Naohiro Kishida

Effectiveness of oxidation-reduction potential and pH as monitoring and control parameters for nitrogen removal in swine wastewater treatment by sequencing batch reactors.

Two bench-scale sequencing batch reactors (SBRs) were operated in a fixed hydraulic retention time study to investigate the effectiveness of oxidation-reduction potential (ORP), pH and dissolved oxygen as parameters for indicating denitrification followed by nitrification in SBRs for swine wastewater treatment. The ORP and pH profiles were monitored and evaluated under different denitrification and nitrification conditions with and without a supplemental carbon source. With a low C/N ratio, and using a suitable C/N ratio adjustment control, ORP and pH could be used as monitoring and control parameters in both the anoxic and oxic phases for practical swine wastewater treatment. High-level accumulation of nitrate was observed without any C/N ratio adjustment. In this case, ORP and pH were not useful for monitoring denitrification followed by nitrification in SBRs. According to our research, with regard to N removal, it would be better to use pH as a parameter during the oxic phase and ORP as a parameter during the anoxic phase. Using a suitable adjustment of a ON ratio in the influent by adding swine slurry, a high total nitrogen removal efficiency of up to 95.5% was reached. It was found that, in this case, the use of ORP and pH as parameters for real-time control processes was possible in swine wastewater treatment.

Behavior of polymeric substrates in an aerobic granular sludge system.

Particulate and slowly biodegradable substrates form an important fraction of industrial wastewater and sewage. To study the influence of suspended solids and colloidal substrate on the morphology and performance of aerobic granular sludge, suspended and soluble starch was used as a model substrate. Degradation was studied using microscopy, micro-electrode measurements, batch experiments and long term laboratory scale reactor operation. Starch was removed by adsorption at the granule surface, followed by hydrolysis and consumption of the hydrolyzed products. Aerobic granules could be maintained on starch as sole influent carbon source, but their structure was filamentous and irregular. It is hypothesized that this is related to the low starch hydrolysis rates, leading to available substrate during the aeration period (extended feast period) and resulting in increased substrate gradients over the granules. The latter induces a less uniform granule development. Starch adsorbed and was consumed at the granule surface instead of being accumulated inside the granules as occurs for soluble substrates. Therefore the simultaneous denitrification efficiencies remained low. Moreover, many protozoa and metazoans were observed in laboratory reactors as well as in pilot- and full-scale Nereda(®) reactors, indicating an important role in the removal of suspended solids too.

Removal of radioactive iodine and cesium in water purification processes after an explosion at a nuclear power plant due to the Great East Japan Earthquake.

The presence of radionuclides at five water purification plants was investigated after an explosion at a nuclear power plant hit by the Great East Japan Earthquake on 11 March 2011. Radioactive iodine (¹³¹I) and cesium (¹³⁴Cs and ¹³⁷Cs) were detected in raw water in Fukushima and neighboring prefectures. ¹³¹I was not removed by coagulation-flocculation-sedimentation. ¹³¹I was removed by granular activated carbon (GAC) and powdered activated carbon (PAC) at a level of about 30%-40%, although ¹³¹I was not removed in some cases. This was also confirmed by laboratory-scale experiments using PAC. The removal percentages of ¹³¹I in river and pond waters by 25 mg dry/L of PAC increased from 36% to 59% and from 41% to 48%, respectively, with chlorine dosing before PAC. ¹³⁴Cs and ¹³⁷Cs were effectively removed by coagulation at both a water purification plant and in laboratory-scale experiments when turbidity was relatively high. In contrast, ¹³⁴Cs and ¹³⁷Cs in pond water with low turbidity were not removed by coagulation. This was because ¹³⁴Cs and ¹³⁷Cs in river water were present mainly in particulate form, while in pond water they were present mainly as cesium ions (¹³⁴Cs+ and ¹³⁷Cs+). However, the removal of ¹³⁴Cs and ¹³⁷Cs in pond water by coagulation increased markedly when ¹³⁴Cs and ¹³⁷Cs were mixed with sediment 24 h before coagulation.

