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Papers by H. Grigoropoulou

Environmental Science and Pollution Research, Nov 28, 2023

Journal of Environmental Science and Health, Part A, 2002

In the present study, the coagulation of paint industry wastewater was examined. Ferrous and alum... more In the present study, the coagulation of paint industry wastewater was examined. Ferrous and aluminum sulphate and polyaluminum chloride (PACl) were used as coagulation agents and the influence of the coagulant dose and effective pH on the quality of treated wastewater was investigated. Optimum pH for FeSO4 addition was near 9.7, the required coagulant dose was about 2 g/L and average process efficiency varied between 30 and 80% in COD and between 70 and 99% in turbidity terms, for a wide spectrum of wastewater batches. In the case of Al2(SO4)3, no pH adjustment was needed and process efficiency varied between 70 and 95% in COD and between 90 and 99% in turbidity terms, for an effective dose of 2.5 g/L. Further improvement of process efficiency was possible by raising the pH of the supernatant liquid after alum-sludge sedimentation to 10. In the case of PACl optimum pH was around 7 and process efficiency was about 98% based on both quality parameters, for an effective dose of 4 g/L. Cationic polyelectrolytes were proved to have a higher potential vs. coagulation than anionic ones when acting as primary coagulants. Combination of Al2(SO4)3 or PACl with polyelectrolytes resulted in high process efficiencies, while maintaining liquid pH values at acceptable limits.

Industrial & Engineering Chemistry Research, 2006

Chemical and Biochemical Engineering Quarterly, 1997

A set of rhodium catalysts supported on γ-alumina was prepared using the wet impregnation procedu... more A set of rhodium catalysts supported on γ-alumina was prepared using the wet impregnation procedure. The catalysts were tested under steady-state CO-NO reaction. A kinetic study was performed so as to simulate the experimental data to a kinetic expression. Inhibition effects were observed dictating an expression having a denominator in terms of NO concentration. The pH of the impregnation solution was the crucial variable in the preparation of four catalysts of ω=0.22-0.24% Rh at initial pH ranging from 1 to 4.6. The impregnant pH influenced the catalytic performance: catalysts prepared under basic conditions showed a higher catalytic activity than those prepared under acidic conditions.

The feasibility of incorporation of recycled gypsum derived from post-consumer (construction and ... more The feasibility of incorporation of recycled gypsum derived from post-consumer (construction and demolition) gypsum-based waste into the plasterboard manufacturing process up to a maximum target of 30% w/w in feedstock is investigated and the resulting impact on variable plasterboard manufacturing costs is techno-economically assessed, based on data collected from pilot projects in five European plasterboard plants and according to a generic process model. ASPEN Plus 2006 Simulation Software is used for the calculations. The functional unit is 1 m of standard type plasterboard (12,5 mm thickness). The rate of incorporation achieved ranges between 20-30% (average 25,2%), which results in an average 0,6% reduction of the total variable cost per m of plasterboard. According to the cost analysis, this impact is caused by the considerable decrease of raw materials’ cost, which compensates for cost increases in other process parameters (additives, water demand and electrical energy).

Europe’s water service providers are under increasing pressure to deliver improved and affordable... more Europe’s water service providers are under increasing pressure to deliver improved and affordable water services to a growing population, whilst reducing the amount of energy used, lowering the environmental impact of water and wastewater treatment processes, and coping with climate change. These challenges have prompted research on natural processes for wastewater treatment, such as constructed wetlands (CWs), in providing low-energy treatment potential and storage capacity. As the performance of natural treatment processes may be limited by several factors (e.g. climatic conditions, space restrictions), considerable research concentrates on investigating their combination with engineered preor post-treatment processes to improve their performance and increase their treatment resilience. The aim of this paper is to assess and demonstrate the advantages of combined natural and engineered systems (cNES) over purely engineered treatment systems in delivering safe, reliable and efficie...

Issue 3, 2013

The leachability of Pb2+ from natural greek clinoptilolite was investigated according to the stan... more The leachability of Pb2+ from natural greek clinoptilolite was investigated according to the standard procedures TCLP/EPA/RCRA (1311), EPA Methods 1310, 1320 and DIN 38414-S4. Through SEM/EDAX analysis it was shown that lead was uniformly loaded onto the particles subjected to acid treatment. Sorption was fast during the first few hours and equilibrium was practically attained after 24 h. pH was the dominant factor affecting leaching and for values 3 and higher less than 1% of the metal was leached out while at pH=1 up to 20% of the lead initially present on the solid was leached out. At 1.5 and 2, lead was re-adsorbed after initial leaching. % leaching after 24h was found to increase with increasing initial load (17 to 44% for 15 to100 mgPb2+/gclin). Agitation rate (50-180 rpm) and particle size (1.4-2 mm and 5-6 mm) did not affect leaching. Higher temperature (25-40 oC) resulted in increased leaching rates. Despite the limited number of data, leaching seems to follow third-order k...

