Toward Sustainable Urban Stormwater Management with New, Green, Low-Cost Sorbent-Coated Wood MulchEPA Grant Number: SV839355
Title: Toward Sustainable Urban Stormwater Management with New, Green, Low-Cost Sorbent-Coated Wood Mulch
Investigators: Deng, Yang
Institution: Montclair State University
EPA Project Officer: Page, Angela
Project Period: March 1, 2018 through February 29, 2020
Project Amount: $75,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet - Phase 2 (2017)
Research Category: P3 Awards , Sustainability , P3 Challenge Area - Water
The long-range goal is to develop innovative, environmentally friendly, low-cost, technically viable and simple-maintenance treatment technologies to support sustainable urban stormwater management.
The primary objective of this Phase II proposal is to enable pilotscale design capable of demonstrating long-term performance of the coated mulch-based filtration systems in the alleviation of urban stormwater pollution. Besides the traditional benefits of mulch (e.g. erosion control, moisture retention, and weed control), wood mulches serve as an inert supporter for active adsorbent coatings. Our Phase I studies demonstrate that the two lowcost adsorbent coatings, i.e. WTRs and oak-based biochar, provide complimentary adsorption capabilities. In Phase II, we will test oak-based biochar used in Phase I and also municipal sewage sludge derived biochar (SSDB) in order to pursue a more sustainable urban water management system. Particularly, a whole or part of energy for the SSDB synthesis will derive from anaerobic digestion of municipal sewage sludge. A student team composed of four students from different disciplines, of whom two participated in the Phase I study, will be assembled. To achieve the goal, three specific objectives will be pursued.
Objective 1. to synthesize and characterize SSDB and to analyze energy for anaerobic digestion of sewage sludge and for the SSDB pyrolysis.
Objective 2. to optimize pilot-scale coated much-based filtration design and evaluate the long-term performance.
Objective 3. to characterize spent coated mulch and establish mathematic modeling.
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 one-year, four-task plan is proposed: Task 1: Synthesis and characterization of LAC wood mulch; Task 2: Batch tests; Task 3: Column tests; Task 4: Life cycle assessment.
Task 1, LAC mulch was prepared and characterized. In the subsequent 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 III 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 are 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).
Major findings and their implications are discussed as 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.
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.