Influent Organic Loading Rate Research Articles

Potential of direct granulation and organic loading rate tolerance of aerobic granular sludge in ultra-hypersaline environment

Salt-tolerant aerobic granular sludge (SAGS) technology has shown potentials in the treatment of ultra-hypersaline high-strength organic wastewater. However, the long granulation period and salt-tolerance acclimation period are still bottlenecks that hinder SAGS applications. In this study, “one-step” development strategy was used to try to directly cultivate SAGS under 9% salinity, and the fastest cultivation process was obtained under such high salinity compared to the previous papers with the inoculum of municipal activated sludge without bioaugmentation. Briefly, the inoculated municipal activated sludge was almost discharged on Day 1–10, then fungal pellets appeared and it gradually transitioned to mature SAGS (particle size of ∼4156 μm and SVI30 of 57.8 mL/g) from Day 11 to Day 47 without fragmentation. Metagenomic revealed that fungus Fusarium played key roles in the transition process probably because it functioned as structural backbone. RRNPP and AHL-mediated systems might be the main QS regulation systems of bacteria. TOC and NH4+-N removal efficiencies maintained at ∼93.9% (after Day 11) and ∼68.5% (after Day 33), respectively. Subsequently, the influent organic loading rate (OLR) was stepwise increased from 1.8 to 11.7 kg COD/m3·d. It was found that SAGS could maintain intact structure and low SVI30 (< 55 mL/g) under 9% salinity and the OLR of 1.8–9.9 kg COD/m3·d with adjustment of air velocity. TOC and NH4+-N (TN) removal efficiencies could maintain at ∼95.4% (below OLR of 8.1 kg COD/m3·d) and ∼84.1% (below nitrogen loading rate of 0.40 kg N/m3·d) in ultra-hypersaline environment. Halomonas dominated the SAGS under 9% salinity and varied OLR. This study confirmed the feasibility of direct aerobic granulation in ultra-hypersaline environment and verified the upper OLR boundary of SAGS in ultra-hypersaline high-strength organic wastewater treatment.

Aerobic post-treatment of effluent from anaerobic reactors fed with residues from 1G and 2G sugarcane biorefineries.

This study aimed to evaluate an activated sludge system as a post-treatment step of anaerobic effluents from the co-digestion of sugarcane vinasse and hemicelluloses hydrolysate. The system consisted, initially, of a two-stage anaerobic system followed by a continuously fed activated sludge, all in bench scale. After adaptation of aerobic microorganisms to effluent conditions, the anaerobic digestion was conducted in a single-stage anaerobic reactor, increasing the influent organic loading rate (OLR) of activated sludge from 0.73 to an average of 2.36 gCOD/L·day. Under optimal conditions (12-h hydraulic retention time [HRT]), a 62 ± 9% efficiency was observed on the aerobic post-treatment, resulting in effluent chemical oxygen demand (COD) of 414.3 ± 95 mg/L. Overall efficiency of the combined system (anaerobic + aerobic) averaged 88 ± 3%. Influent and effluent characteristics were then analyzed by Folin-Ciocalteau method, UV-Vis spectrophotometry, and gas chromatography-mass spectrometry (GC-MS) for identification of potentially toxic and recalcitrant compounds. Compounds that absorb light within the visible spectra were well removed by the combined treatment system. Most compounds identified by GC-MS in the influent were completely removed by aerobic microorganisms. Saturated fatty acids such as adipic acid, hexadecanoic acid, and octadecanoic acid were observed in the final effluent, as well as other potentially toxic compounds such as stigmasterol, di-isobutyl phthalate, and benzene. Activated sludge proved to be an efficient post-treatment for anaerobic co-digestion, able to cope with changes of anaerobic effluent quality and providing a final effluent of stable organic load. However, phenol removal was not efficient and further studies could be performed to optimize its degradation. PRACTITIONER POINTS: Conventional activated sludge with a 12-h HRT was capable of handling significant OLR variation, providing a final effluent with lower and stable COD concentration. Glucose addition for carbon supplementation was necessary during the start-up of activated sludge. Compounds that absorb light within the visible spectra were mostly removed by the combined (anaerobic-aerobic) treatment system. Most potentially toxic compounds were well removed in the post-treatment system. Saturated fatty acids, VFA, phenols, and low molecular weight aromatic compounds remained in the final effluent.

Mesophilic and thermophilic biohydrogen production using cassava starch wastewater in a CSTR

The objective of this work is to compare and evaluate the production of biohydrogen (bio-H2) from cassava starch wastewater at mesophilic and thermophilic conditions and to elucidate the metabolic routes involved. This system consisted of a continuous stirred-tank reactor for hydrogen production under the influent organic loading rate (OLRs) of 2.08, 5.05, 12.04, 23.34, and 30.87 kg COD/(m3•d) for mesophilic temperature and 2.29, 4.47, 12.52, 22.09 and 28.86 kg COD/(m3•d) for thermophilic temperature with Hydraulic Retention Time of 24, 16, 12 and 8 hours and pH maintained 5 to 6. The steady state of hydrogen production was 3131 ml/L•d obtained at the OLR of 23.34 kg COD/(m3•d) with the COD removal of 85%, and the hydrogen production of 2007 ml/L.d with a COD removal of % was obtained at the OLR of 28.86 kg COD/(m3•d). The maximum of 85% of the cassava starch wastewater was converted to hydrogen at the OLR of 23.34 kg COD/(m3•d) at mesophilic conditions with HRT of 8 h and hence the mesophilic condition favoured the hydrogen production using cassava starch wastewater.

Improving simultaneous N, P, and C removal and microbial population dynamics in an anaerobic–aerobic–anoxic SBR (A-O-A-SBR) treating municipal wastewater by altering organic loading rate (OLR)

To assess the impacts of the influent organic loading rate (OLR) on the performance of an improved sequencing batch reactor (A-O-A-SBR system), four OLRs (1.35, 2.03, 2.70, and 3.38 g-COD/L/d) were used for enhancing simultaneous N, P, and C removals in the system. Results showed that high simultaneous N, P, and C removal efficiencies of the A-O-A-SBR were achieved with an OLR of 2.03 g-COD/L/d. The corresponding TN, TP, and COD removal efficiencies were 98.10%, 87.01%, and 93.43%, respectively. Dominant phyla, including Proteobacteria, Planctomycetes, Candidatus Saccharibacteria, Bacteroidetes, and critical genus Thiothrix, and essential classes such as Gammaproteobacteria, Betaproteobacteria, Sphingobacteriia, contributed to the excellent A-O-A-SBR performance. Functional genes forecasts demonstrated that the metabolic potential on pollutants degradation metabolism improved with the proper OLR condition.

Mathematical modeling of methane production and sulfate reduction in upflow anaerobic sludge blanket reactors: Calibration, validation and prediction of reciprocal effects

Mathematical models are important tools for understanding and optimizing the performance of biotechnological processes. A user-friendly mathematical model is developed to simulate the sulfate reduction and methanogenesis of upflow anaerobic sludge blanket reactors. The good fit between the simulated and experimental concentrations reflects the model’s capability in simulating reactor performance when there are variations in operational conditions. The model with optimized parameters is used to quantitatively and systematically account for the interaction of influent organic loading rate and the ratio of organic to sulfate, influent chemical oxygen demand and sulfate concentrations, and influent organic composition and chemical oxygen demand concentration. The interaction between the OLR (3 ∼ 72 g-COD/L/d) and C/S ratio (0.5 ∼ 20) greatly influenced the ethanol concentration, yield ratio of methane and sulfate concentration. The removal of sulfate in the reactor was more influenced by the C/S ratio than the OLR. It provides a theoretical basis for reactor process optimization and control and greatly saves time required for experimental investigations. • The reaction of MPA and SRB in UASB were simulated by a user-friendly model. • Calibration and validation were thoroughly carried out using experimental studies. • The reciprocal effects of conditions were quantitatively predicted by the simulation. • The competition or cooperation relations between MPA and SRB were explained.

