title: Early warning indicators for process failure due to organic overloading by rapeseed oil in one-stage continuously stirred tank reactor, sewage sludge and waste digesters.
abstract: Early warning indicators for process failures were investigated to develop a reliable method to increase the production efficiency of biogas plants. Organic overloads by the excessive addition of rapeseed oil were used to provoke the decrease in the gas production rate. Besides typical monitoring parameters, as pH, methane and hydrogen contents, biogas production rate and concentrations of fatty acids; carbon dioxide content, concentrations of calcium and phosphate were monitored. The concentration ratio of volatile fatty acids to calcium acted as an early warning indicator (EWI-VFA/Ca). The EWI-VFA/Ca always clearly and reliably indicated a process imbalance by exhibiting a 2- to 3-fold increase 3-7days before the process failure occurred. At this time, it was still possible to take countermeasures successfully. Furthermore, increases in phosphate concentration and in the concentration ratio of phosphate to calcium also indicated a process failure, in some cases, even earlier than the EWI-VFA/Ca.
authors.affiliation: Microbial GeoEngineering, Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, 14473 Potsdam, Germany. Anne.Kleyboecker@gfz-potsdam.de
authors.forename: A
authors.initials: A
authors.lastname: Kleyböcker
authors.forename: M
authors.initials: M
authors.lastname: Liebrich
authors.forename: W
authors.initials: W
authors.lastname: Verstraete
authors.forename: M
authors.initials: M
authors.lastname: Kraume
authors.forename: H
authors.initials: H
authors.lastname: Würdemann
mesh_terms: D001673:Biodegradation, Environmental; D019149:Bioreactors; D001709:Biotechnology / Q000295:instrumentation* / Q000379:methods*; D002118:Calcium / Q000032:analysis; D005229:Fatty Acids, Monounsaturated; D005232:Fatty Acids, Volatile / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D009930:Organic Chemicals / Q000032:analysis*; D010710:Phosphates / Q000032:analysis; D010938:Plant Oils / Q000737:chemistry*; D000074262:Rapeseed Oil; D012722:Sewage / Q000737:chemistry*; D012972:Sodium Hydroxide / Q000737:chemistry; D014866:Waste Products / Q000032:analysis*
chemical_list: D005229:Fatty Acids, Monounsaturated; D005232:Fatty Acids, Volatile; D009930:Organic Chemicals; D010710:Phosphates; D010938:Plant Oils; D000074262:Rapeseed Oil; D012722:Sewage; D014866:Waste Products; D012972:Sodium Hydroxide; D002118:Calcium