Combination of a membrane bioreactor with a rotating biological contactor holding several diverse metazoans can reduce excess sludge with fouling mitigation.

In a membrane bioreactor (MBR) system, in situ sludge reduction techniques induce membrane fouling. To address this challenge, we incorporated a rotating mesh carrier, which can adsorb organic matter and provide a habitat for metazoans, into the anoxic tank of a conventional anoxic/oxic-MBR (A/O-MBR) system, termed rotating biological contactor-MBR (RBC-MBR), and evaluated treatment performance. Over 151 days, lab-scale RBC-MBR and A/O-MBR were used to treat municipal sewage. Both reactors showed similar COD and NH4+ removal rates. However, RBC-MBR reduced excess sludge by approximately 45 % compared with A/O-MBR. Microscopic observation and 18S rRNA gene-based microbial analysis revealed the persistence of microfauna and metazoans (oligochaetes, nematodes, and rotifers) in RBC, which are typically absent in activated sludge. Additionally, the metazoan's population in the RBC-MBR membrane tank was two-fold that of A/O-MBR, indicating enhanced sludge reduction through predation. Despite these reductions, the increase in transmembrane pressure was similar between RBC-MBR and A/O-MBR, suggesting that sludge holding by RBC mesh media degrade fouling substances, such as proteins and polysaccharides and improves sludge filterability, resulting in membrane fouling mitigation. Microbial communities in both reactors were similar, indicating that the installation of RBC did not alter the microbial community of sludge. Network analysis suggested potential symbiotic or prey-predator relationships between bacteria and metazoans. This study reveals that RBC-MBR effectively reduced the excess sludge while mitigating membrane fouling, highlighting one of the promising technology for applying metazoan predation into MBR.

Integration of down-flow hanging sponge reactor to oreochromis niloticus - Brassica oleracea aquaponics system.

Aquaponics is a promising solution for addressing food security concerns. Nonetheless, an effective water-purification system is necessary to achieve high and stable yields of fish and vegetables. This study aimed to evaluate the nitrification and oxygen transfer performance of a laboratory-scale down-flow hanging sponge (DHS) reactor with a Brassica oleracea aquaponics system to treat water in an Oreochromis niloticus closed-aquaculture system. The DHS reactor showed a higher oxygen transfer coefficient (KLa) than the conventional aerator and provided an adequate dissolved oxygen (DO) concentration of approximately 5.5 mg/L essential for O. niloticus growth throughout the experimental period. The evaluated DHS-based aquaponic system maintained high water quality in an aquaculture tank, with a survival rate of 97%. The O. niloticusgrew at a low feed conversion ratio of 1.5-2.1 and a low feeding rate of 0.5% at high stocking densities of 17.5-22.2 kg-fish-weight/m3. 16S rRNA gene sequencing indicated that the DHS sponge carrier effectively retained nitrifying bacteria such as Nitrosomonas and Nitrospira. This study demonstrated that the DHS reactor provided a high DO concentration and that a simultaneous DHS reactor with a hydroponic tank provided a low-cost aquaponic system that could be applied for food production in the aquaculture industry.

Application of Biofloc-Down flow hanging sponge system to remove nitrogen components in recirculating zero water exchange aquaculture system.

This study presents a novel approach to sustainable aquaculture by integrating biofloc technology (BFT) with a compact down-flow hanging sponge (DHS) reactor. The integrated BFT-DHS system effectively removed nitrogen compounds while maintaining ammonia-nitrogen (NH4+-N) concentrations below 1 mg-N L-1 without water exchange. Application of this system in a tank bred with juvenile Oreochromis niloticus showed a high NH4+-N removal rate of up to 97 % and nitrite (NO2- -N) concentrations were maintained at 0.1 ± 0.1 mg-N L-1. Microbial analysis revealed Gordonia as the predominant genus in the biofloc contributing to heterotrophic nitrification, while the Peptostreptococcaceae family dominated the DHS reactor. Heterotrophic nitrification seemed to be the primary process for enhanced nitrogen removal. Pathogenic bacteria, Vibrio sp. was absent throughout the study. This study highlights the potential integration of BFT and DHS system for sustainable aquaculture practice with effective nitrogen removal.

