Sludge dewatering is a key element in the processing and management of municipal sewage sludge. The efficiency of this task, in turn, results from the selection of the dewatering method and conditioning of the sludge before dewatering. This study was conducted with the purpose of understanding the characteristics of extra cellular polymeric substances (EPS) for two different sludge types and exploring the effect of conditioning on EPS composition. To achieve these objectives, thickened unconditioned (TU) and sludge samples were collected from two wastewater treatment plants (WWTPs) in Milan metropolitan area. Thickened conditioned (TC) sludge samples at selected dosages of 4 and 8 g/kgDS were prepared in the laboratory by means of jar tests. Then, characterization of TU and TC samples in terms of dry solids (DS), volatile solids (VS), total suspended solids (TSS), volatile suspended solids (VSS), zeta potential (ZP) and capillary suction time (CST) was carried out. The EPS content of sludge samples was determined by the combination of physical and chemical methods. EPS were characterized in terms of total levels, protein to carbohydrate (P:C) ratio and repartition as soluble (S-EPS), loosely bound (LB-EPS) and tightly bound (TB-EPS). When analysing the EPS characteristics of two WWTPs (WWTP1 and WWTP2), It was noticed that TB EPS fraction is predominant in both WWTPs samples. Then the effect of conditioning was observed with the EPS analysis of TC samples. According to results, it was observed that the polyelectrolyte conditioner increases the sludge dewaterability while decreasing the total EPS content in the sludge. However strong correlation between the total EPS and dewaterability of sludge was not observed.
La disidratazione dei fanghi è un elemento chiave nel trattamento e nella gestione dei fanghi di depurazione municipali. L'efficienza di questo processo, a sua volta, deriva dalla scelta del metodo di disidratazione e dal condizionamento dei fanghi prima della disidratazione. Questo studio è stato condotto con lo scopo di comprendere le caratteristiche delle sostanze polimeriche extracellulari in due diversi tipi di fanghi ed esplorare l'effetto del condizionamento sulla composizione dell'EPS. Per raggiungere questi obiettivi, sono stati prelevati campioni di fanghi ispessiti non condizionati da fanghi da due impianti di trattamento delle acque reflue nell'area metropolitana di Milano. Campioni di fango ispessito (TC) a dosaggi selezionati di 4 e 8 g/kgDS sono stati preparati in laboratorio mediante jar test. Quindi e stata effettuata, la caratterizzazione dei campioni TU e TC in termini di sostanza secca (DS), solidi volatili (VS), solidi sospesi totali (TSS), solidi sospesi volatili (VSS), potenziale zeta (ZP) e tempo di aspirazione capillare (CST).Il contenuto di EPS dei campioni di fango è stato determinato mediante la combinazione di metodi fisici e chimici. Gli EPS sono stati caratterizzati in termini di livelli totali, rapporto proteine/carboidrati (P: C) e ripartizione come solubili (S-EPS), debolmente legati (LB-EPS) e strettamente legati (TB-EPS). Analizzando le caratteristiche dell'EPS di due WWTP (WWTP1 e WWTP2), è stato notato che la frazione di TB EPS è predominante in entrambi i campioni di WWTP. Quindi è stato osservato l'effetto del condizionamento con l'analisi EPS dei campioni TC. In base ai risultati, è stato osservato che il condizionatore polielettrolitico aumenta la disidratazione dei fanghi diminuendo il contenuto totale di EPS nei fanghi. Tuttavia non è stata osservata una forte correlazione tra l'EPS totale e la disidratazione dei fanghi.
Characterization of extracellular polymeric substances in sewage sludge : influence of conditioning
KOMBUGE, RUMESH UMAYANTHA
2020/2021
Abstract
Sludge dewatering is a key element in the processing and management of municipal sewage sludge. The efficiency of this task, in turn, results from the selection of the dewatering method and conditioning of the sludge before dewatering. This study was conducted with the purpose of understanding the characteristics of extra cellular polymeric substances (EPS) for two different sludge types and exploring the effect of conditioning on EPS composition. To achieve these objectives, thickened unconditioned (TU) and sludge samples were collected from two wastewater treatment plants (WWTPs) in Milan metropolitan area. Thickened conditioned (TC) sludge samples at selected dosages of 4 and 8 g/kgDS were prepared in the laboratory by means of jar tests. Then, characterization of TU and TC samples in terms of dry solids (DS), volatile solids (VS), total suspended solids (TSS), volatile suspended solids (VSS), zeta potential (ZP) and capillary suction time (CST) was carried out. The EPS content of sludge samples was determined by the combination of physical and chemical methods. EPS were characterized in terms of total levels, protein to carbohydrate (P:C) ratio and repartition as soluble (S-EPS), loosely bound (LB-EPS) and tightly bound (TB-EPS). When analysing the EPS characteristics of two WWTPs (WWTP1 and WWTP2), It was noticed that TB EPS fraction is predominant in both WWTPs samples. Then the effect of conditioning was observed with the EPS analysis of TC samples. According to results, it was observed that the polyelectrolyte conditioner increases the sludge dewaterability while decreasing the total EPS content in the sludge. However strong correlation between the total EPS and dewaterability of sludge was not observed.| File | Dimensione | Formato | |
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2021_12_KOMBUGE.pdf
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Descrizione: Thesis_Kombuge Rumesh Umayantha
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https://hdl.handle.net/10589/183804