Sludge Granulation Research Articles

Deciphering the effect of algae sources on the formation of algal-bacterial granular sludge: Endogenous versus exogenous algae

As a key factor affecting the granulation of symbiotic sludge , the evaluation of the influence of algae sources on the ABGS system is expected to further optimize the cultivation of ABGS. In this study, formation of algal-bacterial granular sludge (ABGS) cultivated with endogenous algae and exogenous algae was comparatively investigated. During ABGS formation, the presence of algae facilitated the settleability improvement and biomass growth. ABGS cultivated with endogenous algae achieved a faster granulation (39 days) than that with exogenous algae (46 days). Inoculating exogenous algae could significantly improve the nutrient removal efficiency at the start-up stage. Tightly-bound extracellular polymeric substances (TB-EPS) were crucial for ABGS formation and maintenance, especially protein (PN) components. More EPS enriched in the mature ABGS enhanced by endogenous algae. The spatial distribution of protein and α-D-glucopyranose was obviously affected by algal sources. During ABGS formation, there was a directional selection in algal species , and the operation condition of the system was the key factor affecting the structure of algae community. The effect of algae sources on the bacterial community structure of ABGS took time to manifest. Correlation analysis showed that endogenous algae contributed more to the metabolism and property improvement of sludge than exogenous algae. • ABGS cultivated by the endogenous algae achieved a faster granulation. • Inoculating EX-A obviously improved the nutrient removal at the initial stage. • Mature ABGS cultivated with endogenous algae could secrete more EPS. • Algae source was not the dominant factor in determining the algal community in ABGS. • The genes related to metabolism were more enriched by endogenous algae in mature ABGS.

How weak static magnetic field contributes to rapid granulation and better performance of microalgal-bacterial granular sludge?

Microalgal-bacterial granular sludge (MBGS) has received considerable attention as an emerging sustainable process for wastewater treatment, whereas achieving rapid granulation is still challenging. Herein, we applied a static magnetic field (5 mT) to accelerate MBGS granulation in photo-sequencing batch reactors (PSBRs). Results showed that complete granulation of MBGS in the reactor with magnetic field (RM) was achieved 20 days before that in the control reactor (RC). The magnetic field significantly promoted microbial growth, sludge settleability and granule density. The treatment performance for COD (84.1 %–96.7 %), ammonium (91.7 %–100 %) and phosphorus (71.5 %–83.3 %) was efficient and similar in both reactors. However, the volumetric removal rate for total nitrogen (TN) was greatly improved by magnetic field due to increased nitrogen assimilation and denitrification. Moreover, mature MBGS in RM showed higher specific oxygen production rate (SOPR) and specific oxygen uptake rate (SOUR), approximately 90 % and 16 % greater than those in RC. The accumulation of metal ions (iron and calcium), the enhanced production of extracellular polymeric substances (EPS, especially proteins (PN)), and the enrichment of functional bacteria (EPS producers and potential denitrifiers) and phototrophs (Tetradesmus, Monoraphidium and Desmodesmus) contributed to rapid granulation and better performance of MBGS. This study provides an economic, effective and environmental-friendly method for rapid cultivation of MBGS, which would be helpful for large scale applications of MBGS.

Phosphorus Removal from Aerobic Granular Sludge: Proliferation of Polyphosphate-Accumulating Organisms (PAOs) under Different Feeding Strategies

Aerobic granular sludge (AGS) is known for high phosphorus removal from wastewaters, and phosphorus can be recovered from high phosphorus-containing waste sludge granules. This study aimed at determining the feeding strategy that provides the best performance in terms of the proliferation of polyphosphate-accumulating organisms (PAOs) and phosphorus removal. Using three AGS bioreactors, this study compared phosphorus removal and the proliferation dynamics of PAOs under three different feeding strategies: anaerobic slow feeding (R1), pulse feeding + anaerobic mixing (R2), and pulse feeding (R3). Results indicate that R1 and R2 achieved significantly higher phosphorus removal (97.6 ± 3% for R1 and 98.3 ± 1% for R2) than R3 (55 ± 11%). The anaerobic slow feeding procedure (R1) achieved the highest specific phosphorus release rate (SPRR) and specific phosphorus uptake rate (SPUR) as compared to the other two feeding conditions. 16S ribosomal ribonucleic acid (rRNA) gene sequencing assay of the microbial community for the three feeding strategies indicated that although the feeding strategy impacted reactor performance, it did not significantly alter the microbial community. The bacteria community composition maintained a similar degree of diversity. Proteobacteria, Bacteroidetes, and Verrucomicrobia were the dominant bacterial phyla in the system. Dominant PAOs were from the class Betaproteobacteria and the genera Paracoccus and Thauera. Glycogen-accumulating organisms were significantly inhibited while other less-known bacteria such as Wandonia and Hyphomonas were observed in all three reactors.

