Jianghua Yu

Performance evaluation of various stormwater best management practices.

Many best management practices have been developed and implemented to treat the nonpoint source pollution of the aquatic environment in Koreas four major river basins. The performance and cost of these facilities were evaluated and compared using broad categories, including grassed swales, constructed wetlands, vegetated filter strips, hydrodynamic separators, media filters, and infiltration trenches, based on the monitoring and maintenance work undertaken between 2005 and 2012. Constructed wetlands, media filters, and infiltration trenches generally performed better in removing pollutants than other types of facilities, while media filters were the most expensive factor in terms of construction and operational costs. In addition, constructed wetlands incurred the least operational cost, as well as helping to control the quantity of runoff. This illustrates that a high cost facility does not necessarily give a better performance. A slightly more expensive facility, such as wetland, could prove to be a reasonably effective treatment. The selection of the most appropriate treatment for stormwater runoff should be based on an overall analysis of performance and cost.

Removal of non-point pollutants from bridge runoff by a hydrocyclone using natural water head

A hydrocyclone using natural water head provided by bridge was operated for the treatment of stormwater runoff. The hydrocyclone was automatically controlled using electronic valve which is connected to a pressure meter. Normally the hydrocyclone was open during dry days, but it was closed after the capture of the first flush. The results indicated that the average pressure and the flow rate were directly affected by the rainfall intensity. The pressure head was more than 2 m when the rainfall intensity was above 5 mm·h−1. The percentage volume of underflow with high solids concentration decreased as the pressure and flow rate increased, but the percentage volume of overflow with almost no solids showed the opposite behavior. The total suspended solids (TSS) concentration ratio between the overflow and inflow (TSSover/TSSin) decreased as a function of the operational pressure, while the corresponding ratio of underflow to inflow (TSSunder/TSSin) increased. The TSS separation efficiency was evaluated based on a mass balance. It ranged from 25% to 99% with the pressure head ranging from 1.4 to 9.7 m, and it was proportional to pressure and flow rate. Normally, the efficiency was more than 50% when the pressure was higher than 2 m. The analysis of the water budget indicated that around 13% of the total runoff was captured by the hydrocyclone as a first flush, and this runoff was separated as underflow and overflow with the respective percentage volumes of 29% and 71%. The pollutants budget was also examined based on a mass balance. The results showed that the percentage of TSS, chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) in underflow were 73%, 59%, 7.6%, and 49%, respectively. Thus, it can be concluded that the hydrocyclone worked well. It separated the first flush as solids-concentrated underflow and solids-absent overflow, and effectively reduced the runoff volume needing further treatment. Finally, four types of optional post treatment design are presented and compared.

Developed Mathematical Equation for Predicting Turbidity Removal Using Synthetic Fiber Filter

A new mathematical model for predicting the contact efficiency of a single collector in the treatment of turbid water is presented in this study. The removal mechanisms applied were interception, diffusion, and sedimentation. In order to obtain the model for the single-collector efficiency, the effect of the density current caused by turbidity and differences in temperature was considered and the impact of multiple-size particles was also included when calculating the respective mechanisms. The sticking coefficient was also calculated, including the effect of the van der Waals attraction energy and electrical double layer forces. The result of the modeling indicated that the predicted efficiency using the developed equation showed good agreement with the experimental values over a wide range of parameters and the increases and decreases in the model performance were simulated very well. The quality of the data was analyzed and this indicated that the experimental work and the developed model showed fairly good agreement.

Model development and application design of fiber mat used for turbid runoff treatment

Performance of a synthetic-fibre mat was investigated for the treatment of high-turbidity runoff. The impact of different operating parameters, such as hydraulics (flow rate and exchange rate), density current due to temperature and turbidity differences, mat conditions (thickness and number) and particle size were studied. The experimental results showed that increasing the mat thickness and number enhanced turbidity removal. The density current showed significant inverse effect on mat performance. Turbidity removal decreased with the increasing flow rate and exchange rate. Particle size also indicated an influence on removal efficiency. Predictive correlations for turbidity removal efficiency and mat design were established using dimensionless groups based on the experiment. The simulation results indicated that the predicted values correlated with the experimental ones significantly. Finally, the application design process was demonstrated.

Operation and performance evaluation of high-speed filter using porous non-woven filamentous fibre for the treatment of turbid water.

ABSTRACT This study was carried out to identify the filter performance of fibre filter module treating high-turbidity water at extremely high filtration rates (1000–2500 m/day). The effects of filter aid chemical (polyaluminium chloride (PAC)), filtration rate and particles size on filter performance were investigated. It was found that PAC was a crucial factor influencing the separation process. Even though the optimum PAC dose for the raw water with turbidity of 50 nephelometric turbidity units (NTU) was 0.5 mg/L, the turbidity removal efficiencies were similar as the raw water turbidity was no more than 50 NTU. As expected, the filter performance was negatively affected by the increased filtration rate. However, the turbidity removal efficiency at an extremely high filtration rate still was amazing and attractive (∼80% at 2500 m/day). Moreover, the D50 and uniformity coefficient of the particles in raw water were not the factors greatly affecting the filter performance. The empirical model for the filter processes of granular filters did not work; therefore, an empirical model towards fibre filters at a high flow rate was suggested, which can be used to predict the treatment performance.

Post-treatment schemes of the outflow from hydrocyclone treating paved-road stormwater runoff

Abstract Results of water quality analysis indicated that the outflow from a hydrocyclone treating road runoff still requires further treatment before discharging into receiving waters. Hence, several treatment designs were presented for the post-treatment of the hydrocyclone outflow (including pollutant-concentrated underflow and pollutant-separated overflow). The design criteria were based on some of the main affecting factors, such as treatment level, land availability, and construction cost. With respect to the determination of the treatment goal, the primary consideration should lie on the water quality requirement. The treatment should normally include both underflow and overflow depending on the required discharged water quality. In terms of the treatment method selection, land availability and construction cost should be considered first in the design. In order to achieve the most appropriate treatment, the design process should be based on the overall analysis of the affecting factors and local c...

Nutrients transport in the bare urban redeveloped soil system during runoff process

ABSTRACT Stormwater pollution in redeveloped soils mixed with construction wastes imposes a serious impact to receiving waters. The transport and distribution of rainfall water and nutrients in the surface-flow and subsurface-flow (including side-flow and down-flow) of bare redeveloped soil runoff system were determined. Results indicated that the flow patterns and pollutants transport of surface-flow were different from those in subsurface-flow. The flowrate of surface-flow increased at the beginning and reached to a stable state, and then disappeared immediately after the rainfall stopped. While the flow rate of subsurface-flow was persisted and decreased gradually artery the rainfall. Most of the pollutants were carried in the surface-flow, which directly results in polluting the surface-receiving waters. And the pollutants distribution percent in side-flow was higher than that in down-flow. Results obtained in this study will provide information for the management of stormwater pollution in the bare redeveloped soil mixed with construction wastes.