Evaluation of Retention Pond and Constructed Wetland BMPs for Treating Particulate-bound Heavy Metals in Urban Stormwater Runoff

The pollutants in urban stormwater runoff, which lead to non-point source contamination of water environment around cities, are of great concern. Lignocellulose fiber filters have potential to treat urban stormwater runoff because they are cheap and environmentally friendly, and can effectively remove particulate pollutants. However, the fiber filters alone cannot sufficiently remove soluble pollutants including heavy metals, nitrogen compounds, and phosphate. In this study, techniques for chemical modification of lignocellulose fiber filter were implemented to enhance the treatment efficiency of soluble pollutants in urban stormwater runoff. Using these chemically modified fiber filters together with polymer filter media, a new treatment device was examined to control the pollutants in first flush of stormwater. The results indicated that the filters incorporated into the treatment unit allow the control of urban stormwater runoff with minimal cost and high efficiency.

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Removal of Heavy Metals, Nutrients and Sediment by a Stormwater Treatment Train; a Southeast Queensland, Medium-Density Residential Case Study

10.20944/preprints201807.0322.v1 ◽

2018 ◽

Author(s):

Darren Drapper ◽

Andy Hornbuckle

Keyword(s):

Heavy Metals ◽

Stormwater Runoff ◽

Medium Density ◽

Stormwater Treatment ◽

Urban Stormwater ◽

Total Copper ◽

Treatment Train ◽

The Media ◽

Urban Stormwater Runoff ◽

Southeast Queensland

Urban stormwater runoff from a medium-density residential development in southeast Queensland has been monitored in the field since November 2013. A treatment train installed on the site includes rainwater tanks collecting roofwater, 200-micron mesh baskets installed in grated gully pits and two 850 mm high media filtration cartridges installed in an underground 4 m3 vault. A monitoring protocol developed by research partners, Queensland University of Technology (QUT), guided the monitoring process over a 4.5-year period. Heavy metals were included in the list of analytes during the monitoring period as the catchment is within 1 km of the environmentally-sensitive Moreton Bay, Queensland. Removal efficiencies observed at this site for the regulated pollutants; total suspended solids (TSS), total phosphorus (TP) and total nitrogen (TN) for the pit baskets were 61%, 28% and 45% respectively. The cartridge filters removed 78% TSS, 59% TP, 42% TN, 40% total copper and 51% total zinc. As the measured influent concentrations to the cartridge filters were low when compared to industry guidelines, the dataset was merged with international field results for TSS (n=39) and TP (n=32) but truncated within anticipated guideline levels. The combined dataset for the media filter demonstrates performance at 89% TSS, 66% TP and 42% TN. The total gross pollutant generation rate from the medium-density residential catchment was observed to be 0.24 m3/Ha/year, with a corresponding air-dried mass of 142.5 kg/Ha/year. Less than 2% of the gross pollutant mass was anthropogenic. The findings of this research suggest that the treatment train, and in particular the media filter, holds promise for the removal of total copper and total zinc, in addition to TSS, TP and TN, from urban stormwater runoff. Based on a maximum, low risk trigger TN concentration of 1.5 mg/L, the field test data from 4.5 years of operation and standard maintenance, suggests a 5.5-year replacement interval for the media filters.

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