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Tofu is widely processed in East and Southeast Asian countries. During the production, highly polluted wastewater is discharged. This wastewater is commonly treated using a high-rate anaerobic wastewater treatment process; however, several organic compounds and nitrogen remain in the anaerobic effluent. The aim of this study was to develop a combined upflow anaerobic sludge blanket (UASB) and downflow hanging sponge (DHS) biosystem that that serves as a post-treatment for an expanded granular sludge blanket reactor used for treating tofu-processing wastewater in Japan for 699 days. The UASB reactor played a role in treating of COD, with 58 ± 16% and 74 ± 20% of total COD and soluble COD removed anaerobically. Besides, methane was recovered from removed soluble COD were 63 ± 28% and 87 ± 64% at winter and summer. Meanwhile, the DHS reactor showed its potential in treatment of BOD and TSS. The final effluents were recorded as 67 ± 38 mg L-1, 50 ± 26 mg L-1, and 22 ± 16 mg L-1 of total COD, BOD and total suspended solids, respectively. This indicates that the proposed UASB-DHS system has proven its suitability as post-treatment system for anaerobically treated tofu-processing wastewater.

Heterotrophic manganese (Mn)-oxidizing microorganisms responsible for biogenic manganese oxide (Bio-MnOx) production are fastidious. Their enrichment is not easily accomplished by merely adding a soluble organic substrate to non-sterile mixed cultures. The objective of this study was to evaluate polycaprolactone (PCL), an aliphatic polyester, as an effective solid organic substrate for the enrichment of marine Mn-oxidizing microorganisms. We successfully obtained marine microbial enrichment with the capacity for dissolved Mn removal and MnOx production using PCL as a solid organic substrate. The removal of dissolved Mn by the Mn-oxidizing enrichment culture followed first-order kinetics with a rate constant of 0.014 h−1. 16S rRNA gene amplicon sequencing analysis revealed that the Mn-oxidizing enrichment culture was highly dominated by operational taxonomic units related to the bacterial phyla Cyanobacteria, Planctomycetes, and Proteobacteria. Our data demonstrate that PCL can serve as a potential substrate to enrich Mn-oxidizing microorganisms with the ability to produce MnOx under marine conditions.

Biofilm development on the membrane surface is one of the main reasons for membrane fouling in membrane bioreactors (MBRs) and it is a big problem for their stable operation. Precise information on the microbial community composition of the biofilm is needed for a better understanding of biofilm development. However, there have been limited investigations of the relationship between the biofilm formation process and the microbial community of activated sludge and biofilm in MBRs treating real sewage. In this study, relationships between the microbial community structure of biofilm and activated sludge at each biofilm formation stage were investigated and biofilm growth was elucidated by nondestructive observations. Two anoxic/oxic MBRs were operated and membrane fouling was induced. Permeability rapidly decreased in both reactors and live cell microcolonies were formed on dead cell conditioning film on the membrane surface. Principal component analysis based on 16S rRNA gene sequences showed that the biofilm microbial community changed significantly from middle stage to mature biofilm when compared with that of activated sludge. The abundance of specific bacteria, such as unclassified Neisseriaceae, increased in middle-stage biofilm and the diversity indexes of middle-stage biofilm were lower than those of mature biofilm and activated sludge. These results suggested that the presence of specific bacteria with colonization ability played a crucial role in biofilm formation. Strategies are needed to target membrane fouling mitigation during early- and middle-stage biofilm formation to reduce MBR membrane fouling. KEY POINTS: • Microbial community of mature biofilm was approached to that of activated sludge. • In the middle-stage biofilm, live cells colonized on a dead-cell-conditioning-film. • Microbial diversity was lower in live cell colonizing stage than in activated sludge.

Given the toxicity and widespread occurrence of hexavalent chromium [Cr(VI)] in aquatic environments, we investigated the feasibility of a down-flow hanging sponge (DHS) biofilm reactor for the enrichment of microbial communities capable of Cr(VI) removal. In the present study, a laboratory-scale DHS reactor fed with a molasses-based medium containing Cr(VI) was operated for 112 days for the investigation. The enrichment of Cr(VI)-removing microbial communities was evaluated based on water quality and prokaryotic community analyses. Once the DHS reactor began to operate, high average volumetric Cr(VI) removal rates of 1.21-1.45 mg L-sponge

Partial water exchange is one of the most common conventional methods used to maintain water quality and aesthetic beauty in recirculating aquarium systems (RASs). However, this method uses substantial amount of water. The ozone-down-flow hanging sponge-up-flow sludge blanket (ozone-DHS-USB) system attempts to be a more responsible method for aquarium maintenance. It eliminates the necessity for water exchange in aquarium by maintaining nitrogen concentrations at a safe level and by reducing yellow substances. Also, the impact of O

This study was carried out to explore the importance of adsorption and biodegradation mechanisms for methylene blue (MB) removal by a novel natural adsorbent (purified coconut fibre; PCF) incorporated to a down-flow hanging fibre (DHF) reactor. An adsorption DHF (Ads-DHF) reactor demonstrated the adsorption removal mechanism, while a combined adsorption-biological DHF (Bio-DHF) reactor simulated the processes of both adsorption and biodegradation were investigated for the MB removal capability. PCF prepared from coconut fibre waste was applied as a media in the DHF reactors. The process performance and the removal mechanisms of the DHF reactors were evaluated for 62 days. The results showed that a total MB removal efficiency of 93 ± 7% was achieved for the Bio-DHF reactor and 36 ± 25% for the Ads-DHF reactor. The combined adsorption and biological degradation in the Bio-DHF reactor enhanced the removal efficiency and the life-time of the reactor compared with the performance of the adsorption process alone in the Ads-DHF reactor. Moreover, microbial community analysis revealed that microorganisms, commonly involved in the biodegradation of dyes, were predominant in the Bio-DHF reactor. The PCF media of the Bio-DHF reactor was essential to keep the dye degrading bacteria in the reactor. Therefore, it can be concluded that the Bio-DHF reactor is an appropriate treatment system for treating dyes wastewater. This research is significant and useful for environmental protection and reuse of biomass wastes.

This study was conducted to assess the potential of a sponges-submerged anaerobic baffled reactor (SS-ABR) for enhancing the processing performance of azo dye-contaminated wastewater. A lab-scale four–compartment SS-ABR, with a total volume of 10 L, was operated at 30 °C for 180 days. A total of 14 polyurethane sponges were added in each compartment to treat synthetic wastewater including a commercial azo dye Hellozol HSR Reactive Black. During the entire operation, in synthetic wastewater, starch was used as a sole carbon source, and the true color level was maintained at 1050 ± 98 Pt/Co. Meanwhile, the hydraulic retention time (HRT) and total COD (T-COD) in the influent were changed to evaluate the SS-ABR treatment performance. After the start-up phase, true color and T-COD removal efficiencies were recorded as 65 ± 3% and 83 ± 2%, 68 ± 5% and 81 ± 4%, and 70 ± 5% and 84 ± 2% for HRT and influent T-COD concentration of 18.6 h and 260 mg L−1, 14.6 h and 260 mg L−1, and 14.6 h and 460 mg L−1, respectively. The microbial community analysis showed that bacterial groups involved in dye degradation, such as Clostridium sp., and sulfate-reducing bacteria Desulfomonile sp. and Desulfovibrio sp. were detected prominently in the SS-ABR. Interestingly, the SS-ABR exhibited the dominance of both Geobacter sp. and Methanosarcina sp., and their occurrences in all columns were proportional to each other, revealing the formation of syntrophic relationships.

Modified polyvinyl alcohol (PVA) beads serve as effective anaerobic microbe immobilization carriers. PVA beads were mixed with different conductive materials, activated carbon, magnetite, and green tuff stone powder. In this study, modified PVA beads were used to investigate the effect of using, promote methane production, and enhance direct interspecies electron transfer (DIET) on the anaerobic syntrophic degradation of propionate, which is an essential intermediate process for generating methane in anaerobic digesters. The batch experiment showed that PVA mixed with activated carbon had the highest methane conversion rate of 72%, whereas the rates for control (sludge) was 61%. Moreover, the lag time during the second and third feedings was shorter by 5-fold than for the first feeding when modified PVA beads were added. The syntrophic propionate degrading microorganisms in the modified PVA beads was Syntrophobacter and Methanobacterium, either Methanoculleus or Methanosaeta. The modified PVA beads hold at least 10 times larger syntrophs than normal PVA. Therefore, composite PVA with conductive materials can promote methane production, accelerate propionate consumption, and enhance electron transfer in related microbial species., Energy; Chemical engineering; Environmental science; Environmental chemical engineering; Environmental engineering; Environmental management; Environmental pollution; Conductive materials; Direct interspecies electron transfer; Methane production, Polyvinyl alcohol bead; Syntrophic propionate degradation

Anaerobic ammonia oxidation to nitrogen gas using nitrite as the electron acceptor (anammox process) is considered a cost-effective solution for nitrogen removal after an anaerobic pre-treatment process. In this study, we conducted a laboratory-scale experiment to develop a single-stage partial nitritation–anammox process in a sponge-based trickling filter (STF) reactor, inoculated with anammox sludge, simulating the treatment of anaerobically pretreated concentrated domestic sewage without mechanical oxygen control. The influent ammonia concentration was 100 mg-N·L−1. The KLa of the STF reactor was higher than those observed for conventional activated sludge processes. The STF reactor performed at 89.8 ± 8.2% and 42.7 ± 16.9% ammonia and TN removal efficiency, respectively, with a nitrogen loading rate of 0.55 ± 0.20 kg-N·m−3·day−1 calculated based on sponge volume. Microbial community analysis of the STF-retained sludge indicated that both autotrophic and heterotrophic nitrogen removal occurred in the reactor.

Membrane fouling in membrane bioreactors (MBR) remains a major issue and knowledge of microbes associated with biofilm formation might facilitate the control of this phenomenon, Thus, an anoxic/oxic membrane bioreactor (A/O-MBR) was operated under an extremely low organic loading rate (0.002 kg-COD·m−3·day−1) to induce membrane fouling and the major biofilm-forming bacteria were identified. After operation under extremely low organic loading condition, the reactor showed accumulation of total nitrogen and phosphorus along with biofilm development on the membrane surface. Thus, membrane fouling induced by microbial cell lysis was considered to have occurred. Although no major changes were observed in the microbial community structure of the activated sludge in the MBR before and after membrane fouling, uncultured bacteria were specifically increased in the biofilm. Therefore, bacteria belonging to candidate phyla including TM6, OD1 and Gammaproteobacteria could be important biofilm-forming bacteria.

The spent mushroom substrate (SMS) generated by mushroom production is applicable to the anaerobic digestion process. However, SMS-anaerobic digestion residue (ADR) can be produced. In this study, SMS-ADR was used as a medium base material for Enokitake (Flammulina velutipes) mushroom cultivation to examine the potential for food production. Two types of pretreated SMS-ADR prior to the anaerobic digestion process-KOH pretreated (KOH-treated SMS-ADR), and NaOH pretreated (NaOH-treated SMS-ADR) were carried out in this study. The KOH- and NaOH-treated SMS-ADR contained 1340.6 mg/100 g-Dry Matter (D.M.) of K, and 941.2 mg/100 g-D.M. of Na, respectively, indicating a large inorganic component derived from the chemicals used for pretreatment. The yields were 244.1 ± 3.7 g-Fresh Matter (F.M.)/bottle (10.5 ± 0.2 g-F.M./10 g medium-D.M.) for KOH-treated SMS-ADR with 75% and 255.5 ± 4.3 g-F.M./bottle (11.7 ± 0.5 g-F.M./10 g medium-D.M.) for NaOH-treated SMS-ADR with 50% as medium base material, which were closed to the standard medium. In KOH- and NaOH-treated SMS-ADR medium, the spread of the fungus on the 29th day of culture was more than 90%, suggesting sufficient mycelial growth. The amounts of general components, inorganic components and free amino acids in the fruiting bodies were the same as those obtained from the standard medium. In addition, we prepared the testing section, where SMS not applied to the anaerobic digestion process was used as the medium base material, and the inhibition of mycelial growth and fruiting bodies were observed.

