Community Of Sequencing Batch Reactor Research Articles

Potential positive effects of natural sunlight on a biological system for landfill leachate treatment

AbstractActivated sludge filtration performance is a significant mean to evaluate membrane fouling trend for wastewater treatment. Here the impact of sunlight irradiation on activated sludge filtration performance and microbial communities in sequencing batch reactors (SBRs) when treating raw landfill leachate were studied. The sludge in photic SBR (i.e., SBR exposed to natural sunlight) exhibited better filtration performance compared to dark SBR (i.e., SBR unexposed to sunlight). The removal efficiency of COD and NH4+‐N in the photic SBR were slightly higher than those in the dark SBR. The contents of the extracellular polymeric substances (EPSs) of sludge in both SBRs initially increased and then decreased. However, in the later period, the sludge filtration performance worsened due to the fungal activity in the dark SBR. Natural sunlight irradiation promoted sludge filtration performance by affecting the microorganism structure in the photic SBR. The bacterial genus Thauera was dominant in the photic SBR (39.35%), whereas Planktosalinus and Ottowia were dominant in the dark SBR (16.84% and 12.55%, respectively). Natural sunlight irradiation had a prominent effect on the fungal diversity in the system, and filamentous bulking caused by the fungi genus Trichosporon’s proliferation was observed in the dark SBR but not in the photic SBR, which also increased the polysaccharide content.

Structure of fungal communities in sequencing batch reactors operated at different salinities for the selection of triacylglyceride-producers from a fish-canning lipid-rich waste stream

Oleaginous fungi natively accumulate large amounts of triacylglycerides (TAG), widely used as precursors for sustainable biodiesel production. However, little attention has been paid to the diversity and roles of fungal mixed microbial cultures (MMCs) in sequencing batch reactors (SBR). In this study, a lipid-rich stream produced in the fish-canning industry was used as a substrate in two laboratory-scale SBRs operated under the feast/famine (F/F) regime to enrich microorganisms with high TAG-storage ability, under two different concentrations of NaCl (SBR-N: 0.5 g/L; SBR-S: 10 g/L). The size of the fungal community in the enriched activated sludge (EAS) was analyzed using 18S rRNA-based qPCR, and the fungal community structure was determined by Illumina sequencing. The different selective pressures (feeding strategy and control of pH) implemented in the enrichment SBRs throughout operation increased the abundance of total fungi. In general, there was an enrichment of genera previously identified as TAG-accumulating fungi (Apiotrichum, Candida, Cutaneotrichosporon, Geotrichum, Haglerozyma, Metarhizium, Mortierella, Saccharomycopsis, and Yarrowia) in both SBRs. However, the observed increase of their relative abundances throughout operation was not significantly linked to a higher TAG accumulation.

Effects of poly (1,4-butanediol succinate) carrier on the nitrogen removal performance and microbial community of sequencing batch reactors

The C/N ratio and carrier type strongly affect aerobic denitrification and are critical for nitrogen removal by sequencing batch reactor (SBR) processes. Poly (1,4-butanediol succinate) (1,4-PBS) is a biodegradable material that provides electrons to denitrifying microorganisms. The effect of carrier on the aerobic denitrifying microorganisms is worth further studying. In this study, aerobic denitrifying microorganisms were combined with 1,4-PBS to evaluate the effects of microbial biomass on the biodegradable carriers and nitrogen removal efficiency. High-throughput sequencing results indicated that after 45 days of the operation, the Shannon index of bacteria in the 1,4-PBS group increased from 4.48 (phase I, C/N = 5 at 1–8 days) to 5.74 (phase II, C/N = 10 at 9–20 days) and continuously increased to 6.68 in phase III (C/N = 20, 21–45 days). The peak total nitrogen (TN), NH4+-N and total organic carbon (TOC) removal efficiencies were 56.4%, 75.49% and 59.56% respectively at high C/N of 20. This result indicated that PBS significantly increased microbial diversity and indirectly changed the structure of microbial communities. Moreover, principal component analysis (PCA) showed that 1,4-PBS might change the microbial community. Specifically, 1,4-PBS might increase microbial diversity and indirectly change the structure of microbial communities. Meanwhile, the content of extracellular polymeric substances increased to 416.33 g g−1 VSS. 3D-EEM spectra showed that protein-like and humic acid-like substances were the main components in SMPs, and the fluorescence intensity increased in the initial 31 days and decreased in the following 14 days. Therefore, 1,4-PBS can efficiently improve the nitrogen removal performance of microbial communities. This study offers a reliable reference for the effects of biodegradable carriers on the nitrogen removal performance of microorganisms.

