Several process units at a wastewater treatment plant (WWTP) can produce a significant level of s... more Several process units at a wastewater treatment plant (WWTP) can produce a significant level of sound and thus induce sound nuisance for nearby residents. The risk for sound nuisance should be considered by making a prognosis of sound impact in an early project phase (planning, design). A prognosis requires information with respect to the sound characteristics of the different process units. This paper reports the development of empirical models for the sound power of relevant process units in the water line at Aquafin WWTPs. The used methodology for model derivation and validation allowed us to minimize the required number of measurements. Besides the methodology, the paper describes in detail the derivation and validation of the empirical model for the splashing water of screw pumps. Also the use of all the derived empirical models to determine the sound impact of a wastewater treatment plant at close distance is illustrated with a case-study.
A standard methodology is presented to remediate odour nuisance at sewage treatment plants. The b... more A standard methodology is presented to remediate odour nuisance at sewage treatment plants. The basic procedure of this methodology is formed by a conscious scheme which integrates all relevant steps in the remediation process (investigative actions, migitating measures, communication, etc.). Theaim of this methodology is to obtain a realistic plan of action, keeping count with local boundary conditions (available resources, available knowledge, certainty about the causes, etc.). In this way, the methodology functions also as a backbone when a well defined odour regulation is lacking, as is the case in Flanders for the moment.
Water reclamation implementation and management practices at municipal wastewater treatment plant... more Water reclamation implementation and management practices at municipal wastewater treatment plants throughout the world are reviewed and some implementation and operational issues are defined. The information is based on a conventional literature survey, on an in depth survey study of European, Israeli and Australian medium and large-scale water reclamation utilities and on the findings of a dedicated international workshop. The review identified over 3,300 water reclamation projects and designed the map of the main process technologies and their fields of product water application. The main conclusion of the enquiry is that the technological risks no longer represent a major concern for the development of water reclamation projects, rather issues such as the financing, failure management and social acceptance have become more critical.
ABSTRACT This chapter presents preliminary results regarding ethene removal from waste gases with... more ABSTRACT This chapter presents preliminary results regarding ethene removal from waste gases with a conventional trickling filter. It also discusses the possibility of adding an organic solvent as an ethene vector to increase the sorption of ethene. Biological waste-gas treatment can be an alternative for physico-chemical treatment, but the use of biological systems may become critical, as the organic compound becomes less water soluble. Experiments are carried out in a continuously operated lab-scale trickling filter. The trickling filter consists of a rectangular shaped plexi-glass column. The preliminary results show that the biomass growth on the packing material could be enhanced by loading the trickling filter with a secondary ordinary carbon source through the liquid circuit. The use of a solvent to increase the sorption of ethene is probably not possible, because ethene shows a low solubility in organic solvents. In addition, the use of a solvent to increase the sorption of ethene is probably not possible, because ethene shows also a low solubility in organic solvents.
Water science and technology : a journal of the International Association on Water Pollution Research, 2001
Several process units at a wastewater treatment plant (WWTP) can produce a significant level of s... more Several process units at a wastewater treatment plant (WWTP) can produce a significant level of sound and thus induce sound nuisance for nearby residents. The risk for sound nuisance should be considered by making a prognosis of sound impact in an early project phase (planning, design). A prognosis requires information with respect to the sound characteristics of the different process units. This paper reports the development of empirical models for the sound power of relevant process units in the water line at Aquafin WWTPs. The used methodology for model derivation and validation allowed us to minimize the required number of measurements. Besides the methodology, the paper describes in detail the derivation and validation of the empirical model for the splashing water of screw pumps. Also the use of all the derived empirical models to determine the sound impact of a wastewater treatment plant at close distance is illustrated with a case-study.
Several process units at a wastewater treatment plant (WWTP) can produce a significant level of s... more Several process units at a wastewater treatment plant (WWTP) can produce a significant level of sound and thus induce sound nuisance for nearby residents. The risk for sound nuisance should be considered by making a prognosis of sound impact in an early project phase (planning, design). A prognosis requires information with respect to the sound characteristics of the different process
Municipal and industrial wastewater treatment plants produce large amounts of sludge. This excess... more Municipal and industrial wastewater treatment plants produce large amounts of sludge. This excess sludge is an inevitable drawback inherent to the waste activated sludge process. Both the reduction of the amount of sludge produced and improving its dewaterability are of paramount importance. Novel pre-treatment processes have been developed in order to improve sludge dewatering, handling and disposal. This paper discusses the oxidation process utilising the catalytic activation of H 2 O 2 by iron salts, referred to as Fenton's reagent. In previous work, the authors described the experimental laboratory results of H 2 O 2-oxidation of thickened sludge. Based upon the optimum conditions obtained in these laboratory tests, pilot-scale experiments are conducted. Peroxidation under its optimum conditions, i.e. (i) through addition of 25 g H 2 O 2 kg −1 DS (dry solids content), (ii) in the presence of 1.67 g Fe 2+-ions kg −1 DS, (iii) at pH 3, and (iv) at ambient temperature and pressure, significantly reduces the amounts of sludge and improves the product quality: the amount DS per equivalent inhabitant per day (DS/IE.d) was reduced from 60 to 33.1 g DS/IE.d and the percentage DS of the sludge cake was 47%, which is high compared with the 20-25% achieved in a traditional sludge dewatering facility. An economic assessment for a wastewater treatment plant of 300 000 IE confirms the benefits. Considering the fixed and variable costs and the savings obtained when the sludge is incinerated after dewatering, a net saving of approx. 950 000 per year or 140 per ton DS can be expected.
Municipal and industrial wastewater treatment plants produce large amounts of sludge, containing ... more Municipal and industrial wastewater treatment plants produce large amounts of sludge, containing organic and mineral components and being mechanically dewatered to e.g. 20-25% DS in centrifuges. Both the reduction of the amount of sludge produced and improving its dewaterability are hence of paramount importance. Hot acid hydrolysis can meet these objectives. The current paper describes the results of detailed investigations with respect to acid hydrolysis of thickened sludge (5-6% DS content). A comparison with traditional thermal hydrolysis is also included. As a result of the experimental investigations, it can be concluded that hot acid hydrolysis is efficient in both reducing the residual sludge amounts and improving the dewaterability. Under the proposed optimum conditions it is found that (i) the amount of hydrolysed DS is approximately 70% lower than the initial untreated amount, (ii) the DS-solid content of the dewatered cake is increased from 22.5% (initial untreated) to at least twice this value, (iii) the rate of mechanical dewatering is not significantly affected. The preferential release of ODS into the water phase, and the increased BOD/COD-ratio through hydrolysis, turn this recycle water phase into a possible carbon-source for nitrification/denitrification. Heavy metals and phosphates are also released in the water phase, and can be subsequently precipitated.
Municipal and industrial wastewater treatment plants produce large amounts of sludge, mostly mech... more Municipal and industrial wastewater treatment plants produce large amounts of sludge, mostly mechanically dewatered to approx. 25% DS and containing organic and mineral components. This sludge needs to be evacuated. Possible reductions of the amount of sludge produced are, hence, important. This paper describes the experimental results of peroxidation of thickened sludge (6% DS content). It can be concluded that peroxidation is efficient in reducing the residual sludge amounts. The optimum conditions correspond with adding 0.037 g H2O2/100 mL sludge at pH = 3 and in the presence of Fe2+ ions (1 mg Fe2+/100 mL sludge). Under these conditions, the rate of mechanical dewatering is significantly improved, and the amount of DS to be dewatered is reduced to approx. 80% of the initial untreated amount. Peroxidation preferentially releases ODS into the water phase. The slightly increased BOD/COD ratio converts this water phase into a more biodegradable and accessible carbon source for nitrification/denitrificatio...