The effects of temperature and hydraulic retention time on the sewage treatment performance of mesh rotating biological reactor (MRBR) were investigated. The MRBR contained net-like 3D plastic mesh disks instead of conventional rotating disks. A laboratory-scale MRBR was used to treat real sewage for over 1 year. The soluble chemical oxygen demand concentrations for the effluent were 48–64 mg/L whether the hydraulic retention time was 2 or 4 h and when the influent sewage temperatures was between 12.2 and 24.5 °C. The sewage temperature strongly affected the NH 4 + -N removal rete, which decreased by 0.1 kg N m − 3 day − 1 for each 12 °C decrease in temperature. Even though the NH 4 + -N removal rate was low, simultaneous nitrification and denitrification occurred at a removal efficiency of 95%. The microbial community structure in the biofilm attached to the MRBR disks was different to the microbial community structure of conventional activated sludge that had been used to treat the same sewage. The microbial community structure of the MRBR biofilm sludge was stable throughout winter and summer regardless of the hydraulic retention time. This suggested that the microbial community was initially controlled by the influent sewage but then became to specific to the MRBR. This was attributed to the high degree of simultaneous nitrification and denitrification that occurred.

The aim of this study was to evaluate the effect of salinities on the nitrogen removal performance of a pilot-scale down-flow hanging sponge (DHS) reactor and an up-flow sludge blanket (USB) reactor which was installed in a closed recirculating aquaculture system for the purpose to maintain the water quality in the aquaculture tank. In this study, water quality and the growth of the Longtooth grouper, Epinephelus bruneus, were investigated at 30‰, 22.5‰, and 15‰ salinity for over 1000 days. The tested DHS reactor has successfully maintained total ammonium nitrogen in aquaculture tank at less than 1.0 mg-N·L−1 at various salinities. The abundance of nitrifying bacteria detected in the DHS reactor was higher at salinities of 15‰ and 22.5‰ than at 30‰. The USB reactors achieved a nitrate removal efficiency of over 60%. All fish survived all salinity conditions, exhibiting the highest daily weight gain of 2.0 ± 3.4 g-fish·day−1 at 15‰ salinity, which was 1.6 times higher than that at 30‰. The DHS-USB system could exert nitrogen removal under changing salinity conditions.

In this study, a photo-baffled reactor was operated to assess the performance of microalgal-nitrifying bacteria consortia in treating ammonia with its input concentration up to 180 mg-N·L−1. The six-compartment reactor, with a total effective volume of 3.2 L, was run continuously for 350 days at 30 °C. Overall, 66 ± 11% of ammonia was removed at a nitrogen loading rate of 0.083 ± 0.011 kg-N·m−3·day−1. In addition, long-term, stable partial nitrification was confirmed with nitrite concentration of 60 ± 26 mg-N·L−1 in effluent. On days 200 and 350, due to inhibition from the nitrite-oxidizing bacteria (NOB) activity, the dissolved oxygen and the free ammonia concentration was recorded as low as 0.3–0.7 mg·L−1 and 14–24 mg-N·L−1 in each column, respectively. The special configuration of the photo-baffled reactor created a competitive environment between Chlorella vulgaris and nitrifying bacteria. The microbial community structure of the retained sludge indicated that although detected at only 2–3% upstream, ammonia-oxidizing bacteria Nitrosomonas europaea increased downstream of the reactor. Meanwhile, the detection rate of NOB was less than 0.05% in each column and based on quantitative polymerase chain reaction analysis, NOB growth was inhibited. Therefore, these microalgae-nitrifying bacteria consortia have the potential to be a novel partial nitrification process for post-treatment using the anammox process.

Various toxic chemicals in textile wastewater can cause serious problems for the ecosystem and human health if it is discharged without proper treatment. In this study, the performance of textile wastewater treatment using an anaerobic membrane bioreactor (AnMBR) combined with a downflow hanging sponge (DHS) reactor is evaluated. An AnMBR with a working volume of 5 L and a third-generation DHS with a working volume of 0.5 L is used to treat synthetic textile wastewater containing Reactive Black 5 azo dye. The experiment is performed under ambient conditions using AnMBR hydraulic retention times (HRTs) of 12 and 24 h, DHS HRTs of 1.4 and 2.8 h, and membrane fluxes of 2.65 and 5.21 LMH. The AnMBR-DHS combination significantly reduces the biochemical oxygen demand, chemical oxygen demand, and color of the synthetic textile wastewater by approximately 97.3 ± 1.8%, 94.4 ± 4.8%, and 95.0 ± 1.6%, respectively. Most of the reduction occurs in the AnMBR. The HRT and membrane flux do not significantly affect the performance of the AnMBR-DHS system. The microbial community in the AnMBR is dominated by the phyla Euryarchaeota, Caldiserica, and Proteobacteria, whereas that in the DHS is dominated by Proteobacteria. Some of the genera found in the AnMBR can reportedly reduce azo dyes, whereas some of those found in the DHS can reportedly degrade sulfonated aromatic amines.

