[Intensification of Microbial Decomposition of Organic Fraction of Municipal Waste: Laboratory and Field Experiments].

Methods of intensifying the anaerobic microbial decomposition of the organic fraction of municipal solid waste (MSW) on an MSW landfill and in anaerobic reactors were studied. It was discovered that it is preferable for the initiation and stabilization of the process of anaerobic digestion of organic waste in laboratory bioreactors at 20 and 50 degrees C to use a mixture of activated suspension of soil from the anaerobic zone of the landfill and digested sewage sludge. Stimulation of methanogenesis was shown in field conditions when digested sewage sludge was added directly into the upper layer of anaerobic zone of the landfill. The investigation of methane production during fermentation of concentrated food waste with a mixture of excessive activated sludge in the laboratory under thermophilic conditions (50 degrees C) has shown that the main problem at the first stage of the process was the acidification of the digested mixture due to the accumulation of volatile fatty acids. It was shown that for stable operation of the bioreactor under thermophilic conditions the amount of inoculum added during the start up should be no less than 30%-50%--based on volatile suspended solids. A sharp decrease in the digestion temperature from 50 to 20 degrees C did not cause methanogenesis termination, since the thermophilically fermented biomass contained both thermophilic and mesophilic methanogens.

[Detection of anaerobic processes and microorganisms in immobilized activated sludge of a wastewater treatment plant with intense aeration].

Attached activated sludge from the Krasnaya Polyana (Sochi) wastewater treatment plant was studied after the reconstruction by increased aeration and water recycle, as well as by the installation of a bristle carrier for activated sludge immobilization. The activated sludge biofilms developing under conditions of intense aeration were shown to contain both aerobic and anaerobic microorganisms. Activity of a strictly anaerobic methanogenic community was revealed, which degraded organic compounds to methane, further oxidized by aerobic methanotrophs. Volatile fatty acids, the intermediates of anaerobic degradation of complex organic compounds, were used by both aerobic and anaerobic microorganisms. Anaerobic oxidation of ammonium with nitrite (anammox) and the presence of obligate anammox bacteria were revealed in attached activated sludge biofilms. Simultaneous aerobic and anaerobic degradation of organic contaminants by attached activated sludge provides for high rates of water treatment, stability of the activated sludge under variable environmental conditions, and decreased excess sludge formation.

Enumeration of methanotrophic bacteria in the cover soil of an aged municipal landfill.

The enumeration of methanotrophic bacteria in the cover soil of an aged municipal landfill was carried out using (1) fluorescent in situ hybridization (FISH) with horseradish peroxidase-labeled oligonucleotide probes and tyramide signal amplification, also known as catalyzed reporter deposition-FISH (CARD-FISH), and (2) most probable number (MPN) method. The number of methanotrophs was determined in cover soil samples collected during April-November 2003 from a point with low CH(4) emission. The number of types I and II methanotrophs obtained by CARD-FISH varied from 15 +/- 2 to 56 +/- 7 x 10(8) cells g(-1) absolute dry mass (adm) of soil and methanotrophs of type I dominated over type II. The average number of methanotrophs throughout the cover soil profile was highest during May-September when the cover soil temperature was above 13 degrees C. Methanotrophs accounted for about 50% of the total bacterial population in the deepest cover soil layer owing to higher availability of substrate (CH(4)). A lower number of methanotrophs (7 x 10(2) to 17 x 10(5) cells g(-1) adm of soil) was determined by the MPN method compared to the CARD-FISH counts, thus confirming previous results that the MPN method is limited to the estimation of the culturable species that can be grown under the incubation conditions used. The number of culturable methanotrophs correlated with the methane-oxidizing activity measured in laboratory assays. In comparison to the incubation-based measurements, the number of methanotrophs determined by CARD-FISH better reflected the actual characteristics of the environment, such as release and uptake of CH(4), temperature, and moisture, and availability of substrates.

[Methane oxidation in landfill cover soil].