Nitrification characteristics and microbial community changes during conversion of freshwater to seawater in down-flow hanging sponge reactor.

In recirculating aquaculture systems (RAS), maintaining water quality in aquaculture tanks is a paramount factor for effective fish production. A down-flow hanging sponge (DHS) reactor, a trickling filter system used for water treatment of RAS that employs sponges to retain biomass, has high nitrification activity. However, nitrification in seawater RAS requires a long start-up time owing to the high salinity stress. Therefore, this study aimed to evaluate the nitrification characteristics and changes in the microbial community during the conversion of freshwater to seawater in a DHSreactor fed with ammonia-based artificial seawater. The total ammonia nitrogen concentration reached 1.0 mg-N·L-1 (initial concentration 10 mg-N·L-1) within 11 days of operation, and nitrate production was observed. The 16 S rRNA gene sequence of the DHS-retained sludge indicated that the detection rate of the ammonia-oxidizing archaeon Candidatus Nitrosocosmicus decreased from 23.9 % to 14.0 % and 25.8-17.6 % in the upper and lower parts of the DHS reactor, respectively, after the introduction of seawater. In contrast, the nitrite-oxidizing bacteria Nitrospira spp. increased from 0.1 % to 9.5 % and from 0.5 % to 10.5 %, respectively. The ammonia oxidation rates of 0.12 ± 0.064 and 0.051 ± 0.0043 mg-N·g-MLVSS-1·h-1 on the 37th day in the upper and bottom layers, respectively. Thus, nitrification in the DHS reactor performed well, even under high-salinity conditions with short operational days. This finding makes the transition from freshwater to saltwater fish in the RAS system simple and economical, and has the potential for early start-up of the RAS.

Azo dye anaerobic treatment in anaerobic reactors coupled with PVA/Fe/Starch gel bead.

A novel bio-carrier, PVA/Fe/starch gel bead, was fabricated and developed to enhance the anaerobic treatment performance of synthetic azo dye-containing wastewater. PVA-gel beads with 5 % magnetite and 0.5 % starch were optimal for physical strength and treatment performance. A pair of 2 L-up-flow anaerobic sludge blankets (UASB), one with the bead (UB) and another without (U) as a controller, operated continuously at 30 °C and an HRT of 11-24 h for 302 days. UB showed better performance than U in most phases, especially with influent dye of 200 mg·L-1, suggesting a greater tolerance to dye toxicity of UB than U. Microbial analysis revealed that the PVA/Fe/starch gel beads successfully captured the dye degrader Clostridium. Diversity indices indicated that PVA/Fe/Starch gel beads effectively support microbial diversity and resilience under varying dye concentrations. Overall, these findings demonstrate the potential of PVA/Fe/Starch gel beads to improve the stability and efficiency of the dye treatment system.

Distinct comammox Nitrospira in high-rate down-flow hanging sponge reactor treating municipal wastewater.

A down-flow hanging sponge (DHS) reactor is a trickling filter system used for wastewater treatment, which employs sponges to retain biomass. This study assessed the process performance of a compact DHS combined with a sedimentation tank with seven phases at varying hydraulic retention times (HRT) over 500 days. The BOD of the DHS effluent was maintained at 4.0 ± 0.5 mg·L-1 for the shortest HRT 0.3 ± 0.1 h. The nitrification efficiency was considerably impacted by the reduced HRT, with NH4+-N and NO3--N concentrations of 9.0 ± 1.2 mgN·L-1 and 2.2 ± 0.5 mgN·L-1, respectively. Nevertheless, the effluent complied with effluent discharge standards throughout the trial period. The number of comammox 16S rRNA gene copies ranged from 5.58 to 13.2 × 107 copies·mL-1, indicating that sponges biomass retained carrier can provide favorable conditions for comammox growth and could contribute to nitrification in the high-rate DHS reactor.

Corallococcus caeni sp. nov., a novel myxobacterium isolated from activated sludge.

Two myxobacterial strains (KH5-1T and NO1) were isolated from the activated sludge tanks treating municipal sewage wastewater in Japan. These strains were recognised as myxobacteria based on their phenotypic characteristics of swarming colonies and fruiting bodies. Phylogenetic analyses using the 16S rRNA gene revealed that strains KH5-1T and NO1 were affiliated with the genus Corallococcus, with the closest neighbours being Corallococcus exercitus AB043AT (99.77% and 99.84%, respectively). Genome comparisons using orthologous average nucleotide identity (orthoANI) and digital DNA-DNA hybridisation similarity (dDDH) with strains KH5-1T and NO1 and their phylogenetically close relatives in Corallococcus spp. were below the thresholds. The major cellular fatty acids of strains KH5-1T and NO1 were iso-C15:0 (31.9%, 30.0%), summed feature 3 (comprising C16:1ω7c and/or C16:1ω6c) (20.2%, 17.7%), and iso-C17:0 (12.1%, 14.8%), and the major respiratory quinone was found to be menaquinone (MK)-8. Based on the phenotypic, chemotaxonomic, and phylogenetic evidence, strains KH5-1T and NO1 represent a new species in the genus Corallococcus, for which the proposed name is Corallococcus caeni sp. nov. The type strain is KH5-1T (= NCIMB 15510T = JCM 36609T).

Harnessing iron materials for enhanced decolorization of azo dye wastewater: A comprehensive review.

Highly colored azo dye-contaminated wastewater poses significant environmental threats and requires effective treatment before discharge. The anaerobic azo dye treatment method is a cost-effective and environmentally friendly solution, while its time-consuming and inefficient processes present substantial challenges for industrial scaling. Thus, the use of iron materials presents a promising alternative. Laboratory studies have demonstrated that systems coupled with iron materials enhance the decolorization efficiency and reduce the processing time. To fully realize the potential of iron materials for anaerobic azo dye treatment, a comprehensive synthesis and evaluation based on individual-related research studies, which have not been conducted to date, are necessary. This review provides, for the first time, an extensive and detailed overview of the utilization of iron materials for azo dye treatment, with a focus on decolorization. It assesses the treatment potential, analyzes the influencing factors and their impacts, and proposes metabolic pathways to enhance anaerobic dye treatment using iron materials. The physicochemical characteristics of iron materials are also discussed to elucidate the mechanisms behind the enhanced bioreduction of azo dyes. This study further addresses the current obstacles and outlines future prospects for industrial-scale application of iron-coupled treatment systems.

Development of an internal two-stage upflow anaerobic reactor integrating biostimulation strategies to enhance the degradation of aromatic compounds in wastewater from purified terephthalic acid and dimethyl terephthalate manufacturing processes.

In this study, we aimed to establish high-rate biological treatment of purified terephthalic acid (PTA) and dimethyl terephthalate (DMT) wastewater that minimizes the inhibitory effects of high concentration benzoate and acetate. To achieve this, we developed a novel bioreactor system and biostimulation strategy. An internal two-stage upflow anaerobic (ITUA) reactor was operated with (i) a packed bed containing green tuff medium underlying (ii) a compartment seeded with anaerobic granular sludge. Ethylene glycol was amended to stimulate syntrophic interactions. Continuous operation of the system for 1,026 days achieve an organic removal rate of 11.0 ± 0.6 kg COD/m3/d. The abundance of aromatic degraders significantly increased during operation. Thus, we successfully developed a high-rate treatment system to treat wastewater from the PTA/DMT manufacturing processes by activating syntrophs in an ITUA reactor.

Draft genome sequences of Corallococcus strains KH5-1 and NO1, isolated from activated sludge.

Myxobacteria are known as prolific producers of secondary metabolites with a unique and wide spectrum of bioactivities. Here, we report draft genome sequences of KH5-1 and NO1, myxobacteria isolated from activated sludge, which consist of 9.89 and 9.86 Mb, both of which have G + C contents of 70.7%.

Identification and cultivation of anaerobic bacterial scavengers of dead cells.

The cycle of life and death and Earth's carbon cycle(s) are intimately linked, yet how bacterial cells, one of the largest pools of biomass on Earth, are recycled back into the carbon cycle remains enigmatic. In particular, no bacteria capable of scavenging dead cells in oxygen-depleted environments have been reported thus far. In this study, we discover the first anaerobes that scavenge dead cells and the two isolated strains use distinct strategies. Based on live-cell imaging, transmission electron microscopy, and hydrolytic enzyme assays, one strain (designated CYCD) relied on cell-to-cell contact and cell invagination for degrading dead food bacteria where as the other strain (MGCD) degraded dead food bacteria via excretion of lytic extracellular enzymes. Both strains could degrade dead cells of differing taxonomy (bacteria and archaea) and differing extents of cell damage, including those without artificially inflicted physical damage. In addition, both depended on symbiotic metabolic interactions for maximizing cell degradation, representing the first cultured syntrophic Bacteroidota. We collectively revealed multiple symbiotic bacterial decomposition routes of dead prokaryotic cells, providing novel insight into the last step of the carbon cycle.

Metabolic implications for predatory and parasitic bacterial lineages in activated sludge wastewater treatment systems.

Deciphering unclear microbial interactions is key to improving biological wastewater treatment processes. Microbial predation and parasitism in wastewater treatment ecosystems are unexplored survival strategies that have long been known and have recently attracted attention because these interspecies interactions may contribute to the reduction of excess sludge. Here, microbial community profiling of 600 activated sludge samples taken from six industrial and one municipal wastewater treatment processes (WWTPs) was conducted. To identify the shared lineages in the WWTPs, the shared microbial constituents were defined as the family level taxa that had ≥ 0.1% average relative abundance and detected in all processes. The microbial community analysis assigned 106 families as the shared microbial constituents in the WWTPs. Correlation analysis showed that 98 of the 106 shared families were significantly correlated with total carbon (TC) and/or total nitrogen (TN) concentrations, suggesting that they may contribute to wastewater remediation. Most possible predatory or parasitic bacteria belonging to the phyla Bdellovibrionota, Myxococcota, and Candidatus Patescibacteria were found to be the shared families and negatively correlated with TC/TN; thus, they were frequently present in the WWTPs and could be involved in the removal of carbon/nitrogen derived from cell components. Shotgun metagenome-resolved metabolic reconstructions indicated that gene homologs associated with predation or parasitism are conserved in the Bdellovibrionota, Myxococcota, and Ca. Patescibacteria genomes (e.g., host interaction (hit) locus, Tad-like secretion complexes, and type IV pilus assembly proteins). This study provides insights into the complex microbial interactions potentially linked to the reduction of excess sludge biomass in these processes.

Investigate the anaerobic degradation of high-acetone latex wastewater with magnetite supplement.

This study evaluated the effects of acetone on the anaerobic degradation of synthetic latex wastewater, which was simulated from the wastewater of the deproteinized natural rubber production process, including latex, acetate, propionate, and acetone as the main carbon sources, at a batch scale in 5 cycles of a total of 60 days. Fe3O4 was applied to accelerate the treatment performance from cycle 3. Acetone was added in concentration ranges of 0%, 0.05%, 0.1%, 0.15%-included latex, and 0.15%-free latex (w/v). In the Fe3O4-free cycles, for latex-added vials, soluble chemical oxygen demand (sCOD) was removed at 43.20%, 43.20%, and 12.65%, corresponding to the input acetone concentrations varying from 0.05% to 0.15%, indicating the interference of acetone for COD reduction. After adding Fe3O4, all flasks reported a significant increase in COD removal efficiency, especially for acetone-only and latex-only vials, from 36.9% to 14.30%-42.95% and 83.20%, respectively. Other highlighted results of COD balance showed that Fe3O4 involvement improved the degradation process of acetate, propionate, acetone, and the other COD parts, including the intermediate products of latex reduction. Besides, during the whole batch process, the order of reduction priority of the carbon sources in the synthetic wastewater was acetate, propionate and acetone. We also found that the acetate concentration appeared to be strongly related to reducing other carbon sources in natural rubber wastewater. Microbial community analysis revealed that protein-degrading bacteria Bacteroidetes vadinHA17 and Proteinniphilum and methylotrophic methanogens might play key roles in treating simulated deproteinized-natural-rubber wastewater.

