This work presents the results of a technical and economic assessment of alkali, thermal and thermo-alkali pretreatments at low temperatures (below 100°C) for the improvement of the anaerobic digestion of sewage sludge in Castiglione Torinese wastewater treatment plant (WWTP). Samples of waste activated sludge (WAS) were collected from the WWTP and subjected to alkali, and thermo-alkali pretreatments with NaOH and Ca(OH)2 with dosage range from 0.04 to 0.20 g alkali/g TS, for 1.5 and 3 hours contact time at 20, 70 and 90°C. The performance of each treatment process was assessed first by determining the Disintegration Rate (DR) and then performing anaerobic digestion tests in batch modality (mesophilic conditions). Test results proved higher efficiency of NaOH compared to Ca(OH)2 in sludge disintegration and soluble COD release. It was observed that with low dosage of NaOH (0.04 g NaOH/g TS) at 20°C DR equal to 15-20 % can be achieved. The combined effect of the chemicals and temperature at 90°C made possible to obtain DR value increases about equal to 40%. The results of the biogas potential tests revealed that the methane yield increased of 28.0, 44.8 and 68.1%, in comparison to the untreated sample, when WAS samples were treated with a NaOH dose of 0.04 g/g TS at respectively 20, 70 and 90°C. Based on a cost analysis that involved the increase in the methane production and the costs of chemicals and thermal treatment, it can be concluded that an increase in the methane yield in the range 15-20% made the pretreatment economically sustainable. This increase in the methane yield can be obtained with a pretreatment carried out at room temperature (20°C) with a small dose of alkali (0.04 g/g TS).

Thermo-alkali pretreatment for the improvement of the anaerobic digestion of waste activated sludge in the largest Italian WWTP / Campo, Giuseppe; Ruffino, Barbara; Zanetti, Mariachiara; Cerutti, Alberto; Scibilia, Gerardo; Lorenzi, Eugenio; Genon, Giuseppe. - ELETTRONICO. - (2016). (Intervento presentato al convegno SludgeTech 2016 tenutosi a Guildford (UK) nel 27-29 Giugno 2016).

Thermo-alkali pretreatment for the improvement of the anaerobic digestion of waste activated sludge in the largest Italian WWTP

CAMPO, GIUSEPPE;RUFFINO, BARBARA;ZANETTI, Mariachiara;CERUTTI, ALBERTO;GENON, Giuseppe
2016

Abstract

This work presents the results of a technical and economic assessment of alkali, thermal and thermo-alkali pretreatments at low temperatures (below 100°C) for the improvement of the anaerobic digestion of sewage sludge in Castiglione Torinese wastewater treatment plant (WWTP). Samples of waste activated sludge (WAS) were collected from the WWTP and subjected to alkali, and thermo-alkali pretreatments with NaOH and Ca(OH)2 with dosage range from 0.04 to 0.20 g alkali/g TS, for 1.5 and 3 hours contact time at 20, 70 and 90°C. The performance of each treatment process was assessed first by determining the Disintegration Rate (DR) and then performing anaerobic digestion tests in batch modality (mesophilic conditions). Test results proved higher efficiency of NaOH compared to Ca(OH)2 in sludge disintegration and soluble COD release. It was observed that with low dosage of NaOH (0.04 g NaOH/g TS) at 20°C DR equal to 15-20 % can be achieved. The combined effect of the chemicals and temperature at 90°C made possible to obtain DR value increases about equal to 40%. The results of the biogas potential tests revealed that the methane yield increased of 28.0, 44.8 and 68.1%, in comparison to the untreated sample, when WAS samples were treated with a NaOH dose of 0.04 g/g TS at respectively 20, 70 and 90°C. Based on a cost analysis that involved the increase in the methane production and the costs of chemicals and thermal treatment, it can be concluded that an increase in the methane yield in the range 15-20% made the pretreatment economically sustainable. This increase in the methane yield can be obtained with a pretreatment carried out at room temperature (20°C) with a small dose of alkali (0.04 g/g TS).
File in questo prodotto:
Non ci sono file associati a questo prodotto.
Pubblicazioni consigliate

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11583/2645815
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo