Grantee Research Project Results
Final Report: Low-Cost Active Coating Mulch for Urban Runoff
EPA Grant Number: SU836773Title: Low-Cost Active Coating Mulch for Urban Runoff
Investigators: Deng, Yang
Institution: Montclair State University
EPA Project Officer: Page, Angela
Phase: I
Project Period: September 1, 2016 through August 31, 2017
Project Amount: $15,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2016) RFA Text | Recipients Lists
Research Category: P3 Awards , P3 Challenge Area - Safe and Sustainable Water Resources , Sustainable and Healthy Communities
Objective:
The long-range goal is to develop effective, low-cost, and simple maintenance filter media to support sustainable urban stormwater management. The primary objective of this Phase I project is to synthesize, characterize, and test a novel media, i.e., wood mulch coated with biochar and water treatment residuals (WTRs, a recycled industrial waste) — for retention of multiple contaminants from urban runoff. Our central hypothesis is that WTR and biochar can irreversibly adsorb certain pollutants from urban runoff without any significant leaching, thereby offering a sustainable solution to polluted urban stormwater. To achieve the objective, a 1-year, four-task plan is proposed: Task 1: Synthesis and characterization of low-cost active coating (LAC) wood mulch; Task 2: Batch tests; Task 3: Column tests; and Task 4: Life cycle assessment.
Task 1, LAC mulch was prepared and characterized. In Task 2, beaker tests were performed to obtain key kinetics and thermodynamic parameters and evaluate the performance of LAC mulch for select contaminants in simulated urban runoff. This provided input data for Task 3 column tests that evaluate the best LAC mulch determined from Task 2 in terms of hydraulic properties and treatment efficacy with synthetic and real urban runoff under continuous flow conditions. Finally, the ranges of operational parameters for application are recommended. In Task 4, life cycle analysis is performed. Select target pollutants include: (1) toxic heavy metals, i.e., Cu, Zn, and Pb; (2) phosphorus (P); and (3) organic pollutants, i.e., benzene (a representative priority pollutant).
Summary/Accomplishments (Outputs/Outcomes):
The output includes the new adsorbent coated mulches that have been optimally synthesized with adequately high surface areas. The new filter media has been analyzed using a range of traditional and advanced analytical techniques. Output also includes the adsorption kinetics and isotherm data for WTR and biochar adsorption of target urban runoff pollutants such as heavy metals and phosphate. The pollutant adsorption rates followed a second-order reaction pattern. The adsorption is kinetically controlled. Therefore, the effluent pollutant concentration depends upon contact time of the runoff in a coated mulch filtration bed. The adsorption capacity was fit to the Langmuir adsorption isotherm models. More importantly, we noticed that WTRs and biochar provide complementary adsorption capabilities for multiple urban runoff pollutants. WTRs are effective for the removal of heavy metal cations and phosphate, while biochar readily adsorbs certain synthetic organic pollutants (e.g., benzene).
Outcomes of the Phase I project are factual. Batch and column studies show that application of the modified mulch can directly mitigate urban stormwater pollution with none to minimal leaching or desorption based on our TCLP and SPLP tests. Although the costs associated with the application of these adsorbent coated mulches are moderately increased (54% more costly than uncoated mulch), the prices are acceptable for water managers, engineers, and homeowners due to their potential to reduce the pollution in surface water, top soil, and aquifers. Our ongoing lifecycle analysis will provide quantitative information on the trade-offs between improved environmental quality and the incremental climate, energy, and economic costs of implementing a representative low impact development (LID) technique with raw mulch versus coated mulch in a typical U.S. Northeast coastal urban watershed.
Encouraging results from the Phase I demonstrate that WTR-coated and biochar-coated mulches are capable of alleviating multiple typical urban runoff pollutants with insignificant desorption or leaching of unwanted chemicals, thereby having a potential to transform mulching, a common landscaping practice, into a new and sustainable in-situ urban stormwater management approach. Major findings and their implications are below:
1. WTR considerably adsorbs toxic metal cations and phosphate in urban runoff, but almost ineffective for organic pollutants. In contrast, biochar has limited adsorption efficiencies for metal and phosphate in urban runoff, but can effectively adsorb certain synthetic organic pollutants.
2. Results from the batch tests suggest that WTR or biochar adsorption of target runoff pollutants is kinetically controlled. That is, the effluent concentration relies heavily upon contact time between the adsorbent coating and pollutants of concern.
3. Results from column studies demonstrate that wood mulch alone exhibits a limited and even negative removal for certain urban runoff pollutants (e.g., P). However, the combination of WTR and biochar coated mulches can significantly reduce effluent concentrations of target pollutants (e.g., heavy metals and phosphate).
4. Desorption of undesirable chemicals (e.g., toxic metals) sorbed to the coated mulches is insignificant under rainfall and landfilling disposal scenarios.
5. Aluminum leaching from WTR is minor, suggesting that the toxicity assoicated with aluminum in the proposed research is not a concern.
6. Costs associated with the coated mulch based urban stormwater treatment are acceptable.
Conclusions:
Based on the results from batch and column tests, WTR and biochar-coated mulches are demonstrated to have a potential to effectively adsorb heavy metals, phosphate, and synthetic organic compounds from urban runoff with insignificant leaching of undesirable chemicals. Therefore, the innovative filter media provides a potentially revolutionized technology to address urban stormwater pollution, which has long remained a challenge as a major non-point pollution in urban areas. The project deserves an in-depth investigation to test the long-term performance of the new technology under field conditions.
Journal Articles:
No journal articles submitted with this report: View all 5 publications for this projectSupplemental Keywords:
urban stormwater pollution; sustainable infrastructure design; reuse; heavy metals; phosphorus; synthetic crganic compounds; water treatment residuals; biochar; wood mulch; municipal sewage sludge; adsorptionP3 Phase II:
Toward Sustainable Urban Stormwater Management with New, Green, Low-Cost Sorbent-Coated Wood Mulch | 2018 Progress Report | 2019 Progress Report | 2020 Progress Report | Final ReportThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.