Waste activated sludge (WAS) contains various organic and inorganic substances that should be treated for a safe disposal. Anaerobic digestion (AD) is the most widely accepted method for stabilizing WAS. This work presents preliminary results concerning the technical and economic feasibility of alkali and hybrid thermo-alkali pretreatments for the improvement of WAS anaerobic digestion. Chemicals used for pretreatments were NaOH and Ca(OH)2, with doses in the range of 0.04-0.2 g alkali/g TS. The same substances were used for hybrid pretreatments at low temperature (70 and 90°C). Test outcomes demonstrated that NaOH was a more performing chemical in sludge disintegration and COD liberation than Ca(OH)2. NaOH showed good performances already at low doses (0.08 g NaOH/g TS) with disintegration rates in the order of 20%. Thermal effect improved alkali performance, in fact the biogas yield increased of 13.2% and 26.8% when samples were treated respectively at 20°C and 70°C with 0.04 g NaOH/g TS for 90 minutes. However, until nowadays economic issues (mainly the cost of chemicals for alkali pretreatments and pH conditioning) have limited the real-world applications of alkali and hybrid pretreatments. The preliminary economic analysis performed in this work demonstrated that, if the pretreatment was carried out with a dose of alkali of 0.08 g NaOH/g TS, only an increase in the methane yield in the order of 60% could offset the cost of chemicals. On the other hand, if the alkali dose was of only 0.04 g NaOH/g TS, increases in the methane yields in the order of 15-20% were sufficient.
Preliminary technical and economic analysis of alkali and low temperature thermo-alkali pretreatments for the anaerobic digestion of waste activated sludge / Ruffino, Barbara; Campo, Giuseppe; Cerutti, Alberto; Zanetti, Mariachiara; Lorenzi, Eugenio; Scibilia, Gerardo; Genon, Giuseppe. - In: WASTE AND BIOMASS VALORIZATION. - ISSN 1877-2641. - STAMPA. - 7:(2016), pp. 667-675. [10.1007/s12649-016-9537-x]
Preliminary technical and economic analysis of alkali and low temperature thermo-alkali pretreatments for the anaerobic digestion of waste activated sludge
RUFFINO, BARBARA;CAMPO, GIUSEPPE;CERUTTI, ALBERTO;ZANETTI, Mariachiara;SCIBILIA, GERARDO;GENON, Giuseppe
2016
Abstract
Waste activated sludge (WAS) contains various organic and inorganic substances that should be treated for a safe disposal. Anaerobic digestion (AD) is the most widely accepted method for stabilizing WAS. This work presents preliminary results concerning the technical and economic feasibility of alkali and hybrid thermo-alkali pretreatments for the improvement of WAS anaerobic digestion. Chemicals used for pretreatments were NaOH and Ca(OH)2, with doses in the range of 0.04-0.2 g alkali/g TS. The same substances were used for hybrid pretreatments at low temperature (70 and 90°C). Test outcomes demonstrated that NaOH was a more performing chemical in sludge disintegration and COD liberation than Ca(OH)2. NaOH showed good performances already at low doses (0.08 g NaOH/g TS) with disintegration rates in the order of 20%. Thermal effect improved alkali performance, in fact the biogas yield increased of 13.2% and 26.8% when samples were treated respectively at 20°C and 70°C with 0.04 g NaOH/g TS for 90 minutes. However, until nowadays economic issues (mainly the cost of chemicals for alkali pretreatments and pH conditioning) have limited the real-world applications of alkali and hybrid pretreatments. The preliminary economic analysis performed in this work demonstrated that, if the pretreatment was carried out with a dose of alkali of 0.08 g NaOH/g TS, only an increase in the methane yield in the order of 60% could offset the cost of chemicals. On the other hand, if the alkali dose was of only 0.04 g NaOH/g TS, increases in the methane yields in the order of 15-20% were sufficient.Pubblicazioni consigliate
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
https://hdl.handle.net/11583/2646565
Attenzione
Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo