Sewer Channel Research Articles

Advancing Urban Wastewater Management: Optimizing Sewer Performance through Innovative Material Selection for the Armlet with a Wet Circuit Measurement System

Rainwater infiltration presents substantial challenges for urban wastewater management systems. This article delves into enhancing the quality of wastewater systems by proposing a novel device designed to tackle this issue comprehensively. The focal point of our research revolves around the conceptualization, construction, rigorous testing, and the potential multifaceted applications of this innovative wastewater device. Our study is dedicated to assessing the viability of a cutting-edge apparatus that empowers municipal entities in swiftly identifying rainwater ingress points within channels during precipitation events. Our findings vividly showcase the device’s remarkable capability to directly measure moisture levels along the channel’s path, eliminating the arduous need for manual data input, extensive data collection, and intricate water analysis procedures. To ensure the seamless flow of both sewage and water within the sewer channel, the use of a relatively slender strap is conventionally favored. However, factoring in the requisite structural robustness, we recommend a minimum thickness of 4 mm for 3D printing applications. For instances where maintaining the channel’s cross-sectional area integrity is paramount, opting for an armlet with a wet circuit measurement thickness of up to 7 mm is vital. In the realm of material selection, our investigation advocates for the utilization of PC/ABS (polycarbonate/Acrylonitrile Butadiene Styrene), ABS, ASA (Acrylonitrile Styrene Acrylate), or HIPS (High Impact Polystyrene) for strap housing. For sewer diameters surpassing 315 mm, the application of thin-walled PVC (Poly Vinyl Chloride) emerges as a practical recommendation. Notably, the incorporation of PVC flat bars is discouraged, as their presence might potentially hinder the fluidity of sewage flow, thereby compromising the precision of wet circuit measurements. The pivotal innovation lies in the armlet with a wet circuit measurement system, harboring immense potential for broad-scale integration across municipal facilities. This solution emerges as a streamlined and efficient strategy, offering a comprehensive avenue for continuously monitoring, fine-tuning, and optimizing the structural soundness and operational efficacy of sewer systems.

Numerical Investigation on the Evaluation of the Sediment Retention Efficiency of Invert Traps in an Open Rectangular Combined Sewer Channel

Numerical Investigation on the Evaluation of the Sediment Retention Efficiency of Invert Traps in an Open Rectangular Combined Sewer Channel

A model for non-uniform sediment transport induced by flushing in sewer channels

A novel unsteady flow numerical model for the simulation of the transport of non-uniform non-cohesive sediment mixtures (SM) during flushing operation in sewers is presented in this paper. The model was applied to the case of a flush experimental test that was recently carried out in a combined sewer channel of the sewer system of Paris city that exhibits depositional problems due to relatively coarse sediments. The model output was compared to the results of the field experiments as well as to those obtained with a model for the transport of uniform sediments (US). The model for SM provided a reliable interpretation of the selective transport of the sediments deposited in the channel bed as induced by the flush. The comparison showed the model for SM to provide an enhanced description of the erosional effects of the flush on the deposits, including improved evaluation of the volume of sediments flushed out of the experimental channel in the field.

More accurate prediction of the complex velocity field in sewers based on uncertainty analysis using extreme learning machine technique

ABSTRACT In this study, we present a novel procedure to simulate the velocity distribution of a narrow sewer channel using a combination of a simple and accurate machine learning tool, namely, extreme learning machine (ELM). We also examined the uncertainty associated with the model in simulating the more complex velocity–depth profiles in narrow sewer channels using the 95 percent predicted uncertainties (95PPU%) and d-factor indices. The data for estimating the velocity distribution were measured at a municipal sewer pipe in France. We measured the velocity distribution in a cross section for 10 different depths with width-to-depth ratios ranging from 1.75 to 2.44. The new ELM model has the 95PPU% and the d-factor of 53.25% and 0.36, respectively, in the training dataset and 84.93% and 1.9 in the test dataset. The error analysis confirmed that ELM model outperforms all existing models for predicting velocity profile in narrow sewers. The proposed method is compared with existing methods, and it appears that in addition to being simpler and having no limitations, this model exhibits better performance as well (root mean square error (RMSE) = 0.04 and mean absolute percentage error (MAPE) = 3.56%).

