Paulina Rusanowska

Structure of nitrogen-converting communities induced by hydraulic retention time and COD/N ratio in constantly aerated granular sludge reactors treating digester supernatant.

This study investigated how hydraulic retention time (HRT) and COD/N ratio affect nitrogen-converting consortia in constantly aerated granules treating high-ammonium digester supernatant. Three HRTs (10, 13, 19 h) were tested at COD/N ratios of 4.5 and 2.3. Denaturing gradient gel electrophoresis and relative real-time PCR were used to characterize the microbial communities. When changes in HRT and COD/N increased nitrogen loading, the ratio of the relative abundance of aerobic to anaerobic ammonium-oxidizers decreased. The COD/N ratio determined the species composition of the denitrifiers; however, Thiobacillus denitrificans, Pseudomonas denitrificans and Azoarcus sp. showed a high tolerance to the environmental conditions and occurred in the granules from all reactors. Denitrifier genera that support granule formation were identified, such as Pseudomonas, Shinella, and Flavobacterium. In aerated granules, nirK-possessing bacteria were more diverse than nirS-possessing bacteria. At a low COD/N ratio, N2O-reducer diversity increased because of the presence of bacteria known as aerobic denitrifiers.

Community dynamics of denitrifying bacteria in full-scale wastewater treatment plants

ABSTRACT Effective and stable nitrogen removal from wastewater requires abundant and active denitrifying populations. In this study, a one-year investigation of the population dynamics of phylogenetic groups known to harbor nitrate reducers was conducted in three municipal wastewater treatment plants (WWTPs). The bacterial community composition was determined by amplicon sequencing of the 16S rRNA gene, and putative nitrate reducers were identified by sequencing narG and napA genes. Fluorescence in situ hybridization with oligonucleotide probes targeting known nitrate reducers in wastewater revealed that certain bacteria predominated in the WWTPs: Curvibacter-related bacteria, Comamonadaceae, Azoarcus, Thauera, Dechloromonas, and Candidatus Accumulibacter within Rhodocyclaceae. The data showed high diversity in the nitrate-reducing community and a large degree of redundancy, with a relatively stable core group of bacteria in each plant that ensured small yearly variation in nitrate reduction rates.

Microbiota of anaerobic digesters in a full-scale wastewater treatment plant

Abstract Anaerobic digestion is an important technology for the bio-based economy. The stability of the process is crucial for its successful implementation and depends on the structure and functional stability of the microbial community. In this study, the total microbial community was analyzed during mesophilic fermentation of sewage sludge in full-scale digesters. The digesters operated at 34–35°C, and a mixture of primary and excess sludge at a ratio of 2:1 was added to the digesters at 550 m3/d, for a sludge load of 0.054 m3/(m3·d). The amount and composition of biogas were determined. The microbial structure of the biomass from the digesters was investigated with use of next-generation sequencing. The percentage of methanogens in the biomass reached 21%, resulting in high quality biogas (over 61% methane content). The abundance of syntrophic bacteria was 4.47%, and stable methane production occurred at a Methanomicrobia to Synergistia ratio of 4.6:1.0. The two most numerous genera of methanogens (about 11% total) were Methanosaeta and Methanolinea, indicating that, at the low substrate loading in the digester, the acetoclastic and hydrogenotrophic paths of methane production were equally important. The high abundance of the order Bacteroidetes, including the class Cytophagia (11.6% of all sequences), indicated the high potential of the biomass for efficient degradation of lignocellulitic substances, and for degradation of protein and amino acids to acetate and ammonia. This study sheds light on the ecology of microbial groups that are involved in mesophilic fermentation in mature, stably-performing microbiota in full-scale reactors fed with sewage sludge under low substrate loading.

Operation mode and external carbon dose as determining factors in elemental composition and morphology of aerobic granules

Abstract The elemental composition and morphology of aerobic granules in sequencing batch reactors (GSBRs) treating high-nitrogen digester supernatant was investigated. The investigation particularly focused on the effect of the number of anoxic phases (one vs. two) in the cycle and the dose of external organics loading (450 mg COD/(L·cycle) vs. 540 mg COD/(L·cycle)) on granule characteristics. Granules in all reactors were formed of many single cells of rod and spherical bacteria. Addition of the second anoxic phase in the GSBR cycle resulted in enhanced settling properties of the granules of about 10.6% and at the same time decreased granule diameter of about 19.4%. The study showed that external organics loading was the deciding factor in the elemental composition of biomass. At 540 mg COD/(L·cycle) the granules contained more weight% of C, S and N, suggesting more volatile material in the granule structure. At lower organics loadings granules had the higher diameter of granules which limited the diffusion of oxygen and favored precipitation of mineral compounds in the granule interior. In this biomass higher content of Mg, P and Ca, was observed.

Influence of static magnetic field on sludge properties

Abstract The study investigated the influence of static magnetic field on sedimentation of activated sludge, coagulation efficiency in the bioreactors and dewaterability of the sludge. The sedimentation was improved when magnetizers were applied on the bioreactor and on the settling tank. The application of magnetizers only on the settling tank decreased the sedimentation properties of the sludge. The filamentous bacteria Type 0092 dominated in both bioreactors, but the significant differences were observed in its length. No effect of the static magnetic field on coagulation with the utilization of iron-based coagulant was observed. However, the static magnetic field enhanced coagulation with the utilization of aluminum-based coagulant. The results suggest that increased sedimentation of colloids and activated sludge, can in practice mean a reduction in the size of the necessary equipment for sedimentation with an unchanged efficiency of the process. Moreover, static magnetic field significantly reduced the COD concentration in filtrate and shorted capillary suction time during the dewaterability of waste activated sludge.

