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TREATMENT OF STORMWATER BY NATURAL ORGANIC MATERIALS
Citation:
Wojtenko**, I, A. B. Ray*, AND R Field*. TREATMENT OF STORMWATER BY NATURAL ORGANIC MATERIALS. Presented at ASCE Urban Water Resources Research Council/Engineering Foundation Conf, Snowmass, CO, August 19 - 24, 2001.
Impact/Purpose:
To inform the public.
Description:
The overall objective of this study was to evaluate the feasibility of using low-cost natural filter materials for stormwater (SW) treatment. Generic mulch, pine bark mulch, and processed jute were evaluated for metal and organic pollutant removal from actual SW samples collected from a "hot-spot" (commercial parking lot) site in NJ. The retention and release behavior of pollutants in different filter materials was evaluated using a specially constructed bench-scale filtration apparatus which allowed for the simultaneous testing of up to ten different media conditions. SW flowrates (fluxes) through the individual columns as well as the sorption capacity of each filter medium were studied under a wide variety of conditions. The benefits of combining mulch or jute with sand to improve the hydraulic properties (filter flux), removal ability, and cumulative capacity of the filter for a specific pollutant were evaluated. Initial tests were performed to evaluate the basic performance of the mulch and jute materials. This performance was compared with the performance of the materials whose particle size was altered. This alteration of the size of particles within the filter materials was done by separating the mulch materials into "coarse" and "fine" fractions. Jute fiber was cut into significantly smaller pieces. The effectiveness of the filtration process was found to be dependent upon the physical characteristics of the filter media. Both the sand content and the particle size of the filter media affected flowrates of SW and their pollutant removal capacities. Copper and benzo(a)pyrene were used as surrogates for heavy metals and organics, respectively. Removals as high as 100% of copper were observed for all of the combinations of sand with mulch or jute. The removal of benzy(a)pyrene was found to be dependent upon the media to sand ratios and ranged from 68-94%. No significant amount of either pollutant was released from any of the media when the columns were flushed with distilled water. Both mulch and jute appear to be suitable filter materials. Additional investigations, however, are necessary to evaluate the practicality of field applications of mulch or jute in the treatment of SW runoff.