A comparative study for hybrid UASB reactor performance using polyethylene media and luffa sponge as biofilm support.

This paper study the performance of a lab-scale hybrid up-flow anaerobic sludge blanket (UASB) reactor treating low-strength synthetic wastewater using different biofilm supporting materials. Two identical reactors are constructed and operated at constant up-flow velocity of 0.1m/hr., inflow rate of 9.76L/d, and hydraulic retention time (HRT) of 8.26hours. The Start-up phase, using seed sludge for existing wastewater treatment plant, lasted until the efficiency of chemical oxygen demand (COD) removal of both reactors reached 80%. Polyethylene (PE) media are added to one of the reactors and luffa sponge is used in the second reactor. Results show increased COD removal efficiency up to about 90% at 20°C and biogas production rates from 3.8*10-3 till 7.5*10-3m3 CH4/kg CODr using PE media. The COD removal efficiency reaches about 95% at 20°C using luffa sponge and biogas production rates up to 6.5*10 -3m3 CH4/kg CODr are achieved before clogging problem is observed. Effect of HRT reduction, from 8.26 to 4.13hours, on removing clogging is investigated. Reduction in COD removal efficiencies is observed at low ambient temperatures during seasonal variations of 15-25°C. AFM and SEM analysis are used to examine sludge granulation and biofilm formation.

Aerobic Granulation Stability and Microbial Diversity of Filamentous Bulking Sludge

Filamentous bacteria, as one of the common bacteria types in wastewater biological treatment, are considered to be the main factor to induce sludge bulking. However, because of its special filamentous shape, it plays a crucial role in the formation of sludge particles. Taking filamentous bulking sludge as the research object, the effect of filamentous bacteria on the sludge granulation process and maintaining the stability of sludge granules was studied, and the microbial diversity of the sludge system was analyzed. Filamentous bulking sludge (SVI=241.56 mL·g-1) and flocculated sludge (SVI=64.22 mL·g-1) were respectively inoculated to carry out granulation culture. The results showed that the time of particle appearance of bulking sludge and flocculated sludge was 20 days and 40 days, respectively; the mature particle sizes were 650 μm and 700 μm, respectively; and the granulation time of bulking sludge was only half that of flocculated sludge. After adding the anoxic zone, the granules were broken to differing degrees, but the SV30/SV5 value of mature granules recovered to 1 after short-term fluctuation, and the stability of the mature granules was stronger. The analysis of microbial community structure showed that the relative abundance of norank_o__Saccharimonadales, unclassified_o__Saccharimonadales, and unclassified_f__Saccharimonadaceae increased from 0.05%, 0.01%, and 0.01% to 4.09%, 3.15%, and 1.12%. The existence and accumulations of these hydrophobic bacteria were important for rapid granulation. The removal rates of COD, NH4+-N, and TN were 94%, 99%, and 35% and 92%, 97%, and 30%, respectively, in SBR1 of bulking sludge and SBR2 of flocculated sludge, and the removal rates of TP were 60% and 30%, respectively.

Comparison and Optimization of Continuous Flow Reactors for Aerobic Granule Sludge Cultivation from the Perspective of Hydrodynamic Behavior.

Improving treatment efficiency and reducing investment and operating costs make aerobic granular sludge technology (AGS) a promising technology for treating aquaculture wastewater. The development of continuous flow reactors (CFRs) has become a new direction in the research of AGS. This study clarifies the granulation effect, hydrodynamic behavior and particle separation of three different CFRs (R1 to R3). The established CFD model was able to explain the hydrodynamic behavior in all three CFRs; in particular, R3 performed the best from the perspective of hydrodynamic behavior due to its abundant turbulence. In addition, the optimal baffle distance and baffle angle of R3 were simulated to be 40 mm and 60°, respectively, due to them providing the best turbulent flow and particle separation effect. However, an overlarge baffle angle could weaken the turbulent pattern in the reactor. The retention time distribution further confirmed the reasonability of these optimal parameters with the highest effective volume ratio of 0.82. In short, this study gives an instruction for exploring the rapid formation mechanism of AGS in a CFR to promote its engineering application.

Sludge granulation in ASBR: Reactor performance, sludge physiochemical properties evolution and the unique clustered structure of the granular sludge

Anaerobic granular sludge was successfully cultivated in the anaerobic sequencing batch reactor (ASBR) after 45 days of operation. The results showed that the mature granular sludge exhibited better physicochemical characteristics: granule percentage of 62.6 ± 8.8 %, 0.8–1.2 mm in diameter, with smooth edges and regular shapes, and sludge volume index of 20.0 mL/g SS. 16S rRNA-targeted fluorescence in situ hybridisation (FISH) and scanning electron microscope (SEM) examination revealed that the granular sludge had a unique clustered microbial community structure, which would to be an optimal microbial arrangement for syntrophic colonies. The large substrate concentration gradient that derived from the feast-famine alternation regime of the substrate in a running cycle of ASBR was the major cause of the clustered microbial distribution structure. Lots of syntrophic consortia formed by acetogens and methanogens randomly distributed throughout the interior of the granules, furthermore, the cavities existing amongst the syntrophic consortia were convenient for substrate transfer and biogas liberation, thus enhancing the digestion performance of ASBR and preventing granule disintegration caused by gas scour. With sludge granulation, the methane yield of ASBR increased from the initial 0.23 L/g COD to 0.28 L/g COD, meanwhile, the maximum specific methanogenic activities (SMAs) of acetoclastic and hydrogenotrophic methanogens respectively increased from 0.51 gCOD/(gVSS·d) to 0.73 gCOD/(gVSS·d) and from 0.35 gCOD/(gVSS·d) to 0.62 gCOD/(gVSS·d). The exploration of granular sludge formation, sludge characteristic evolution and treatment performance in ASBR reactor has theoretical value for its engineering promotion.

Fast formation of anammox granules using a nitrification-denitrification sludge and transformation of microbial community

A lengthy start-up period has been one of the key obstacles limiting the application of the anammox process. In this investigation, a nitrification-denitrification sludge was used to start-up the anammox EGSB process. The transformation process from nitrification-denitrification sludge to anammox granule sludge was explored through the aspects of nitrogen removal performance, granule properties, microbial community structure, and evolution route. A successful start-up of the anammox process was achieved after 94 days of reactor operation. The highest nitrogen removal rate (NRR) obtained was 7.25±0.16 gN/L/d at a nitrogen loading rate (NLR) of 8.0 gN/L/d, and the corresponding nitrogen removal efficiency was a high 90.61±1.99%. The results of the microbial analysis revealed significant changes in anammox bacteria, nitrifying bacteria, and denitrifying bacteria in the sludge. Notably, the anammox bacteria abundance increased from 2.5% to 29.0% during the operation, and Candidatus Kuenenia and Candidatus Brocadia were the dominant genera. Distinct-different successions on Candidatus Brocadia and Candidatus Kuenenia were also observed over the long-term period. In addition, the settling performance, anammox activity and biomass retention capacity of the granules were significantly enhanced during this process, and the corresponding granule evolution route was also proposed. The results in this study indicate the feasibility of using available seed sludge source for the fast-transformation of anammox granules, it is beneficial to the large-scale application of anammox process and the utilization of excess sludge.

Effect of zero-valent iron and iron-carbon particles on the denitrification efficiency of anammox process under gradual cooling conditions

Nitrogen pollution in water bodies mainly comes from industrial wastewater discharge, urban sewage discharge, and agricultural pollution. Nitrogen in a nitrate form can adversely affect human health and the environment. In this study, the effects of adding zero-valent iron (ZVI) and iron-carbon (Fe-C) particles on the performance of the anaerobic ammonia oxidation (anammox) process and sludge properties under gradual cooling conditions were investigated. Inoculating a portion of mature anammox granular sludge can speed up the rapid start of anammox. After 90 d of domestication and cultivation, the sludge granulation was achieved, and the influent load was increased. After 30 d of incubation, the total nitrogen (TN) removal efficiency can reach 95.08%. Through batch tests, the short-term effects of adding ZVI and Fe-C particles on anammox sludge were studied. It was found that when 100 mg/L dosage of ZVI was added, the denitrification effect of anammox sludge is the best. When Fe-C particles with Fe/C ratio of 2:1 were added, the anammox sludge had the best denitrification effect. Fe-C particles addition increased the pH of the reaction environment and sludge activity was affected. Continuous flow experiments under gradual cooling conditions showed that the effect of adding Fe-C particles on anammox was better than that of ZVI. After adding ZVI under 15 °C, NH 4 + -N and NO 2 - -N removal efficiency was 78% and 86%. Compared with the low temperature non-dosing ZVI, TN removal load was 1.77 kg/(m 3 ·d), and efficiency was improved by 10.2%. Addition of Fe-C particles promoted the denitrification efficiency, NH 4 + -N and NO 2 - -N removal efficiency was 83.90% and 88.84%. As compared to control the TN removal load was 1.90 kg/(m 3 ·d), and efficiency was improved by 8.4%. The sludge concentration showed a positive correlation with temperature. Results from this study show that simple addition of ZVI and Fe-C particles can stimulate microorganisms to secrete more EPS even under lower temperature. The outcomes of study are significant for wastewater management and pollution control in the waterbodies.

Effects of long-term exposure to ciprofloxacin on the performance of an enhanced biological phosphorus removal (EBPR) and its microbial structure

In this study, the long-term impacts of ciprofloxacin (CIP) on the performance as well as the microorganisms of an EBPR system were assessed in a sequencing batch reactor (SBR). The results showed that nitrogen and phosphorus removal performance was significantly inhibited (P < 0.01) by CIP. Semi-inhibitory concentration (IC50) of anaerobic phosphate release, aerobic phosphate uptake and ammonia oxidation (1.9, 1.5 and 1.2 mg·L−1) suggested that the inhibition of CIP on ammonia oxidation was the strongest. Meanwhile, the diversity and evenness of microorganisms were reduced greatly (P < 0.01) due to the toxicity of CIP. Lysobacter, however, gradually dominated because of its strong resistance to CIP. The tolerance ability of functional microorganisms related to phosphorus and nitrogen removal to CIP was as follows: nitrite-oxidizing bacteria (NOB) > phosphorus-accumulating bacteria (PAOs) >Zoogloea > glycogen-accumulating bacteria (GAOs). It was also found that tightly bound EPS (TB-EPS) concentration decreased companying with a decrease of sludge activity as CIP addition increased. Moreover, an obvious sludge granulation was observed with protein (PN) proportion increased and polysaccharide (PS) proportion decreased. Nevertheless, the results of recovery experiment showed that the deterioration of the EBPR caused by long-term exposure to CIP could be replenished within 10 days, implying the inhibitory effect of CIP on EBPR was reversible.

Effects of pharmaceuticals compounds and calcium on granulation, microbiology, and performance of anaerobic granular sludge systems.

Granular sludge is a promising biotechnology to treat sewage contaminated with pharmaceuticals due to its increased toxicity resistance. In this context, this study evaluated the potential of Ca2+ as a granulation precursor and how pharmaceutical compounds (loratadine, prednisone, fluconazole, fenofibrate, betamethasone, 17α-ethinyl estradiol, and ketoprofen) affect granulation. Continuous and intermittent dosages of Ca2+ in the presence and absence of pharmaceuticals were evaluated. The results showed that intermittent addition of Ca2+ reduces the time for anaerobic sludge granulation, and pharmaceuticals presence did not impair granulation. 10% of the granules presented mean diameters greater than 2.11 mm within 93 days with intermittent Ca2+ dosage in the pharmaceuticals' presence. In contrast, no granules higher than 2.0 mm were observed with no precursor addition. The pharmaceuticals' toxicity may have created a stress condition for the microbial community, contributing to more EPS production and a greater potential for granulation. It was also verified that pharmaceuticals' presence did not decrease organic matter, total alkalinity, and volatile fatty acids removals. The 16S rRNA gene analysis revealed taxa resistance to recalcitrant compounds when pharmaceuticals were added. Besides, the efficiency of a granular sludge bioreactor (EGSB) was evaluated for pharmaceuticals removal, and betamethasone, fenofibrate, and prednisone were effectively removed.

