Classification and description of the drainage state of manholes in urban drainage systems.

Manholes are important structures in urban storm drainage systems connecting roads and underground drainage networks, and they are also an important part of the research on improving urban resistance to storm flooding. Due to cost and space constraints, most of the existing experimental data on manholes come from scale model experiments obtained by scaling according to Froude's similarity criterion, and there is a lack of validation based on full-size experimental data. This also leads to inconsistencies in the form and parameter values of the manhole flow exchange equations derived from different experiments. To remedy this deficiency, a full-scale urban drainage engineering physics model was developed in this study with the aim of investigating the flow exchange of surface water as it flows through manholes into the sewer system. Experiments were conducted under steady flow conditions and compared with predictions from the existing models. The results show that the predictions of the existing model deviate significantly from the measured values when the flow is between free weir flow and submerged orifice flow. Therefore, we constructed a weighting equation based on weir and orifice flows and found that the weighting coefficients decayed exponentially during the transition from weir to orifice flow.

Management of the designed risk level of urban drainage system in the future: Evidence from haining city, China.

The design of urban drainage infrastructure is mainly based on historical conditions. Under global warming, more intense precipitation extremes will pose severe risk to current infrastructure. The evaluation of where and by how much design standards need to change, is urgently needed to help maintain well-functioning drainage systems. In this study, we used climate projections from the Coupled Model Intercomparison Project Phase 6 (CMIP6) and InfoWorks Integrated Catchment Modeling (ICM) to simulate urban flooding. According to the latest design standard of urban drainage infrastructure, we assess the risk of future urban flooding, and evaluate the effect and benefit of drainage infrastructure adaptation measures. The results showed that, under the shared socioeconomic pathway (SSP) 5-8.5 scenario, a 35% increase in extreme rainfall would be expected. Under a 1-in-30-year precipitation event, the maximum depth would increase by 5.59%, and the withdrawal time would rise by 2.94% in the future period, relative to the baseline level. After the enlargement of drainage infrastructure in local areas, 10% pipe enlargement has a better effect to reduce risk and higher benefits than 5% pipe enlargement. These findings provide valuable insights for policymakers in enhancing the drainage system and adapting to climate change.

Physical modelling of energy losses at surcharged three-way junction manholes in drainage system.

Motivated by the observation that vortex flow structure was evident in the energy loss at the surcharged junction manhole due to changes of hydraulic and geometrical parameters, a physical model was used to calculate energy loss coefficients and investigate the relationship between flow structure and energy loss at the surcharged three-way junction manhole. The effects of the flow discharge ratio, the connected angle between two inflow pipes, the manhole geometry, and the downstream water depth on the energy loss were analyzed based on the quantified energy loss coefficients and the identified flow structure. Moreover, two empirical formulae for head loss coefficients were validated by the experimental data. Results indicate that the effect of flow discharge ratio and connected angle are significant, while the effect of downstream water depth is not obvious. With the increase of the lateral inflow discharge, the flow velocity distribution and vortex structure are both enhanced. It is also found that a circular manhole can reduce local energy loss when compared to a square manhole. In addition, the tested empirical formulae can reproduce the trend of total head loss coefficient.

A biogeographic 16S rRNA survey of bacterial communities of ureolytic biomineralization from California public restrooms.

In this study, we examined the total bacterial community associated with ureolytic biomineralization from urine drainage systems. Biomineral samples were obtained from 11 California Department of Transportation public restrooms fitted with waterless, low-flow, or conventional urinals in 2019. Following high throughput 16S rRNA Illumina sequences processed using the DADA2 pipeline, the microbial diversity assessment of 169 biomineral and urine samples resulted in 3,869 reference sequences aggregated as 598 operational taxonomic units (OTUs). Using PERMANOVA testing, we found strong, significant differences between biomineral samples grouped by intrasystem sampling location and urinal type. Biomineral microbial community profiles and alpha diversities differed significantly when controlling for sampling season. Observational statistics revealed that biomineral samples obtained from waterless urinals contained the largest ureC/16S gene copy ratios and were the least diverse urinal type in terms of Shannon indices. Waterless urinal biomineral samples were largely dominated by the Bacilli class (86.1%) compared to low-flow (41.3%) and conventional samples (20.5%), and had the fewest genera that account for less than 2.5% relative abundance per OTU. Our findings are useful for future microbial ecology studies of urine source-separation technologies, as we have established a comparative basis using a large sample size and study area.

Initial allocation of flood drainage rights based on a PSR model and entropy-based matter-element theory in the Sunan Canal, China.

The pursuit of flood prevention safety and the mitigation of drainage contradiction against an unnecessary influx of floodwater require a modern and efficient model to optimize the management of the initial allocation of flood drainage rights. We attempted to formulate a framework for initial flood drainage rights allocation to promote the sustainable drainage of the Sunan Canal, China. The Pressure-State-Response (PSR) model was constructed using a literature review and interviews with experts and directors using 18 key indicators being determined from field surveys and library studies. We then assessed the flood status of Zhenjiang City, Changzhou City, Wuxi City and Suzhou City in the Sunan Canal zone using an entropy-based matter-element model. The flood drainage rights for a total of 400m3/s was allocated to the four cities in accordance with their flood status. Our research demonstrated that, overall, the four cities may gain the flood drainage rights of 106.67m3/s,120.40m3/s, 118.22m3/s and 54.71m3/s, respectively. Specifically, the calculation of the flood drainage for Wuxi was very close to the actual allocation in 2016, whereas there were differences in the other cities that should not be neglected.

An integrated assessment of drainage system reconstruction based on a drainage network model.

In order to mitigate urban flooding and combined sewer overflows, an integrated assessment method was proposed to identify the optimum reconstruction scheme of a drainage system by considering environment, economy, and society. The integrated assessment framework consisted of the drainage system model establishment, analytic hierarchy process theory, and regret value method. Five drainage system reconstruction schemes for Chaohu city were proposed in this study, and they were evaluated according to nine assessment factors by the integrated assessment method at the initial and future stages. The integrated assessment results show that setting up interceptive equipment for a combined drainage network is the optimal reconstruction scheme at both the initial and future stages of the life cycle. This means that an interceptive combined drainage network is better than a separate drainage network or setting up storage tanks in particular situations from a comprehensive perspective.

Runoff simulation of two typical urban green land types with the Stormwater Management Model (SWMM): sensitivity analysis and calibration of runoff parameters.

The characteristics of surface runoff and the infiltration properties of urban green land are important to determine the effects of runoff reduction by low-impact development (LID) facilities. In this paper, two typical types of urban green land (lawn and shrub) in Shanghai were selected to study the runoff characteristics under eight rainfall events. The sensitivity of the runoff parameters was analyzed, and then, the optimal parameters were determined using the Stormwater Management Model (SWMM). The results showed that the interception and infiltration capacities of shrub were greater than those of lawn. The rainfall intensity and rainfall pattern were the major factors that influenced the interception and infiltration of rainwater. The threshold value that generates runoff varied across the eight rainfall events ranged from 1.6 to 28.5 mm for lawn and 4.5 to 32.0 mm for shrub. The maximum reduction ratios of runoff and peak flow for shrub were 52 and 57% higher than them for lawn, respectively. The parameters for shrub were more sensitive to runoff and peak flow compared with those for lawn. Under light rainfalls with a short duration, the maximum infiltration rate and depression storage were more sensitive than those under heavy rainfalls with a long duration. Antecedent dry weather period was not found to be a sensitive parameter except for the shrub under light rainfalls. The relative errors of runoff and dynamic mean runoff (60 min) for lawn and shrub were within ± 9.5%. The errors of peak flow ranged between - 21 and 16.6%. The dynamic runoff characteristics and the parameters for lawn and shrub determined in this study can provide references for simulating urban runoff and planning LID areas.

The impact of household connection to public network wastewater systems: regulatory impact assessment.

Brazil faces a severe lack of wastewater coverage. Even in urban areas, wastewater is directly disposed of in watercourses without any treatment for a large part of the population. Although the federal, state, and local governments have invested in water and wastewater services (WWS), the expected results have not been achieved. To overcome this problem, the present paper provides an opportunity to observe an ex-ante regulatory impact assessment (RIA) as a policy tool in Brazil. The regulatory policy options will be appraised through the multiple criteria decision analysis (MCDA) according to the following objectives: (i) protect the customers with respect to social aspects; (ii) safeguard the economic, operational and infrastructure sustainability; and (iii) protect the environment. The results show that by making decisions based on evidence, policy makers should reduce the households not connected to wastewater services by 75% and for that they should incur BRL 33 million to the year 2023. Hence, the extra revenues to be obtained with these new connections are capable of making a surplus estimated as BRL 42 million for the same period. This study promotes the use of RIA as a rational, robust and transparent decision framework by the regulatory agencies worldwide.

