title: Ammonia sanitisation of sewage sludge using urea.
abstract: The aim of the study was to develop a simple, low-cost treatment for sewage sludge using urea as a sanitising agent. Sewage sludge was spiked with Enterococcus faecalis and Salmonella typhimurium, treated with 0.5, 1, 1.5 and 2% w/w urea at laboratory scale, and the viability was monitored during 4 months of storage at 4, 10 and 22 °C (only 0.5%). A linear relationship was identified between Salmonella spp. inactivation rate and ammonia (NH3) concentration. Temperature had a positive impact on Salmonella spp. inactivation at higher temperatures, but in the range 4-10 °C temperature influenced this inactivation merely by its impact on the ammonia equilibrium. Enterococcus spp. was more persistent and a lag phase of up to 11 weeks was observed. Higher temperature and ammonia concentration reduced the lag phase duration significantly, and also had a clear effect on the inactivation rate for the treatments with 0.5% urea at 22 °C and 2% urea at 4 and 10 °C. Urea sanitisation of sewage sludge can give a 2 log10 reduction of Enterococcus spp. and more than a 5 log10 reduction of Salmonella spp. within 6 weeks with either 0.5% w/w urea at 22 °C or 2% urea at 10 °C.
authors.affiliation: Department of Energy & Technology, Swedish University of Agricultural Sciences, Box 7032, SE-750 07 Uppsala, Sweden E-mail: jorgen.fidjeland@slu.se; Department of Chemistry, Environment and Food Security, National Veterinary Institute, SE-751 89 Uppsala, Sweden.
authors.forename: Jørgen
authors.initials: J
authors.lastname: Fidjeland
authors.forename: Cecilia
authors.initials: C
authors.lastname: Lalander
authors.forename: Håkan
authors.initials: H
authors.lastname: Jönsson
authors.forename: Björn
authors.initials: B
authors.lastname: Vinnerås
mesh_terms: D000641:Ammonia; D004203:Disinfection / Q000379:methods*; D016983:Enterococcus; D013293:Enterococcus faecalis; D006863:Hydrogen-Ion Concentration; D012475:Salmonella; D012486:Salmonella typhimurium; D012722:Sewage / Q000382:microbiology*; D013696:Temperature; D014508:Urea / Q000008:administration & dosage
chemical_list: D012722:Sewage; D000641:Ammonia; D014508:Urea