Katarzyna Bernat

Removal of bisphenol A (BPA) in a nitrifying system with immobilized biomass.

The potential for bisphenol A (BPA) removal by mixed consortia of immobilized microorganisms with high nitrification activity was investigated with BPA concentrations in the influent from 2.5 to 10.0 mg/L. The presence of BPA limited ammonium oxidation; nitrification efficiency decreased from 91.2±1.3% in the control series to 47.4±9.4% when BPA concentration in wastewater was the highest. The efficiency of BPA removal rose from 87.1±5.5% to 92.9±2.9% with increased BPA concentration in the influent. Measurement of oxygen uptake rates by biomass exposed to BPA showed that BPA was mainly removed by heterotrophic bacteria. A strong negative correlation between the BPA removal efficiency and nitrification efficiency indicated the limited contribution of ammonia-oxidizing bacteria (AOB) to BPA biodegradation. Exposure of biomass to BPA changed the quantity and diversity of AOB in the biomass as shown by real-time PCR and denaturing gradient gel electrophoresis.

Nitritation-denitritation in landfill leachate with glycerine as a carbon source.

The effects of limited oxygen concentration (0.7 mg O2/L) in the aeration phase of the SBR cycle and glycerine as an additional carbon source on the effectiveness of nitritation-denitritation and sludge production during municipal landfill leachate treatment were examined. As carbon sources, sodium acetate (Ac) and sodium acetate (Ac) with glycerine (Gly) in the proportions of 3:1 (v/v) and 1:1 (v/v) were added. Low dissolved oxygen concentration inhibited the second stage of nitrification and nitrites were the main final products. Nitritation effectiveness was ca. 98-99%. Denitritation efficiency was relatively low (61%) in the reactor fed with Ac, which may be linked with high sludge production (Yobs - 0.6 mgVSS/mg COD). Glycerine addition (Ac:Gly 1:1, v/v) caused an increase in process efficiency to 75.6% with a concurrent significant decrease in biomass production (Yobs - 0.46 mg VSS/mg COD).

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.

Treatment of high-ammonium anaerobic digester supernatant by aerobic granular sludge and ultrafiltration processes.

Anaerobic sludge digester supernatant characterized by 569 mg TKN L(-1), high color and a COD/N ratio of 1.4 was treated in granular sequencing batch reactors (GSBRs) followed by post-denitrification (P-D) and ultrafiltration (UF) steps. The use of granular sludge allowed for the oxidation of ammonium in anaerobic digester supernatant at all investigated GSBR cycle lengths of 6, 8 and 12 h. The highest ammonium removal rate (15 mg N g(-1) VSS h(-1)) with removal efficiency of 99% was noted at 8 h. Since the GSBR effluent was characterized by a high concentration of nitrites, slowly-degradable substances and biomass, additional purification steps were applied. In P-D stage, the microbial activity of granular biomass in the GSBR effluent was implemented. The P-D was supported by external carbon source addition and the most advantageous variant comprised dosing of half of the theoretical acetate dose for nitrite reduction in the 3-h intervals. The use of the system consisting of the GSBR with 8 h, an optimal P-D variant and a UF for the treatment of anaerobic digester supernatant allowed for the 99%, 71% and 97% reductions of TKN, COD and color, respectively.

Nitrogen removal from wastewater with a low COD/N ratio at a low oxygen concentration

The goal of the study was to determine the effectiveness of nitrification and denitrification and the kinetics of ammonia removal from a mixture of wastewater and anaerobic sludge digester supernatant in an SBR at limited oxygen concentration. In addition, the COD removal efficiency and sludge production were assessed. In the SBR cycle alternating aerobic and anaerobic phases occurred; in the aeration phase the dissolved oxygen (DO) concentration was below 0.7 mg O(2)/L. The low DO concentration did not inhibit ammonia oxidation-nitrification and the efficiency was ca. 96-98%. However, a relatively high COD concentration in the effluent was detected. The values of K(m) and V(max), calculated from the Michaelis-Menten equation, were 43 mg N-NH(4)/L and 15.64 mg N-NH(4)/L h, respectively. Activated sludge production was almost stable (0.62-0.66 g MLVSS/g COD). A high net biomass production resulted from a low specific biomass decay rate of 0.0015 d(-1).