One-year weekly survey of noroviruses and enteric adenoviruses in the Tone River water in Tokyo metropolitan area, Japan.

To investigate the actual fluctuations in the concentrations of noroviruses (NoVs) GI and GII, and enteric adenoviruses (EAdVs) in river water and its relationship with the number of acute infectious gastroenteritis patients, one-year weekly quantitative monitoring of NoVs GI and GII and EAdVs was performed in the Tone River in Japan where the surface water is utilized for the main production of drinking water for the Tokyo Metropolitan Area from October 2009 to September 2010. Noroviruses GI and GII and EAdVs were detected in 28 (54%), 33 (63%), and 23 (44%) of the 52 samples (1 L each), respectively. The concentrations of NoVs GI and GII and EAdVs fluctuated strongly and were more abundant in winter and early spring. The concentration of NoVs GI was transiently greater than 10,000 copies/L. The number of acute infectious gastroenteritis patients in the upper river basin was highly correlated with all the viral concentrations, while general microbial indicator data such as turbidity and heterotrophic plate count were independent of viral concentration as suggested in previous studies. To the best of our knowledge, this is the first study that clearly shows the strong correlation of the number of gastroenteritis with virus contamination in lower river basin.

Occurrence of pepper mild mottle virus in drinking water sources in Japan.

ABSTRACT Pepper mild mottle virus (PMMoV) is a plant virus that has been recently proposed as a potential indicator of human fecal contamination of environmental waters; however, information on its geographical occurrence in surface water is still limited. We aimed to determine the seasonal and geographic occurrence of PMMoV in drinking water sources all over Japan. Between July 2008 and February 2011, 184 source water samples were collected from 30 drinking water treatment plants (DWTPs); viruses from 1 to 2 liters of each sample were concentrated by using an electronegative membrane, followed by RNA extraction and reverse transcription. Using quantitative PCR, PMMoV was detected in 140 (76%) samples, with a concentration ranging from 2.03 × 103 to 2.90 × 106 copies/liter. At least one of the samples from 27 DWTPs (n = 4 or 8) was positive for PMMoV; samples from 10 of these DWTPs were always contaminated. There was a significant difference in the occurrence of PMMoV among geographical regions but not a seasonal difference. PMMoV was frequently detected in samples that were negative for human enteric virus or Escherichia coli. A phylogenetic analysis based on the partial nucleotide sequences of the PMMoV coat protein gene in 12 water samples from 9 DWTPs indicated that there are genetically diverse PMMoV strains present in drinking water sources in Japan. To our knowledge, this is the first study to demonstrate the occurrence of PMMoV in environmental waters across wide geographical regions.

Modeling the nutrient removal process in aerobic granular sludge system by coupling the reactor- and granule-scale models

We developed a model for nutrient removal in an aerobic granular sludge system. This model can quantitatively describe the start‐up of the system by coupling a model for studying the population dynamics of the granules in the reactor (reactor‐scale model) and a model for studying the microbial community structure in the granules (granule‐scale model). The reactor‐scale model is used for simulation for 10 days from the start, during which the granule size is relatively small; the granule‐scale model is used after Day 10. The present approach proposes the output data of the reactor‐scale model after 10 days as initial conditions for the granule‐scale model. The constructed model satisfactorily describes experimental data in various spatial and temporal scales, which were obtained in this study by performing the anaerobic–aerobic–anoxic cycles using a sequencing batch reactor. Simulations using this model quantitatively predicted that the stability of nutrient removal process depended largely on the dissolved oxygen (DO) concentration, and the DO setpoint adaptation could improve the nutrient removal performance. Biotechnol. Bioeng. 2015;112: 53–64.

Real-time control strategy for simultaneous nitrogen and phosphorus removal using aerobic granular sludge

To achieve stable and simultaneous removal of nitrogen and phosphorus using aerobic granular sludge in a sequencing batch reactor, a real-time control strategy was established, where time derivatives of electric conductivity (EC) and pH were monitored to facilitate the determinations of ends of phosphate release, nitrification and denitrification as well as corresponding optimum time-lengths of anaerobic, oxic, and anoxic phases in treatment cycles. Although biomass concentration in a reactor drastically fluctuated at the startup period because of very short sludge settling time for the formation of aerobic granular sludge, cycle length for proper treatment was automatically adjusted in this control system. Even when characteristics of influent wastewater markedly fluctuated, stable nitrogen and phosphorus removal was successfully attained both before and at pseudo-steady-state. Effluent concentrations of NH4-N, NOx-N and PO4-P were always lower than 0.3 mg/L. On the other hand, when time lengths of the anaerobic/oxic/anoxic phases were fixed, stable nitrogen and phosphorus removal was not accomplished. Therefore, it is clear that the designed control system is very effective to obtain stable treatment performance in simultaneous nitrogen and phosphorus removal by aerobic granular sludge.

Quantitative detection of human enteric adenoviruses in river water by microfluidic digital polymerase chain reaction

We describe an assay for simple and accurate quantification of human enteric adenoviruses (EAdVs) in water samples using a recently developed quantification method named microfluidic digital polymerase chain reaction (dPCR). The assay is based on automatic distribution of reaction mixture into a large number of nanolitre-volume reaction chambers and absolute copy number quantification from the number of chambers containing amplification products on the basis of Poisson statistics. This assay allows absolute quantification of target genes without the use of standard DNA. Concentrations of EAdVs in Japanese river water samples were successfully quantified by the developed dPCR assay. The EAdVs were detected in seven of the 10 samples (1 L each), and the concentration ranged from 420 to 2,700 copies/L. The quantified values closely resemble those by most probable number (MPN)-PCR and real-time PCR when standard DNA was validated by dPCR whereas they varied substantially when the standard was not validated. Accuracy and sensitivity of the dPCR was higher than those of real-time PCR and MPN-PCR. To our knowledge, this is the first study that has successfully quantified enteric viruses in river water using dPCR. This method will contribute to better understanding of existence of viruses in water.

Rapid start-up of a nitrifying reactor using aerobic granular sludge as seed sludge

In this study, the effectiveness of aerobic granular sludge as seed sludge for rapid start-up of nitrifying processes was investigated using a laboratory-scale continuous stirred-tank reactor (CSTR) fed with completely inorganic wastewater which contained a high concentration of ammonia. Even when a large amount of granular biomass was inoculated in the reactor, and the characteristics of influent wastewater were abruptly changed, excess biomass washout was not observed, and biomass concentration was kept high at the start-up period due to high settling ability of the aerobic granular sludge. As a result, an ammonia removal rate immediately increased and reached more than 1.0 kg N/m(3)/d within 20 days and up to 1.8 kg N/m(3)/d on day 39. Subsequently, high rate nitritation was stably attained during 100 days. However, nitrite accumulation had been observed for 140 days before attaining complete nitrification to nitrate. Fluorescence in situ hybridization analysis revealed the increase in amount of ammonia-oxidizing bacteria which existed in the outer edge of the granular sludge during the start-up period. This microbial ecological change would make it possible to attain high rate ammonia removal.

Development and evaluation of a reverse transcription-loop-mediated isothermal amplification assay for rapid and high-sensitive detection of Cryptosporidium in water samples

We describe a novel assay for simple, rapid and high-sensitive detection of Cryptosporidium oocysts in water samples using a reverse transcription-loop-mediated isothermal amplification (RT-LAMP). The assay is based on the detection of 18S rRNA specific for Cryptosporidium oocysts. The detection limit of the developed RT-LAMP assay was as low as 6 x 10(-3) oocysts/test tube, which theoretically enables us to detect a Cryptosporidium oocyst and perform duplicated tests even if water samples contain only one oocyst. The developed RT-LAMP assay could more sensitively detect Cryptosporidium oocysts in real water samples than the conventional assay based on microscopic observation.