Stormwater runoff treatment filtration system and backwashing system.

This study has been carried out to evaluate the applicability of the pilot scale hybrid type of stormwater runoff treatment system for treatment of combined sewer overflow. Also, to determine the optimum operation parameter such as coagulation dosage concentration, effectiveness of coagulant usage, surface loading rate and backwashing conditions. The pilot scale stormwater filtration system (SFS) was installed at the municipal wastewater plant serving the city of Cheongju (CWTP), Korea. CWTP has a capacity of 280,000 m3/day. The SFS consists of a hydrocyclone coagulation/flocculation with polyaluminium chloride silicate (PACS) and an upflow filter to treat combined sewer overflows. There are two modes (without PACS use and with PACS use) of operation for the SFS. In case of no coagulant use, the range of suspended solids (SS) and turbidity removal efficiency were 72.0-86.6% (mean 80.0%) and 30.9-71.1% (mean 49.3%), respectively. And, the recovery rate of filter was 79.2-83.6% (mean 81.2%); the rate of remaining solid loading in filter media was 16.4-20.8% (mean 18.8%) after backwashing. The influent turbidity, SS concentrations were 59.0-90.7 NTU (mean 72.0 NTU), 194.0-320.0 mg/L (mean 246.7 mg/L), respectively. The range of PACS dosage concentration was 6.0-7.1 mg/L (mean 6.7 mg/L). The range of SS and turbidity removal efficiency was 84.9-98.2 (mean 91.4%) and 70.7-96.3 (mean 84.0%), respectively. It was found that removal efficiency was enhanced with PACS dosage. The recovery rate of filter was 92.0-92.5% (mean 92.3%) the rate of remaining solid loading in filter media was 6.1-8.2% (mean 7.2%) after backwashing. In the case of coagulant use, the particle size of the effluent is bigger than influent particle size. The results showed that SFS with PACS use more effective than without PACS use in SS and turbidity removal efficiency and recovery rate of filter.

Detection of extraneous water ingress into the sewer system using tandem methods - a case study in Trondheim city.

Infiltration and inflow (I/I) of extraneous water in separate sewer systems are serious concerns in urban water management for their environmental, social and economic consequences. Effective reduction of I/I requires knowing where excess water ingress and illicit connections are located. The present study focuses on I/I detection in the foul sewer network of a catchment in Trondheim, Norway, during a period without snowmelt or groundwater infiltration. Fiber-optic distributed temperature sensing (DTS) was used for the first time in Norway to detect I/I sources in tandem with closed-circuit television inspection (CCTV) and smoke testing. DTS was an accurate and feasible method for I/I detection, though it cannot identify exact types of failure and sources of I/I. Therefore, other complementary methods must be used, e.g. CCTV or smoke testing. However, CCTV was not completely useful in confirming the DTS results. This study provides practical insights for the rehabilitation and repair of sewer networks that suffer from the undesirable I/I of extraneous water.

Evaluation of the bio-protection mechanism in diffusive exchange permeable reactive barriers for the treatment of acid mine drainage.

This research studied the bio-protection mechanism based on chemical gradients in diffusive exchange permeable reactive barriers, evaluating the thickness of the reactive layers in the treatment of concentrated acid mine drainage (AMD). Six bench-scale reactors were constructed with reactive layer thicknesses of 2.5, 5, and 7.5 cm in duplicate. The reactors were first fed a sulfated solution for 55 days, followed by concentrated AMD for 166 days. The change of feed to AMD mainly affected the reactors with thinner 2.5 cm layers in comparison to the reactors with 5 and 7.5 cm layers. Cu and Zn removal efficiency was practically 100% in all the reactors; however, in the thinner layer reactors, metal breakthrough occurred towards the end of the experiment concurrently with inhibitory metal concentrations in the reactive layers. On the contrary, the reactors with layer thicknesses of 5 and 7.5 cm evaluated did not present toxic concentrations of these metals at any of the monitoring points. The bio-protection criterion qD correctly predicted that the thin-layer reactor would be the most affected by the toxicity of AMD. The criterion also indicated that all the reactors should fail. Nevertheless, the fault in the thinner layer reactor registered in the effluent after >150 days; therefore, the possibility of failure in the 5 and 7.5 cm thickness reactors is not rejected, as it could have occurred if the experiment had continued.