Accelerating anaerobic hydrolysis acidification of dairy wastewater in integrated floating-film and activated sludge (IFFAS) by using zero-valent iron (ZVI) composite carriers

Flocculent sludge system usually shows a low treatment efficiency and bad resistance to the feeding shock in the hydrolysis acidification. Integrated floating-film and activated sludge (IFFAS) is a favored system to resist shock, and zero-valent iron (ZVI) is an attractive material to enhance hydrolysis acidification. In this study, an IFFAS equipped with ZVI composite carriers was used to stably increase the degree of acidification (DA) in the anaerobic treatment of dairy wastewater. At the influent organic loading rate of 24.0 kg COD/m3/d with the hydraulic retention time of 3 h, the DA in the reactor filled with ZVI composite carriers was as high as 51.6%, which increased by 9.5% and 7.7%, respectively, comparing with the reactor without biofilm carriers and the reactor filled with polyethylene biofilm carriers. Also, the ZVI composite carriers optimized the biofilm formation and enhanced the activity of protease, pyruvate oxidoreductase, and acetate kinase. Microbial community analysis revealed that hydrolysis acidification bacteria of Comamonas (47.0%) and Petrimonas (2.6%), and acetotrophic methanogens of Methanosarcina (47.1%) and Methanothrix (16.0%) were enriched in the biofilm of ZVI composite carriers. Apart from the main enhancement of mediated interspecies electron transfer, a potential direct interspecies electron transfer also might be established for the presence of Comamonas, Petrimonas, Methanosarcina, and Methanothrix, accelerating the syntrophic production of short-chain volatile fatty acids and methane.

Performance of anaerobic sludge and the microbial social behaviors induced by quorum sensing in a UASB after a shock loading

To understand the microbial social behaviors regulated by acyl-homoserine lactones (AHLs) in the upflow anaerobic sludge blanket (UASB) during the restored process after a shock loading, the correlation analyses of AHLs and components of extracellular polymeric substances (EPS), AHLs genes and microbes, and AHLs and microbes were investigated. The results showed that the performance could be restored by regulating influent organic loading rate stage-by-stage. A variation in microbial community and endogenous AHLs was also found during the restoration process. It was found that C14-HSL had improved the synthesis of protein in EPS and resulted in better aggregation of microbes. C4-HSL, as well as C8-HSL and 3-oxoC14-HSL, could prompt the metabolism of acidogenic fermentation bacteria. While 3-oxoC6-HSL was identified as the key signal molecule in enhancing methanogenesis. The present work advanced the understanding of microbial social behaviors and provided an attractive strategy for the restoration of anaerobic digestion after shock loadings.

Pollutants removal, greenhouse gases emission and functional genes in wastewater ecological soil infiltration systems: influences of influent surface organic loading and aeration mode.

The influences of influent surface organic loading rate (SOLR) and aeration mode on matrix oxygen, organic matter, nitrogen, phosphorus removal, greenhouse gases emission and functional gene abundances in lab-scale wastewater ecological soil infiltration systems (WESISs) were investigated. In WESISs, intermittent or continuous aeration improved oxygen supply at 50 cm depth and hardly changed anaerobic condition below 80 cm depth, which enhanced chemical oxygen demand (COD), NH4+-N, total nitrogen (TN) removal, the abundances of bacterial 16S rRNA, amoA, nxrA, narG, napA, nirK, nirS, qnorB, nosZ genes and reduced CH4, N2O conversion efficiencies with SOLR of 16.9 and 27.6 g BOD/(m2 d) compared with non-aeration. Increased SOLR resulted in high TN removal, low N2O emission in aeration WESIS, which was different from non-aeration WESIS. High average COD removal efficiency of 90.7%, NH4+-N removal efficiency of 87.0%, TN removal efficiency of 84.6%, total phosphorus (TP) removal efficiency of 93.1% and low average N2O emission rate of 12.8 mg/(m2 d) were achieved with SOLR of 16.9 g BOD/(m2 d) in intermittent aeration WESIS. However, continuous aeration WESIS obtained high average removal efficiencies of 90.1% for COD, 87.5% for NH4+-N, 84.1% for TN, 92.9% for TP and low average emission rate of 13.1 mg/(m2 d) for N2O with SOLR of 27.6 g BOD/(m2 d). Aeration could be an optional strategy for WESISs to achieve high pollutants removal and low CH4, N2O emission when treating wastewater with high SOLR.