A field experiment to evaluate the cleaning performance of sewer flushing on non-uniform sediment deposits

The results of a field experiment to evaluate the scouring effect of a single flush operation in a compound-section sewer channel in Paris, France, are presented in this paper. Full monitoring of the experiment allowed identifying flush-related transport/deposition key processes playing a role on the evolution of the deposited sediments. Overall, the flush was able to scour sediments accumulated over the channel invert up to a significant distance from the gate. The analysis of the results revealed that the flush had a different impact on the various sediments present in the bed mixtures, with most of the eroded volume including sediment particles smaller than the median grain size.

Transformation of AgCl nanoparticles in a sewer system — A field study

Silver nanoparticles (Ag-NP) are increasingly used in consumer products and their release during the use phase may negatively affect aquatic ecosystems. Research efforts, so far, have mainly addressed the application and use of metallic Ag(0)-NP. However, as shown by recent studies on the release of Ag from textiles, other forms of Ag, especially silver chloride (AgCl), are released in much larger quantities than metallic Ag(0). In this field study, we report the release of AgCl-NP from a point source (industrial laundry that applied AgCl-NP during a piloting phase over a period of several months to protect textiles from bacterial regrowth) to the public sewer system and investigate the transformation of Ag during its transport in the sewer system and in the municipal wastewater treatment plant (WWTP). During the study period, the laundry discharged ~85g of Ag per day, which dominated the Ag loads in the sewer system from the respective catchment (72–95%) and the Ag in the digested WWTP sludge (67%). Combined results from electron microscopy and X-ray absorption spectroscopy revealed that the Ag discharged from the laundry to the sewer consisted of about one third AgCl and two thirds Ag2S, both forms primarily occurring as nanoparticles with diameters<100nm. During the 800m transport in the sewer channel to the nearby WWTP, corresponding to a travel time of ~30min, the remaining AgCl was transformed into nanoparticulate Ag2S. Ag2S-NP also dominated the Ag speciation in the digested sludge. In line with results from earlier studies, the very low Ag concentrations measured in the effluent of the WWTP (<0.5μgL−1) confirmed the very high removal efficiency of Ag from the wastewater stream (>95%).

Fate and transformation of silver nanoparticles in urban wastewater systems

Discharge of silver nanoparticles (Ag-NP) from textiles and cosmetics, todays major application areas for metallic Ag-NP, into wastewater is inevitable. Transformation and removal processes in sewers and wastewater treatment plants (WWTP) will determine the impact of Ag-NP on aquatic and terrestrial environments, via the effluents of the WWTP and via the use of digested sludge as fertilizer. We thus conducted experiments addressing the behavior of Ag-NP in sewers and in WWTP.We spiked Ag-NP to a 5 km long main trunk sewer and collected 40 wastewater samples after 500 m, 2400 m and 5000 m each according to the expected travel times of the Ag-NP. Excellent mass closure of the Ag derived by multiplying the measured Ag concentrations times the volumetric flow rates indicate an efficient transport of the Ag-NP without substantial losses to the sewer biofilm. Ag-NP reacted with raw wastewater in batch experiments were sulfidized to roughly 15% after 5 h reaction time as revealed by X-ray absorption spectroscopy (XAS). However, acid volatile sulfide (AVS) concentrations were substantially higher in the sewer channel (100 μM) compared to the batch experiments (3 μM; still sufficient to sulfidize spiked 2 μM Ag) possibly resulting in a higher degree of sulfidation in the sewer channel. We further investigated the removal efficiency of 10 nm and 100 nm Ag- and gold (Au)-NP coated with citrate or polyvinylpyrrolidone in activated sludge batch experiments. We obtained very high removal efficiencies (∼99%) irrespective of size and coating for Ag- and Au-NP, the latter confirming that the particle type was of minor importance with respect to the degree of NP removal. We observed a strong size dependence of the sulfidation kinetics. We conclude that Ag-NP discharged to the wastewater stream will become sulfidized to various degrees in the sewer system and are efficiently transported to the WWTP. The sulfidation of the Ag-NP will continue in the WWTP, but primarily depending on the size the Ag-NP, may not be complete. Very high removal efficiencies in the WWTP will divert most of the Ag-NP mass flow to the digester and only a small fraction of the Ag will be released to surface waters.