Adding waste iron shavings in a pilot-scale two-stage SBRs to develop aerobic granular sludge treating real wastewater

A pilot-scale two-stage SBRs added waste iron shavings was proposed and established to develop aerobic granular sludge for real wastewater treatment based on a previous lab-scale study. The results showed that aerobic granular sludge was successfully cultivated, and the treatment performance was satisfactory. The sludge volume index at 30 min (SVI30) was approximately 25.0 mL/g and the mean particle size reached approximately 0.8 mm. The mixed liquor suspended solids (MLSS) exceeded 14 g/L and 10 g/L in the two SBRs. The average removal rates of chemical oxygen demand (COD), total phosphorus (TP), ammonia nitrogen (NH4+-N), total nitrogen (TN), and suspended solids (SS) were 95.2%, 99.2%, 96.1%, 82.9%, and 95.0%, respectively. In addition, low total iron (TFe) concentrations were unlikely to impact the effluent. Two-stage SBRs can efficiently reduce the effluent SS concentration during early in the operation process, and improve the utilisation of carbon source from raw wastewater for denitrification. Overall, the coupling of iron shavings micro-electrolysis and biological processes promoted aerobic sludge granulation and pollutant removal.

The Role of Extracellular Polymeric Substances in the Toxicity Response of Anaerobic Granule Sludge to Different Metal Oxide Nanoparticles.

Wastewater treatment plants (WWTP) are regarded as the last barriers for the release of incompletely separated and recycled nanoparticles (NPs) into the environment. Despite the importance and ubiquity of microbial extracellular polymeric substances (EPSs) in the complex wastewater matrix, the interaction between NPs and EPSs of anaerobic microflora involved in wastewater treatment and the resultant impact on the biomass metabolomics are unclear. Thus, the impacts of different metal oxide (TiO2, ZnO, and CuO) NPs on functional bacteria in anaerobic granular sludge (AGS) and the possible toxicity mechanisms were investigated. In particular, the binding quality, enhanced resistance mechanism, and chemical fractional contribution of EPSs from AGS against the nanotoxicity of different NPs was assessed. The results showed that CuO NPs caused the most severe inhibition towards acetoclastic and hydrogenotrophic methanogens, followed by ZnO NPs, whereas TiO2 NPs caused no inhibition to methanogenesis. Excessive EPS production, especially the protein-like substances, was an effective strategy for reducing certain NPs’ toxicity by immobilizing NPs away from AGS cells, whereas the metabolism restriction on inner microorganisms of AGS induced by CuO NPs can deteriorate the protective role of EPS, indicating that the roles of EPS may not be amenable to generalizations. Further investigations with lactate dehydrogenase (LDH) and reactive oxygen species (ROS) assays indicated that there are greatly essential differences between the toxicity mechanisms of metal NPs to AGS, which varied depending on the NPs’ type and dosage. In addition, dynamic changes in the responses of EPS content to different NPs can result in a significant shift in methanogenic and acidogenic microbial communities. Thus, the production and composition of EPSs will be a key factor in determining the fate and potential effect of NPs in the complex biological matrix. In conclusion, this study broadens the understanding of the inhibition mechanisms of metal oxide NPs on the AGS process, and the influence of EPSs on the fate, behavior, and toxicity of NPs.

Anaerobic treatment of sugarcane vinasse pretreated with a calcium-based biopolymer

This study investigated the influence of a previous sugarcane vinasse coagulation, by using a calcium-based biopolymer, on anaerobic treatment in a lab-scale reactor. Two anaerobic reactors (R1 and R2) were operated for 155 days. R1 was fed only with raw sugarcane vinasse and R2 was fed with pretreated effluent. The operation was divided into three stages: E1 (inoculation and adaptation); E2; and E3. The major difference between E2 and E3 was the fact that R2 failed at the end of E2. Thus, R2 was recovered by applying a low organic loading rate (OLR) of raw vinasse for 29 days. In E2 and E3, for both reactors, pH, alkalinity, COD (influent and effluent samples), and methane production were monitored. During E1, an OLR of 2.0 kgCOD. m-3.d-1 1 was applied, and R1 and R2 sludges showed good adaptation to the wastewater in this condition. Then, the OLR was progressively increased to 7.0 kgCOD.m-3.d-1 in both systems. The average COD removal efficiencies were 82.9 ± 4.4% and 72.2 ± 18.1% for R1 and R2, respectively. R2, operated with pretreated vinasse, showed a decrease in the COD removal and methane production, which could be caused by the biopolymer presence. The average COD removal efficiencies in E3 were 77.5 ± 9.4% and 79.2 ± 9.7% for R1 and R2, respectively. After 155 days of operation, a decrease in the COD removal and methane production was identified again in R2, indicating a new failure. The quality of sludge granules from the inoculum and also from the granules developed at the end of R1 and R2 operation was analyzed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). These analyses indicated a rise in the rugosity of R1 and R2 granules, possibly due to the deposition of sedimentable compounds present in both raw and pretreated vinasse. The EDS analyses indicated a high presence of calcium in R2 granules, indicating that this compound acted in the reduction of mass transfer between organic load from vinasse and the granules’ microbiota.

Study on the treatment of tempering lubricant wastewater in steel industry by anaerobic/aerobic process

Tempering lubricant wastewater (TLW) is alkaline oily wastewater produced in the cold rolling process of steel, which has multiple contaminants in high concentration including complex organic components, oil, and surfactants. And the ratio of BOD/COD was only around 0.1. This study evaluated the performance of the combined anaerobic/aerobic (A/O) batch reactors for treating real TLW under different organic load rates (OLRs). The results of 140 days monitoring indicated that A/O process was effective to TLW treatment, the removal efficiencies of TOC and total nitrogen (TN) reached 86.2% and 81.5% when OLR was 5 g-COD/L/d. It was also found that OLR had much effect on the microorganism's distribution in the anaerobic reactor. The abundance of Firmicutes increasing at higher OLR (over 5 g-COD/L/d) caused volatile fatty acids accumulation during anaerobic treatment and then inhibited TLW degradation, especially for TOC removal. Based on the sludge characters and microbial community analyses, aerobic granule sludge formed in aerobic reactor contributed to TN removal by simultaneous nitrification and denitrification. Functional genes were also detected through real-time quantitative PCR analysis.

Unveiling significance of Ca2+ ion for start-up of aerobic granular sludge reactor by distinguishing its effects on physicochemical property and bioactivity of sludge

Almost all of the aerobic granular sludge (AGS) reactors were fed on certain amounts of Ca2+ ion, but whether and why it was necessary for reactor start-up remain unknown. Herein, this study conducted a set of comparative experiments in three AGS reactors, which were operated in parallel with Ca2+ addition in R3, hydroxyapatite (HAP) addition in R1, and without any forms of Ca addition in R2. Results showed that R3 not only achieved the complete granulation of sludge, but exhibited superior performance of COD and nutrient removal. In contrast, R1 had a slightly quicker granulation rate than R3 (R1: 0.07 day−1; R3: 0.06 day−1), but the formed granules could not efficiently degrade pollutants. In R2, both sludge granulation and pollutants removal did not proceed normally. Further investigations found that the Ca2+ ion acted in three ways: (1) it increased inorganic composition of sludge to promote granulation; (2) the transformed HAP strengthened stability of granular structure; (3) it ensured bioactivity of granules by driving enrichment of functional microbes and synthesis of metabolism enzymes. Overall, this study systemically proved significance of Ca2+ ion for the start-up of AGS reactors and its influencing mechanisms on different properties of granules.

Microbial and functional characterization of granulated sludge from full-scale UASB thermophilic reactor applied to sugarcane vinasse treatment

ABSTRACT Considering the scarcity of data in the literature regarding phylogenetic and metabolic composition of different inocula, especially those from thermophilic conditions, this research aimed at characterizing the microbial community and preferable metabolic pathways of an UASB reactor sludge applied to the thermophilic treatment (55°C) of sugarcane vinasse, by means of shotgun metagenomics. After its metabolic potential was depicted, it was possible to observe several genes encoding enzymes that are of great importance to anaerobic digestion processes with different wastes as substrate, especially regarding the biodegradation of carbohydrates and ligninolytic compounds, glycerolypids, volatile fatty acids and alcohols metabolism and biogas (H2 and CH4) production. The genera identified in higher relative abundances for Bacteria domain were Sulfirimonas (37.52 ± 1.8%), possibly related to the sludge endogenic activity due to its strong relation with a peptidoglycan lyase enzymes family, followed by Fluviicola (5.01 ± 1.0%), Defluviitoga (4.36 ± 0.2%), Coprothermobacter (4.32 ± 0.5%), Fervidobacterium (2.93 ± 0.3%), Marinospirillum (2.75 ± 0.2%), Pseudomonas (2.14 ± 0.2%) and Flavobacterium (1.78 ± 0.1%), mostly related with carbohydrates fermentations and/or H2 production. For Archaea domain, Methanosarcina (0.61 ± 0.1%), Methanothermobacter (0.38 ± 0.0%), Methanoculleus (0.30 ± 0.1%), Thermococcus (0.03 ± 0.0%), Methanolobus (0.02 ± 1.8%), Methanobacterium (0.013 ± 0.0%), Aciduliprofundum and Pyrococcus (0.01 ± 0.0%) were the most dominant ones, being Methanosarcina the most related with methanogenesis. It was concluded that the robust inoculum description performed in this study may subside future biotechnological researches by using similar inocula (UASB sludges), focusing on the obtainment of value-added by-products by means of anaerobic digestion, such as volatile fatty acids, alcohols and biogas (H2 and CH4), by using several types of waste as substrate.

Enhanced nitrate removal by biochar supported nano zero-valent iron (nZVI) at biocathode in bioelectrochemical system (BES)

In this study, activated biochar (BC), nano zero-valent iron (nZVI) and biochar supported nano zero-valent iron (BC-nZVI) were used to remove cathodic nitrate in bioelectrochemical system (BES). With an initial NO3–-N concentration of 100 mg/L, it was found that the complete nitrate removal could be observed within 28 h for the group of BC-nZVI, whereas the accumulated ammonia reached 63.33 mg/L. Meanwhile, nitrate removal reaction rate constants reached 0.171, 0.110, 0.023 and only 0.010 h−1 for BC-nZVI, nZVI, BC and the Control groups, respectively. Besides, enzymatic activity of nicotinamide adenine dinucleotide (NADH) and nitrous oxide reductase (NOS) of the BC-nZVI group reached the peak faster than three other groups. As a carrier for nZVI, loading of nZVI onto BC could increase the surface area of BC-nZVI other than nZVI for microbial aggregation, while embedded nZVI would contribute to the granulation of sludge and nitrate reduction. Moreover, Cyclic Voltammetry (CV) and chronoamperometry (CA) indicated that BC-nZVI group obtain better electrochemical performances. Importantly, it was found that not only abundances of microbial genus, but relative abundances of those iron mediated enzymes responsible for electro-consuming, hydrogen production and preferential ammonia accumulated nitrate removal could all be enriched. Therefore, BC-nZVI could be implemented to enhance the nitrate removal at biocathode in BES.

Enhanced aerobic granular sludge formation by applying Phanerochaete chrysosporium pellets as induced nucleus.

The long start-up period is a major challenging issue for the widespread application of aerobic granular sludge (AGS). In this study, a novel rapid start-up strategy was developed by inoculating Phanerochaete chrysosporium (P. chrysosporium) pellets as the induced nucleus in a sequencing batch airlift reactor (SBAR) to enhance activated sludge granulation. The results demonstrated that P. chrysosporium pellets could effectively shorten the aerobic granulation time from 32 to 20days. The AGS promoted by P. chrysosporium pellets had a larger average diameter (2.60-2.74mm) than that without P. chrysosporium pellets (1.78-1.88mm) and had better biomass retention capacity and sedimentation properties; its mixed liquor suspended solids (MLSS) and sludge volume index (SVI30) reached approximately 5.2g/L and 45mL/g, respectively. The addition of P. chrysosporium pellets promoted the secretion of extracellular polymeric substances (EPS), especially protein (PN). The removal efficiencies of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), total nitrogen (TN), and total phosphorus (TP) in P. chrysosporium pellets reactor were 98.91%, 89.17%, 64.73%, and 94.42%, respectively, which were higher than those in the reactor without P. chrysosporium pellets (88.73%, 82.09%, 55.75%, and 88.92%). High throughput sequencing analysis indicated that several functional genera that were responsible for the formation of aerobic granules and the removal of pollutants, such as Acinetobacter, Pseudomonas, Janthinobacterium, and Enterobacter, were found to be predominant in the mature sludge granules promoted by P. chrysosporium pellets.

Polyaniline improves granulation and stability of aerobic granular sludge

Polyaniline improves granulation and stability of aerobic granular sludge