Mitigating peak pressure of storm geysering by orifice plates installed at the top of vent pipes.

Large air pockets can be trapped in storm sewer systems during intense rain events. Uncontrolled release of these air pockets may cause geysering and pressure surges, resulting in flooding, pipe failures and safety issues. Thus, there is a great need to develop methods to retrofit existing sewer systems and to provide guidance on system design. A large-scale physical model was established to evaluate air-control orifice plates in reducing geysering intensity by utilizing air cushion effects over the process of air escape. Experimental results indicate that the magnitude of pressure fluctuations can be reduced significantly with partially open vent pipes. The maximum pressure head can be reduced by approximately two-thirds, and the magnitude of relative pressure oscillation decreased by about 95% when the diameter ratio of the air-control orifice to the vent pipe is below 25%. Air-water mixture jets can be avoided in such cases. The effect of using multiple vent pipes with orifice plates was also evaluated and found to be effective. Thus, air-control vent pipes can be applied to alleviate geysering and related pressure transients.

Modulation of transient pressure by an air pocket in a horizontal pipe with an end orifice.

In urban drainage systems, a sudden increase in the flow rate can cause the transition of the flow from open channel to pipe flow, and the entrapment of large air pockets in sewers, which might result in serious geysers and water-hammer like pressure events. This paper presents a numerical analysis of flow processes associated with the pressurization and release of an air pocket in order to study its influence on transient pressure in a horizontal pipe with an end orifice. The influence of the air pocket inside the pipe on the peak pressure can be described in two distinct regimes. In regime I for the pipe with a small orifice, the peak pressure is modulated by the pressurization and expansion of the air pocket and its subsequent damping. In regime II for the pipe with a large orifice, air can be quickly expelled, and the water column directly impinges on the pipe end wall and causes water-hammer like pressure. With the increase of the orifice size, the peak pressure decreases due to the change in the water velocity. In the study cases, the peak pressure in regime I is about two times the inlet pressure, while it can be more than forty times in regime II.

A robust and accurate surrogate method for monitoring the frequency and duration of combined sewer overflows.

Discharges of untreated wastewater from combined sewer overflows (CSOs) can affect hydraulic stress and have significant environmental impacts on receiving water bodies. Common flow rate and water level sensors for monitoring of CSO events are expensive in terms of investment costs, installation, operation and maintenance. This paper presents a novel surrogate method to detect CSO events by using two low-cost temperature sensors. The novelty is the experimental setup for installation of temperature sensors in CSO structures and an algorithm developed to automatically calculate the duration of CSO events considering the response time of the system. The occurrence and duration of CSO events is computed based on the convergence of the two temperature signals. The method was tested under field conditions in a CSO structure, and the results were compared to the information gathered from a parallel installed flow sensor. The application of two temperature sensors installed inside a CSO structure was proven to be robust and accurate for the automatic detection of the occurrence and duration of CSO events. Within the 7-month test phase, 100% of the 20 CSO events could be detected without false detections. The accuracy of detecting the start and end of the CSO events was 2 min in comparison to the flow sensor.

Effect of Doppler flow meter position on discharge measurement in surcharged manholes.

Determining the proper installation location of flow meters is important for accurate measurement of discharge in sewer systems. In this study, flow field and flow regimes in two types of manholes under surcharged flow were investigated using a commercial computational fluid dynamics (CFD) code. The error in measuring the flow discharge using a Doppler flow meter (based on the velocity in a Doppler beam) was then estimated. The values of the corrective coefficient were obtained for the Doppler flow meter at different locations under various conditions. Suggestions for selecting installation positions are provided.

Virtual reality in urban water management: communicating urban flooding with particle-based CFD simulations.

For communicating urban flood risk to authorities and the public, a realistic three-dimensional visual display is frequently more suitable than detailed flood maps. Virtual reality could also serve to plan short-term flooding interventions. We introduce here an alternative approach for simulating three-dimensional flooding dynamics in large- and small-scale urban scenes by reaching out to computer graphics. This approach, denoted 'particle in cell', is a particle-based CFD method that is used to predict physically plausible results instead of accurate flow dynamics. We exemplify the approach for the real flooding event in July 2016 in Innsbruck.