Methane oxidation in the cover soil of the Khmet'evo municipal landfill in Moscow oblast was investigated. Methane emission from the experimental parcel of the site was highly inhomogeneous. At a depth of 45-60 cm, the pore gas mainly consisted of CH4 (60-70%) and CO2 (30-40%). In the upper horizons of the cover soil, the concentration of these gases sharply decreased. Techniques for estimation of the methane-oxidizing activity in the cover soil of the landfill were tested. The rate of methane oxidation in the soil, the factor limiting methane emission from the surface of the site, correlated with the cell number of culturable methanotrophic bacteria. The method of indirect immunofluorescence revealed ten known species of methanotrophic bacteria in enrichment cultures obtained from samples of the cover soil. Our results also indicate the presence of unknown psychrotolerant methanotrophs that are active at the low temperatures characteristic of Moscow oblast.

Production and oxidation of methane at low temperature by the microbial population of municipal sludge checks situated in north-east Europe.

Methanogenic and methane-oxidizing activities of the microbial population of sewage sludge checks (Moscow and Syktyvkar regions) were studied at temperatures ranging from 5 to 25 degrees C. The number of methanogens in silt samples reached 10(10) cells/ml. A temperature decrease from 25 to 5 degrees C led to a sharp decrease of methanogenesis in the silt samples. Nevertheless, methanogenesis was still significant even at 5 degrees C. Different organic substrates, including polymeric and aromatic compounds, were degraded with methane production at 6 degrees C. At depths of 20-40 cm the number of methanotrophic bacteria reached 10(11) cells/ml. Methane oxidative activity of the microbial populations in the silt was less sensitive to the 25 degrees to 5 degrees C temperature decrease. Ten methanotrophic species, able to grow at 6 degrees C, were enriched from the Syktyvkar sludge lagoon and identified by indirect immunofluorescence. Enrichments obtained from the Syktuvkar region (62 N) contained more species of methane oxidizing bacteria able to grow at low temperature then methanogenic enrichments obtained from Moscow region (56 N).

[Microbiologic characteristics of a trisectional horizontal biogas tank running on cow manure]. / Mikrobiologicheskaia kharakteristika trekhsektsionnoi gorizontal'noi biogazovoi ustanovki, rabotaiushchei na otkhodakh krupnogo rogatogo skota.

The methanogenic activity of manure destructors was investigated at different stages of cattle manure utilization at 35 degrees in a three-section horizontal methane tank manufactured by "Enbom" company (Finland). The association of microorganisms was found to have the highest activity at the last stage of the process, while the least activity was observed in case of fresh manure. A considerable increase of the methanogenic activity in the methane tank was proved by the radioisotopic method and by calculation of the population size of microorganisms from different groups by the series dilution method. Acetic and propionic acids were absent in samples from the third section of the methane tank, while the maximum concentration of the acids was found in the manure storage and in the first section of the methane tank. A significant part of active methanogenic microorganisms was removed with the effluent. Therefore, partial recirculation of the biomass should be used to increase the efficiency of the methane tank.

[Organotrophic growth and the synthesis of an autoregulatory factor in Pseudomonas carboxydoflava]. / Organotrofnyi rost i sintez autoreguliatornogo faktora u Pseudomonas carboxydoflava.

The organotrophic growth of Pseudomonas carboxydoflava Z-1107 was studied in media limited or non-limited with respect to carbon and nitrogen sources. The organotrophic growth was found to decelerate not only when carbon and nitrogen sources were exhausted but also when their content was high enough. At all of the growth phases, P. carboxydoflava could synthesize butanol-soluble substances capable of inhibiting the respiration and growth of the microorganism (the autoregulator factor d) and release them into the cultural broth. The dynamics of accumulation of the factor d in the cultural broth was determined using an arbitrary criterion (the inhibition of respiration in the control culture). The authors discuss a possibility to explain the deceleration of P. carboxydoflava organotrophic growth in a medium which is not limited with carbon and nitrogen sources in terms of the accumulation of the factor d in the culture, as well as possible reasons for the absence of a direct correlation between the activity of the factor and the growth rate of the culture.