Improving sulfonamide antibiotics removal from swine wastewater by supplying a new pomelo peel derived biochar in an anaerobic membrane bioreactor

Sulfonamide antibiotics (SMs), as a class of antibiotics commonly used in swine industries, pose a serious threat to animal and human health. This study aims to evaluate the performance of an anaerobic membrane bioreactor (AnMBR) with and without supplying a new pomelo peel derived biochar to treat swine wastewater containing SMs. Results show that 0.5 g/L biochar addition could increase more than 30% of sulfadiazine (SDZ) and sulfamethazine (SMZ) removal in AnMBR. Approximately 95% of chemical oxygen demand (COD) was removed in the AnMBR at an influent organic loading rate (OLR) of 3.27 kg COD/(m3·d) while an average methane yield was 0.2 L/g CODremoved with slightly change at a small dose 0.5 g/L biochar addition. SMs inhibited the COD removal and methane production and increased membrane fouling. The addition of biochar could reduce the membrane fouling by reducing the concentration of SMP and EPS.

Achieving simultaneous biological nutrient removal and sludge minimization from marine ship sewage based on an innovative Landscape Integrated Ecological Treatment System (LIETS)

The implementation of latest emission standards of International Maritime Organization (IMO) has raised more stringent dicharge limitations for marine domestic ship sewage. Hence, availability of highly-efficient, eco-friendly and profitable ship-generated sewage biological strategy is necessary. In this study, an innovative landscape integrated ecological treatment system (LIETS) based on modified denitrifying phosphorus removal (mDPR) process for sustaining marine ship sewage treatment was investigated. Over 200 days experimental results revealed that the satisfactory TN, TP and COD removal efficiencies of 82.0%, 81.0% and 94.0% were achieved, leading to the effluent concentration were 10.9 mg·L−1, 0.97 mg·L−1 and 17.8 mg·L−1, respectively. The mean nutrient removal efficiency maintained above 90.0% despite 1.5–2.0 times influent organic loading rate (OLR) shock, along with the SS and BOD5 achieving less than 20.0 mg·L−1 and 17.0 mg·L−1, while polysaccharide (PS)/protein (PN) ratio reached the valley value causing the excellent sludge flocculation and sedimentation during anaerobic period. Promoting aeration rate rather than NOx−-N recirculation was demonstrated as an efficient strategy for minimizing the inhibitory effect of excess organic shock. Furthermore, Aeromonas (42.31%) belonging to γ-Proteobacteria was identified as critical denitrifying phosphorus accumulating organisms (DPAOs) responsible for the desirable performance. The mixture mode of excess sludge and feed played significant roles in sludge reduction, and LIETS was proved to be a promising opportunity for marine ship sewage treatment application.

Enhanced medicinal herbs wastewater treatment in continuous flow bio-electro-Fenton operations along with power generation

In this study, we proposed a microbial fuel cell (MFC) system with anodic bio-oxidation inoculated with seed sludge as active biocatalyst coupled to cathodic electro-Fenton equipped with a composite electrode of Fe@Fe2O3/graphite for the enhanced medicinal herbs wastewater treatment as a bio-electro-Fenton (BEF) system. The influence of hydraulic retention time (HRT) and influent organic loading rate (OLR) on the treatment performance and energy balance of the BEF system was examined. The maximum chemical oxygen demand (COD) removal of 93% and the BOD5/COD of 0.89 in the continuous BEF system were desirable with an OLR of 0.58 g L−1 d−1 and HRT of 83.33 h. The maximum current density of 603.86 mA m−2, a voltage of 892 mV, a power density of 183.06 mW m−2 were achieved with an OLR 5.77 g L−1 d−1 and HRT 5.21 h. The coulombic and energy efficiencies were 5.36 and 65.33%, respectively. The optimum HRT was found to be around 11–21 h for electricity production and COD removal simultaneously from the wastewater.

Performance and kinetics analysis of an aerobic sequencing batch flexible fibre biofilm reactor for milk processing wastewater treatment

In this study, a sequencing batch flexible fibre biofilm reactor (SB-FFBR) is used for efficient and cost-effective treatment of milk processing wastewater (MPW). The SB-FFBR, modified type of a typical sequencing batch reactor (SBR), is made up of eight bundles of flexible fibre as a supporting media for microorganisms'growth. The working volume and the cycle length of the bioreactor are 8 L and 24 h, respectively. The biological performance of the bioreactor is studied at 10, 3 and 10 various levels of the influent chemical oxygen demand (CODin; 610–8193 mg L−1), retention time (RT; 1, 1.6 and 2 days), and organic loading rate (OLR; 0.38–8.19 gCOD m−3d−1), respectively. From the results, the minimum COD and total suspended solids (TSS) removal efficiency of 86.8% and 77.3% were achieved at OLR of 8.2 kg COD m−3d−1, CODin of 8193 mg L−1 and RT of 1 day. While, an excellent COD and TSS removal efficiency were found to be 97.5% and 99.3%, respectively, at low OLR of 0.4 kg COD m−3d−1, CODin of 945 mg L−1 and RT of 2 days. Furthermore, the kinetic coefficients of COD removal were computed using a first order substrate removal model at different COD concentrations. The first order kinetic constant, (k), was 0.60, 0.65 and 0.357 h−1 for 500, 810 and 2000 mg COD L−1, respectively. The use of the flexible fibre as a packing material provided a huge surface area for more microorganism attachment. Therefore, the results demonstrated the SB-FFBR has acted as a suitable and effective strategy in treatment of milk processing industrial wastewater.

Impact of goethite dosed continuous stirred tank reactor on continuous methane production at different organic loading rates.

Iron oxides facilitated anaerobic digestion process has been attracted more and more attention in the renewable energy production area. In the current study, goethite was added into the continuous stirred tank reactor with glucose as the substrate. Effect of the influent organic loading rate (OLR) on the reactor performances was explored. Results showed that goethite promoted the methane production significantly (p<0.05) when OLR was changed between 1.20 and 1.80g glucoseL-1 day-1 . Compared to the control reactor, addition of goethite improved the methane production by13.4%-22.9%. The iron reduction rate had a positive correlation with the methane production rate. Microbial community analysis results showed that OLRs influenced the dominant methanogenic species in the both reactors. Methanothrix, Methanobacterium, Methanosarcina, and Methanocella were dominant under various OLR levels. PRACTITIONER POINTS: Goethite could promote the methanogenic process of glucose in the CSTRs under certain levels of OLRs. Iron reduction rate had a positive correlation with the methane production rate. OLRs influenced the dominant methanogenic species in the goethite-dosed reactors.

Anaerobic Membrane Bioreactor for Urban Wastewater Valorisation: Operative Strategies and Fertigation Reuse

In European scenario, the potential source for water supply from treated wastewater is actually estimated in 1,100 Mm3/y (EU-ENV, 2015). Anaerobic processes compared with conventional aerobic ones, cause a net reduction of the operative costs and possible reuse for fertigation purposes. The tested anaerobic pilot (HRT 6 h and T 30°C) is constituted from a UASB reactor (16 L). Increment of influent organic loading rate (OLR) was studied for 1 year from 1 to 2 kgCOD/m3/d by feeding raw wastewater (Period 1), methanol (Period 2) and fermented supernatant from cellulosic sludge (Period 3).The biogas production was assessed equal to 0.13 m3biogas/kgCOD (Period 1), to 0.57 m3biogas/kgCOD (Period 2) and to 0.24 m3biogas/kgCOD (Period 3) with methane percentages constant around 33%. UASB effluent has not the final quality to comply limit values for water reuse and fertigation, especially for microbiological parameters. Further treatments could be necessary to achieve the removals of bacteria, such as E.Coli, recalcitrant organic traces and metals. Therefore, some advanced post treatments have been studied in this paper after UASB treatments, like UV disinfection, UV coupled with H2O2 and GAC adsorption. The innovative solution is coupling UASB reactor with anaerobic submerged sidestream AnMBR (UF hollow fiber membrane with 0.03 µm of nominal pore-size and 0.5 m2 of surface area KOCH, Puron single bundle). Membrane cleaning was carried out using sodium hypochlorite solution (400 ppm) each 45 days to remove organic fouling and to recover the initial permeability of the membrane. The average operative flux at process temperature was equal to 8.8±1.9 L/h/m2 and operating TMP of 44.6±8.5 mbar was detected. The removal of E.Coli was investigated in the effluent from UASB and in the permeate from AnMBR process. At clean membrane conditions, complete removal of bacteria (99±1%) was found. Furthermore, the determination of microplastics distribution was carried out both in the experimental anaerobic pilot and in the conventional full scale aerobic treatment plant. The effluent microplastics were quantified and the removal role of the different operative units was studied.

