The main obstacle to the widespread use of hydrothermal liquefaction (HTL) for waste and wet biomass recycling is the formation of a significant amount of highly polluted wastewaters. This paper presents an analysis of the chemical composition and toxicity of aqueous phase from the HTL (HTL-AP) of primary and secondary sludge. It was shown that HTL-AP has a high level of organic pollution (total organic carbon (TOC) = 4.2–9.6 g/dm³, chemical oxygen demand (COD) = 7.9–14.0 g/dm³, BOD₅ = 6.0–8.1 g/dm³) and high biological toxicity for traditional test organisms (so that dilution ratio, ensuring the death of no more than 50% of organisms (DR₅₀), varied within 64.7–142.2 and 44.9–81.7 for Artemia salina and Paramecium caudatum, respectively). An analysis of HTL-AP composition with NMR-spectroscopy method allowed us to establish that the share of carbon in aliphatic chains was 34.05–41.82% and the content of carbon in carboxyl groups and aromatic rings was 26.42–34.44%. As a result, we can conclude that the main HTL-AP components are fatty carboxylic acids and their derivatives, aromatic carboxylic acids. The content of aldehydes, ketones, and lignin is less than 8%. Biological treatment of HTL-AP in a lab-scale aerobic reactor turned out to be successful, so average COD reduction was 67–95%. Sludge from an industrial waste water treatment plant (petrochemical sector) with a microorganism concentration of 2.7 g/dm³ was used as inoculum. HTP-AP was diluted 1:10 with tap water. The duration of the process was 18 h.

The article presents the culturing of nine microalgae strains from the IPPAS collection of IFR RAS using components of the aqueous phase of the excessive activated sludge hydrothermal revitalization process as a substrate. In order to select the most promising cultures, their growth characteristics and efficient removal of NH₄⁺ ions, PO₄^3- and organic compounds were studied. All the studied cultures are shown to be able to utilize components of the aqueous phase as a nutrient substrate. The highest specific growth rate of 0.92 day^-1 was observed in the strain Chlorella sp. IPPAS C-1210. However, the Parachlorella kessleri IPPAS C-9 and Chlorella minutissima IPPAS C-123 strains were also promising in terms of their efficiency of pollutant removal from the medium: efficiency of ammonium nitrogen assimilation was 78 and 81%, while phosphate ion assimilation was 89 and 91%, respectively. The biomass composition of C-9 and C-123 cultures was investigated, mainly consisting of polysaccharides – at 41 and 44% – and proteins – at 31 and 25% of the total mass, respectively. A high degree of neutralization of the medium was additionally achieved as a result of consecutive two-stage purification of the aqueous phase of the process of hydrothermal revitalization of excessive activated sludge with the use of microorganisms-destructors (Paenarthrobacter nicotinovorans and Comamonas testosteroni) and the studied microalgae cultures. During 17 days of the purification process, the concentration of ammonium ions decreased from 289.8±14.9 to 51.1±2.2 mg/dm³, phosphates from 116.3±8.1 to 11.3 mg/dm³; the overall efficiency of the process of pollutants removal from the aqueous phase was up to 90%.

