Hydrologic and Water Quality Evaluation of a Permeable Pavement and Biofiltration Device in Series

Abstract

Two stormwater control measures (SCMs) installed in series were monitored for their individual impact on the hydrology and water quality of stormwater runoff from a 0.08-hectare watershed in Fayetteville, North Carolina, for 22 months. Runoff was first treated by permeable interlocking concrete pavement (PICP), the underdrain of which discharged into a proprietary box filter (Filterra ® biofiltration) which combined high-flow-engineered media with modest biological treatment from a planted tree. Due to a deteriorating contributing drainage area and high ratio of impervious area to permeable pavement area (2.6:1), clogging of the permeable pavement surface caused an estimated 38% of stormwater to bypass as surface runoff. Fifty-six percent of runoff volume infiltrated underlying soils, and the remaining 6% exited the Filterra ® as treated effluent; the hydrologic benefit of the Filterra ® was minimal, as expected. Primary treatment through the PICP significantly reduced event mean concentrations (EMCs) of total suspended solids (TSS), total phosphorus (TP), total nitrogen (TN), and total Kjeldahl nitrogen (TKN) but contributed to a significant increase in nitrate/nitrite (NO 2,3-N) concentrations. Secondary treatment by the Filterra ® further reduced TSS and TP concentrations and supplemented nitrogen removal such that treatment provided by the overall system was as follows: TSS (removal efficiency (RE): 96%), TP (RE: 75%), TN (RE: 42%), and TKN (RE: 51%). EMCs remained unchanged for NO 2,3-N. Despite EMC reductions, additional load reduction due to the Filterra ® was modest (less than 2%). This was because (1) a majority of pollutant load was removed via PICP exfiltration losses, and (2) nearly all of the export load was from untreated surface runoff, which bypassed the Filterra ® , and therefore the manufactured device never had the opportunity to treat it. Cumulative load reductions (based only upon events with samples collected at each sampling location) were 69%, 60%, and 41% for TSS, TP, and TN, respectively. When surface runoff was excluded, load reductions increased to over 96%; lower run-on ratios (which would reduce clogging rate) and/or increased maintenance frequency might have improved pollutant load removal.

Rainfall Runoff Mitigation by Retrofitted Permeable Pavement in an Urban Area

“…There is also a need to select the best materials for the subgrade of the PICP system so that it can decrease the more rainfall runoff as well as to enhance the infiltrated water quality. In the future, to enhance the PCIP system in terms of rainfall runoff quantity and quality performance, it is necessary to combine the PICP system with other suited LID facilities [26] in such a way that it can provide multiple benefits (hydrological + water quality improvements) in the urban area.…”

“…Infiltration of the underlying subgrade soil was the main factor for the rainfall runoff reduction through the PICP. Every rain event, hydrological properties for the inflow (INFLOW), PICP outflow (OUTFLOW) after infiltration the outflow runoff and peak flow reduction were calculated by using the volume reduction (VR, Equation (1) [26]), and the peak flow reduction (QR, Equation (2) [26]) as shown below.…”

Optimal Planning of Low-Impact Development for TSS Control in the Upper Area of the Cau Bay River Basin, Vietnam

“…Hatt et al [8] investigated the TSS removal efficiency of three field-scale biofiltration systems in two different climates, and concluded that TSS was effectively removed with load reductions generally in excess of more than 90%. Braswell et al [9] indicated that the TSS removal efficiency of a series consisting of permeable interlocking concrete pavement and a proprietary box filter reached 96%. Abdollahian and Kazemi [10] pointed out that the TSS removal efficiency of permeable pavement was in the range of 47-69%.…”

An Analogue Experiment on Pervious Concrete Subject to Dust Fall Blocking

“…Urban areas are constantly looking for ways to reduce runoff, and subsequently the pollutants. Proposed solutions, which are generally termed storm water control measures, include bio retention, swales, storm water wetlands and permeable pavements and among these; permeable structures are the most favoured [5]. This is because of their multi-purpose functions such car parking.…”