Tadashi Tagawa

Removal of human pathogenic viruses in a down-flow hanging sponge (DHS) reactor treating municipal wastewater and health risks associated with utilization of the effluent for agricultural irrigation

A down-flow hanging sponge (DHS) reactor has been developed as a cost-effective wastewater treatment system that is adaptable to local conditions in low-income countries. A pilot-scale DHS reactor previously demonstrated stable reduction efficiencies for chemical oxygen demand (COD) and ammonium nitrogen over a year at ambient temperature, but the pathogen reduction efficiency of the DHS reactor has yet to be investigated. In the present study, the reduction efficiency of a pilot-scale DHS reactor fed with municipal wastewater was investigated for 10 types of human pathogenic viruses (norovirus GI, GII and GIV, aichivirus, astrovirus, enterovirus, hepatitis A and E viruses, rotavirus, and sapovirus). DHS influent and effluent were collected weekly or biweekly for 337 days, and concentrations of viral genomes were determined by microfluidic quantitative PCR. Aichivirus, norovirus GI and GII, enterovirus, and sapovirus were frequently detected in DHS influent, and the log10 reduction (LR) of these viruses ranged from 1.5 to 3.7. The LR values for aichivirus and norovirus GII were also calculated using a Bayesian estimation model, and the average LR (±standard deviation) values for aichivirus and norovirus GII were estimated to be 1.4 (±1.5) and 1.8 (±2.5), respectively. Quantitative microbial risk assessment was conducted to calculate a threshold reduction level for norovirus GII that would be required for the use of DHS effluent for agricultural irrigation, and it was found that LRs of 2.6 and 3.7 for norovirus GII in the DHS effluent were required in order to not exceed the tolerable burden of disease at 10-4 and 10-6 disability-adjusted life years loss per person per year, respectively, for 95% of the exposed population during wastewater reuse for irrigation.

Microfluidic PCR Amplification and MiSeq Amplicon Sequencing Techniques for High-Throughput Detection and Genotyping of Human Pathogenic RNA Viruses in Human Feces, Sewage, and Oysters

Detection and genotyping of pathogenic RNA viruses in human and environmental samples are useful for monitoring the circulation and prevalence of these pathogens, whereas a conventional PCR assay followed by Sanger sequencing is time-consuming and laborious. The present study aimed to develop a high-throughput detection-and-genotyping tool for 11 human RNA viruses [Aichi virus; astrovirus; enterovirus; norovirus genogroup I (GI), GII, and GIV; hepatitis A virus; hepatitis E virus; rotavirus; sapovirus; and human parechovirus] using a microfluidic device and next-generation sequencer. Microfluidic nested PCR was carried out on a 48.48 Access Array chip, and the amplicons were recovered and used for MiSeq sequencing (Illumina, Tokyo, Japan); genotyping was conducted by homology searching and phylogenetic analysis of the obtained sequence reads. The detection limit of the 11 tested viruses ranged from 100 to 103 copies/μL in cDNA sample, corresponding to 101–104 copies/mL-sewage, 105–108 copies/g-human feces, and 102–105 copies/g-digestive tissues of oyster. The developed assay was successfully applied for simultaneous detection and genotyping of RNA viruses to samples of human feces, sewage, and artificially contaminated oysters. Microfluidic nested PCR followed by MiSeq sequencing enables efficient tracking of the fate of multiple RNA viruses in various environments, which is essential for a better understanding of the circulation of human pathogenic RNA viruses in the human population.

Assessment of UASB–DHS technology for sewage treatment: a comparative study from a sustainability perspective

ABSTRACT This paper assesses the technical and economic sustainability of a combined system of an up-flow anaerobic sludge blanket (UASB)–down-flow hanging sponge (DHS) for sewage treatment. Additionally, this study compares UASB–DHS with current technologies in India like trickling filters (TF), sequencing batch reactor (SBR), moving bed biofilm reactor (MBBR), and other combinations of UASB with post-treatment systems such as final polishing ponds (FPU) and extended aeration sludge process (EASP). The sustainability of the sewage treatment plants (STPs) was evaluated using a composite indicator, which incorporated environmental, societal, and economic dimensions. In case of the individual sustainability indicator study, the results showed that UASB-FPU was the most economically sustainable system with a score of 0.512 and aeration systems such as MBBR, EASP, and SBR were environmentally sustainable, whereas UASB–DHS system was socially sustainable. However, the overall comparative analysis indicated that the UASB–DHS system scored the highest value of 2.619 on the global sustainability indicator followed by EASP and MBBR with scores of 2.322 and 2.279, respectively. The highlight of this study was that the most environmentally sustainable treatment plants were not economically and socially sustainable. Moreover, sensitivity analysis showed that five out of the seven scenarios tested, the UASB–DHS system showed good results amongst the treatment system. GRAPHICAL ABSTRACT

Characteristics of DO, organic matter, and ammonium profile for practical-scale DHS reactor under various organic load and temperature conditions

ABSTRACT Profile analysis of the down-flow hanging sponge (DHS) reactor was conducted under various temperature and organic load conditions to understand the organic removal and nitrification process for sewage treatment. Under high organic load conditions (3.21–7.89 kg-COD m−3 day−1), dissolved oxygen (DO) on the upper layer of the reactor was affected by organic matter concentration and water temperature, and sometimes reaches around zero. Almost half of the CODCr was removed by the first layer, which could be attributed to the adsorption of organic matter on sponge media. After the first layer, organic removal proceeded along the first-order reaction equation from the second to the fourth layers. The ammoniacal nitrogen removal ratio decreased under high organic matter concentration (above 100 mg L−1) and low DO (less than 1 mg L−1) condition. Ammoniacal nitrogen removal proceeded via a zero-order reaction equation along the reactor height. In addition, the profile results of DO, CODCr, and NH3-N were different in the horizontal direction. Thus, it is thought the concentration of these items and microbial activities were not in a uniform state even in the same sponge layer of the DHS reactor.

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.

Characterization of sludge properties for sewage treatment in a practical-scale down-flow hanging sponge reactor: oxygen consumption and removal of organic matter, ammonium, and sulfur

The characteristics of sludge retained in a down-flow hanging sponge reactor were investigated to provide a better understanding of the sewage treatment process in the reactor. The organic removal and sulfur oxidation conditions were found to differ between the first layer and the following three layers. It was found that 63% and 59% of the organic matter was removed in the first layer, even though the hydraulic retention time was only 0.2 h. It is thought that the organic removal resulted from aerobic and anaerobic biodegradation on the sponge medium. The sulfate concentration increased 1.5-1.9-fold in the first layer, with almost no subsequent change in the second to fourth layers. It was shown that oxidation of sulfide in the influent was completed in the first layer. The result of the oxygen uptake rate test with an ammonium nitrogen substrate suggested that the ammonium oxidation rate was affected by the condition of dissolved oxygen (DO) or oxidation-reduction potential (ORP).

Evaluation of a Novel Sewage Treatment System by Combining a Primary Settled Basin with DHS Reactor

At present, 95 % of the total population of the Egypt country takes up residency in areas around of Nile, irrigation agriculture caused by using raw sewage exacerbate the issue of environmental health hazard risk in arid regions of Egypt. So, Egypt country goes ahead with effective utilization of treated sewage for irrigation, our international research consortium has proposed a novel concept of sewage treatment technology for risk reduction of health hazard and we focus on down-flow hanging sponge reactor (DHS) as sewage treatment technology. DHS behaved extremely well as sewage treatment technology in India and it is widely expected to dominate in a developing country. The method is a combination of the DHS for posttreatment and primary sedimentation tank for pretreatment. This method went live in Egypt in 2014. So, KNCT tried demonstrating experiment in Japan with the use of share of the same design as method. Preliminary experiment has confirmed the feasibility to satisfy a criterion for irrigation in EGYPT as an objective. Irrigation standard (TSS < 60 mg/L, BOD < 60 mg/L, CODtotal < 80 mg/L, \( {\text{NO}}_{3}^{ - } \) < 50 mg/L) set by Egypt government has achieved effective utilization of treated sewage for irrigation as objective. When hydraulic retention time (HRT) set 1 h as DHS’s volume load of target, condition of operation of experiment is controlled by varying treatment quantity of sewage. We started up the experiment provided that treatment quantity of sewage: 5 m3/day, HRT: 4 h. The experiment is performed in five stages. It has continued since March 2013 (Phase 1: HRT 4 h, Phase 2: HRT 2 h, Phase 3: HRT 1 h, Phase 4: HRT 2 h, and Phase 5: HRT 4 h). The preliminary experiment indicates the possibility of effective utilization of treated sewage for irrigation. The removal rate of biochemical oxygen demand (BOD) and suspended solids (SS) retains sufficient strength to meet irrigation standards. (Phase 1: 82 %(BOD) 97 %(SS), Phase 2: 92 %(BOD) 81 %(SS), Phase 3: 76 %(BOD) 65 %(SS) Phase 4: 81 %(BOD) 68 %(SS), Phase 5: 89 %(BOD) 88 %(SS)). The result of the profile analysis indicated that organics destruction occurred from the top of the reactor (1st stage) to the 3rd stage and the nitrification process proceed from the 4th stage to the 5th stage. On the other hand, the nitrification process of \( {\text{NH}}_{3}^{ - } \)–N was poor at Phase 3. We believe that this related to a blocked gap of media sponge. At Phase 4 and Phase 5, the removal rate of BOD and nitrification of the water was provided so as to lengthen the processing time. Improvement in the ability to remove \( {\text{NH}}_{3}^{ - } \)–N is vital to use the primary settled-DHS process for irrigation, because \( {\text{NH}}_{3}^{ - } \)–N is a toxic substance for agricultural irrigation.