The aim of this study was to evaluate the contribution of dissolved organic carbon (DOC) and microbial community dynamics to membrane fouling development in membrane bioreactor (MBR). We operated laboratory-scale anoxic/oxic-MBRs under prolonged starvation conditions in different seasons and the dynamics and diversity of the microbial communities were investigated. Although fouled-MBRs showed DOC accumulation in the activated sludge (AS), the fouling-mitigated MBR suggested that dissolved oxygen was consumed and DOC of the sludge supernatant was degraded. 16S rRNA genes analysis of AS in the MBRs revealed that Chitinophagaceae and Candidatus Promineofilum specifically increased in the fouling-mitigated MBR, suggesting that they played important roles in membrane fouling mitigation; high microbial diversity in the reactor also contributed to fouling mitigation. In the fouled reactor, enrichment of Xanthomonadaceae might be related to fouling causing substances formation leading to membrane fouling development; lower microbial diversity also contributed to fouling development in the fouled MBR.

The textile industry discharges large amounts of polluted wastewater containing synthetic dyes. A down-flow hanging sponge (DHS) reactor is a novel aerobic wastewater treatment process that utilizes a sponge as a biomass-retaining carrier. This sponge carrier has both aerobic and anaerobic zones owing to different dissolved oxygen concentrations. In this study, the process performance of a DHS reactor treating actual textile wastewater obtained from a factory in Japan was evaluated. The effects of hydraulic retention time (HRT) and effluent recirculation (recirculation ratio = 1) on the DHS process performance were investigated. The DHS reactor showed good organic (up to 93 ± 13% of BOD) and nitrogen removal (56 ± 14% of TN) abilities during the entire experimental period. The color removal efficiencies of the DHS reactor were 55 ± 15%, 53 ± 26%, 72 ± 34%, and 35 ± 22% with HRTs of 4 h, 4 h + effluent recirculation (R = 1), 8 h + effluent recirculation (R = 1), and 8 h, respectively. Microbial community structure analysis of the DHS retained sludge showed that genus Acinetobacter was detected predominantly and reported as an azo dye-degrading bacterium. Effluent recirculation was also observed to increase the presence of aromatic-degrading bacteria and protists in the DHS reactor. These results suggest that the DHS reactor is suitable for textile wastewater treatment. Furthermore, the effluent recirculation is effective for enhancing decolorization performance.

Water-soluble copolymers such as polyvinylpyrrolidone and polyvinyl alcohol have been widely used as detergents, paints, and chemical intermediates in many industrial processes, leading to environmental concerns associated with high-volume organic compound wastewater. Therefore, in this study, a combined upflow anaerobic sludge blanket (UASB) reactor and downflow hanging sponge (DHS) biosystem has been applied for the treatment of synthetic water-soluble copolymer wastewater. Copolymer consisted of ethylene glycol and propylene glycol with a total molecular weight of 8,500, commonly preferred in the automobile parts processing factory, were included in influent. Overall, the whole UASB–DHS system achieved a favorable chemical oxygen demand (COD) removal efficiency of 86% ± 7%. In more detail, with an organic loading rate of 2.12 kg-COD ⋅ m−3 ⋅ day −1, the UASB reactor enhanced the biodegradability of wastewater, and reached COD removal efficiency of 61% ± 16%. Meanwhile, gel permeation chromatography analysis indicated that the molecular weight of the wastewater was primarily reduced in the DHS reactor. In addition, massive 16S rRNA gene sequencing showed that polyethylene-glycol-degrading bacteria Pelobacter sp. was predominant in the UASB granular sludge.

In this study, granular sludge formation was carried out using an aluminum chloride supplement in an upflow anaerobic sludge blanket (UASB) reactor treating natural rubber processing wastewater. Results show that during the first 75 days after the start-up of the UASB reactor with an organic loading rate (OLR) of 2.65 kg-COD·m−3·day−1, it performed stably with a removal of 90% of the total chemical oxygen demand (COD) and sludge still remained in small dispersed flocs. However, after aluminum chloride was added at a concentration of 300 mg·L−1 and the OLR range was increased up to 5.32 kg-COD·m−3·day−1, the total COD removal efficiency rose to 96.5 ± 2.6%, with a methane recovery rate of 84.9 ± 13.4%, and the flocs began to form granules. Massively parallel 16S rRNA gene sequencing of the sludge retained in the UASB reactor showed that total sequence reads of Methanosaeta sp. and Methanosarcina sp., reported to be the key organisms for granulation, increased after 311 days of operation. This indicates that the microbial community structure of the retained sludge in the UASB reactor at the end of the experiment gave a good account of itself in not only COD removal, but also granule formation.

