Background The study aimed to evaluate the influence of the duration times of anaerobic phases on the bacterial biocenosis characterisation while denitrifying dephosphatation in the Integrated Fixed-Film Activated Sludge – Moving-Bed Sequencing Batch Biofilm Reactor (IFAS-MBSBBR). The experiment was conducted in a laboratory model. The study consisted of four series, which differed in terms of the ratio of the anaerobic phases. duration concerning the overall reaction time in the cycle. The anaerobic phases covered from 18 to 30% of the whole cycle duration. During the reactor performance that took 9 months, the influent and effluent were monitored by analysis of COD, TKN, NH 4 -N, NO 2 -N, NO 3 -N, TP, PO 4 -P, pH, alkalinity and the phosphorus uptake batch tests. Characterisation of the activated sludge and the biofilm biocenosis was based on fluorescent in situ hybridisation (identification of PAO and GAO) and the denaturing gradient gel electrophoresis patterns. Results The organic compounds removal was high (more than 95.7%) independently of cycle configuration. The best efficiency for nitrogen (91.1%) and phosphorus (98.8%) removal was achieved for the 30% share of the anaerobic phases in the reaction time. Denitrifying PAO (DPAO) covered more than 90% of PAO in the biofilm and usually around 70% of PAO in the activated sludge. A substantial part of the polyphosphate accumulating organisms (PAO) community were Actinobacteria . The denitrifying dephosphatation activity was performed mainly by Accumulibacter phosphatis . Conclusions High nutrient removal efficiencies may be obtained in IFAS-MBSBBR using the denitrifying dephosphatation process. It was found that the length of anaerobic phases influenced denitrification and the biological phosphorus removal. The extension of the anaerobic phases duration time in the reaction time caused an increase in the percentage share of denitrifying PAO (DPAO) in PAO. The biocenosis of the biofilm and the activated sludge reveal different species patterns and domination of the EBPR community.

The main goal of the study was to evaluate the effects of mechanical sludge disintegration in enhancing full-scale anaerobic digestion of municipal sludge. Batch disintegration tests and lab dewatering tests were performed to determine the release of organic compounds and to assess the impact of disintegration of excess sludge before the fermentation process of mixed sludge on the dewaterability of post-fermented sludge, respectively. In the study, a disc disintegrator driven by a motor with a power of 30 kW, revolutions n= 2950 rpm, was used. It was shown that increased amounts of organic compounds were released from the sludge along with an increase in energy consumed in the disintegration. A part of the organic compounds were volatile fatty acids (VFAs). The highest share of VFAs in the released organic compounds (COD:VFA in the range of 6.6 divided by 8.2) was obtained by performing disintegration at an energy density of 140 kJ/L. It was also documented that the introduction of excess sludge disintegration prior to the fermentation tank resulted in a significant increase in biogas production (by an average of 33.9%) and in an increase in volatile total solids reduction in the fermented sludge (by an average of 22.7%). Such a surplus of produced biogas would allow to produce ca. 1600 kWh/d net electricity and 7.5 GJ/d (2080 kWh/d) of heat. Moreover, it was documented that the share of disintegrated waste activated sludge in the mixed sludge subjected to the fermentation process could favourably influence the efficiency of post-fermented sludge dewatering.

The main goal of the study was to evaluate the effects of mechanical sludge disintegration for enhancing full scale anaerobic digestion of municipal sludge. Batch disintegration tests and lab dewatering tests were also performed aiming at determining the release of organic compounds and assessing the impact of disintegration of excess sludge before the fermentation process of mixed sludge on the dewaterability of post-fermented sludge, respectively. In the study a disc disintegrator driven by a motor with a power of 30 kW, revolutions n = 2950 rpm has been used. It was shown that with increase of energy consumed in the disintegration, the increased amounts of organic compounds were released from the sludge. It was also documented that the introduction of the excess sludge disintegration prior to fermentation tank, resulted in a significant increase in biogas production (by an average of 33.9%) and in increase in volatile total solids reduction in the fermented sludge (by an average of 22.7%). Moreover, the obtained results indicate the possibility of obtaining a higher degree of sludge dewatering, which was subjected to anaerobic stabilization with using disintegrated excess sludge.