We examine the agglutinating ability of five compounds, namely, A1, A2, A3, A4 and BS1, isolated from activated sludge on selective media typical of a number of dominant microbial cultures that contribute to the formation of microbial aggregates. The morphological properties of the isolates and their lectin activity, as well as the physiological and biochemical properties of individual isolates were studied; microorganisms in their composition were identified. We assessed the capacity of the isolates under study to synthesize an exopolysaccharide matrix, as well as the sedimentation of activated sludge under the action of the native solution and culture liquid of the BS1 isolate. Based on their capacity to agglutinate, the BS1 and A2 isolates were selected for further research as producers of extracellular lectins and objects of agglutination, respectively. The biophysiochemical properties and molecular-genetic identification of the BS1 isolate allowed the degree of identity with r. Bacillus to be defined (96.19%); for the A2 isolate, 92.93% identity with p. Shigella and p. Escherichia was determined. To assess the capacity to synthesize a biofilm matrix, the BS1 and A2 isolates were cultivated on an agar nutrient solution using Congo Red dye. According to the obtained results, the isolates are capable of synthesizing an exopolysaccharide matrix, the main component of bacterial biofilms. The research results on the sedimentation of activated sludge induced by the native solution and culture liquid of BS1 showed the following. The sedimentation rate of activated sludge increased significantly at the beginning of the process upon adding a BS1 cell suspension, while the introduction of the native solution of BS1 intensified the process following 5 minutes of contact. The obtained experimental data suggest that the media containing extracellular bacterial lectins can be effectively used as a coagulant (flocculant) for the sedimentation of activated sludge.

Bacteria most commonly exist in nature in the form of bacterial biofilms, i.e. associations of cells attached to a substrate surrounded by a polymer matrix. Research into biofilm formation and functioning is fundamental to the management of microbial associations in ecology, biotechnology and medicine. This task requires the development of analytical approaches capable of providing timely information throughout the life cycle of microbial communities at the same time as maintaining their intact structure. In this paper, we apply scanning electron microscopy and IR spectroscopy as rapid methods for analysing microbial biofilms. To this end, the growth kinetics of a Bacillus subtilis culture cultivated on a solid substrate for 24 h was comparatively studied by the methods of classical microbiology and biochemistry, electron scanning microscopy and Fourier-transform IR spectroscopy. The biofilm morphology was found to vary from a uniform settlement of planktonic cells over the substrate surface at the initial stage of growth (6 h) followed by the accumulation of the extracellular matrix and the formation of microcolonies at the exponential and stationary stage (12–18 h) and a gradual depletion of the matrix at the stage of cell death (24 h). The results of IR spectroscopy were established to agree well with those of biochemical studies, thereby demonstrating the potential of the method for a timely evaluation of the accumulation of proteins, polysaccharides and nucleic acids and for obtaining information about their structural state in the studied biofilm. It is concluded that scanning electron microscopy and Fourier-transform IR spectroscopy can be used for obtaining complementary information about the morphology and chemical composition of microbial biofilms during their cultivation.

Bioleaching of spodumene mineral of Lovozero deposit by two related strains of Aspergillus niger AM1 VKM F-4815D and AM2 VKM F-4816D and extraction of rare element lithium from it were investigated. The study showed that the selected strains carry out bioleaching of spodumene and convert lithium into water-soluble form.

Qualitative and quantitative characteristics of the aqueous phase obtained as a result of hydrothermal liquefaction of biomass of excessive activated sludge from municipal and domestic sewage treatment plants in Kaliningrad have been investigated experimentally. The content of organic compounds averaged 11 592 ± 571 mg O/dm³, and the biochemical index was 0.57. Aromatic compounds, carboxylic acids, and heterocyclic nitrogen-containing compounds were found in the composition of the aqueous phase. From activated sludge of treatment facilities of PJSC Nizhnekamskneftekhim, Republic of Tatarstan, 11 isolates–destructors of components of the aqueous phase were isolated. Their cultural and morphological characteristics were evaluated, and the necessary dilution of the aqueous phase for their cultivation was determined. It was noted that, in the process of cultivation of isolates, S2, S7, and S11 are able to neutralize components of the aqueous phase effectively in comparison with other isolated cultures: the efficiency of degradation by COD was 69, 73, and 75%, respectively. Based on 16S rRNA gene sequencing, isolate S2 had the highest similarity to Pseudomonas glycinae MS586 (99.52%), S7 with Paenarthhobacter nicotinovorans DSM 420 (99.8%), and isolate S11 with Comamonas testosteroni KS 0043 (99.6%). The most active isolates can be used for the treatment of highly concentrated wastewater before preliminary discharge into the sewerage network and natural water bodies.