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We conducted laboratory experiments under varied solar radiation and salinity levels to investigate their influences on the natural attenuation of multiple promising microbial indicators including fecal bacteria and two types of bacteriophages. Inactivation coefficients were estimated and compared following first-order kinetics. Somatic coliphage was found to be the most resistant, while fecal bacteria exhibited higher susceptibility to both factors. The estimated inactivation coefficients of E. coli were applied to a 3D water quality model and validated with a daily basis monitoring dataset. The validation revealed high consistency among modelled and monitored concentrations, with a less than 1-log concentration difference. Further, the effect of actual solar radiation and salinity on E. coli inactivation after a rainfall event was calculated and compared. The results exhibited that solar radiation is a stronger influential factor. Simulation illustrated that lower-strength radiation exposure can limit E. coli inactivation, enabling them to survive up to one week after combined sewer overflow (CSO) discharge. The model revealed a promising capacity as a tool for the timely prediction of the CSO-induced severity of microbial contamination and associated risk, as well as associated natural attenuation; thus, this model can enhance the competency of public water managers for decision making. [ABSTRACT FROM AUTHOR]

Biological filters effectively remove ammonium from drinking water via nitrification. In a pilot-scale upflow biological contact filter (U-BCF), complete ammonia oxidizers (comammox), which are capable of oxidizing ammonia to nitrate in one cell, were more abundant than ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). However, little information is available on the contribution of comammox to nitrification. In this study, we evaluated the autotrophic growth activity of comammox associated with biological activated carbon (BAC) in a U-BCF by DNA-stable isotope probing (DNA-SIP). BAC samples collected from the U-BCF were continuously fed mineral medium containing 0.14 mg N L−1 ammonium and 12C- or 13C-labeled bicarbonate for 20 days. DNA-SIP analysis revealed that comammox (clades A and B) as well as AOA assimilated bicarbonate after 10 days of incubation, proving that dominant comammox could contribute to nitrification. Contrarily, AOB remained inactive throughout the observation period. Amplicon sequencing of the 13C-labeled DNA fractions of comammox revealed that specific genotypes other than the most dominant genotype in the original sample were more enriched under the incubation condition for the DNA-SIP experiment. Thus, dominant genotypes of comammox in a U-BCF might utilize organic nitrogen to fuel nitrification in ammonia-limited environments. [ABSTRACT FROM AUTHOR]

Many urban flood models employ coarse grids to reduce the computational cost of real‐time forecasting. Such a coarse grid, however, may result in poor predictions of the discharge rate of surface water because of difficulties in representing the detailed features of drainage facilities. In the present study, an urban flood model that consists of a one‐dimensional (1D) river flow model, a two‐dimensional (2D) ground surface flow model, and a 1D sewer network model was developed. A coarse grid is used for the 2D ground surface flow model, and the tail networks of the sewer systems are neglected to reduce computational cost. A novel approach is proposed for determining the integrated water discharge from the ground surface to the trunk sewer network to retain the accuracy of a simplified coarse‐grid system. Numerical experiments were performed to evaluate the performance of the proposed method. Measured water levels at manholes were employed to examine the accuracy of the model. The results show that this approach significantly improves the accuracy of the simulated water level in a sewer network with enhanced computational efficiency. [ABSTRACT FROM AUTHOR]

Integrated flood models have been previously developed to simulate diverse inundation situations and combined with models of storm surges and river floods. However, drainage systems, ground elevation, and surface information of human settlements have only been digitized in large cities. Digitization of surface information is essential for developing a drainage system model for pluvial flood analysis. Occasionally, suburban drainage areas exhibit various complex land-use conditions, including residential and green areas, agricultural land with drainage, and irrigation channels. Herein, UAV photogrammetry was applied to obtain high-resolution geospatial data associated with small-scale flood-prone areas whose elevation, land-use, and waterway networks have not been elucidated sufficiently. The resolution of elevation and land-use data ranged from 2.61–5.22 cm/mesh. The measurement accuracy of the width and depth of the open channels was high, and the errors were mostly within 10%. A drainage system model was developed using data on open channel, elevation, and land-use. [ABSTRACT FROM AUTHOR]

Compared to pumping stations, pump gates have small sites and are constructed for a low cost over a short period of time. A new type of horizontal axial submersible pump that is optimal for pump gates has recently been developed. Since the new type of pump can be operated at full speed regardless of water level, it is possible to conduct standby operations in preparation for stormwater runoff inflows. In a simulation comparing the conventional pumps and the new type of pump, there was no serious inundation condition in the new pump up to 70 mm/h, which is 140% of the design's rainfall intensity. As a result, it was clarified that standby operations can keep the peak water level low and maximize the water storage capacity of the drainage channel. [ABSTRACT FROM AUTHOR]