Granulation of halophilic sludge inoculated with estuarine sediments for saline wastewater treatment

As a solution of the sludge loss in the treatment of saline wastewater, the granulation of halophilic sludge was explored in this study. The inoculated estuarine sediment was granulated to an average diameter of 1155 ± 102 μm under the selective settling pressure in the airlift sequencing batch reactor (SBR) when the influent organic loading rate (OLR) was doubled to 0.36 g COD/L·day. The results indicated that the OLR doubled the amount of total extracellular polymeric substance (EPS) and that protein was predominant in the EPS (72.8 ± 2.0%). The correlation between aggregate size and protein content was better than that between aggregate size and polysaccharide content. The amount of alginate-like exopolysaccharides (ALE) increased linearly at the mature granular stage, co-occurring with the compact and elastic structure of the granules. According to the results of 16S rRNA high -throughput sequencing, the Shannon-Weaver index of mature granule decreased by >50% compared to the inoculated sediment. Bacteria of Propionibacteriaceae family constituted 34% of the population in granules and were in symbiotic relationship with halophiles of family Rhodocyclaceae, Vibrionaceae, Flavobacteriaceae, and Cryomorphaceae. The aerobic halophilic granular sludge showed COD removal efficiency of 90.9 ± 0.8% and ammonia removal efficiency of 72.6 ± 4.0% for 30 g/L saline wastewater. An average nitrite accumulation ratio of 94.5 ± 2.9% was observed during nitrification. Granulation of halophilic sludge provides an effective solution to the saline sludge loss problem, which is a step forward to realize the biological treatment of saline wastewater by halophiles.

Coproduction of hydrogen and methane in a CSTR-IC two-stage anaerobic digestion system from molasses wastewater.

A continuous hydrogen and methane production system in a two-stage process has been investigated to increase energy recovery rate from molasses wastewater in this study. This system consisted of a continuous stirred-tank reactor for hydrogen production and an internal circulation (IC) reactor for methane production, and was studied under the influent organic loading rate (OLR) of 18, 24, 30 and 36kg COD/(m3·d) (COD: chemical oxygen demand). The maximum volumetric hydrogen production rate of 2.41 L/(L·d) was obtained at the OLR of 30kg COD/(m3·d) with a hydrogen content of 42%, and the maximum volumetric methane production rate of 2.4 L/(L·d) with a methane content of 74.45% was obtained at the OLR of 36kg COD/(m3·d) using the effluents of hydrogen fermentation as substrate. The maximum of 71.06% of the molasses wastewater energy was converted to biogas (hydrogen and methane) at the OLR of 30kg COD/(m3·d).

Effective Anaerobic Bio-Treatment of Fresh Leachate From Municipal Solid Waste Incineration Plant by Full-Scale Internal Circulation Reactor