A packed granular activated carbon (GAC) biobed, inoculated with the ethane-degrading strain Myco... more A packed granular activated carbon (GAC) biobed, inoculated with the ethane-degrading strain Mycobacterium E3, was used to study ethene removal from a synthetic waste gas. Ethene, for which the dimensionless partition coefficient for an air-water system at 20 degrees C is about 7.6, was used as a model compound for poorly water soluble gaseous pollutants. In a first mode or operation, the GAC biobed was sprinkled intermittently and the waste gas influent was continuously pre-humidified, establishing relatively moist conditions (water content >40% to 45%). A volumetric ethene removal rate of 0.382 kg COD x m(-3) x d(-1) (0.112 kg ethene x m(-3) x d(-1)) was obtained for an influent concentration of 125 ppm, a superficial waste gas velocity of 3.6E-3 m x s(-1) and a pseudo residence time of 45 s. However, in the second mode of operation, omitting the pre-humidification of the waste gas influent and establishing a "dry" biobed (water content <40% to 45%), and thus obtaining better mass transfer to the biofilm, the ethene removal could be doubled for otherwise comparable operating parameters. Furthermore, under decreased wetting and for the given experimental conditions (influent concentration 125 to 816 ppm, waste gas superficial velocity 3.0E-3 m x s(-1), pseudo waste gas residence time 43 s), the ethene removal was not limited by mass transfer of ethene through the water layer covering the biofilm.
Municipal and industrial wastewater treatment plants produce large amounts of sludge, mostly mech... more Municipal and industrial wastewater treatment plants produce large amounts of sludge, mostly mechanically dewatered to approx. 25% DS and containing organic and mineral components. This sludge needs to be evacuated. Possible reductions of the amount of sludge produced are, hence, important. This paper describes the experimental results of peroxidation of thickened sludge (6% DS content). It can be concluded that peroxidation is efficient in reducing the residual sludge amounts. The optimum conditions correspond with adding 0.037 g H2O2/100 mL sludge at pH = 3 and in the presence of Fe2+ ions (1 mg Fe2+/100 mL sludge). Under these conditions, the rate of mechanical dewatering is significantly improved, and the amount of DS to be dewatered is reduced to approx. 80% of the initial untreated amount. Peroxidation preferentially releases ODS into the water phase. The slightly increased BOD/COD ratio converts this water phase into a more biodegradable and accessible carbon source for nitrification/denitrificatio...
Municipal and industrial wastewater treatment plants produce large amounts of sludge, containing ... more Municipal and industrial wastewater treatment plants produce large amounts of sludge, containing organic and mineral components and being mechanically dewatered to e.g. 20-25% DS in centrifuges. Both the reduction of the amount of sludge produced and improving its dewaterability are hence of paramount importance. Hot acid hydrolysis can meet these objectives. The current paper describes the results of detailed investigations with respect to acid hydrolysis of thickened sludge (5-6% DS content). A comparison with traditional thermal hydrolysis is also included. As a result of the experimental investigations, it can be concluded that hot acid hydrolysis is efficient in both reducing the residual sludge amounts and improving the dewaterability. Under the proposed optimum conditions it is found that (i) the amount of hydrolysed DS is approximately 70% lower than the initial untreated amount, (ii) the DS-solid content of the dewatered cake is increased from 22.5% (initial untreated) to at least twice this value, (iii) the rate of mechanical dewatering is not significantly affected. The preferential release of ODS into the water phase, and the increased BOD/COD-ratio through hydrolysis, turn this recycle water phase into a possible carbon-source for nitrification/denitrification. Heavy metals and phosphates are also released in the water phase, and can be subsequently precipitated.
Municipal and industrial wastewater treatment plants produce large amounts of sludge. This excess... more Municipal and industrial wastewater treatment plants produce large amounts of sludge. This excess sludge is an inevitable drawback inherent to the waste activated sludge process. Both the reduction of the amount of sludge produced and improving its dewaterability are of paramount importance. Novel pre-treatment processes have been developed in order to improve sludge dewatering, handling and disposal. This paper discusses the oxidation process utilising the catalytic activation of H 2 O 2 by iron salts, referred to as Fenton's reagent. In previous work, the authors described the experimental laboratory results of H 2 O 2-oxidation of thickened sludge. Based upon the optimum conditions obtained in these laboratory tests, pilot-scale experiments are conducted. Peroxidation under its optimum conditions, i.e. (i) through addition of 25 g H 2 O 2 kg −1 DS (dry solids content), (ii) in the presence of 1.67 g Fe 2+-ions kg −1 DS, (iii) at pH 3, and (iv) at ambient temperature and pressure, significantly reduces the amounts of sludge and improves the product quality: the amount DS per equivalent inhabitant per day (DS/IE.d) was reduced from 60 to 33.1 g DS/IE.d and the percentage DS of the sludge cake was 47%, which is high compared with the 20-25% achieved in a traditional sludge dewatering facility. An economic assessment for a wastewater treatment plant of 300 000 IE confirms the benefits. Considering the fixed and variable costs and the savings obtained when the sludge is incinerated after dewatering, a net saving of approx. 950 000 per year or 140 per ton DS can be expected.