Performance evaluation, enzymatic activity and microbial community of sequencing batch reactor under hydroxyl-functionalized multi-walled carbon nanotubes (MWCNTs-OH) stress

The nitrogen removal, microbial communities and enzymatic activities of sequencing batch reactors (SBRs) had been compared under long-term exposure of different hydroxyl-functionalized multi-walled carbon nanotubes (MWCNTs-OH) concentrations. Compared with 0 mg/L MWCNTs-OH, the chemical oxygen demand (COD) and nitrogen removals had no obvious change at 10 and 30 mg/L MWCNTs-OH during the whole operation process. However, the microbial oxygen uptake rate, nitrifying rate, denitrifying rate, dehydrogenase activity, nitrifying enzymatic activity and denitrifying enzymatic activity decreased with the increase of MWCNTs-OH concentration and operation time owing to the toxicity of MWCNTs-OH. The microbial reactive oxygen species production and lactate dehydrogenase release under MWCNTs-OH stress kept an ascending trend as the operation time increased, which might affect the normal microbial functions. The presence of MWCNTs-OH varied the microbial community structure of SBR. The relative abundances of Nitrosomonas, Nitrosospira, Nitrospira and denitrifying genera displayed some evident changes under MWCNTs-OH stress.

Single and combined impacts of nickel and cadmium on the performance, microbial community and enzymatic activity of sequencing batch reactors

The performance, microbial enzymatic activities and the microbial community of sequencing batch reactors (SBRs) were evaluated under the single and combined nickel (Ni2+) at 20 mg/L and cadmium (Cd2+) at 10 mg/L. The single and combined Ni2+ and Cd2+ had no adverse impacts on the COD removal, whereas the NH4+-N removal efficiency declined sharply from about 99% to 34.42% and 42.67% under the single Ni2+ and combined Ni2+ and Cd2+. Compared with the absence of Ni2+ or Cd2+, the specific oxygen uptake rate (SOUR), ammonia-oxidizing rate (SAOR), nitrite-oxidizing rate (SNOR), nitrite-reducing rate (SNIRR) and nitrate-reducing rate (SNRR) declined by 24.09%, 56.63%, 51.50%, 58.01% and 52.09% under the combined Ni2+ and Cd2+, which were slower than the sum of those under single Ni2+ and Cd2+. The dehydrogenase, ammonia monooxygenase, nitrite oxidoreductase, nitrate reductase and nitrite reductase activities showed the similar varying trends to the SOUR, SAOR, SNOR, SNIRR and SNRR, suggesting that the combined Ni2+ and Cd2+ displayed antagonistic inhibition on the nitrogen removal rates and microbial enzyme activities. The combined Ni2+ and Cd2+ declined the microbial diversity and richness less than the sum of those under single Ni2+ and Cd2+. The relative abundance of Nitrosomonas, Nitrospira and identified denitrifying bacteria displayed some changes under single and combined Ni2+ and Cd2+. These findings would contribute to better understand the combined impacts of multiple heavy metals on biological wastewater treatment systems.

Performance and Biomass Characteristics of SBRs Treating High-Salinity Wastewater at Presence of Anionic Surfactants.

Sodium dodecylbenzene sulfonate (SDBS) and sodium dodecyl sulfate (SDS), as two anionic surfactants, have diffused into environments such as surface water and ground water due to extensive and improper use. The effects on the removal performance and microbial community of sequencing batch reactors (SBRs) need to be investigated in the treatment of saline wastewater containing 20 g/L NaCl. The presence of SDS and SDBS could decrease the removal efficiencies of ammonia nitrogen and total phosphorus, and the effect of SDS was more significant. The effect of surfactants on the removal mainly occurred during the aeration phase. Adding SDS and SDBS can reduce the content of extracellular polymeric substances (EPS). In addition, SDS and SDBS also can reduce the inhibition of high salinity on sludge activity. A total of 16 s of rRNA sequencing analysis showed that the addition of surfactants reduced the diversity of microbial communities; besides, the relative abundance value of the dominant population Proteobacteria increased from 91.66% to 97.12% and 93.48% when SDS and SDBS were added into the system, respectively.

