Abstract
To optimize the bioretention mixed fillers with better removal of phosphorus, this paper studies the adsorption characteristics of single filler and modified mixed filler through static adsorption experiments, and adopts the dynamical mini-column experiments to examine the adsorption capacities of the soil and modified mixed fillers. Results show that, in the static adsorption experiments, both water treatment residual (WTR) and fly ash exhibit good adsorption capacity when used as a single filler and modifier. Adsorption capacity increases with increasing WTR and fly ash dosage in the mixed filler. The modified mixed filler with WTR exerts a clear effect in the dynamic adsorption experiment, which is unsaturated when influent phosphorus concentration is 1 mg/L and inflow amount is equivalent to 15 years of precipitation. The adsorption capacity of WTR is 3.5–4.5 times that of other mixed fillers. Fly ash as a modifier shows a poor dynamic adsorption effect and thus must be continuously studied. In this study, WTR is recommended as a bioretention phosphorus removal additive. In engineering applications, the amount of WTR added can be controlled within 5–10% (by mass) according to influent phosphorus concentration.
Highlights
IntroductionWith the accelerating pace of urbanization, the structure and function of the city’s underlying surface have gradually changed, and numerous water areas, forest lands, grasslands, and farmlands have been replaced by impervious cement, asphalt, and other impermeable materials
With the accelerating pace of urbanization, the structure and function of the city’s underlying surface have gradually changed, and numerous water areas, forest lands, grasslands, and farmlands have been replaced by impervious cement, asphalt, and other impermeable materials.This phenomenon has led to a decrease in water permeability of the underlying surface of the city, followed by an increase in surface runoff, a reduction in confluence time, and an increase in flood peaks [1]
After completion of the modified filler dynamic adsorption experiment, the peristaltic pump was controlled to run in the reverse direction, residual water was drained, the influent water was replaced with distilled water, the rainfall intensity (2.11 mL/min) was returned during the 3a return period, and the operation continued for 4.24 days, which is equivalent to five years of rainfall
Summary
With the accelerating pace of urbanization, the structure and function of the city’s underlying surface have gradually changed, and numerous water areas, forest lands, grasslands, and farmlands have been replaced by impervious cement, asphalt, and other impermeable materials. Bioretention is an efficient and economical rainwater treatment in the Low Impact Development (LID) management system This treatment considerably affects runoff and peak reduction and effectively and steadily removes the pollutants, such as suspended matter, heavy metal, oil, and oil and pathogenic bacteria in urban surface runoff [10,11,12]; the removal efficiency of nutrient elements such as phosphorus exhibits a certain fluctuation [13,14,15], in which the background value of phosphorus and the desorption of soluble phosphorus adsorbed at the later stages are the main causes of its destabilization. The adsorption capacity of the bioretention fillers after modifier addition was studied using the state adsorption experiment, which provides a reference for the ratio of phosphorus retention material in the biological field of Feng Xi New city
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