Comparative evaluation of sludge surface charge as an indicator of process fluctuations in a biogas reactor.

The current political situation imposes high demands on the economic feasibility of biogas plants. High prizes for biogas substrates and a trend to reduced feed-in tariffs generated an increasing need to optimize substrate exploitation and operation conditions. This includes a comprehensive and reliable biogas process monitoring.

The use of 13C-labelled polycyclic aromatic hydrocarbons for the analysis of their transformation in soil.

The formation of non-extractable residues during biodegradation and humification processes in soils and sediments represents a major sink for organic contaminants. The mode of incorporation of polycyclic aromatic hydrocarbons (PAH) and their metabolites into macromolecular organic matter during microbial degradation was studied applying 13C-labelled compounds. Mineralisation rates were determined by measuring the 13CO2 production.

Impact of inoculation protocols, salinity, and pH on the degradation of polycyclic aromatic hydrocarbons (PAHs) and survival of PAH-degrading bacteria introduced into soil.

Degradation of polycyclic aromatic hydrocarbons (PAHs) and survival of bacteria in soil was investigated by applying different inoculation protocols. The soil was inoculated with Sphingomonas paucimobilis BA 2 and strain BP 9, which are able to degrade anthracene and pyrene, respectively. CFU of soil bacteria and of the introduced bacteria were monitored in native and sterilized soil at different pHs.

Microbial degradation of polycyclic aromatic hydrocarbons in soils affected by the organic matrix of compost.

This paper describes the degradation of naphthalene, phenanthrene, anthracene, fluoranthene, and pyrene in soil and soil/compost mixtures. Compost addition facilitated the degradation of 500 mg naphthalene/kg soil and 100 mg/kg each of other polycyclic aromatic hydrocarbons (PAH) within 25 days in soil systems with water contents below the water-holding capacity. By means of a humic acid extraction, it was demonstrated that the decrease of PAH concentrations after compost addition was not caused by a sorption to organic matter preventing PAH analysis.

Fate of 14C-labeled anthracene and hexadecane in compost-manured soil.

Experiments were carried out to evaluate the impact of the addition of ripe compost on the degradation of two 14C-labeled hydrocarbon model compounds (anthracene and hexadecane) in soil. The addition of mature compost (20% dry wt./dry wt) stimulated significantly the disappearance of the extractable fraction of both compounds.