We evaluated greenhouse gases (GHGs) emissions from an open-type anaerobic system (OAS) treating ribbed smoked sheets (RSS) wastewater in a processing factory. The emitted biogas comprised 57.7%–60.8% methane, 14.5%–31.5% carbon dioxide, 10.8%–24.7% nitrogen, and 329–423 ppm of nitrous oxide. In the OAS, the chemical oxygen demand (COD) degraded as the methane emission rate increased from influent to effluent. Finally, 94.4% of the total COD was removed. More than 90% of the removed COD converted to methane. Methane emitted from the bottom and the wall surface of the OAS. Methane-producing bacteria was detected by a cloning analysis of the 16S rRNA gene. The predominant species differed depending on the degradation characteristics of the RSS wastewater in the OAS. The emission rate of methane and nitrous oxide ranged between 2.58 and 8.85 NL/(m 2 hr) and between 0.074 and 0.410 NL/(m 2 /hr), respectively. Moreover, 0.153 t-CO 2eq of GHGs were emitted from 1 m 3 of RSS wastewater treatment. Nitrous oxide accounted for 65% of the total GHGs emissions because of its high global warming potential. Therefore, both nitrous oxide and methane that emitted from the treatment of wastewater from a natural rubber processing factory must be considered as significant contributors to the GHGs.

Natural rubber processing wastewater contains high concentrations of organic compounds, nitrogen, and other contaminants. In this study, a treatment system composed of a baffled reactor (BR), an upflow anaerobic sludge blanket (UASB) reactor, and a downflow hanging sponge (DHS) reactor was used to treat natural rubber processing wastewater in Vietnam. The BR showed good total suspended solids (TSS) removal of 47.6%, as well as acidification of wastewater. The UASB reactor achieved a high chemical oxygen demand (COD) removal efficiency of 92.7 ± 2.3% and energy recovery in the form of methane with an organic loading rate of 12.2 ± 6.6 kg-COD m−3 day−1. The DHS reactor showed high performance in residual organic matter removal from UASB effluent. In total, the system achieved high-level total COD removal of 98.6% ± 1.2% and TSS removal of 98.0% ± 1.4%. Massive parallel 16S rRNA gene sequencing of the retained sludge in the UASB reactor showed the predominant microbial phyla to be Bacteroidetes, Firmicutes, ...

The fundamental properties and performance of sewage treatment by a mesh rotating biological reactor (MRBR) were investigated. MRBR is an improved type of rotating biological contactor (RBC) reactor. Municipal wastewater treatment with a MRBR exhibited 67 % soluble chemical oxygen demand (sCOD) removal at the surface area loading rate of 22 g sCOD·m−2·day−1, and an average of 41 % ammonium nitrogen removal at a ammonium nitrogen surface area loading rate of 3.5 g-N·m−2·day−1. During a continuous experiment, there was no increase in nitrate nitrogen or nitrite nitrogen corresponding to a decrease in ammonium nitrogen, so simultaneous nitrification and denitrification was occurring in the MRBR. The volumetric oxygen transfer coefficient (KLa) of MRBR was 49.0 d−1 at a rotational speed of 5.0 rpm, comparable to the KLa of other RBCs even with the use of only one mesh disk. The biomass in the MRBR was 18,000 g TVS·m−3, which is the first report of the sludge concentration on the MRBR mesh disks. The high sewage treatment performance of the MRBR was attributed to the fundamental properties of the reactor, such as KLa and sludge amount. Microbial community analysis revealed that the MRBR attached biomass harbored a broad range and high abundance of nitrifying and denitrifying bacteria, indicating the development of an optimal microbial community related to the relatively high simultaneous nitrification and denitrification ratio.

