sulfides and soluble chromium were reduced by 100% in both cases, while the mean anode efficiency was 81 g h(-1) A(-1) m(-2) and 1.9 g h(-1) A(-1) m(-2). Also, the mean energy consumption was 4.8 kwh kg(-1) of COD reduced and 200 kwh kg(-1) of COD reduced for 0.5 and 3 h, respectively. These results strongly indicate that this electrolytic method of total oxidation of TWL cannot be cost effective for wide use. However, it can be used as an effective pretreatment stage for detoxification of the wastewater, owing to great efficiency especially with respect to COD and toxicity (phenolics) reduction.

Ethanol production from potato peel waste (PPW)

Considerable concern is caused by the problem of potato peel waste (PPW) to potato industries in Europe. An integrated, environmentally-friendly solution is yet to be found and is currently undergoing investigation. Potato peel is a zero value waste produced by potato processing plants. However, bio-ethanol produced from potato wastes has a large potential market. If Federal Government regulations are adopted in light of the Kyoto agreement, the mandatory blending of bio-ethanol with traditional gasoline in amounts up to 10% will result in a demand for large quantities of bio-ethanol. PPW contain sufficient quantities of starch, cellulose, hemicellulose and fermentable sugars to warrant use as an ethanol feedstock. In the present study, a number of batches of PPW were hydrolyzed with various enzymes and/or acid, and fermented by Saccharomyces cerevisae var. bayanus to determine fermentability and ethanol production. Enzymatic hydrolysis with a combination of three enzymes, released 18.5 g L(-1) reducing sugar and produced 7.6 g L(-1) of ethanol after fermentation. The results demonstrate that PPW, a by-product of the potato industry features a high potential for ethanol production.

Electrochemical treatment in relation to pH of domestic wastewater using Ti/Pt electrodes

This paper describes an electrochemical treatment of domestic wastewater (DW) using 0.8% (w/v) sodium chloride as electrolyte. In this technique, DW was passed through an electrolytic cell using Ti/Pt as anode and Stainless Steel 304 as cathode. Due to the strong oxidizing potential of the chemicals produced (chlorine, oxygen, hydroxyl radicals and other oxidants), the organic pollutants and nutrients (organic nitrogen, phosphorous) were wet oxidized to carbon dioxide, and nitrogen as well as phosphorous was precipitated as Ca(3)(PO(4))(2). Experiments were run in a continuous, laboratory-scale, pilot plant, at 40 degrees C and the efficiency of oxidation was studied in relation to pH. It was found that in alkaline conditions the electrolysis was more efficient. At pH 9, NaCl concentration 0.8% (w/v), current density 0.075 A/cm(2) and for 1h of electrolysis, COD was reduced by 89%, volatile suspended solids (VSS) by 90%, ammonia nitrogen by 82% and total phosphorous by 98%. The efficiency of electrolysis went up to 35 g COD(r)/(hm(2)A) and the energy consumption to 12.4 kWh/kg COD(r). It is concluded that the application of electrolytic oxidation of DW is more advantageous compared to conventional biological treatment especially for small works.

Study of a demonstration plant for the co-composting of olive-oil-processing wastewater and solid residue

Abstract The co-composting of the solid residue and wastewaters from the olive-oil production process has been studied as a new method for the treatment of wastewater containing high organic and toxic pollutants. The experimental results for a demonstration plant using solid residue from olive extraction as bulking material and olive-oil-processing effluents as continuously fed wastewater are reported. Composting temperature was controlled between 45 and 65°C by air supply and the wastewater addition was fed mainly in order to keep the moisture in the range of 45 to 60% and secondly to replace the carbon substrate. During 23 days of operation in the thermophilic region, the system was fed with 263 m 3 wastewater in total, which means an average rate of 11.4 m 3 /day wastewater or 2.9 kg wastewater per kg solid residue. The total bioenergy production was estimated to be about 90 000 000 kcal. Then followed a 3 months stabilization period in the mesophilic region until the final product reached ambient temperature.