IMPACT OF STATIC MAGNETIC FIELD ON EFFICIENCY OF FINE-BUBBLE AERATION OF LIQUID

Aeration is the main item in the operating costs of most wastewater treatment plants. New, efficient methods of aeration are constantly requested. Even a small increase in the efficiency on the larger scale of the process provides significant financial savings. The paper presents the possibility of increasing the efficiency of oxygen transfer through the use of a static magnetic field. The aim of the study was to evaluate impact of static magnetic field on efficiency of fine-bubble aeration of liquid. The experiment were conducted in constant temperature (24 °C) at pH 8.25. The aeration intensity was 58 L/h. The mean magnetic field induction ranged from 10 mT in a series 1, to 14 mT in a series 2 and 16 mT in a series 3. The OC value in case of the use of the lowest induction was 75.22 g/ (m3·h). In series 2 the OC value was an average of 77.7 g/(m3·h). In series 3, when magnetic field with the highest induction was used, the OC value was 92.72 g/(m3·h). While in the control series, without the use of static magnetic field, the OC was only 60.5 g/(m3·h). Positive experiments results in laboratory scale tent to research on possibility for application of static magnetic field to enhance the efficiency of aeration in industrial devices.

Influence of microwave heating on biogas production from Sida hermaphrodita silage

This study compared the effects on biogas production of suspended sludge versus a combination of suspended sludge and immobilized biomass, and microwave versus convection heating. Biogas production was the highest in the hybrid bioreactor heated by microwaves (385L/kg VS) and also the most stable, as shown by the FOS/TAC ratio and pH. Regardless of the type of heating, biogas production was 8% higher with immobilized biomass than without. Although the lag phase of biogas production was shorter with microwave heating than without, the log phase was longer, and biogas production in the microwave heated bioreactors took about twice as long (ca. 40days) to plateau as in the conventionally heated bioreactors. These differences in the profile of biogas production are likely due to the athermal effects of microwave irradiation.

Changes in extracellular polymeric substances (EPS) content and composition in aerobic granule size-fractions during reactor cycles at different organic loads

This study aimed to systematically investigate the effect of organic loading on granule diameters, and on the composition of extracellular polymeric substances (EPS) in granules in various size-fractions at the beginning and end of the cycle of granular sludge sequencing batch reactor (GSBR). The organic loadings were 0.78 kg COD/(m3·d) (GSBR1), 1.16 kg COD/(m3·d) (GSBR2) and 1.53 kg COD/(m3·d) (GSBR3). Granules with a diameter of 0.5-1 mm had the most stable EPS content and composition. The smallest granules had the largest amount of bound EPS. The amount of loosely-bound EPS increased as granule diameters decreased; it was lowest in the famine phase at end of the cycle. The proteins/polysaccharides ratio decreased below 1 only in soluble EPS in the famine period. In GSBR1, granules with a diameter <0.5 mm predominated, and the increase in soluble EPS at end of the cycle was most substantial resulting in the lowest COD removal.

Effect of Inorganic Coagulants on the Characteristics in Anaerobic Digested Distillery Stillage Valorization

The aim of the study was to determine the possibility of using coagulation for treatment of anaerobically digested distillery stillage. Post-fermentation sludge from waste product of bioethanol production is usually drained. Then, condensed sediments are directed as a fertilizer for arable fields. The remaining liquid phase due to the high content of organic compounds cannot be discharged to environment. The study used inorganic salts of iron and aluminum as coagulants to treatment liquid fraction obtained after methane fermentation of distillery stillage. In valorization process, the reduction of organic compounds and suspended solids was not sufficient. The highest doses of coagulants reduced COD concentration of about 80% and lower the pH of the solution. However, the dose 10 mL/L is not economically profitable and due to concentration of aluminum or iron it is too harmful for environment.

Application of an Innovative Ultrasound Disintegrator for Sewage Sludge Conditioning Before Methane Fermentation

Ultrasonic disintegration is one of the most interesting technologies among all known and described technologies for sewage sludge pre-treatment before the process of methane fermentation. This study was aimed at determining the effects of an innovative ultrasonic string disintegrator used for sewage sludge pre-treatment on the effectiveness of methane fermentation process. In this experiment, we used a device for disintegration of organic substrates, including sewage sludge, with the use ultrasonic waves. Its technical solution is protected by a patent no. P. 391477 – Device for destruction of tissue and cell structures of organic substrate. The volume of biogas produced ranged from 0.194±0.089 dm3/g o.d.m. at loading of 5.0 g o.d.m./dm3 and power of 50 W to 0.315±0.087 dm3/g o.d.m. at loading of 4.0 g o.d.m./dm3 and ultrasounds power of 125 W. The study demonstrated a positive effect of sewage sludge sonication on the percentage content of methane in biogas. Sewage sludge exposure to 125 W ultrasounds increased methane content in biogas to 68.3±2.5 % at tank loading of 3.0 g o.d.m./dm3.