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The main objective of this study was to investigate the cause of gel fouling in membrane bioreactors (MBRs) treating real sewage in terms of soluble microbial products (SMPs) and microbial aspects. Two anoxic/oxic-MBRs were operated as the control reactor (S1) and the sludge loading rate increased reactor (S2). The reactors were operated under low-temperature around 11 °C conditions. Membrane permeability substantially decreased in S2, and gel layer biofilm was formed on membrane surface. In contrast, the permeability of S1 gradually decreased and cake layer formed. When gel fouling occurred, the protein and polysaccharide of SMP in S2 were 47 and 23 mg L

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.

A high-rate nitrogen removal process is required to maintain the water quality in aquaculture tanks used to produce high-density fish populations in recirculating aquaculture systems. In this study, a combined pilot-scale system of down-flow hanging sponge (DHS) reactors and upflow sludge blanket (USB) reactors was applied as a nitrogen removal system for a longtooth grouper Epinephelus bruneus recirculating aquaculture system. The DHS reactors demonstrated high total ammonium nitrogen (TAN) removal efficiencies and the TAN concentration in the aquaculture tank was maintained at 0.32 ± 0.12 mg-N·L−1. The USB reactor fed with sodium acetate acted as a denitrification unit and adjusted the pH through denitrification reaction. All E. bruneus survived the entire experimental period and the daily weight gain rate of 0.6%·day−1 was comparable to that in marine aquaculture. This result shows that the DHS-USB system to be a novel applicable system for nitrogen removal processes in recirculating aquaculture systems and further study at a large scale should be recommended.

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.

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