Issue 2, 2013

At present, chemical processes are widely used to remove phosphorus and organic matter from water... more At present, chemical processes are widely used to remove phosphorus and organic matter from water or wastewater either as the only advanced treatment method or as a pre-treatment stage to biological treatment, and aluminium salts have been traditionally used as coagulants. In the present study removal of orthophosphate or dissolved organic matter with the use of two aluminium sources: alum [Al2(SO4)3•18H2O] and aluminium hydroxide [Al(OH)3(s)] is examined for the wastewater treatment process. Amorphous aluminium hydroxide was chosen because it is the hydrolyzed (olated) product of alum and an important adsorbent of inorganic and organic substances in soils since bayerite, gibbsite and boehmite contain a large portion of aluminium hydroxides. Laboratory jar test studies were carried out using either an orthophosphate solution (10 mg l-1) or a tannic acid solution (50 mgC l-1) as simulated wastewater and the effect of parameters such as coagulant dose (up to 15 mg Al l-1 in the case o...

Separation and Purification Technology, 2005

Microporous and Mesoporous Materials, 2003

Water Science and Technology, Jun 13, 2017

Journal of Remanufacturing

Issue 2

Μany applications in water quality management have a common key water quality parameter, dissolve... more Μany applications in water quality management have a common key water quality parameter, dissolved oxygen, resulting to the critical role of aeration. On the other hand, in municipal and industrial wastewater, especially where aeration is applied, the presence of volatile organic compounds (VOCs) causes several concerns including a direct threat to humans, partly due to their emission from treatment tanks. pH, temperature and Henry’s Law govern VOCs’ speciation and consequently their emission characteristics. Limited data and simplifications of available mass-transfer models pose obstacles to a realistic approach, especially in the presence of a chemical equilibrium, for example in the case of mercaptans. In the present study the importance of oxygen transfer and stripping of a VOC (n-butyl mercaptan) on aeration’s overall effectiveness are examined separately. Clean water oxygenation and stripping of mercaptan to an inert gas (nitrogen) were studied aiming to consider mass transfer...

Waste and Biomass Valorization, 2016

Samples were taken from Metamorphosis/Attica combined treatment plant for municipal wastewater an... more Samples were taken from Metamorphosis/Attica combined treatment plant for municipal wastewater and septage, which treats about 12000 m 3 d -1 of municipal wastewater and 8000 m 3 d -1 of septage, and analyzed for solids, COD, ammonia, nitrate, orthophosphate, polyphosphate and total phosphorus. Ammonia is almost completely eliminated within the plant. Orthophosphates show a removal of about 28%, while

EXTENDED ABSTRACT Fixed bed is the most frequently used operation for ion exchange and adsorption... more EXTENDED ABSTRACT Fixed bed is the most frequently used operation for ion exchange and adsorption and although the fact that this mode of operation is highly useful, its analysis is complex. A predictive model for fixed bed systems requires extensive experimental information, complex mathematical tools and in many cases, for complicated wastewater, the full modeling of the process may be

Water science and technology : a journal of the International Association on Water Pollution Research, 2005

In the present study, phosphorus removal was studied using as coagulant spent alum sludge from a ... more In the present study, phosphorus removal was studied using as coagulant spent alum sludge from a water treatment plant of EYDAP (Athens Water Supply and Sewerage Company) and compared to alum (Al2(SO4)3.18H2O), iron chloride (FeCl3.7H2O), iron sulfate (Fe2(S04).10H2O) and calcium hydroxide (Ca(OH)2) at a constant pH (equal to 6). The comparison was based on their efficiency to remove phosphorus in synthetic wastewater consisting of 10 mg/L P as potassium dihydrogen phosphate and 50 mg/L N as ammonium chloride, The experiments were carried out using a jar-test apparatus and the measurements were performed according to the Standard Methods for the Examination of Water and Wastewater. Pure alum, iron chloride and iron sulfate were much more efficient in phosphorus removal than the spent alum sludge but in the case of calcium hydroxide, phosphorus removal was very low in pH = 6. Specifically, orthophosphate were totally removed by alum using 15 mg/L as Al, by alum sludge using 75 mg/L a...