Long-term effect of different Cu(II) concentrations on the performance, microbial enzymatic activity and microbial community of sequencing batch reactor

The performance, microbial community and enzymatic activity of sequencing batch reactors (SBRs) were investigated under 75-day exposure of different Cu(II) concentrations. Cu(II) at 0–5 mg/L had no distinct impact on the chemical oxygen demand (COD) and nitrogen removal, oxygen-uptake rate (OUR), nitrification and denitrification rate, and microbial enzymatic activity. The inhibitory effects of Cu(II) at 10 and 30 mg/L on the nitrogen removal rate, OUR, and microbial enzymatic activity of SBR increased with an increment in operation time due to the Cu(II) biotoxicity and the Cu(II) accumulation in activated sludge. The changes of microbial reactive oxygen species production, lactate dehydrogenase release, catalase activity and superoxide dismutase activity demonstrated that Cu(II) at 10 and 30 mg/L broke the equilibrium between the oxidation and antioxidation processes in microbial cells and also damaged the cytomembrance integrity, which could affect the COD and nitrogen removal performance and change normal microbial cell morphology. The Cu(II) in the influent could be removed by the microbial absorption and accumulated in the activated sludge under long-term exposure. The microbial community displayed some distinct changes from 0 to 30 mg/L Cu(II). In contrast with 0 mg/L Cu(II), Nitrosomonas, Nitrospira and some denitrifying bacteria obviously decreased in relative abundance under long-term exposure of 10 and 30 mg/L Cu(II).

Insights into long-term effects of amino-functionalized multi-walled carbon nanotubes (MWCNTs-NH2) on the performance, enzymatic activity and microbial community of sequencing batch reactor

Carbon nanotubes (CNTs) inevitably enter domestic sewage and industrial wastewater with the continuous increase of their production and application field. The potential effect of CNTs on biological wastewater treatment processes has raised wide concerns due to their biotoxicity. In the present study, the performance, microbial community and enzymatic activity of sequencing batch reactors (SBRs) were evaluated under 148-day exposure of amino-functionalized multi-walled CNTs (MWCNTs-NH2) at 10 and 30 mg/L. The COD removal efficiency at 10 and 30 mg/L MWCNTs-NH2 gradually reduced from 91.03% and 90.43% on day to 89.11% and 86.70% on day 148, respectively. The NH4+-N removal efficiency at 10 and 30 mg/L MWCNTs-NH2 gradually reduced from 98.98% and 98.46% on day 1 to 96.65% and 63.39% on day 148, respectively. Compared to 0 mg/L MWCNTs-NH2, the oxygen-utilizing rate, ammonia-oxidizing rate, nitrite-oxidizing rate, nitrite-reducing rate and nitrate-reducing rate at 30 mg/L MWCNTs-NH2 were decreased by 52.35%, 60.58%, 55.12%, 56.56% and 57.42% on day 148, respectively. The microbial reactive oxygen species and lactate dehydrogenase release on day 148 was increased by 59.71% and 55.28% at 30 mg/L MWCNTs-NH2, respectively. The key microbial enzymatic activity related to nitrogen removal decreased with the increase of operation time under MWCNTs-NH2 stress. The relative abundances of Nitrosomonas, Nitrosospira, Nitrospira and some denitrifying bacteria at 10 mg/L MWCNTs-NH2 gradually reduced with an increment in operation time. The changes of nitrogen removal rate, microbial community and enzymatic activity of SBR were related to the time-cumulative nonlinear inhibition effect under long-term exposure.

Effects of biochar on the phenol treatment performance and microbial communities shift in sequencing batch reactors

The extensive application of biochar (BC) attracts concerns regarding its environmental effect. Wastewater treatment systems are potential BC recipients; however, the impacts of BC on these systems are still unclear. In this study, effects of BC on the phenol treatment performance and shift in microbial communities in sequencing batch reactor (SBR) were investigated. The phenol degradation rates were enhanced in all BC-treated SBRs during the whole operation due to promotion of key enzymes involved in phenol degradation. The decrease in abundance of intracellular reactive oxygen species (ROS) in SBRs indicated that BC protected microorganisms by ameliorating phenol toxicity, leading to a decrease in the secretion of extracellular polymeric substances (EPS). The functional groups, protein (C=O, –CO–NH), polysaccharide (C–OH, C–O–C, C–O), and nucleic acids (O–P–O) associated bonds of EPS decreased or disappeared in BC-treated SBRs. Miseq sequencing revealed significant decrease in bacterial diversity and remarkable changes in the bacterial community structure in BC-treated SBRs. Abundances of Comamonas and Cupriavidus increased significantly upon BC exposure, which contributed to phenol degradation. Treatment with relatively high BC dosage exhibited considerable inhibition on Thauera. Canonical correspondence analysis (CCA) indicated that the shift in abundances of these genera was closely associated with BC dosage. This study suggested that BC exerted protective effects on sludge microbes of phenol wastewater treatment systems, while it affected the bacterial community structure and diversity at test concentrations. Thus, this study elucidates the comprehensive effects of BC on wastewater treatment process.