The adjustment of hydraulic retention time (HRT) and the supplement of titanium(III) nitrilotriacetate (Ti(III)-NTA) as a reducing agent were implemented in an anaerobic downflow hanging sponge (DHS) reactor with the aims to (i) improve nitrogen removal performance and to (ii) eliminate N2O emission. A laboratory-scale DHS reactor was operated at 35 °C, under autotrophic denitrification conditions with methane gas (14.2 L d−1) as the main carbon source, NaNO3 and NaNO2 (20 mg N L−1 per compound) as nitrogen sources. The sufficient HRT for simultaneously removing nitrate and nitrite in this reactor was found at 12 h when HRT was reduced from 24 to 6 h. Then at the HRT of 12 h, the addition of Ti(III)-NTA at a final concentration of 25 μM Ti(III) boosted the reactor’s nitrogen removal rates from 1.4 ± 0.6 to 4.1 ± 1.9 g NO3−-N m−3 d−1 and 3.2 ± 2.8 to 6.6 ± 3.3 g NO2−-N m−3 d−1. Furthermore, this study is the first to consider the N2O emission in a continuous reactor applying denitrification coupled to anaerobic methane oxidation (DAMO) process. Produced N2O in this DHS reactor was from 10.6 × 10−4% to 89.0 × 10−4% of removed NOx− without Ti(III)-NTA and from 0.7 × 10−4% to 61.4 × 10−4% of removed NOx− with Ti(III)-NTA. Overall, these findings suggested the advantage of Ti(III)-NTA as an oxygen scavenger for denitrification processes and the potential of the anaerobic DHS reactor for facilitating the DAMO processes and mitigating N2O gas.

Anaerobic/anoxic denitrifying reactors, such as an upflow sludge blanket (USB) reactor, can retain high concentration of biomass inside of the reactor as granular sludge, which allows high nitrogen removal performance from wastewaters. However, granular sludge is critical to high nitrogen removal performance. In this study, simple granulation method was developed in a denitrifying USB reactor fed with municipal sewage and 50 mg-N ⋅ L − 1 of sodium nitrate as an easily available nitrate source, and granular formation, nitrogen removal performance, and microbial community structure were investigated. A 11.4-L USB reactor was operated at an upflow velocity of 50 cm ⋅ h − 1 , and hydraulic retention time of 2.9 h under ambient temperature. Granular sludge with up to 3.8 mm of diameter was formed within 15 days, and the nitrate removal rate increased 9.8 mg-N ⋅ gMLVSS − 1 ⋅ h − 1 to 22.5 mg-N ⋅ gMLVSS − 1 ⋅ h − 1 at batch exam. 16S rRNA amplicon sequencing indicated that Cloacibacterium sp. was the most abundant in the granular sludge with detection rate of 6.11% to 12.95%. Also, propionate-producing bacterium Paludibacter sp., acetate-utilizing denitrifying bacterium Acidovorax sp. and Dechloromonas sp. were also abundant in the granular sludge. Denitrifying granular sludge was successfully formed in the USB reactor treating real municipal sewage with sodium nitrate feeding.

Highly colored wastewater from the textile industry, can threaten the natural environment if discharged into water bodies without any treatment. In this study, a laboratory-scale​ system combining an anaerobic baffled reactor (ABR), with the total volume of 10 L and a down-flow hanging sponge reactor (DHS), with the total volume of 4.14 L was designed to treat synthetic dyeing wastewater containing the commercial azo dye Hellozol HSR Reactive Black at 30 °C with a hydraulic retention time (HRT) of 23.2 h. Synthetic wastewater with 260 ± 40 mg.L − 1 of chemical oxygen demand concentration (COD) and 1020 ± 70 Pt/Co of true color level was prepared based on the characteristics of an actual effluent from an Indonesian textile factory. The combined system showed maximum COD and color removal efficiencies of 90% and 58%, respectively, with the removal majority taking place in the ABR. Moreover, microbial community analysis conducted on sludge retained from the ABR indicated that Proteobacteria, Firmicutes, WWE1, Spirochaetes, Bacteroidetes, Chloroflexi, OP8, andEuryarchaeota were predominant phyla. Among them, Clostridium sp was discovered and reported to have potential to degrade a wide range of azo dyes.