The objective of this study is to compare wastewater treatment effectiveness in sequencing batch reactor (SBR) and integrated fixed-film activated sludge-moving-bed sequencing batch biofilm reactor (IFAS-MBSBBR) systems in specific technological conditions. The comparison of these two technologies was based on the following assumptions, shared by both series, I and II: the reactor's active volume was 28 L; 8-hour cycle of reactor's work, with the same sequence and duration of its consecutive phases; and the dissolved oxygen concentration in the aerobic phases was maintained at a level of 3.0 mg O2/L. For both experimental series (I and II), comparable effectiveness of organic compound (chemical oxygen demand (COD)) removal, nitrification and biological phosphorus removal has been obtained at levels of 95.1%, 97% and 99%, respectively. The presence of the carrier improved the efficiency of total nitrogen removal from 86.3% to 91.7%. On the basis of monitoring tests, it has been found that the ratio of simultaneous denitrification in phases with aeration to the total efficiency of denitrification in the cycle was 1.5 times higher for IFAS-MBSBBR.

This article presents the results of research into the influence of one, two and three wastewater feedings in a cycle on efficiency and performance of combined biological nitrogen and phosphorus removal in an integrated fixed-film activated sludge and moving-bed sequencing batch biofilm reactor (IFAS-MBSBBR). The experiment lasted 158 days and was conducted in two laboratory models of the IFAS-MBSBBR with an active volume of 28 L. It was found that along with an increase in the number of wastewater feedings, an increase in nitrogen removal efficiency was observed (from 56.9 ± 2.30% for a single feeding to 91.4 ± 1.77% for three feedings). Moreover, the contribution of simultaneous nitrification/denitrification in nitrogen removal increased (from 2.58% for a single feeding to 69.5% for three feedings). Systems with a greater number of feedings stimulated the process of denitrifying phosphorus removal. Regardless of the way in which wastewater feeding was applied to the IFAS-MBSBBR, highly efficient chemical oxygen demand (COD) removal (94.8 ± 1.80%) and biological phosphorus removal (98.9 ± 0.87%) were achieved.

The objective of this study was to establish such operating conditions in a sequencing batch reactor (SBR) that will enable the achievement of the highest possible share of denitrifying P removal in nutrient elimination. Two different operating strategies for SBRs were analysed. Both of these strategies used a forced anoxic phase in the SBR treatment cycle. The first one was based on an intermittent aeration, which led to periodic occurrence of anoxic conditions when the uptake of P-PO4(3-) could occur. The second strategy was based on mimicking the A2O process and forcing an anoxic phase straight after an anaerobic phase. The experiments were performed in a laboratory reactor operating at a maximum fill of 26.8-27.7 litres and a constant temperature of 18 degrees C. It was found that a SBR configuration with intermittent aeration did not allow the achievement of significant denitrifying P removal, despite the DPAO/PAO ratio being equal to 50.5%. Almost the entire load of orthophosphates was being removed in aerobic conditions right after the anaerobic phase, even though this aerobic period lasted only 20 minutes. However, a SBR with a forced anoxic phase occurring after an anaerobic phase and created by an introduction of NO(x) rich stream of wastewater guaranteed the highest DPAO/PAO ratio of 82.8% and the highest share of denitrifying P removal (above 80%) in the total removal of phosphorus.

We attempt to answer the question whether it is possible to directly compare the results of phosphorus uptake batch tests (PUBT) conducted by researchers who use different methods of determining the DPAOsto-PAOs ratio. This issue is raised because personally obtained results clearly show that DPAO fractions calculated with various methods proposed in the literature differ significantly. In the article the factors influencing the results of PUBT are discussed in detail. The study demonstrated that errors in determined values of DPAO fraction may be caused by the invitation of inappropriate value of reduction coefficient for anoxic conditions (η). The conclusion is that the η value should be accurately estimated in each test, independently for every active sludge.

This paper presents results of wastewater treatment in a sequencing batch reactor operating at a dissolved oxygen (DO) setpoint of 1 mg O-2 l(-1) in the aerobic phase. It has been demonstrated that depending on the DO concentration profile (in time) in aerobic phases, paths of N and P removal in the reactor are different. Simultaneous denitrification depends on the amount of time when DO concentration is below 1 mg O-2 l(-1). A relatively large uptake of easily biodegradable organic substrates in the first anoxic/anaerobic phase (I A/A) results in the reduction of nitrates in aerobic phases with internally stored organics as a carbon source. This may promote the growth of denitrifying phosphorus-accumulating organisms in the process. In the second A/A phase, synergic N and P removal was observed. The process was limited by nitrite and nitrate concentrations.