Reconsideration on the effect of nitrogen on mixed culture polyhydroxyalkanoate production toward high organic loading enrichment history

In most of the operating strategies for mixed microbial cultures polyhydroxyalkanoate (PHA) production, moderate organic loads and low nitrogen concentrations are used, however, the real waste streams contain variable concentrations of carbon and nitrogen. To evaluate the effect of enrichment history on PHA producer and production the various carbon and nitrogen levels were utilized during the accumulation phase. Different operating strategies were applied in three sequencing batch reactors (SBRs) subjected to aerobic dynamic feeding. The maximum PHA production of the enriched cultures under nutrient excess, limitation and starvation (Cmol/Nmol ratio of 8, 40 and 1, respectively) was evaluated in batch assays. A higher PHA content and biomass growth were achieved in the nutrients presence in comparison to the nutrient starvation condition. The cultures from the SBR treated under short sludge retention time, high organic loading rate, short cycle length (SBR#3) and nutrient excess reached the maximum PHA content (54.9%) and biomass increase (38.9%). Under nutrient limitation, the negative biomass growth was observed under nutrient starvation because of the sampling loss. The succession of microbial communities in SBRs and batch assays was analyzed using terminal restriction fragment length polymorphism. The SBR#3 had the best overall PHA production performance considering its high PHA content and productivity in all nutrient content, it indicates that nitrogen has a substantial impact on PHA yield especially when high organic loading rate enrichment history is involved.

Long-term impacts of carboxyl functionalized multi-walled carbon nanotubes on the performance, microbial enzymatic activity and microbial community of sequencing batch reactor

The performance, microbial community and enzymatic activity of sequencing batch reactors (SBRs) were evaluated under long-term exposure of 0, 10 and 30 mg/L carboxyl functionalized multi-walled carbon nanotubes (MWCNTs-COOH). The presence of 10 mg/L MWCNTs-COOH displayed no adverse impacts on the COD and NH4+-N removal of SBR, whereas 30 mg/L MWCNTs-COOH declined the COD and NH4+-N removal. MWCNTs-COOH inhibited the denitrifying process and led to the accumulation of effluent NO2−-N concentration. The inhibition of MWCNTs-COOH on the oxygen utilization rate, nitrogen removal rate and enzymatic activity of activated sludge gradually enhanced with the increase of operating time and influent MWCNTs-COOH concentration. MWCNTs-COOH stimulated more reactive oxygen species production and lactate dehydrogenase release, which might affect the microbial physiological functions and morphology. The microbial diversity and richness was declined evidently after long-term exposure of MWCNTs-COOH. The relative abundance of nitrifying and denitrifying bacteria showed some changes under MWCNTs-COOH stress.

Corrigendum to “Decay Experiments of Effective N-Removing Microbial Communities in Sequencing Batch Reactors”

Corrigendum to “Decay Experiments of Effective N-Removing Microbial Communities in Sequencing Batch Reactors”

Removal of artificial sweeteners and their effects on microbial communities in sequencing batch reactors