This study focuses on the potential of anaerobic baffled reactor (ABR) for treating the fishmeal wastewater. This wastewater has a high organic content (140 g COD ⋅ L−1), which consists of 60% (w/w) oil and grease (O&G), 27% (w/w) protein, and 13% (w/w) mixture of suspended solids and soluble organic. The ABR reactor volume was 60 L. The ABR was operated with a hydraulic retention time of 20 days. During the operation period, the reactor achieved high performance with the average total and soluble COD removal of approximately 98% and 94%, respectively. The design of ABR compartmentalization advanced this high organic removal performance. There was also the symbiotic activity of specific microbial communities such as Syntrophobacter sulfatireducens and Methanosaeta observed in the reactor’s column which contributes to the high organic degradation process of ABR. Overall, this study demonstrated that the application of ABR could be used to treat fishmeal wastewater

This study was carried out to evaluate the potential application of agricultural waste coconut (Cocos nucifera) fibre in its purified form for decolorization of dye-containing effluent from...

Greenhouse gas (GHG) emissions from both open-type and closed anaerobic wastewater treatment systems in a natural rubber processing factory in Vietnam were surveyed. In this factory, wastewater was treated by an open-type anaerobic baffled reactor (OABR) that comprised 60 compartments. A part of the wastewater was fed to a pilot-scale up-flow anaerobic sludge blanket (UASB) reactor to enable a comparison of the process performance and GHG emission characteristics with those of the OABR. In the OABR, 94.4% of the total chemical oxygen demand (COD) and 18.1% of ammonia nitrogen was removed. GHGs emitted from the OABR included both methane and nitrous oxide. The total GHGs emitted from the OABR was 0.153 t-CO2eq/m3-wastewater. Nitrous oxide accounted for approximately 65% of the total GHGs emitted from the OABR. By contrast, 99.6% of the methane emission and 99.9% of nitrous oxide emission were reduced by application of the UASB. However, the ammonia removal efficiency of the UASB was only 2.2%. Furthermore, Acinetobacter johnsonii, which is known as a heterotrophic ammonia remover, was detected only in the OABR. These results indicated that high nitrous oxide emissions were caused by denitrification in the OABR and that application of the closed anaerobic system could drastically reduce the emissions of both methane and nitrous oxide.

In recirculating aquaria system (RAS), partial water exchange was performed regularly as a part of aquaria maintenance for maintaining water quality and aesthetic beauty. To reduce large consumption of water during maintenance, this study proposed a biological nitrogen removal system consisted of down-flow hanging sponge (DHS) and an up-flow sludge blanket (USB) system with combination of ozone (O3) to simultaneously maintain nitrogen compounds concentration and remove yellow substances that implicate color in aquaria without performing water exchange. The performance of the system was evaluated using on site freshwater aquaria at ambient temperature (20–34 °C). NH3, \( {\text{NO}}_{2}^{ - } \), and \( {\text{NO}}_{3}^{ - } \) concentration detected was 0.10 ± 0.12, 0.03 ± 0.13 and 6.40 ± 7.46 mg N L−1 respectively. Color were maintained at 6 color units at phase 2 and 4 when O3 was applied continuously for 8 h per day. In addition, 16S rRNA gene of microorganisms from the bioreactors were sequenced to identify the microbial communities present. The analysis revealed that ammonia oxidizing archaea (AOA) such as Ca. Nitrososphaera played important role in nitrification and Thauera played important role in denitrification. Fish survived throughout the study despite no water exchange was performed for 425 days. The application of O3 in combination with DHS-USB system appeared to be a promising technology towards less-maintenance aquaria.

Natural rubber processing wastewater contains high concentration of organic compounds mainly acids and ammonia. This wastewater also contains large amount of residual rubber particles. In this study, a laboratory-scale experiment was conducted to evaluate process performance of anaerobic baffled reactor (ABR) treating this wastewater. In addition, microbial community structure in different compartments of ABR was characterized. The highest COD removal efficiency of 92.3 ± 6.3% was observed when operated under organic loading rate of 1.4 ± 0.3 kg-COD·m−3·day−1. Maximum methane gas production of 29.8 NL·day−1 was observed on day 177. Massively parallel next generation sequencing showed the difference of acetogen community could be caused by the difference in pH of these compartments. Acetate utilizing methanogen Methanosaeta was predominantly detected in the 3rd and 4th compartments with abundance of 9.8% to 16.4%. This result indicated that the ABR is considered as a novel applicable treatment system for this wastewater.