Simulation of the hydraulic performance of highway filter drains through laboratory models and stormwater management tools.

Road drainage is one of the most relevant assets in transport infrastructure due to its inherent influence on traffic management and road safety. Highway filter drains (HFDs), also known as "French Drains", are the main drainage system currently in use in the UK, throughout 7000 km of its strategic road network. Despite being a widespread technique across the whole country, little research has been completed on their design considerations and their subsequent impact on their hydraulic performance, representing a gap in the field. Laboratory experiments have been proven to be a reliable indicator for the simulation of the hydraulic performance of stormwater best management practices (BMPs). In addition to this, stormwater management tools (SMT) have been preferentially chosen as a design tool for BMPs by practitioners from all over the world. In this context, this research aims to investigate the hydraulic performance of HFDs by comparing the results from laboratory simulation and two widely used SMT such as the US EPA's stormwater management model (SWMM) and MicroDrainage®. Statistical analyses were applied to a series of rainfall scenarios simulated, showing a high level of accuracy between the results obtained in laboratory and using SMT as indicated by the high and low values of the Nash-Sutcliffe and R 2 coefficients and root-mean-square error (RMSE) reached, which validated the usefulness of SMT to determine the hydraulic performance of HFDs.

Effect of a 1-Piece Drainable Pouch on Incontinence-Associated Dermatitis in Intensive Care Unit Patients With Fecal Incontinence: A Comparison Cohort Study.

PURPOSE: The purpose of this study was to compare the effect of a 1-piece drainable pouch to standard care on occurrences of incontinence-associated dermatitis (IAD) in intensive care unit (ICU) patients with fecal incontinence (FI). DESIGN: Nonrandomized comparison cohort (quasi-experimental) study. METHODS: Sixty-two bedridden patients with FI and indwelling urinary catheters in the ICU of the Shunde Hospital, Southern Medical University, Foshan, China, participated in the study. Thirty-one were assigned to the control group (standard IAD preventive care alone) and 31 to the intervention group (standard IAD preventive care plus application of a 1-piece drainable pouch). Stool consistency was evaluated via the Bristol Stool Scale. Trained nurses assessed the status of IAD using the Incontinence-Associated Dermatitis Intervention Tool. The incidence of IAD and the perianal skin status were investigated over a 7-day period. RESULTS: Participants in the experimental group had fewer IAD occurrences than participants in the control group (12.9% vs 41.9%, P < .05). Occurrences of IAD in the perianal were also significantly lower in the experimental group than in the control group (χ = 7.884, P < .05). CONCLUSION: Applying a 1-piece drainable pouch may reduce occurrences of IAD in ICU patients with FI compared with the patients receiving standard IAD preventive care.

Street floods in Metro Manila and possible solutions.

Urban floods from thunderstorms cause severe problems in Metro Manila due to road traffic. Using Light Detection and Ranging (LiDAR)-derived topography, flood simulations and anecdotal reports, the root of surface flood problems in Metro Manila is identified. Majority of flood-prone areas are along the intersection of creeks and streets located in topographic lows. When creeks overflow or when rapidly accumulated street flood does not drain fast enough to the nearest stream channel, the intersecting road also gets flooded. Possible solutions include the elevation of roads or construction of well-designed drainage structures leading to the creeks. Proposed solutions to the flood problem of Metro Manila may avoid paralyzing traffic problems due to short-lived rain events, which according to Japan International Cooperation Agency (JICA) cost the Philippine economy 2.4billionpesos/day.

Urban Stormwater Characterization, Control, and Treatment.

A summary of 246 studies published in 2016 on topics related to the characterization and management of urban stormwater runoff is presented in the following review. The review is structured along three major topical areas: (1) general characterization of stormwater quantity and quality; (2) engineered systems for stormwater control and treatment, including erosion and sediment control practices, constructed stormwater ponds and wetlands, bioretention, permeable pavement, greenroofs, and rainwater harvesting and (3) watershedscale application of stormwater treatment and control practices. Common research themes and needs highlighted throughout this review include efforts to better understand stormwater transport and treatment mechanisms and their representation in models, advancements to optimize the design of stormwater control measures to meet specific hydrologic and/or water quality targets, and increasing understanding of the biophysical and social factors that influence watershed-scale implementation of low impact development and other stormwater control measures.