Water reclamation implementation and management practices at municipal wastewater treatment plant... more Water reclamation implementation and management practices at municipal wastewater treatment plants throughout the world are reviewed and some implementation and operational issues are defined. The information is based on a conventional literature survey, on an in depth survey study of European, Israeli and Australian medium and large-scale water reclamation utilities and on the findings of a dedicated international workshop. The review identified over 3,300 water reclamation projects and designed the map of the main process technologies and their fields of product water application. The main conclusion of the enquiry is that the technological risks no longer represent a major concern for the development of water reclamation projects, rather issues such as the financing, failure management and social acceptance have become more critical.
The treatment of poorly water soluble waste gas compounds, such as ethene, is associated with low... more The treatment of poorly water soluble waste gas compounds, such as ethene, is associated with low substrate concentration levels in the liquid phase. This low concentration level might hamper the optimal development of a microbial population. In this respect, the possible benefit of introducing nitrifying activity in the heterotrophic removal of ethene at moderate concentrations (< 1000 ppm) from a waste gas was investigated. Nitrifying activity is known to be associated with (i) the production of soluble microbial products, which can act as (co-)substrates for heterotrophic micro-organisms and (ii) the co-oxidation of ethene. The used reactor configuration was a packed granular activated carbon biobed inoculated with the heterotrophic strain Mycobacterium E3. The nitrifying activity was introduced by regular submersion in a nitrifying medium prepared from (i) compost or (ii) activated sludge. In both cases a clear enhancement of the volumetric removal rate of ethene could be obs...
Several process units at a wastewater treatment plant (WWTP) can produce a significant level of s... more Several process units at a wastewater treatment plant (WWTP) can produce a significant level of sound and thus induce sound nuisance for nearby residents. The risk for sound nuisance should be considered by making a prognosis of sound impact in an early project phase (planning, design). A prognosis requires information with respect to the sound characteristics of the different process units. This paper reports the development of empirical models for the sound power of relevant process units in the water line at Aquafin WWTPs. The used methodology for model derivation and validation allowed us to minimize the required number of measurements. Besides the methodology, the paper describes in detail the derivation and validation of the empirical model for the splashing water of screw pumps. Also the use of all the derived empirical models to determine the sound impact of a wastewater treatment plant at close distance is illustrated with a case-study.
A standard methodology is presented to remediate odour nuisance at sewage treatment plants. The b... more A standard methodology is presented to remediate odour nuisance at sewage treatment plants. The basic procedure of this methodology is formed by a conscious scheme which integrates all relevant steps in the remediation process (investigative actions, migitating measures, communication, etc.). Theaim of this methodology is to obtain a realistic plan of action, keeping count with local boundary conditions (available resources, available knowledge, certainty about the causes, etc.). In this way, the methodology functions also as a backbone when a well defined odour regulation is lacking, as is the case in Flanders for the moment.
Water reclamation implementation and management practices at municipal wastewater treatment plant... more Water reclamation implementation and management practices at municipal wastewater treatment plants throughout the world are reviewed and some implementation and operational issues are defined. The information is based on a conventional literature survey, on an in depth survey study of European, Israeli and Australian medium and large-scale water reclamation utilities and on the findings of a dedicated international workshop. The review identified over 3,300 water reclamation projects and designed the map of the main process technologies and their fields of product water application. The main conclusion of the enquiry is that the technological risks no longer represent a major concern for the development of water reclamation projects, rather issues such as the financing, failure management and social acceptance have become more critical.