The treatment of anaerobic digester supernatant by combined partial ammonium oxidation and denitrification

Abstract Although the most common method of municipal reject water management is treating in the main flow of a wastewater treatment plant, an alternative method is purifying it separately in a side-stream. This helps to reduce the load of nitrogen and carbon entering the sewage treatment system. This paper reports the results of the application of the SBR for the treatment of anaerobic sludge digester supernatant. At a reduced dissolved oxygen (DO) concentration of 0.7 mg O2/l in the aeration phase, application of mixing phases and pH regulation at the beginning of the SBR cycle (pH 8) allowed to obtain a suitable Anammox influent (50/50 ammonium:nitrite). Applying low oxygen concentrations and a one-hour long mixing phase enabled heterotrophic denitrification in the reactor. The partial use of organic compounds in this process resulted in a COD/N ratio in the effluent of ca. 1, which is favourable for the Anammox influent.

Nitrogen removal from wastewater and bacterial diversity in activated sludge at different COD/N ratios and dissolved oxygen concentrations

The impact of the organic carbon to nitrogen ratio (chemical oxygen demand (COD)/N) in wastewater and dissolved oxygen (DO) concentration on carbon and nitrogen removal efficiency, and total bacteria and ammonia-oxidizing bacteria (AOB) communities in activated sludge in constantly aerated sequencing batch reactors (SBRs) was determined. At DO of 0.5 and 1.5 mg O2/L during the aeration phase, the efficiency of ammonia oxidation exceeded 90%, with nitrates as the main product. Nitrification and denitrification achieved under the same operating conditions suggested the simultaneous course of these processes. The most effective nitrogen elimination (above 50%) was obtained at the COD/N ratio of 6.8 and DO of 0.5 mg O2/L. Total bacterial diversity was similar in all experimental series, however, for both COD/N ratios of 6.8 and 0.7, higher values were observed at DO of 0.5 mg O2/L. The diversity and abundance of AOB were higher in the reactors with the COD/N ratio of 0.7 in comparison with the reactors with the COD/N of 6.8. For both COD/N ratios applied, the AOB population was not affected by oxygen concentration. Amplicons with sequences indicating membership of the genus Nitrosospira were the determinants of variable technological conditions.

Microfauna community during pulp and paper wastewater treatment in a UNOX system

This study characterized the microfauna community during treatment of pulp and paper wastewater in a UNOX system aerated with pure oxygen, and with a high organic loading rate (0.4±0.06kg BOD/kg MLSSday), low sludge retention time (3.73±0.33 day), and high oxygen concentration (≤20mg O2/L) in comparison to municipal treatment systems. In the aeration tank, temperatures were high, averaging 35.7°C (March-May), then 38.9°C (June-August). Effluent quality was acceptable: 180±22mg COD/L, 7.2±2.1mg BOD5/L, and 33±5mg TSS/L. At 35.7°C, 5 taxa were identified in the activated sludge: small flagellates (flagellates <20μm), attached ciliates (Vorticella infusionum, Vorticella octava), crawling ciliates (Chilodonella uncinata) and free-swimming ciliates (Sathrophilus muscorum). During this period, the SBI (Sludge Biotic Index) was 6-7, corresponding to Quality Class II. At 38.9°C, two taxa co-dominated (Vorticella infusionum, Sathrophilus muscorum). When Vorticella infusionum dominated, the SBI was 5 or 7 (Quality Class III/II); when Sathrophilus muscorum dominated, the SBI was 0 (Quality Class IV). Slight changes in the abundance of two opposing Madoni keygroups impeded proper classification of activated sludge. However, effluent quality remained the same, showing that these indicators of activated sludge quality do not always reflect effluent quality.