Field performance of self-siphon sediment cleansing set for sediment removal in deep CSO chamber

This paper presents a study of the self-siphon sediment cleansing set (SSCS), a system designed to remove sediment from the deep combined sewer overflow (CSO) chamber during dry-weather periods. In order to get a better understanding of the sediment removal effectiveness and operational conditions of the SSCS system, we carried out a full-scale field study and comparison analysis on the sediment depth changes in the deep CSO chambers under the conditions with and without the SSCS. The field investigation results demonstrated that the SSCS drains the dry-weather flow that accumulated for 50-57 min from the sewer channel to the intercepting system in about 10 min. It is estimated that the bed shear stress in the CSO chamber and sewer channel is improved almost 25 times on average. The SSCS acts to remove the near bed solids with high pollution load efficiently. Moreover, it cleans up not only the new sediment layer but also part of the previously accumulated sediment.

A River Runs Through It: Application of an Integrated Combined Sewer and Stream Channel Model to Support a Sustainable CSO Control Plan

A River Runs Through It: Application of an Integrated Combined Sewer and Stream Channel Model to Support a Sustainable CSO Control Plan

Migration and transfer of chromium in soil-vegetable system and associated health risks in vicinity of ferro-alloy manufactory

Study was carried out to analyze the distribution and migration patterns, soil-to-plant transfer and potential health risks of chromium in soil-vegetable system in areas near a ferro-alloy manufactory in Hunan province. The results show that soils near sewer outlet, sewer channel and in control area are averaged 2 239.5, 995.33 and 104.9 mg/kg, respectively. The total Cr has a relative accumulation in soil depth of 200-400 mm near the sewer outlet, mainly enriches in the surface layer (0-200 mm) near the sewer channel and decreases gradually in unpolluted soils. The differential concentration level of enrichment between layers is little. The results also indicate that the three vegetables of celery, lettuce and Chinese cabbage are able to convert the potentially toxic Cr (VI) species into the non-toxic Cr (III) species, and the chromium contents in the edible parts of the vegetables are averaged 11.95 mg/kg. The transfer factors of the three vegetables follow the order: Chinese cabbage > lettuce > celery. The estimated total daily intake of chromium substantially exceeds the dietary allowable value, which may pose health risks to local population.

Spatial distribution of chromium in soils contaminated by chromium-containing slag

To evaluate the metal chromium (Cr) contamination of soil at a chromium-containing slag site by ferrochromium production, the contaminated sites, under slag heap, in the vicinity of slag heap and arable soils near the outlet of sewer channel, and unpolluted site 5 km away from one ferroalloy plant in Hunan Province, China, were selected. The concentrations of total Cr and water soluble Cr in bulk soil samples and profile depth samples were determined. The results show that the soils in the vicinity of slag heap have the highest total Cr content followed by the soils under the slag heap and near the outlet of sewer channel of the factory. The mean concentrations of total Cr in the top soils at above three contaminated locations exceed the critical level of Secondary Environmental Quality Standard for Soil in China by 3.5, 5.4 and 1.8 times. In most Cr polluted soils, total Cr has a relative accumulation in soil depth of 40–60 cm, but this trend is not found in unpolluted soils. The average concentrations of water soluble Cr (VI) in top soils under slag heap and in the vicinity of slag heap are 176.9 times and 52.7 times higher than that in the uncontaminated soils, respectively. However, water soluble Cr (VI) contents in soils near sewer channel are all low and the values are close to that in the uncontaminated soils. Although water soluble Cr (VI) content in soil profiles decreases with soil depths, it in soils under slag heap maintains a high level even at a depth of 100–150 cm. The results imply that the transportation of Cr (VI) can result in a potential risk of groundwater system in this area.

