Comparison of different procedures to stabilize biogas formation after process failure in a thermophilic waste digestion system: Influence of aggregate formation on process stability

Journal Article · Fri Jun 15 00:00:00 EDT 2012 · Waste Management

DOI:https://doi.org/10.1016/j.wasman.2012.01.015· OSTI ID:21612982

Kleyboecker, A; Liebrich, M; Kasina, M ^[1]; Kraume, M ^[2]; Wittmaier, M ^[3]; Wuerdemann, H ^[1]

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1. Microbial GeoEngineering, Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, 14473 Potsdam (Germany)
2. Chemical and Process Engineering, Technical University Berlin, 10623 Berlin (Germany)
3. Institute for Recycling and Environmental Protection, Bremen University of Applied Sciences, 28199 Bremen (Germany)

Highlights: Black-Right-Pointing-Pointer Mechanism of process recovery with calcium oxide. Black-Right-Pointing-Pointer Formation of insoluble calcium salts with long chain fatty acids and phosphate. Black-Right-Pointing-Pointer Adsorption of VFAs by the precipitates resulting in the formation of aggregates. Black-Right-Pointing-Pointer Acid uptake and phosphate release by the phosphate-accumulating organisms. Black-Right-Pointing-Pointer Microbial degradation of volatile fatty acids in the aggregates. - Abstract: Following a process failure in a full-scale biogas reactor, different counter measures were undertaken to stabilize the process of biogas formation, including the reduction of the organic loading rate, the addition of sodium hydroxide (NaOH), and the introduction of calcium oxide (CaO). Corresponding to the results of the process recovery in the full-scale digester, laboratory experiments showed that CaO was more capable of stabilizing the process than NaOH. While both additives were able to raise the pH to a neutral milieu (pH > 7.0), the formation of aggregates was observed particularly when CaO was used as the additive. Scanning electron microscopy investigations revealed calcium phosphate compounds in the core of the aggregates. Phosphate seemed to be released by phosphorus-accumulating organisms, when volatile fatty acids accumulated. The calcium, which was charged by the CaO addition, formed insoluble salts with long chain fatty acids, and caused the precipitation of calcium phosphate compounds. These aggregates were surrounded by a white layer of carbon rich organic matter, probably consisting of volatile fatty acids. Thus, during the process recovery with CaO, the decrease in the amount of accumulated acids in the liquid phase was likely enabled by (1) the formation of insoluble calcium salts with long chain fatty acids, (2) the adsorption of volatile fatty acids by the precipitates, (3) the acid uptake by phosphorus-accumulating organisms and (4) the degradation of volatile fatty acids in the aggregates. Furthermore, this mechanism enabled a stable process performance after re-activation of biogas production. In contrast, during the counter measure with NaOH aggregate formation was only minor resulting in a rapid process failure subsequent the increase of the organic loading rate.

• OSTI ID: 21612982
• Journal Information: Waste Management, Vol. 32, Issue 6; Other Information: DOI: 10.1016/j.wasman.2012.01.015; PII: S0956-053X(12)00029-3; Copyright (c) 2012 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0956-053X
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
ACIDIFICATION
ADDITIVES
ADSORPTION
BIODEGRADATION
CALCIUM
CALCIUM OXIDES
CALCIUM PHOSPHATES
CARBON
CARBOXYLIC ACIDS
DIGESTION
METHANE
ORGANIC MATTER
PH VALUE
PHOSPHORUS
PRECIPITATION
SCANNING ELECTRON MICROSCOPY
SODIUM HYDROXIDES
THERMOPHILIC CONDITIONS
VOLATILITY
WASTES
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
ALKALINE EARTH METALS
ALKANES
CALCIUM COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
DECOMPOSITION
ELECTRON MICROSCOPY
ELEMENTS
HYDROCARBONS
HYDROGEN COMPOUNDS
HYDROXIDES
MATTER
METALS
MICROSCOPY
NONMETALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHOSPHATES
PHOSPHORUS COMPOUNDS
SEPARATION PROCESSES
SODIUM COMPOUNDS
SORPTION