Maria Loizidou

Equilibrium and kinetic ion exchange studies of Pb2+, Cr3+, Fe3+ and Cu2+ on natural clinoptilolite

In the present study ion exchange of Pb2+, Cu2+, Fe3+ and Cr3+ on natural clinoptilolite is examined at 27 +/- 1 degree C and initial concentration of 10 meq/dm3. Equilibrium is favorable for Pb2+, unfavorable for Cu2+ and sigmoid for Cr3+ and Fe3+. Selectivity series deduced from equilibrium isotherms is Pb2+ > Cr3+ > Fe3+ > Cu2+, while when maximum exchange levels (MELs) are considered, selectivity series is Pb2+ > Cr3+ approximately = Cu2+ > or = Fe3+. Cu2+ manifests the higher value of diffusion coefficient in the clinoptilolite particles among the metals studied, equal to 1.40 x 10(-9) cm2/s. According to the fixed bed experiments the upflow rate (5-15 Bed Volumes (BV)) is influencing the breakthrough point for all metals studied. The breakthrough point varies between 12.3 BV for Pb2+ and 1.18 for Cu2+. Flow rate is also influencing the operating capacity, giving values between 0.433 meq/g(clinoptilolite) for Pb2+ and 0.053 for Fe3+. Breakthrough point values confirm the selectivity order deduced from the equilibrium isotherms, while operating capacity values confirm the selectivity order deduced from MEL experiments.

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.

Ion exchange of Pb2+, Cu2+, Fe3+, and Cr3+ on natural clinoptilolite: selectivity determination and influence of acidity on metal uptake

In the present study ion exchange of Pb(2+), Cu(2+), Fe(3+), and Cr(3+) on natural Greek clinoptilolite was examined in terms of selectivity toward the above heavy metals in single- and multicomponent solutions in batch systems. Also examined are the influence of clinoptilolite on solution acidity and the effect of acidity on the ion exchange process. Clinoptilolite increases solution acidity due to the exchange of H(+) cations with the cations initially present in its structure. H(+) cations should be considered as competitive ones in ion exchange processes, and consequently ion exchange of metals is favored at high acidity values. Cu(2+) and Cr(3+) are the most sensitive cations with respect to acidity. Selectivity determination demonstrates that the selectivity at total concentration 0.01 N and acidity 2 in both single- and multicomponent solutions is following the order Pb(2+)>Fe(3+)>Cr(3+) > or =Cu(2+). This order is set since the first days of equilibration. However, Cu(2+) shows remarkable changes in selectivity and generally its uptake and selectivity are increasing with time. On the other hand selectivity in single metal solutions where acidity is not adjusted is following the order Pb(2+)>Cr(3+)>Fe(3+) congruent with Cu(2+).

A study on the landfill leachate and its impact on the groundwater quality of the greater area

Characterisation of the leachate originating from the Ano Liosia landfill (situated in Attica region, Greece) as well as assessment on the quality of the local aquifer were carried out. The experimental results showed that most of the parameters examined in the leachate samples such as colour, conductivity, TS, COD, NH3–N, PO4–P, SO42−, Cl−, K+, Fe and Pb were found in high levels. The organic load was quite high since the COD concentrations were in the range of 3250–6125 mg L−1. In addition, the low BOD/COD ratio (0.096–0.195), confirmed that the majority of this organic matter is not easily biodegradable. The groundwater near the landfill site was characterised as not potable and not suitable for irrigation water, since most of the physical and chemical parameters examined – such as colour, conductivity, DS, hardness, Cl−, NH3–N, COD, K+, Na+, Ca2+, Fe, Ni and Pb exceeded the permissible limits given by EE, EPA and the Greek Ministry of Agriculture. Furthermore, this study presents the application of the hydrologic evaluation of landfill performance (HELP) model for the determination of the yearly leakage from the base of the landfill after the final capping.

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.

Generation and management of construction and demolition waste in Greece—an existing challenge

In Greece, the construction industry has been developing rapidly over the past decades and the Olympic Games that, will be held in Athens in 2004 have made this development even more intense. The stream of construction and demolition (C&D) waste must be dealt with special attention because of the shortage of landfill space for disposal and the various dangerous substances contained in it, which, can potentially affect the environment and human life if not managed properly. The working group of the NTUA was provided with a grant by Eurostat in order to collect data and illustrate the current status in the country in regards to C&D waste. This paper presents the results of the study and analyses the generation sources, the estimated quantities of C&D waste as well as the current waste management practices in Greece. Recommendations are made in order to deal with this problem effectively and promote sustainable waste management solutions such as reuse and recycling.

MULTI-CRITERIA ANALYSIS FOR THE DETERMINATION OF THE BEST WEEE MANAGEMENT SCENARIO IN CYPRUS

Waste from electrical and electronic equipment (WEEE) constitutes one of the most complicated solid waste streams in terms of its composition, and, as a result, it is difficult to be effectively managed. In view of the environmental problems derived from WEEE management, many countries have established national legislation to improve the reuse, recycling and other forms of recovery of this waste stream so as to apply suitable management schemes. In this work, alternative systems are examined for the WEEE management in Cyprus. These systems are evaluated by developing and applying the Multi-Criteria Decision Making (MCDM) method PROMETHEE. In particular, through this MCDM method, 12 alternative management systems were compared and ranked according to their performance and efficiency. The obtained results show that the management schemes/systems based on partial disassembly are the most suitable for implementation in Cyprus. More specifically, the optimum scenario/system that can be implemented in Cyprus is that of partial disassembly and forwarding of recyclable materials to the native existing market and disposal of the residues at landfill sites.

Preliminary study for the management of construction and demolition waste

This paper refers to the management of the construction and demolition (C&D) waste since, according to the EU Waste Strategy, C&D waste is considered to be one of the priority waste streams and appropriate actions need to be taken with respect to its effective management. Initially, the paper presents the state-of-the-art of the problem of C&D waste, including the amount and composition of C&D waste in EU countries, differences in the characteristics of this waste stream depending on its origin, as well as collection and management practices that are applied. A methodology is described for the estimation of the quantities of the waste stream under examination, since in most cases quantitative primary data is not available. Next, the fundamentals for the development of an integrated scheme for the management of C&D waste are presented and discussed, such as appropriate demolition procedures and location of waste management (off-site waste management, on-site waste management, direct on-site recovery, centralized on-site recovery). Finally, taking into consideration all relevant parameters, alternative systems that could be applied for the management of the C&D waste are suggested.

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.

Pretreatment of natural clinoptilolite in a laboratory-scale ion exchange packed bed

The impact of the operational and chemical conditions of pretreatment upon the effective capacity of clinoptilolite has been investigated. Pretreatment tests have been performed in an ion exchange packed bed. The parameters examined for the pretreatment solution were the volumetric flow rate, the concentration, the total volume and the pH; and for washing after pretreatment the volume of washing water used. An optimal flow rate and a minimum concentration were determined, for a pretreatment that leads to a high effective capacity of the material, while pH adjustment did not result in a higher effective capacity and one washing (10 bed volumes) after pretreatment was found to be sufficient. Furthermore, the water quality (use of tap water) as well as the surface dust of the original material (about 5% w/w) did not alter its effective capacity.