Initiation and progression of Early-Stage microbial-driven membrane fouling in membrane bioreactors: a review.

Microbial biofilm development on the membrane surface of bioreactors results in membrane flux decline (biofouling). Biofouling is one of the most severe problems limiting the use of these bioreactors. For detailed understanding of the biofouling, microbial community and dissolved organic matter analyses have been performed in recent decades. Although most previous studies have focused on mature biofilms at the end point of biofouling, understanding of the early stages is crucial to mitigate biofilm formation. Thus, recent studies have focused on the impact of early-stage biofilm development and indicated a clear difference in microbial communities between early-stage and mature biofilms. In addition, certain bacteria play a significant role in early-stage biofilms. The present mini-review systematically summarizes the foulants present during early-stage fouling, provides novel perspectives on fouling mechanisms, and discusses the neglected effect of planktonic bacteria.

Characteristics of organic removal for supermarket wastewater treatment with an anaerobic baffled reactor and efficacy evaluation of changing HRT.

An anaerobic baffled reactor (ABR) is one of the useful wastewater treatment technologies, but the knowledge about its treatment performance for actual wastewater with load fluctuation is limited. The organic removal performance of an ABR for treating supermarket wastewater was evaluated. The ABR, which consisted of eight columns, was examined under four hydraulic retention time (HRT) conditions of 19.4, 12.9, 8.0, and 4.4 h. As a result, the unfiltered chemical oxygen demand (COD) removal efficiency was 80 (±8) % at an HRT of 19.4 h. When the HRT was shortened to 12.9 h, the average unfiltered COD removal efficiency decreased to 58 (±15) %. However, it showed buffering effect against high load inflow in the first column, indicating that it is useful as a pretreatment system under this condition. At an HRT of 4.4 h, the unfiltered COD removal efficiency decreased to 9%, indicating the system failed. The results of the microbial community structure analysis showed that the detection frequency of acidogenic bacteria decreased in proportion to the extension of residence time in the reactor. These results indicate that the ABR is useful for the treatment of supermarket wastewater with load fluctuations as a main treatment system at a HRT of 19.4 h and as a pretreatment system at a HRT of 12.9 h.

An increase in sludge loading rate induces gel fouling in membrane bioreactors treating real sewage.

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-1, which were significantly lower than those recorded in S1 accounted for 118 and 68 mg L-1, respectively. Furthermore, the total organic carbon concentration of SMPs was 24 mg L-1, which was lower than the influent in S2, accounted for 62 mg L-1. Finally, Campylobacteraceae which exists in sewage and uncultured OD1, dominated the gel layer biofilm in S2, unlike the cake layer biofilm in S1. These results indicated that the gel layer biofilm might be composed of influent substances, demonstrating the importance of influent decomposition in MBR for gel fouling mitigation.

Effects of denitrifying granular sludge addition on activated sludge and anaerobic-aerobic systems for municipal sewage treatment.

Conventional activated sludge (AS) systems are widely used to treat domestic sewage worldwide. However, the removal of nitrogen in the AS system is limited, and its concentration in the effluent exceeds the recommended values in the discharge standards. In this study, a pilot experiment was conducted to improve nitrogen removal during municipal sewage treatment by operating AS and anaerobic-aerobic (AO) systems under low dissolved oxygen (DO) conditions of less than 0.5 mg L-1 and by adding denitrifying granular sludge. The low DO operation of the AS and AO systems led to the sludge washout and increased the organic content and ammonia and nitrate concentration of the effluent. In contrast, the nitrate concentrations of the effluents produced by the AS and AO systems were 9.4 ± 3.6 and 8.4 ± 0.7 mg-N L-1, respectively, indicated that denitrifying granular sludge addition enhanced denitrification during sewage treatment. The total nitrogen (TN) removal efficiency increased by 13% and 9% for the AS and AO systems despite a decrease in the temperature of 6 °C for the water in the aeration tank. Thus, adding denitrifying granular sludge to the aeration tank is a simple and effective approach to improve organic and nitrogen removal during wastewater treatment.