The series of annual flood disasters that struck Japan in recent years pose challenges to urban stormwater management. Japan has been implementing nation-wide hydrometeorological observation through a dense network of rain gauges. Since the recent decade, ground radars have been deployed to observe heavy rainfall with high spatiotemporal resolution as a countermeasure. While commercial software is popular in designing stormwater drainage systems, several integrated urban flood models have been developed domestically and are applicable in stormwater management. A paradigm shift with the rise of Internet of Things (IoT) provides an inexperienced opportunity in hydrological observation, and has been implemented for monitoring sewer network conditions. Despite this broad scope of research works and technological innovations, such advancement is not internationally recognized yet. The present study aims to review the development and role of science and technology in stormwater management in Japan, focusing specifically on rainfall observation, integrated urban flood modelling, and emerging technologies for stormwater monitoring. In addition, the possible future direction of stormwater management is envisioned. Considering the series of record-breaking rainfall events that struck Japan, we will have to face more severe challenges in urban flood management alongside the impact of global climate change. As compared to structural measures, which are subject to budgetary constraints, the relative importance of non-structural measures is increasing; therefore, effective application of numerical modeling techniques is required. A common weakness of the urban flood modeling framework is the limited availability of observations in sewer networks, which can be relaxed by emerging IoT based observations. The fusion of IoT based observations with an integrated urban flood modeling technique appears to the emerging technology for stormwater management. [ABSTRACT FROM AUTHOR]

Abstract During runoff process, the urban road dust (URD) passes through the road-side gutters and detention tanks, where it gets hold for a certain period of time, hours to weeks, before making its way into the water bodies. A part of the water-exchangeable toxicants are leached by the water, and some strongly bound toxicants remain attached to the URD. Toxicity of urban runoff is dependent on holding time, water volume, and the type and composition of the wet road dust (WeRD) and leachate. However, there are no studies that have elucidated the manner in which toxicities of the WeRD and leachate vary during prolonged holding in the runoff processes. The main objectives of this research were to, i) identify the distribution of toxicants in the WeRD and leachate, and ii) evaluate the change in toxicity during prolonged holding. The URD samples that were collected from residential road, arterial road and highways in Tokyo, Japan, were mixed with moderately hard water in varying ratios (1:2 to 1:16) and were held for a certain time (1 h to 5 days) before centrifuging into the WeRD and leachate. Toxicity test was conducted with ostracod Heterocypris incongruens direct contact test. Toxicity of both the WeRD and leachate from residential area was not significantly greater than the 20% lethal limit. Toxicity of the WeRD from other stations initially decreased, further reached a minimum corresponding to the critical holding time, and it subsequently increased again. Toxicity of the arterial leachate gradually increased, whereas that of the highway leachate gradually decreased during 5 days holding. Unionized ammonia and zinc were confirmed as one of the possible toxicants. This study proposes and verifies a model for the toxicity change of the WeRD during prolonged holding. Graphical abstract Unlabelled Image Highlights • Toxicity change of road dust during runoff process is elucidated. • Toxicity of wet road dust (WeRD) decreased initially and gradually increased. • Unionized ammonia and Zinc were confirmed as one of the toxicants. • Model for the toxicity change of the WeRD during prolonged holding is proposed and verified. [ABSTRACT FROM AUTHOR]

Abstract Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in urban environments. Urban road dust (URD) generated by traffic is an important PAH accumulator. Twelve priority PAHs in < 2000 µm fraction of ten URD samples from Tokyo, Japan were characterized based on profile distributions, carcinogenicity, toxicity, and source apportionment by cluster analysis, biplot and diagnostic ratios. PAH concentrations (mg/kg dry weight) in arterial roads, highways, highway parking, highway drainage pit and residential area URD samples were 2.06–4.24, 0.25–3.37, 3.44, 4.94, and 5.26 respectively, dominated by the ∑4 rings (average 46%) and ∑5 + 6 rings (average 41%) PAHs. Biplot analysis revealed that the antecedent dry weather period, vehicle frequency and organic matter content were the dominant environmental factors governing PAH profiles of different road types. The total amount of carcinogenic PAHs in the residential URD (2.12 mg/kg) was higher than those in the arterial road (0.60–2.00 mg/kg) and highway (0.10–1.84 mg/kg) URD. Toxic equivalent concentrations (TECs) of residential, arterial road and highway URD were 0.54, (0.12–0.57), and (0.02–0.51) mg/kg, respectively. The dominant PAH sources were found to be petrogenic combustion in arterial road and highway URD, and pyrogenic combustion consisting of a mix of biomass, petroleum and traffic-related sources in the residential and highway drainage pit samples. This is also the first study to find that TEC-based toxicity should not be taken as a measure of URD toxicity. Highlights • PAH is characterized based on carcinogenicity, toxicity and source apportionment. • Antecedent dry weather period, vehicles frequency and organic matter governs PAH profile. • PAH source was petrogenic combustion in arterial and highway road dust. • PAH source was pyrogenic combustion in residential and drainage pit road dust. • Toxic equivalent concentration is not a measure of toxicity of road dust. [ABSTRACT FROM AUTHOR]