Simultaneous Nitrification and Denitrification in an SBR with a Modified Cycle During Reject Water Treatment

Abstract In this study, the dependence between volumetric exchange rate (n) in an SBR (Sequencing Batch Reactor) with a modified cycle and simultaneous nitrification and denitrification (SND) efficiency during the treatment of anaerobic sludge digester supernatant was determined. In the SBR cycle alternating three aeration phases (with limited dissolved oxygen (DO) concentration up to 0.7 mg O2/L) and two mixing phases were applied. The lengths of each aeration and mixing phases were 4 and 5.5 h, respectively. Independently of n, a total removal of ammonium was achieved. However, at n = 0.1 d-1 and n = 0.3 d-1 nitrates were the main product of nitrification, while at n = 0.5 d-1, both nitrates and nitrites occurred in the effluent. Under these operational conditions, despite low COD/N (ca. 4) ratio in the influent, denitrification in activated sludge was observed. A higher denitrification efficiency at n = 0.5 d-1 (51.3%) than at n = 0.1 d-1 (7.8%) indicated that n was a crucial factor influencing SND via nitrite and nitrate in the SBR with a low oxygen concentration in aeration phases. SYMULTANICZNA NITRYFIKACJA I DENITRYFIKACJA W SBR ZE ZMODYFIKOWANYM CYKLEM PRACY PODCZAS OCZYSZCZANIA WÓD NADOSADOWYCH W prezentowanych badaniach określono wpływ stopnia wymiany objętościowej (n) SBR ze zmodyfikowanym cyklem pracy na efektywność symultanicznej nitryfikacji i denitryfikacji (SND) podczas oczyszczania wód nadosadowych. Cykl pracy SBR składał się z naprzemiennie występujących trzech faz napowietrzania (limitowane stężenie tlenu do 0,7 mg O2/L) oraz dwóch faz mieszania. Długość każdej z faz napowietrzania i mieszania wynosiła odpowiednio 4 i 5,5 h. Niezależnie od stopnia wymiany objętościowej uzyskano całkowite usunięcie azotu amonowego. Przy n = 0,1 d-1 i n = 0,3 d-1 głównym produktem nitryfikacji był azot azotanowy (V), podczas gdy przy n = 0,5 d-1 w ściekach oczyszczonych występował zarówno azot azotanowy (III) jak i (V). W założonych warunkach technologicznych, pomimo niekorzystnego ilorazu ChZT/N w dopływie (ok. 4), w osadzie czynnym uzyskano denitryfikację. Przy stopniu wymiany objętościowej n = 0,5 d-1 efektywność denitryfikacji wynosiła 51,3% i była kilkukrotnie wyższa niż przy n = 0,1 d-1 (7,8%), co wskazuje, że w warunkach ograniczonego dostępu do tlenu w fazie napowietrzania czynnikiem decydującym o uzyskaniu symultanicznej nitryfikacji i denitryfikacji był stopień wymiany objętościowej.

Biological stability of multi-component agri-food digestates and post-digestates

The use of digestate in agriculture has been an efficient way to mitigate greenhouse gas emissions through the recycling of organic materials. However, harmful effects can arise if the organic matter is unstable. The goal of this study was to determine the biological stability (4-day oxygen demand for degradation of readily biodegradable organic matter (AT4), 21-day anaerobic biogas potential (GP21), and organic matter (VS) content) of six digestates after mesophilic digestion, and that of the corresponding post-digestates after psychrophilic post-digestion. Moreover, the kinetics of the changes in biological stability during post-digestion were determined. Mesophilic digestion of six multi-component agri-food feedstocks consisting of maize silage, bovine manure, mallow silage, pig slurry, glycerin, and spent wash from distillation was carried out at an organic loading rate of 2-3 kg VS/(m3·d), and at a hydraulic retention time of 45-60 days. Digestates were left in stirred reactors, imitating storage digesters, and kept for the next 120 d under anaerobic psychrophilic conditions (20 ± 1 °C) for further stabilization. The additional biogas yields during post-digestion (50.9-114.9 dm3/kg TS) accounted for 8.5-27.4% of the biogas productivity of the feedstocks and 40-80% of that of the digestates. The efficiency of the loss of organic matter content was 22.5-40.2%. The decrease in the values of AT4, GP21 and VS content made the post-digestates more biologically stable than the digestates (digestates: AT4 = 13.7-67.0 mg O2/g TS, GP21 = 71.5-130.1 dm3/kg TS; post-digestates: AT4 = 6.6-37.4 mg O2/g TS, GP21 = 15.7-79.2 dm3/kg TS). For digestates and post-digestates, AT4 values strongly correlated with GP21 values.