Growth of nitrite-oxidizing Nitrospira and ammonia-oxidizing Nitrosomonas in marine recirculating trickling biofilter reactors.

Aerobic ammonia and nitrite oxidation reactions are fundamental biogeochemical reactions contributing to the global nitrogen cycle. Although aerobic nitrite oxidation yields 4.8-folds less Gibbs free energy (∆Gr ) than aerobic ammonia oxidation in the NH4 + -feeding marine recirculating trickling biofilter reactors operated in the present study, nitrite-oxidizing and not ammonia-oxidizing Nitrospira (sublineage IV) outnumbered ammonia-oxidizing Nitrosomonas (relative abundance; 53.8% and 7.59% respectively). CO2 assimilation efficiencies during ammonia or nitrite oxidation were 0.077 µmol-14 CO2 /µmol-NH3 and 0.053-0.054 µmol-14 CO2 /µmol-NO2 - respectively, and the difference between ammonia and nitrite oxidation was much smaller than the difference of ∆Gr . Free-energy efficiency of nitrite oxidation was higher than ammonia oxidation (31%-32% and 13% respectively), and high CO2 assimilation and free-energy efficiencies were a determinant for the dominance of Nitrospira over Nitrosomonas. Washout of Nitrospira and Nitrosomonas from the trickling biofilter reactors was also examined by quantitative PCR assay. Normalized copy numbers of Nitrosomonas amoA were 1.5- to 1.7-folds greater than Nitrospira nxrB and 16S rRNA gene in the reactor effluents. Nitrosomonas was more susceptible for washout than Nitrospira in the trickling biofilter reactors, which was another determinant for the dominance of Nitrospira in the trickling biofilter reactors.

A potential zero water exchange system for recirculating aquarium using a DHS-USB system coupled with ozone.

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 O3 on the DHS-USB system was investigated. The system was assayed using an on-site freshwater aquarium influenced by ambient temperature ranging from 23°C to 34°C. During ozonation Phases 1 and 3, the colour of the water in the aquarium was successfully maintained below 10 colour units. The 16S rRNA gene analysis of microorganisms in the DHS revealed that constant application of O3 has caused a decrease in nitrite-oxidizing bacteria (NOB). Nevertheless, NH3 and NO2- were maintained within 0.1 mg N L-1, and NO3- was maintained at 14.6 ± 9.20 mg N L-1 throughout the study. Carps survived for 425 days without any water exchange performed. Our study supports that the ozone-DHS-USB system has a high potential towards creating low-maintenance aquaria.

Efficiency of high rate treatment of low-strength municipality sewage by a pilot-scale combination system of a sedimentation tank and a down-flow hanging sponge reactor.

Down-flow hanging sponge (DHS) reactor that is sponge-based trickling filter was considered to be an alternative aerobic treatment system for low strength sewage treatment under tropical conditions. This study aims to determine the process performance of the DHS reactor combined with a pre-treatment sedimentation tank (SED) system installed at the municipality sewage treatment plant in Khon Kaen, Thailand over, 1,600 days. The DHS reactor was operated with three operational periods: low (0.2 kgBODm3 per day), high (0.5-1.3 kgBODm3 per day), and super rates (1.7-2.2. kgBODm3 per day). The results showed effective reductions in biochemical oxygen demand (BOD) and suspended solids by more than 74% and 78%, respectively, during the entire experimental period. Moreover, the final effluent met the Thailand discharge standard with an external short hydraulic retention time of 0.2 h. In addition, the combined system facilitates simultaneous nitrification and denitrification and effectively removed up to 43% of total nitrogen. The self-degradation of the organic compounds occurs owing to the retained sludge in the DHS reactor; this leads to undisputed clogging in sponge media. Therefore, the combined SED-DHS system could be an appropriate sewage treatment system for tropical conditions.