Environmental Science and Pollution Research, Nov 28, 2023

Journal of Environmental Science and Health, Part A, 2002

In the present study, the coagulation of paint industry wastewater was examined. Ferrous and alum... more In the present study, the coagulation of paint industry wastewater was examined. Ferrous and aluminum sulphate and polyaluminum chloride (PACl) were used as coagulation agents and the influence of the coagulant dose and effective pH on the quality of treated wastewater was investigated. Optimum pH for FeSO4 addition was near 9.7, the required coagulant dose was about 2 g/L and average process efficiency varied between 30 and 80% in COD and between 70 and 99% in turbidity terms, for a wide spectrum of wastewater batches. In the case of Al2(SO4)3, no pH adjustment was needed and process efficiency varied between 70 and 95% in COD and between 90 and 99% in turbidity terms, for an effective dose of 2.5 g/L. Further improvement of process efficiency was possible by raising the pH of the supernatant liquid after alum-sludge sedimentation to 10. In the case of PACl optimum pH was around 7 and process efficiency was about 98% based on both quality parameters, for an effective dose of 4 g/L. Cationic polyelectrolytes were proved to have a higher potential vs. coagulation than anionic ones when acting as primary coagulants. Combination of Al2(SO4)3 or PACl with polyelectrolytes resulted in high process efficiencies, while maintaining liquid pH values at acceptable limits.

Industrial & Engineering Chemistry Research, 2006

Chemical and Biochemical Engineering Quarterly, 1997

A set of rhodium catalysts supported on γ-alumina was prepared using the wet impregnation procedu... more A set of rhodium catalysts supported on γ-alumina was prepared using the wet impregnation procedure. The catalysts were tested under steady-state CO-NO reaction. A kinetic study was performed so as to simulate the experimental data to a kinetic expression. Inhibition effects were observed dictating an expression having a denominator in terms of NO concentration. The pH of the impregnation solution was the crucial variable in the preparation of four catalysts of ω=0.22-0.24% Rh at initial pH ranging from 1 to 4.6. The impregnant pH influenced the catalytic performance: catalysts prepared under basic conditions showed a higher catalytic activity than those prepared under acidic conditions.

The feasibility of incorporation of recycled gypsum derived from post-consumer (construction and ... more The feasibility of incorporation of recycled gypsum derived from post-consumer (construction and demolition) gypsum-based waste into the plasterboard manufacturing process up to a maximum target of 30% w/w in feedstock is investigated and the resulting impact on variable plasterboard manufacturing costs is techno-economically assessed, based on data collected from pilot projects in five European plasterboard plants and according to a generic process model. ASPEN Plus 2006 Simulation Software is used for the calculations. The functional unit is 1 m of standard type plasterboard (12,5 mm thickness). The rate of incorporation achieved ranges between 20-30% (average 25,2%), which results in an average 0,6% reduction of the total variable cost per m of plasterboard. According to the cost analysis, this impact is caused by the considerable decrease of raw materials’ cost, which compensates for cost increases in other process parameters (additives, water demand and electrical energy).

Europe’s water service providers are under increasing pressure to deliver improved and affordable... more Europe’s water service providers are under increasing pressure to deliver improved and affordable water services to a growing population, whilst reducing the amount of energy used, lowering the environmental impact of water and wastewater treatment processes, and coping with climate change. These challenges have prompted research on natural processes for wastewater treatment, such as constructed wetlands (CWs), in providing low-energy treatment potential and storage capacity. As the performance of natural treatment processes may be limited by several factors (e.g. climatic conditions, space restrictions), considerable research concentrates on investigating their combination with engineered preor post-treatment processes to improve their performance and increase their treatment resilience. The aim of this paper is to assess and demonstrate the advantages of combined natural and engineered systems (cNES) over purely engineered treatment systems in delivering safe, reliable and efficie...

Issue 3, 2013

The leachability of Pb2+ from natural greek clinoptilolite was investigated according to the stan... more The leachability of Pb2+ from natural greek clinoptilolite was investigated according to the standard procedures TCLP/EPA/RCRA (1311), EPA Methods 1310, 1320 and DIN 38414-S4. Through SEM/EDAX analysis it was shown that lead was uniformly loaded onto the particles subjected to acid treatment. Sorption was fast during the first few hours and equilibrium was practically attained after 24 h. pH was the dominant factor affecting leaching and for values 3 and higher less than 1% of the metal was leached out while at pH=1 up to 20% of the lead initially present on the solid was leached out. At 1.5 and 2, lead was re-adsorbed after initial leaching. % leaching after 24h was found to increase with increasing initial load (17 to 44% for 15 to100 mgPb2+/gclin). Agitation rate (50-180 rpm) and particle size (1.4-2 mm and 5-6 mm) did not affect leaching. Higher temperature (25-40 oC) resulted in increased leaching rates. Despite the limited number of data, leaching seems to follow third-order k...