This study aimed to investigate the effectiveness of the full-scale internal circulation (IC) reactor in biodegrading of municipal solid waste (MSW) fresh leachate under mesophilic conditions, where the anaerobic process stability, biogas yield, and sludge granulation were intensively investigated. The effects of operational parameters on the influent organic loading rate (OLR), chemical oxygen demand (COD) removal efficiency, alkalinity (ALK), pH, volatile fatty acids (VFAs) accumulation, and effluent recirculation were also studied. The results showed that the reactor operated stably and effectively. The COD removal efficiency and biogas yield could be maintained at (92.8 ± 2.0)% and (0.47 ± 0.05) m3/kg CODremoval, respectively, with the influent OLR (24.5 ± 0.9) kg COD/(m3 d) and hydraulic retention time (HRT) 2.7d during the stable operation phase. Meanwhile, this study demonstrated that 1.5–3.0 m/h would be the optimal Vup for the reactor, corresponding to the effluent recirculation of 32.5–78.0 m3/h. Moreover, it was found that the content of extracellular polymeric substances (EPS) in the anaerobic sludge increased from 50.3 to 140.7 mg/g volatile suspended solids (VSS), and the sludge had good granular performance during the reactor operation.

Organic loading rate (OLR) regulation for enhancement of aerobic sludge granulation: Role of key microorganism and their function

According to unique growth characteristics of various environmental microorganism specially with different substrates and their levels, aerobic sludge granulation are studied under different operation mode of influent organic loading rate (OLR), and the EPS component, sludge surface characters and functional microbes are analyzed to achieve a novel process for stable sludge granulation. Results showed that activated sludge cultivated under gradient influent OLR decreasing from 5.5 to 3.5 kgCOD m−3 d−1 achieved complete granulation with average size of 438 μm and exopolysaccharide (PS) to protein (PN) ratio over 2.0. Meanwhile, these granules had excellent flocculability and hydrophobicity with Zeta potential and contact angle of −15 mV and 110°, respectively. Principal component analysis (PCA) illustrated that microbes with function of EPS secretion enriched with decreased OLR regulation for their suitable specific growth characteristics, then promoted other microbes aggregation and sludge granulation along with the improvement of cellular surface characters and microbial niche.

Bacterial community analysis in upflow multilayer anaerobic reactor treating high-solids organic wastes.

A novel anaerobic digestion configuration, the upflow multi‐layer anaerobic reactor (UMAR), was developed to treat high‐solids organic wastes. The UMAR was hypothesized to form multi‐layer along depth due to the upflow plug flow; use of a recirculation system and a rotating distributor and baffles aimed to assist treating high‐solids influent. The chemical oxygen demand (COD) removal efficiency and methane (CH4) production rate were 89% and 2.10 L CH4/L/d, respectively, at the peak influent COD concentration (110.4 g/L) and organic loading rate (7.5 g COD/L/d). The 454 pyrosequencing results clearly indicated heterogeneous distribution of bacterial communities at different vertical locations (upper, middle, and bottom) of the UMAR. Firmicutes was the dominant (>70%) phylum at the middle and bottom parts, while Deltaproteobacteria and Chloroflexi were only found in the upper part. Potential functions of the bacteria were discussed to speculate on their roles in the anaerobic performance of the UMAR system. © 2017 The Authors Biotechnology Progress published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers Biotechnol. Prog., 33:1226–1234, 2017

Influence of operational conditions on the stability of aerobic granules from the perspective of quorum sensing

Integrated aerobic granules were first cultivated in two sequencing batch reactors (SBRs) (A1 and A2). Then, A1's influent organic loading rate (OLR) was changed from alternating to constant (cycling time was still 6h), while A2's cycling time varied from 6 to 4h (influent OLR strategy remained alternating). After 30-day operation since the manipulative alternations, granule breakage happened in two reactors at different operational stages, along with the decrease of granule intensity. Granule diameter in A1 declined from the original 0.84 to 0.32cm during the whole operation, while granules in A2 dwindled to 0.31cm on day 22 with similar size to A1. Both the amount of total extracellular polymeric substances (EPSs) and the protein were declining throughout the operation, and the large molecular weight of protein was considered closely related to the stability of aerobic granules. The relative AI-2 level decreased at the same time, and influent OLR strategy might had more evident impact on quorum sensing (QS) ability of sludge compared with starvation period. Combined with microbial results, the decline of total EPS amount in two reactors could be concluded as follows: During the reactor operation, some functional bacteria gradually lost their dominance and were eliminated from the reactors, which finally caused granule disintegration. In summary, the results further confirmed that alternating OLR and proper starvation period were two major factors in effective cultivation and stability of aerobic granules from the perspective of QS.