The aim of the presented study was: a) assessment of activity of microorganisms developed in form of activated sludge and biofilm, b) indirect assessment of the role of analyzed biocoenoses in removal of organic compounds in hybrid reactor with moving bed. Oxygen uptake rate tests (OUR) have been used, and obtained results were presented as volumetric activity ( , expressed as mg O 2 /g VTS · h). Tests were conducted for three different variants, in which, as the biomass: 1) biofilm was used, 2) activated sludge was used, 3) biofilm and activated sludge were used. The biomass was collected from aerobic reactor from a wastewater treatment plant working in IFAS-MBBR system. The highest volumetric activity was observed for variant with biofilm and activated sludge, and the lowest for variant with biofilm only. Nonetheless, the highest value of oxygen uptake rate related to total volatile solids was observed for variant with biofilm and the lowest for activated sludge. Obtained results suggest, that during this research, at the wastewater treatment plant, the main role in removal of organic pollutants played the biomass developed in form of activated sludge.

The aim of the research is to assess the release of organic compounds and nutrients to liquid phase as a result of hydrodynamic disintegration (HD) of sludge. Six batch disintegration tests are conducted. The scope is a complex analysis of the release of organic compounds (soluble chemical oxygen demand [SCOD], volatile fatty acids [VFA]) and nutrients (soluble total nitrogen [STN], NO2−‐N, NO3−‐N, NH4+‐N, soluble total phosphorus [STP], PO43–‐P) depending on the energy density (ϵL) used during the HD process (70–350 kJ L−1). It is shown that an increase in ϵL is correlated with an increase in the disintegration degree (DD). This results in an increase in both the SCOD (including VFA) and in the soluble nutrient concentration (STN and STP). The value of ϵL, at which HD is conducted, also has an influence on the percentage share of VFA in soluble organic compounds released from activated sludge flocs and on the relationship between the SCOD/STN and SCOD/STP ratio. It is also shown that ϵL and the total solids concentration of disintegrated sludge have an influence on the costs of organic compounds acquired by the HD method. Low costs are obtained for ϵL = 350 kJ L−1 (0.7–2.2 € kg−1 SCOD and 12.8–23.64.0 € kg−1 VFA), and for relatively high total solids (TS) concentrations (TS > 4%) (1.5–1.9 € kg−1 SCOD for ϵL = 70 kJ kg−1 and 0.7–0.8 € kg−1 SCOD for ϵL = 350 kJ L−1).

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