The design and operation of the wastewater treatment plant is usually based on the conceptual separation between the wastewater and the sludge streams of the plant. It is important to consider both these aspects of the water purification process in order to achieve the maximum environmental benefits complying with the effluent standards using simple technologies with low energy consumption. Moreover the integration between water and sludge treatment streams could be used to reduce the energy demand of the whole treatment plant as long as the sludge is a potential energy source. The aims of the design and integrated operation with low energy consumption and cost reduction of waste disposal are: to minimize the energy demand of the biological oxidation phase; to maximize the biogas production during the anaerobic stabilization of primary and secondary sludge; to obtain a secondary sludge rich of nutrients, without pathogens and organic micropollutants and with high biological stabilization level in order to use it in agriculture; to obtain the nutrient recovery from liquid side-streams. These objectives can be achieved with a number of improvements on the wastewater treatment plant scheme, such as: 1) Optimization of the COD removal and of the primary sludge production in the primary assisted sedimentation. Inorganic coagulants and/or polyelectrolytes were used in the primary treatment to increase the COD removal efficiency up to 60% and the suspended solids up to 80%. Alternatively lime was used because the coagulant dosage control can be made with a simple pH measure, because the flocs have high settlement velocity and this allows decreasing the settler area and the sludge obtained is more dewatered. The major problem of using lime was the excessive sludge production from the precipitation of the calcium carbonate. The optimization of the exercise conditions was carried out minimizing the lime dosage in the primary treatment and the sludge production operating with pH < 10. 2) Biological treatments. The attached biomass processes can be considered a valid alternative to the traditional activated sludge treatments: they have the benefit of the high removal efficiency of the suspended solids in the primary assisted settler. A biological aerated filter (BAF) was used in order to obtain a highly polished effluent in terms of removal of organic matter, suspended solids and ammonia. Moreover the influence of temperature, pH and nitrite accumulation on the nitrification process were analyzed. Other important improvements are: differentiated treatment for primary and secondary sludge and mechanical or thermal pre-treatment of secondary sludge before the anaerobic stabilization. Since the last two objectives require further research, in this paper we will discuss only the first two topics.

Design and Integrated management of WWTP’S with low energy consumption and cost reduction of waste disposal / Farabegoli, Geneve; R., Ramadori; Rolle, Enrico. - ELETTRONICO. - (2004), pp. ---. (Intervento presentato al convegno Energy, environment and technological innovation tenutosi a Rio de Janeiro, Brasile nel 4-7 Ottobre 2004).

Design and Integrated management of WWTP’S with low energy consumption and cost reduction of waste disposal.

FARABEGOLI, Geneve;ROLLE, Enrico
2004

Abstract

The design and operation of the wastewater treatment plant is usually based on the conceptual separation between the wastewater and the sludge streams of the plant. It is important to consider both these aspects of the water purification process in order to achieve the maximum environmental benefits complying with the effluent standards using simple technologies with low energy consumption. Moreover the integration between water and sludge treatment streams could be used to reduce the energy demand of the whole treatment plant as long as the sludge is a potential energy source. The aims of the design and integrated operation with low energy consumption and cost reduction of waste disposal are: to minimize the energy demand of the biological oxidation phase; to maximize the biogas production during the anaerobic stabilization of primary and secondary sludge; to obtain a secondary sludge rich of nutrients, without pathogens and organic micropollutants and with high biological stabilization level in order to use it in agriculture; to obtain the nutrient recovery from liquid side-streams. These objectives can be achieved with a number of improvements on the wastewater treatment plant scheme, such as: 1) Optimization of the COD removal and of the primary sludge production in the primary assisted sedimentation. Inorganic coagulants and/or polyelectrolytes were used in the primary treatment to increase the COD removal efficiency up to 60% and the suspended solids up to 80%. Alternatively lime was used because the coagulant dosage control can be made with a simple pH measure, because the flocs have high settlement velocity and this allows decreasing the settler area and the sludge obtained is more dewatered. The major problem of using lime was the excessive sludge production from the precipitation of the calcium carbonate. The optimization of the exercise conditions was carried out minimizing the lime dosage in the primary treatment and the sludge production operating with pH < 10. 2) Biological treatments. The attached biomass processes can be considered a valid alternative to the traditional activated sludge treatments: they have the benefit of the high removal efficiency of the suspended solids in the primary assisted settler. A biological aerated filter (BAF) was used in order to obtain a highly polished effluent in terms of removal of organic matter, suspended solids and ammonia. Moreover the influence of temperature, pH and nitrite accumulation on the nitrification process were analyzed. Other important improvements are: differentiated treatment for primary and secondary sludge and mechanical or thermal pre-treatment of secondary sludge before the anaerobic stabilization. Since the last two objectives require further research, in this paper we will discuss only the first two topics.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/323420
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