Yuga Hirakata

Development of downflow hanging sponge (DHS) reactor as post treatment of existing combined anaerobic tank treating natural rubber processing wastewater

Conventional aerated tank technology is widely applied for post treatment of natural rubber processing wastewater in Southeast Asia; however, a long hydraulic retention time (HRT) is required and the effluent standards are exceeded. In this study, a downflow hanging sponge (DHS) reactor was installed as post treatment of anaerobic tank effluent in a natural rubber factory in South Vietnam and the process performance was evaluated. The DHS reactor demonstrated removal efficiencies of 64.2 ± 7.5% and 55.3 ± 19.2% for total chemical oxygen demand (COD) and total nitrogen, respectively, with an organic loading rate of 0.97 ± 0.03 kg-COD m-3 day-1 and a nitrogen loading rate of 0.57 ± 0.21 kg-N m-3 day-1. 16S rRNA gene sequencing analysis of the sludge retained in the DHS also corresponded to the result of reactor performance, and both nitrifying and denitrifying bacteria were detected in the sponge carrier. In addition, anammox bacteria was found in the retained sludge. The DHS reactor reduced the HRT of 30 days to 4.8 h compared with the existing algal tank. This result indicates that the DHS reactor could be an appropriate post treatment for the existing anaerobic tank for natural rubber processing wastewater treatment.

Identification and Detection of Prokaryotic Symbionts in the Ciliate Metopus from Anaerobic Granular Sludge

The aim of the present study was to investigate the prokaryotic community structure of the anaerobic ciliate, Metopus sp. using rRNA sequencing, fluorescence in situ hybridization (FISH), and transmission electron microscopy (TEM). Metopus sp. was physically separated from anaerobic granular sludge in a domestic wastewater treatment plant and anoxically cultivated for 7 d. 16S rRNA gene sequences from the prokaryotes Methanoregula boonei and Clostridium aminobutyricum were abundantly detected in Metopus ciliates. The FISH analysis using the oligonucleotide probes Mg1200b and Cla568 demonstrated that these prokaryotes were localized within Metopus cells. These results identify M. boonei- and C. aminobutyricum-like prokaryotes as novel endosymbionts of Metopus ciliates.

Effects of Predation by Protists on Prokaryotic Community Function, Structure, and Diversity in Anaerobic Granular Sludge

Predation by protists is top-down pressure that regulates prokaryotic abundance, community function, structure, and diversity in natural and artificial ecosystems. Although the effects of predation by protists have been studied in aerobic ecosystems, they are poorly understood in anoxic environments. We herein studied the influence of predation by Metopus and Caenomorpha ciliates—ciliates frequently found in anoxic ecosystems—on prokaryotic community function, structure, and diversity. Metopus and Caenomorpha ciliates were cocultivated with prokaryotic assemblages (i.e., anaerobic granular sludge) in an up-flow anaerobic sludge blanket (UASB) reactor for 171 d. Predation by these ciliates increased the methanogenic activities of granular sludge, which constituted 155% of those found in a UASB reactor without the ciliates (i.e., control reactor). Sequencing of 16S rRNA gene amplicons using Illumina MiSeq revealed that the prokaryotic community in the UASB reactor with the ciliates was more diverse than that in the control reactor; 2,885–3,190 and 2,387–2,426 operational taxonomic units (>97% sequence similarities), respectively. The effects of predation by protists in anaerobic engineered systems have mostly been overlooked, and our results show that the influence of predation by protists needs to be examined and considered in the future for a better understanding of prokaryotic community structure and function.

Performance evaluation of the pilot scale upflow anaerobic sludge blanket – Downflow hanging sponge system for natural rubber processing wastewater treatment in South Vietnam

A pilot-scale upflow anaerobic sludge blanket (UASB)-downflow hanging sponge system (DHS) combined with an anaerobic baffled reactor (ABR) and a settling tank (ST) was installed in a natural rubber processing factory in South Vietnam and its process performance was evaluated for 267days. The UASB reactor achieved a total removal efficiency of 55.6±16.6% for chemical oxygen demand (COD) and 77.8±10.3% for biochemical oxygen demand (BOD) with an organic loading rate of 1.7±0.6kg-COD·m-3·day-1. The final effluent of the proposed system had 140±64mg·L-1 of total COD, 31±12mg·L-1 of total BOD, and 58±24mg-N·L-1 of total nitrogen. The system could significantly reduce 92% of greenhouse gas emissions and 80% of hydraulic retention times compared with current treatment systems.

Microbial community analysis using MiSeq sequencing in a novel configuration fluidized bed reactor for effective denitrification

A novel configured fluidized bed reactor (FBR) with granular rubber as the fluidized media was operated without internal recirculation to achieve denitrification. This FBR could operate under a low hydraulic retention time (HRT) of 50min due to the low rubber media density and absence of recirculation. Synthetic nitrate-rich wastewater with a fixed nitrate (NO3--N) concentration and varying COD concentrations was fed into the FBR. The nitrate removal profile showed a rapid nitrate reduction at the bottom of the reactor with a high performance under the low HRT. Different microbial communities were identified using Illumina Miseq sequencing. The dominant microorganisms belonged to the Beta- and Gamma-proteobacteria classes and played important roles in nitrate reduction. Acidovorax was abundant at low COD: NO3--N ratios, while Rhizobium and Zoogloea were dominant at high COD: NO3--N ratios. The COD: NO3--N ratio strongly influenced the composition of the microbial community including the dominant species.

Ureolytic Prokaryotes in Soil: Community Abundance and Diversity

Although the turnover of urea is a crucial process in nitrogen transformation in soil, limited information is currently available on the abundance and diversity of ureolytic prokaryotes. The abundance and diversity of the soil 16S rRNA gene and ureC (encoding a urease catalytic subunit) were examined in seven soil types using quantitative PCR and amplicon sequencing with Illumina MiSeq. The amplicon sequencing of ureC revealed that the ureolytic community was composed of phylogenetically varied prokaryotes, and we detected 363 to 1,685 species-level ureC operational taxonomic units (OTUs) per soil sample, whereas 5,984 OTUs were site-specific OTUs found in only one of the seven soil types.

A nitrogen removal system to limit water exchange for recirculating freshwater aquarium using DHS–USB reactor

ABSTRACT This study proposes a biological nitrogen removal system for freshwater aquaria consisting of a down-flow hanging sponge (DHS) and an up-flow sludge blanket (USB). DHS–USB systems can perform nitrification and denitrification simultaneously, reducing ammonia (NH3) and nitrate (NO3−) toxicity in the water. The performance of the system was evaluated using on-site fresh water aquaria at ambient temperature (23–34°C) over 192 days. NH3 and nitrite (NO2−) were maintained at a detection limit of 0.01 mg N L−1 and NO3− was maintained below 10 mg N L−1, despite limited water exchange. The 16S rRNA gene of microorganisms from the sludge retained in the bioreactors was sequenced to identify the microbial communities present. Microbial community analysis revealed that ammonia oxidizing archaea (AOA), Ca. Nitrososphaera and Nitrosopumilus, played an important role in nitrification in the DHS reactor, while denitrifying bacteria Thauera played an important role in denitrification in the USB reactor. The proposed DHS–USB system is a promising technological advancement in the development of lower maintenance aquaria.

Defining microbial community composition and seasonal variation in a sewage treatment plant in India using a down-flow hanging sponge reactor

The characteristics of the microbial community in a practical-scale down-flow hanging sponge (DHS) reactor, high in organic matter and sulfate ion concentration, and the seasonal variation of the microbial community composition were investigated. Microorganisms related to sulfur oxidation and reduction (2–27%), as well as Leucobacter (7.50%), were abundant in the reactor. Anaerobic bacteria (27–38% in the first layer) were also in abundance and were found to contribute to the removal of organic matter from the sewage in the reactor. By comparing the Simpson index, the abundance-based coverage estimator (ACE) index, and the species composition of the microbial community across seasons (summer/dry, summer/rainy, autumn/dry, and winter/dry), the microbial community was found to change in composition only during the winter season. In addition to the estimation of seasonal variation, the difference in the microbial community composition along the axes of the DHS reactor was investigated for the first time. Although the abundance of each bacterial species differed along both axes of the reactor, the change of the community composition in the reactor was found to be greater along the vertical axis than the horizontal axis of the DHS reactor.

Process Performance and Microbial Community Structure of an Anaerobic Baffled Reactor for Natural Rubber Processing Wastewater Treatment

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.

Eukaryotic Community in UASB Reactor Treating Domestic Sewage Based on 18S rRNA Gene Sequencing

Microbial eukaryotes play important roles in sewage treatment systems. In an up-flow anaerobic sludge blanket (UASB) reactor fed with domestic sewage, anaerobic bacteria, archaea, and microbial eukaryotes (protist and fungi) coexist. To date, bacterial and archaeal communities in the UASB reactor have been widely studied. However, little is known about the eukaryotic community structure and function in most of anaerobic treatment systems. In this study, we analyzed eukaryotic community in the UASB reactor treating domestic sewage over 2 years operational period based on 18S rRNA gene sequences. In addition, multivariate statistics were applied to elucidate the correlation between eukaryotic community and operational conditions of the UASB reactor. The dominant protist groups observed were from phylum Ciliophora, Apicomplexa, Perkisea and Amoebozoa in the UASB reactor. Followings were flagellate protist such as Cercozoa, Sulcozoa, Bicosoecida, Choanomonada, Dinoflagellata and Metamonada. The result showed protist phylum and water temperature were not correlated. Only phylum Sulcozoa positively correlated with COD and suspended solid (SS), whereas other protist showed low correlation. The dominant fungi groups were LKM11, LKM15 and phylum Ascomycota. Uncultured LKM15 correlated with sulfide whereas phylum Discicristoidea and Chytridiomycota showed negative correlation. Phylum Ascomycota seemed most abundant when sulfide was low, but their association with environmental variables remained unclear. These results suggested that some protist and fungi groups could be used as indicator of environmental parameters in the UASB reactor.