ABSTRACT This chapter presents preliminary results regarding ethene removal from waste gases with... more ABSTRACT This chapter presents preliminary results regarding ethene removal from waste gases with a conventional trickling filter. It also discusses the possibility of adding an organic solvent as an ethene vector to increase the sorption of ethene. Biological waste-gas treatment can be an alternative for physico-chemical treatment, but the use of biological systems may become critical, as the organic compound becomes less water soluble. Experiments are carried out in a continuously operated lab-scale trickling filter. The trickling filter consists of a rectangular shaped plexi-glass column. The preliminary results show that the biomass growth on the packing material could be enhanced by loading the trickling filter with a secondary ordinary carbon source through the liquid circuit. The use of a solvent to increase the sorption of ethene is probably not possible, because ethene shows a low solubility in organic solvents. In addition, the use of a solvent to increase the sorption of ethene is probably not possible, because ethene shows also a low solubility in organic solvents.
Water science and technology : a journal of the International Association on Water Pollution Research, 2001
Several process units at a wastewater treatment plant (WWTP) can produce a significant level of s... more Several process units at a wastewater treatment plant (WWTP) can produce a significant level of sound and thus induce sound nuisance for nearby residents. The risk for sound nuisance should be considered by making a prognosis of sound impact in an early project phase (planning, design). A prognosis requires information with respect to the sound characteristics of the different process units. This paper reports the development of empirical models for the sound power of relevant process units in the water line at Aquafin WWTPs. The used methodology for model derivation and validation allowed us to minimize the required number of measurements. Besides the methodology, the paper describes in detail the derivation and validation of the empirical model for the splashing water of screw pumps. Also the use of all the derived empirical models to determine the sound impact of a wastewater treatment plant at close distance is illustrated with a case-study.
Several process units at a wastewater treatment plant (WWTP) can produce a significant level of s... more Several process units at a wastewater treatment plant (WWTP) can produce a significant level of sound and thus induce sound nuisance for nearby residents. The risk for sound nuisance should be considered by making a prognosis of sound impact in an early project phase (planning, design). A prognosis requires information with respect to the sound characteristics of the different process
Municipal and industrial wastewater treatment plants produce large amounts of sludge. This excess... more Municipal and industrial wastewater treatment plants produce large amounts of sludge. This excess sludge is an inevitable drawback inherent to the waste activated sludge process. Both the reduction of the amount of sludge produced and improving its dewaterability are of paramount importance. Novel pre-treatment processes have been developed in order to improve sludge dewatering, handling and disposal. This paper discusses the oxidation process utilising the catalytic activation of H 2 O 2 by iron salts, referred to as Fenton's reagent. In previous work, the authors described the experimental laboratory results of H 2 O 2-oxidation of thickened sludge. Based upon the optimum conditions obtained in these laboratory tests, pilot-scale experiments are conducted. Peroxidation under its optimum conditions, i.e. (i) through addition of 25 g H 2 O 2 kg −1 DS (dry solids content), (ii) in the presence of 1.67 g Fe 2+-ions kg −1 DS, (iii) at pH 3, and (iv) at ambient temperature and pressure, significantly reduces the amounts of sludge and improves the product quality: the amount DS per equivalent inhabitant per day (DS/IE.d) was reduced from 60 to 33.1 g DS/IE.d and the percentage DS of the sludge cake was 47%, which is high compared with the 20-25% achieved in a traditional sludge dewatering facility. An economic assessment for a wastewater treatment plant of 300 000 IE confirms the benefits. Considering the fixed and variable costs and the savings obtained when the sludge is incinerated after dewatering, a net saving of approx. 950 000 per year or 140 per ton DS can be expected.
Municipal and industrial wastewater treatment plants produce large amounts of sludge, containing ... more Municipal and industrial wastewater treatment plants produce large amounts of sludge, containing organic and mineral components and being mechanically dewatered to e.g. 20-25% DS in centrifuges. Both the reduction of the amount of sludge produced and improving its dewaterability are hence of paramount importance. Hot acid hydrolysis can meet these objectives. The current paper describes the results of detailed investigations with respect to acid hydrolysis of thickened sludge (5-6% DS content). A comparison with traditional thermal hydrolysis is also included. As a result of the experimental investigations, it can be concluded that hot acid hydrolysis is efficient in both reducing the residual sludge amounts and improving the dewaterability. Under the proposed optimum conditions it is found that (i) the amount of hydrolysed DS is approximately 70% lower than the initial untreated amount, (ii) the DS-solid content of the dewatered cake is increased from 22.5% (initial untreated) to at least twice this value, (iii) the rate of mechanical dewatering is not significantly affected. The preferential release of ODS into the water phase, and the increased BOD/COD-ratio through hydrolysis, turn this recycle water phase into a possible carbon-source for nitrification/denitrification. Heavy metals and phosphates are also released in the water phase, and can be subsequently precipitated.
Municipal and industrial wastewater treatment plants produce large amounts of sludge, mostly mech... more Municipal and industrial wastewater treatment plants produce large amounts of sludge, mostly mechanically dewatered to approx. 25% DS and containing organic and mineral components. This sludge needs to be evacuated. Possible reductions of the amount of sludge produced are, hence, important. This paper describes the experimental results of peroxidation of thickened sludge (6% DS content). It can be concluded that peroxidation is efficient in reducing the residual sludge amounts. The optimum conditions correspond with adding 0.037 g H2O2/100 mL sludge at pH = 3 and in the presence of Fe2+ ions (1 mg Fe2+/100 mL sludge). Under these conditions, the rate of mechanical dewatering is significantly improved, and the amount of DS to be dewatered is reduced to approx. 80% of the initial untreated amount. Peroxidation preferentially releases ODS into the water phase. The slightly increased BOD/COD ratio converts this water phase into a more biodegradable and accessible carbon source for nitrification/denitrificatio...
A packed granular activated carbon (GAC) biobed, inoculated with the ethane-degrading strain Myco... more A packed granular activated carbon (GAC) biobed, inoculated with the ethane-degrading strain Mycobacterium E3, was used to study ethene removal from a synthetic waste gas. Ethene, for which the dimensionless partition coefficient for an air-water system at 20 degrees C is about 7.6, was used as a model compound for poorly water soluble gaseous pollutants. In a first mode or operation, the GAC biobed was sprinkled intermittently and the waste gas influent was continuously pre-humidified, establishing relatively moist conditions (water content &gt;40% to 45%). A volumetric ethene removal rate of 0.382 kg COD x m(-3) x d(-1) (0.112 kg ethene x m(-3) x d(-1)) was obtained for an influent concentration of 125 ppm, a superficial waste gas velocity of 3.6E-3 m x s(-1) and a pseudo residence time of 45 s. However, in the second mode of operation, omitting the pre-humidification of the waste gas influent and establishing a &quot;dry&quot; biobed (water content &lt;40% to 45%), and thus obtaining better mass transfer to the biofilm, the ethene removal could be doubled for otherwise comparable operating parameters. Furthermore, under decreased wetting and for the given experimental conditions (influent concentration 125 to 816 ppm, waste gas superficial velocity 3.0E-3 m x s(-1), pseudo waste gas residence time 43 s), the ethene removal was not limited by mass transfer of ethene through the water layer covering the biofilm.
Municipal and industrial wastewater treatment plants produce large amounts of sludge, mostly mech... more Municipal and industrial wastewater treatment plants produce large amounts of sludge, mostly mechanically dewatered to approx. 25% DS and containing organic and mineral components. This sludge needs to be evacuated. Possible reductions of the amount of sludge produced are, hence, important. This paper describes the experimental results of peroxidation of thickened sludge (6% DS content). It can be concluded that peroxidation is efficient in reducing the residual sludge amounts. The optimum conditions correspond with adding 0.037 g H2O2/100 mL sludge at pH = 3 and in the presence of Fe2+ ions (1 mg Fe2+/100 mL sludge). Under these conditions, the rate of mechanical dewatering is significantly improved, and the amount of DS to be dewatered is reduced to approx. 80% of the initial untreated amount. Peroxidation preferentially releases ODS into the water phase. The slightly increased BOD/COD ratio converts this water phase into a more biodegradable and accessible carbon source for nitrification/denitrificatio...
