title: The influence of temperature and SRT on high-solid digestion of municipal sewage sludge.
abstract: The influence of temperature and solids retention time (SRT) on high-solid digestion of municipal sewage sludge was investigated in laboratory-scale reactors. Digestion with high-solid concentration reduces the required digestion volume and is advantageous for urban areas. The experimental conditions comprised total suspended solids (TSS) in digested sludge between 4.0 and 4.6%, temperatures in a range of 33 to 41 °C and the SRT between 10 and 25 d. High-solid digestion operates with increased NH4-N concentrations released from organic compounds. The anaerobic process can be limited by high NH4-N concentration and toxic NH3. In this study a stable digestion was observed up to 2,000 mg L(-1) NH4-N and 75 mg L(-1) NH3. Volatile suspended solids (VSS) and chemical oxygen demand removal was 53% and 57% respectively. However, digestion with 10 d SRT led to a declined VSS removal of 49%. The removal at 41 and 37 °C showed minor differences, while reduced NH4-N release and reduced methane production were observed at 33 °C. For economic reasons, high-solid digestion at 41 °C is not recommended, but will not impair VSS removal. The outcomes of this study confirm that digestion with up to 7.8% TSS in the feed is feasible for the tested temperatures and SRT down to 15 d.
authors.affiliation: Institute for Water Quality, Resource and Waste Management, Vienna University of Technology, Karlsplatz 13/226-1, Vienna 1040, Austria E-mail: ljahn@iwag.tuwien.ac.at.
authors.forename: L
authors.initials: L
authors.lastname: Jahn
authors.affiliation: Institute for Water Quality, Resource and Waste Management, Vienna University of Technology, Karlsplatz 13/226-1, Vienna 1040, Austria E-mail: ljahn@iwag.tuwien.ac.at.
authors.forename: T
authors.initials: T
authors.lastname: Baumgartner
authors.affiliation: Institute for Water Quality, Resource and Waste Management, Vienna University of Technology, Karlsplatz 13/226-1, Vienna 1040, Austria E-mail: ljahn@iwag.tuwien.ac.at.
authors.forename: K
authors.initials: K
authors.lastname: Svardal
authors.affiliation: Institute for Water Quality, Resource and Waste Management, Vienna University of Technology, Karlsplatz 13/226-1, Vienna 1040, Austria E-mail: ljahn@iwag.tuwien.ac.at.
authors.forename: J
authors.initials: J
authors.lastname: Krampe
mesh_terms: D000641:Ammonia / Q000737:chemistry; D057919:Biological Oxygen Demand Analysis; D019149:Bioreactors; D009930:Organic Chemicals; D012722:Sewage / Q000737:chemistry*; D013696:Temperature; D013997:Time Factors
chemical_list: D009930:Organic Chemicals; D012722:Sewage; D000641:Ammonia