Concern is growing over contamination of the environment with artificial sweeteners (ASWs) because of their widespread existence in wastewater treatment plants (WWTPs). To evaluate ASWs removal and the effect on activated sludge, acesulfame (ACE), sucralose (SUC), cyclamate (CYC) and saccharin (SAC) were introduced individually or in mixture to sequencing batch reactors (SBRs) in environmentally relevant concentrations (100 ppb) for 100 days. Comparisons between ACE removal in a full-scale WWTP and in lab-scale SBRs were conducted. Results showed that CYC and SAC were completely removed, whereas SUC was persistent. However, ACE removal in lab-scale SBRs was significantly greater than in the full-scale WWTP. In SBRs, chemical oxygen demand (COD), ammonia nitrogen (NH4+-N) and total nitrogen (TN) removal appeared unchanged after adding ASWs (p > 0.05). Adenosine triphosphate (ATP) concentrations and triphenyl tetrazolium chloride-dehydrogenase activity (TTC-DHA) declined significantly (p < 0.05). The mixed ASWs had more evident effects than the individual ASWs. Microbial community analyses revealed that Proteobacteria decreased obviously, while Bacteroidetes, Chloroflexi and Actinobacteria were enriched with the addition of ASWs. Redundancy Analysis (RDA) indicated ACE had a greater impact on activated sludge than the other ASWs.

Decay Experiments of Effective N-Removing Microbial Communities in Sequencing Batch Reactors

The temporal changes in the compositions of effective N-removing bacterial communities and the decay coefficients of Anammox were studied within the 120-day decay period under anaerobic or aerobic conditions at 25°C. The maximum nitrogen production rate (MNPR) was determined by measuring the temperature, pH, volatile suspended solids (VSSs), and nitrogen-removal efficiency of the microbial communities during the decay period. The decay coefficients under anaerobic and aerobic conditions at 25°C were determined through equation-based fitting to be 0.031 d−1 and 0.070 d−1, respectively. Through molecular biological means and together with quantitative polymerase chain reaction (qPCR), the proportions of AnAOB in the microbial communities dropped from 48.70% to 3.69% under anaerobic condition and from 48.70% to 1.98% under aerobic condition during the decay period.

Comparison of microbial communities in sequencing batch reactors (SBRs) exposed to trace erythromycin and erythromycin-H2O

Wastewater treatment plants (WWTPs) are major collection pools of antibiotics of which low concentrations may induce antibiotic resistance in their microbial communities and pose threat to human health. However, information is still limited on the microbial community alteration in WWTPs upon exposure to low-dose antibiotics due to absence of negative control systems without input of resistant bacteria and resistance genes. Here we report the impact of trace erythromycin (ERY) and dehydrated erythromycin (ERY-H2O) on microbial community dynamics in three long-term (1 year) running sequencing batch reactors (SBRs), R1 (ERY-H2O), R2 (ERY), and negative control R3. The PhyloChip microarray analysis showed that ERY-H2O and ERY significantly altered their microbial communities based on bacterial richness (e.g., 825 operational taxonomic units (OTUs) in R1, 699 OTUs in R2, and 920 OTUs in R3) and population abundance (15 and 48 subfamilies with >80 % abundance decrease in R1 and R2, respectively). ERY-H2O and ERY have broad but distinct antimicrobial spectrums. For example, bacteria of all the major phyla (i.e., Proteobacteria, Actinobacteria, Bacteroidetes, and Chloroflexi) present in SBRs were severely inhibited by ERY-H2O and ERY, but bacteria of Acidobacteria, Chlorobi, Firmicutes, Nitrospira and OP10 phyla were only inhibited by ERY. Very limited bacterial groups showed antibiotic resistance to ERY-H2O or ERY through forming biofilms (e.g., Zoogloea) or synthesizing resistant proteins (e.g., Thauera, Candidatus Accumulibacter, Candidatus Competibacter, and Dechloromonas) in the SBRs. Inhibition was observed to be the main effect of ERY-H2O and ERY on microbial communities in the reactors. The results would broaden our knowledge of effects of low-dose antibiotics on microbial communities in WWTPs.

Analyses of Bioflocculation and Bacterial Communities in Sequencing Batch Reactors

Laboratory experiments were carried out to investigate effects of the sludge retention time (SRT) feeding and organic loading on bioflocculation and bacterial community of activated sludge. Batch scale conventional activated sludge reactors and sequencing batch reactors (SBR) fed on a synthetic wastewater contained different carbon source were operated at an SRT of 5, 10, and 20 days after changing running parameters, that is, the SRT from 5 to 10 days, and feeding from acetate to glucose, and three-time shock loading, the extracellular polymeric substances (EPS), sludge volume index (SVI), and effluent suspended solid (ESS) as well as the bacterial community characterized with denaturing gradient gel electrophoresis (DGGE) were studied. The results showed that longer SRT benefited the settling ability of activated sludge with little change of bacterial community, while alternate substrates and higher organic loading led to higher SVI and deteriorating ESS, which may be caused by shifting of microorganism community.