Municipal and industrial wastewater treatment plants produce large amounts of sludge, containing ... more Municipal and industrial wastewater treatment plants produce large amounts of sludge, containing organic and mineral components and being mechanically dewatered to e.g. 20-25% DS in centrifuges. Both the reduction of the amount of sludge produced and improving its dewaterability are hence of paramount importance. Hot acid hydrolysis can meet these objectives. The current paper describes the results of detailed investigations with respect to acid hydrolysis of thickened sludge (5-6% DS content). A comparison with traditional thermal hydrolysis is also included. As a result of the experimental investigations, it can be concluded that hot acid hydrolysis is efficient in both reducing the residual sludge amounts and improving the dewaterability. Under the proposed optimum conditions it is found that (i) the amount of hydrolysed DS is approximately 70% lower than the initial untreated amount, (ii) the DS-solid content of the dewatered cake is increased from 22.5% (initial untreated) to at least twice this value, (iii) the rate of mechanical dewatering is not significantly affected. The preferential release of ODS into the water phase, and the increased BOD/COD-ratio through hydrolysis, turn this recycle water phase into a possible carbon-source for nitrification/denitrification. Heavy metals and phosphates are also released in the water phase, and can be subsequently precipitated.
Municipal and industrial wastewater treatment plants produce large amounts of sludge. This excess... more Municipal and industrial wastewater treatment plants produce large amounts of sludge. This excess sludge is an inevitable drawback inherent to the waste activated sludge process. Both the reduction of the amount of sludge produced and improving its dewaterability are of paramount importance. Novel pre-treatment processes have been developed in order to improve sludge dewatering, handling and disposal. This paper discusses the oxidation process utilising the catalytic activation of H 2 O 2 by iron salts, referred to as Fenton's reagent. In previous work, the authors described the experimental laboratory results of H 2 O 2-oxidation of thickened sludge. Based upon the optimum conditions obtained in these laboratory tests, pilot-scale experiments are conducted. Peroxidation under its optimum conditions, i.e. (i) through addition of 25 g H 2 O 2 kg −1 DS (dry solids content), (ii) in the presence of 1.67 g Fe 2+-ions kg −1 DS, (iii) at pH 3, and (iv) at ambient temperature and pressure, significantly reduces the amounts of sludge and improves the product quality: the amount DS per equivalent inhabitant per day (DS/IE.d) was reduced from 60 to 33.1 g DS/IE.d and the percentage DS of the sludge cake was 47%, which is high compared with the 20-25% achieved in a traditional sludge dewatering facility. An economic assessment for a wastewater treatment plant of 300 000 IE confirms the benefits. Considering the fixed and variable costs and the savings obtained when the sludge is incinerated after dewatering, a net saving of approx. 950 000 per year or 140 per ton DS can be expected.
Water reclamation implementation and management practices at municipal wastewater treatment plant... more Water reclamation implementation and management practices at municipal wastewater treatment plants throughout the world are reviewed and some implementation and operational issues are defined. The information is based on a conventional literature survey, on an in depth survey study of European, Israeli and Australian medium and large-scale water reclamation utilities and on the findings of a dedicated international workshop. The review identified over 3,300 water reclamation projects and designed the map of the main process technologies and their fields of product water application. The main conclusion of the enquiry is that the technological risks no longer represent a major concern for the development of water reclamation projects, rather issues such as the financing, failure management and social acceptance have become more critical.
The treatment of poorly water soluble waste gas compounds, such as ethene, is associated with low... more The treatment of poorly water soluble waste gas compounds, such as ethene, is associated with low substrate concentration levels in the liquid phase. This low concentration level might hamper the optimal development of a microbial population. In this respect, the possible benefit of introducing nitrifying activity in the heterotrophic removal of ethene at moderate concentrations (< 1000 ppm) from a waste gas was investigated. Nitrifying activity is known to be associated with (i) the production of soluble microbial products, which can act as (co-)substrates for heterotrophic micro-organisms and (ii) the co-oxidation of ethene. The used reactor configuration was a packed granular activated carbon biobed inoculated with the heterotrophic strain Mycobacterium E3. The nitrifying activity was introduced by regular submersion in a nitrifying medium prepared from (i) compost or (ii) activated sludge. In both cases a clear enhancement of the volumetric removal rate of ethene could be obs...
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