A fast hydraulic numerical model for large sewer collection systems

A numerical model for simulating flows in either sewer or open channel systems is presented. The physical phenomenon of one-dimensional unsteady flow described by the St. Venant flow equations is examined for a more accurate and stable solution under a wide variety of physical conditions experienced in sewer or channel systems. A sparse matrix technique associated with a staggered grid numerical system is developed to solve the flow equations implicitly. Use of this sparse matrix technique leads to a substantial reduction in the order of the sparse matrix and the requirement of computer memory. The model is established without any omission of the terms in the St. Venant equations under the flow and depth conditions experienced in the sewer or open channel systems. The application of the model to a large complex looped sewer system shows that the model achieves a significant improvement in computational speed compared with the USEPA EXTRAN model and can still maintain similar accuracy. The model is especially suitable for real time control purposes since the simulation time of the model is almost negligible in comparison to the real time physical process even for a large looped system. The simulation also shows that base flow is practically not required for the model when the system is dry.

Control of VOC emissions from sewers: a multi-parameter assessment

A computational model is described which facilitates multi-parameter analyses of VOC emissions from sewers. The model, CORAL+, was used to simulate more than 3.6 million combinations of five system parameters, including sewer channel slope, relative depth of flow, pipe diameter, Henry's law coefficient, and headspace ventilation rate. Lumped results were analyzed using a graphical frequency array approach to identify parameter combinations that lead to potential VOC emission hot spots. Additional modeling was completed to provide examples of passive VOC emission reductions through control of system parameters. Computational results provide information related to combinations of parameters that either never or always lead to potential VOC emission hot spots, independent of the values associated with all other parameters. Results indicate that the common assumption of infinite ventilation can lead to significant overestimates of VOC emissions, and that controlled headspace ventilation can be used to reduce VOC emissions by an order of magnitude or more. This may be of significance with respect to reducing emissions from on-site industrial sewers by maintaining biodegradable VOCs in solution prior to discharge to a downstream biological treatment system. Results also suggest that VOC emissions are highly sensitive to wastewater flow rate, increasing as flow rate decreases. This is an important observation with respect to the fact that some municipalities encourage industrial discharges at night for purposes of flow equalization.

Control of VOC emissions from sewers: A multi-parameter assessment

A computational model is described which facilitates multi-parameter analyses of VOC emissions from sewers. The model, CORAL+, was used to simulate more than 3.6 million combinations of five system parameters, including sewer channel slope, relative depth of flow, pipe diameter, Henry's law coefficient. and headspace ventilation rate. Lumped results were analyzed using a graphical frequency array approach to identify parameter combinations that lead to potential VOC emission hot spots. Additional modeling was completed to provide examples of passive VOC emission reductions through control of system parameters. Computational results provide information related to combinations of parameters that either never or always lead to potential VOC emission hot spots, independent of the values associated with all other parameters. Results indicate that the common assumption of infinite ventilation can lead to significant overestimates of VOC emissions, and that controlled beadspace ventilation can be used to reduce VOC emissions by an order of magnitude or more. This may be of significance with respect to reducing emissions from on-site industrial sewers by maintaining biodegradable VOCs m solution prior to discharge to a downstream biotogtcal treatment system. Results also suggest that VOC emissions are highly sensitive to wastewater flow rate, increasing as flow rate decreases. This is an important observation with respect to the fact that some municipalities encourage industrial discharges at night for purposes of flow equalization.