Urban stormwater nutrient and metal removal in small-scale green infrastructure: exploring engineered plant biofilter media optimisation

Abstract

The present study evaluated engineered media for plant biofilter optimisation in an unvegetated column experiment to assess the performance of loamy sand, perlite, vermiculite, zeolite and attapulgite media under stormwater conditions enriched with varying nutrients and metals reflecting urban pollutant loads. Sixty columns, 30 unvegetated and 30 Juncus effusus vegetated, were used to test: pollutant removal, infiltration rate, particulate discharge, effluent clarity and plant functional response, over six sampling rounds. All engineered media outperformed conventional loamy sand across criteria, with engineered attapulgite consistently among the best performers. No reportable difference existed in vegetation exposed to different material combinations. For all media, the results show a net removal of NH3-N, PO43−-P, Cd, Cu, Pb and Zn and an increase of NO3−-N, emphasizing the importance of vegetation in biofilters. Growth media supporting increased rate of infiltration whilst maintaining effective remediation performance offers potential for reducing the area required by biofilters, currently recommended at 2% of its catchment area, encouraging the use of small-scale green infrastructure in the urban area. Further research is required to assess the carrying capacity of engineered media in laboratory and field settings, particularly during seasonal change, gauging the substrate's potential moisture availability for root uptake.

Variability of Potential Soil Nitrogen Cycling Rates in Stormwater Bioretention Facilities

“…Targeted design strategies may be capable of increasing synergistic relationships among soil and vegetation structures to create co-benefits. For example increasing vegetation in LID can increase infiltration [68,69], biodiversity [70], and shading, while decreasing nutrient export [71][72][73] and urban heat islands [74].…”

Air Pollutants Removal Using Biofiltration Technique: A Challenge at the Frontiers of Sustainable Environment

“…Aerobic bacteria within biofilter media necessitate nutrients like nitrogen, phosphorus, potassium, sulfur, and minor components, such as additional oxygen and carbon for their development. However, the biofilter media have remaining nutrients; other nutrients are required for the long-term performance of biofilters . Subsequently, nitrogen is the second most significant component in the biomass after carbon; expanding nitrogen to the biofilter media may significantly broaden the biofilter’s performance.…”

“…However, the biofilter media have remaining nutrients; other nutrients are required for the long-term performance of biofilters. 121 Subsequently, nitrogen is the second most significant component in the biomass after carbon; expanding nitrogen to the biofilter media may significantly broaden the biofilter's performance. An investigation of a biofilter processing toluene showed that its performance powerfully depends upon the nitrogen source, and they proposed a stoichiometric mass proportion of 3.8, accepting that microorganisms controlled 13% of their mass as nitrogen and 50% as carbon.…”

Significant antimicrobial-producing vegetation uniquely shapes the stormwater biofilter microbiome with implications for enhanced faecal pathogen inactivation

“…Consequently, most efforts to ameliorate the microbe removal consistency of these systems have focused on design optimisation. While biofilters have been extensively optimised for ecological pollutant removal [13,14], research into their design for enhancing faecal microbe treatment remains comparatively scarce. Limited existing research has focussed on the design and incorporation of a submerged/saturated zone (SZ) [9,15] and filter media (retention-promoting/antimicrobial) for enhanced faecal microbe removal [1,8,11,16,17], with significant advancements having been made.…”