Heavy metals from urban stormwater runoff are important sources of surface water pollutants. Sand, zeolite, sandy loam, and quartz-sand were separately mixed with lignin to form four bioretention media mixes for experimental study using synthetic stormwater runoff. The average removal efficiencies of four heavy metals (Cu, Zn, Cd, and Pb) by the four media mixes were all better than 97% at the optimum pH of 6.05 (ranging from 6 to 8) and the seven-day rainfall-event interval. The influence of the influent concentration and the rainfall-event interval on the removal efficiency of heavy metals by the four media mixes was not significant, but the variation of the removal efficiencies at the four-day rainfall-event interval was large. Under acidic conditions, there was a certain heavy metal dissolution in the four reactors, but the effect on the removal efficiency was minor. Heavy metals were present in the media mainly in the form of the residual fraction (>50%). The accumulation of Cu, Zn, and Cd in the surface planting-soil layer (same humus and sandy-loam mixture for all reactors) was significantly larger than the accumulation at deeper depths but not for Pb. Overall, the heavy metal removal efficiencies by the four media mixes were not significantly different, and the choice of the planting-soil layer can become the control factor of heavy metal removal.

The development of urbanization results in a marked increase in impervious areas, destroying the natural geological features and hydrological properties of the urban developed area. This may cause high risk of flooding, runoff pollution, and water shortages. An integral method is proposed to realize the multi-goals management of stormwater runoff, which called sponge city construction, and taken a pilot area of sponge city construction as an example to evaluate the effect of sponge city construction on stormwater quantity control via InfoWorks Integrated Catchment Model (ICM) model. The results showed that the annual total rainfall volume capture ratio is 77.4%, the drainage pipeline capacity was improved and flooding risk was decreased effectively. The high-risk flooding area was reduced about 44.76% of 50-year return period rainfall event with rainfall duration of 24 h. So, sponge city construction provides a novel method for the stormwater integral management.

An updated two-dimensional flow simulation program, FullSWOF-ZG, which fully (Full) solves shallow water (SW) equations for overland flow (OF) and includes submodules modeling infiltration by zones (Z) and flow interception by grate-inlet (G), was tested with 20 locally depressed curb inlets to validate the inlet efficiency (E_ci), and with 80 undepressed curb inlets to validate the inlet lengths (L_T) for 100% interception. Previous curb inlet equations were based on certain theoretical approximations and limited experimental data. In this study, 1000 road-curb inlet modeling cases from the combinations of 10 longitudinal slopes (S₀, 0.1–1%), 10 cross slopes (S_x, 1.5–6%), and 10 upstream inflows (Q_in, 6–24 L/s) were established and modeled to determine L_T. The second 1000 modeling cases with the same 10 S₀ and 10 S_x and 10 curb inlet lengths (L_ci, 0.15–1.5 m) were established to determine E_ci. The L_T and E_ci regression equations were developed as a function of input parameters (S₀, S_x, and Q_in) and L_ci/L_T with the multiple linear regression method, respectively. Newly developed regression equations were applied to 10,000 inlet design cases (10 S₀, 10 S_x, 10 Q_in, and 10 L_ci combinations) and comprehensively compared with three equations in previous studies. The 100% intercepted gutter flow (Q_g100) equations were derived, and over-prediction of Q_g100 from previous methods was strongly correlated to smaller S₀. Newly developed equations gave more accurate estimations of L_T and E_ci over a wide range of input parameters. These equations can be applied to designing urban drainage and road bioretention facilities, since they were developed using a large number of simulation runs with diverse input parameters, but previous methods often overpredict the gutter flow of total interception when the longitudinal slope S₀ is small.