Issue 2, 2013

At present, chemical processes are widely used to remove phosphorus and organic matter from water... more At present, chemical processes are widely used to remove phosphorus and organic matter from water or wastewater either as the only advanced treatment method or as a pre-treatment stage to biological treatment, and aluminium salts have been traditionally used as coagulants. In the present study removal of orthophosphate or dissolved organic matter with the use of two aluminium sources: alum [Al2(SO4)3•18H2O] and aluminium hydroxide [Al(OH)3(s)] is examined for the wastewater treatment process. Amorphous aluminium hydroxide was chosen because it is the hydrolyzed (olated) product of alum and an important adsorbent of inorganic and organic substances in soils since bayerite, gibbsite and boehmite contain a large portion of aluminium hydroxides. Laboratory jar test studies were carried out using either an orthophosphate solution (10 mg l-1) or a tannic acid solution (50 mgC l-1) as simulated wastewater and the effect of parameters such as coagulant dose (up to 15 mg Al l-1 in the case o...

Separation and Purification Technology, 2005

Microporous and Mesoporous Materials, 2003

Water Science and Technology, Jun 13, 2017

Journal of Remanufacturing

Issue 2

Μany applications in water quality management have a common key water quality parameter, dissolve... more Μany applications in water quality management have a common key water quality parameter, dissolved oxygen, resulting to the critical role of aeration. On the other hand, in municipal and industrial wastewater, especially where aeration is applied, the presence of volatile organic compounds (VOCs) causes several concerns including a direct threat to humans, partly due to their emission from treatment tanks. pH, temperature and Henry’s Law govern VOCs’ speciation and consequently their emission characteristics. Limited data and simplifications of available mass-transfer models pose obstacles to a realistic approach, especially in the presence of a chemical equilibrium, for example in the case of mercaptans. In the present study the importance of oxygen transfer and stripping of a VOC (n-butyl mercaptan) on aeration’s overall effectiveness are examined separately. Clean water oxygenation and stripping of mercaptan to an inert gas (nitrogen) were studied aiming to consider mass transfer...

Waste and Biomass Valorization, 2016

Samples were taken from Metamorphosis/Attica combined treatment plant for municipal wastewater an... more Samples were taken from Metamorphosis/Attica combined treatment plant for municipal wastewater and septage, which treats about 12000 m 3 d -1 of municipal wastewater and 8000 m 3 d -1 of septage, and analyzed for solids, COD, ammonia, nitrate, orthophosphate, polyphosphate and total phosphorus. Ammonia is almost completely eliminated within the plant. Orthophosphates show a removal of about 28%, while

EXTENDED ABSTRACT Fixed bed is the most frequently used operation for ion exchange and adsorption... more EXTENDED ABSTRACT Fixed bed is the most frequently used operation for ion exchange and adsorption and although the fact that this mode of operation is highly useful, its analysis is complex. A predictive model for fixed bed systems requires extensive experimental information, complex mathematical tools and in many cases, for complicated wastewater, the full modeling of the process may be

Water science and technology : a journal of the International Association on Water Pollution Research, 2005

In the present study, phosphorus removal was studied using as coagulant spent alum sludge from a ... more In the present study, phosphorus removal was studied using as coagulant spent alum sludge from a water treatment plant of EYDAP (Athens Water Supply and Sewerage Company) and compared to alum (Al2(SO4)3.18H2O), iron chloride (FeCl3.7H2O), iron sulfate (Fe2(S04).10H2O) and calcium hydroxide (Ca(OH)2) at a constant pH (equal to 6). The comparison was based on their efficiency to remove phosphorus in synthetic wastewater consisting of 10 mg/L P as potassium dihydrogen phosphate and 50 mg/L N as ammonium chloride, The experiments were carried out using a jar-test apparatus and the measurements were performed according to the Standard Methods for the Examination of Water and Wastewater. Pure alum, iron chloride and iron sulfate were much more efficient in phosphorus removal than the spent alum sludge but in the case of calcium hydroxide, phosphorus removal was very low in pH = 6. Specifically, orthophosphate were totally removed by alum using 15 mg/L as Al, by alum sludge using 75 mg/L a...