Grantee Research Project Results
Final Report: Toward Sustainable Urban Stormwater Management with New, Green, Low-Cost Sorbent-Coated Wood Mulch
EPA Grant Number: SV839355Title: 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
Phase: II
Project Period: March 1, 2018 through February 29, 2020 (Extended to December 31, 2021)
Project Amount: $75,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet - Phase 2 (2017) Recipients Lists
Research Category: P3 Awards , Sustainable and Healthy Communities , P3 Challenge Area - Safe and Sustainable Water Resources
Objective:
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 proposal was to enable pilot-scale design capable of demonstrating long-term performance of biochar coated mulch-based filtration systems in the alleviation of urban stormwater pollution. To achieve the goal, three specific objectives were pursued:
to synthesize sewage sludge derived biochar (SSDB), evaluate SSDB for pollutant adsorption, and make energy analysis for the SSDB pyrolysis;
to evaluate SSDB coated mulch filters for treatment of urban runoff;
and to assess the leaching of spent coated mulch.
Summary/Accomplishments (Outputs/Outcomes):
- Synthesis, treatment assessment, and energy analysis of SSDB
Laboratory-scale tests were performed to synthesize SSDB at various pyrolysis conditions (temperature: 300-700oC; and duration: 1- 4 hrs). Sewage sludge was collected from a local wastewater treatment plant. The mass ratio of biochar to original sewage sludge (i.e., biochar yield) declined from 81% to 49% with the increase of pyrolysis temperature from 300oC to 700oC. SSDB was sequentially characterized using different material analytical techniques. Figure 1 shows a scanning electron microscope (SEM) image of SSDB particles synthesized at 600℃ and 1 hr, indicating the small sizes of these particles.
Bench scale kinetics and adsorption isotherm tests were carried out to understand adsorption behaviors of SSDB for typical runoff pollutants in a simulated urban runoff solution. Results show that the adsorption patterns of SSDB for zinc (Zn) and phenol, which represented typical heavy metal and synthetic organic compound (SOC) pollutants in runoff, relied heavily upon pyrolysis conditions. The adsorption kinetic pattern followed the pseudo-second-order rate equation (R2> 0.98). The Zn adsorption complied with the Freundlich model (R2> 0.92), while the phenol immobilization did not well fit the Langmuir or Freundlich model (R2 < 0.67). Higher pyrolysis temperature and longer adsorption duration improved the adsorption rates and increased adsorption capacities. Moreover, SSDB (900oC and 4 hrs) performed better than commercially available oak-based biochar that was able to adsorb phenol, but poorly removed Zn. The better adsorption capability of SSDB may be ascribed to the presence of minerals that rarely exist in oak-based biochar.
Of interest, we noticed that SSDB exported certain nutrients and other constituents in water, such as phosphorus (P), potassium (K), and calcium (Ca). The unwanted leaching could be dramatically inhibited with the increasing pyrolysis temperature. Therefore, SSDB synthesized at the optimal pyrolysis conditions (i.e. 900oC and 4 hrs) was used for the follow-on experiments in term of the adsorption and leaching behaviors.
Additionally, a preliminary energy analysis was made based on the data from literature and the project experiments. If bioenergy recovered from anaerobic digestion of sewage sludge can be applied to pyrolysis of the SSDB, the total biochar synthesis energy is estimated to be reduced approximately by 7.4%.
Figure 1 A SEM image of SSDB at 600℃ and 1 h
2. Field tests
On-site pilot-scale field test devices were installed on the green roof in the Center for Environmental and Life Sciences (CELS) at Montclair State University (MSU) in Montclair, New Jersey (Figure 2). For each precipitation that was sufficiently heavy to produce roof runoff, water samples before and after passing through the filters were collected for analyses. Flow-weighted mean concentrations (FWMC) of different runoff constituents were measured to assess the treatment performance. Generally, the pollutant removal was improved with the increasing hydraulic retention time (HRT) and adsorbent doses. Results show that the biochar-based filters could efficiently remove turbidity (> 94%) and toxic heavy metals (e.g., Zn and Cu) (> 80%) from the runoff within a one-year service time. In the first month, P leaching from the biochar was observed (FWMC = 0.03- 0.09 mg/L as P). However, the leaching gradually declined likely because of depletion of leachable P in the biochar. The treatment performance of other runoff pollutants (e.g., nitrogen and synthetic organic pollutants) in the roof runoff were not evaluated because of their absence in the roof runoff.
Fig. 2 Stormwater treatment devices installed on the green roof of the MSU CLES building
3. Spent adsorbents and cost analysis
Spent adsorbents were collected for synthetic precipitation leaching procedure (SPLP) (EPA SW-846 Methods 1312) and toxicity characteristic leaching procedure (TCLP) (EPA SW-846 Methods 1311) tests. Leaching of toxic (e.g., Cr, Co, Ni, Zn, As, Cd, and Pb) and non-toxic (e.g., Na, Mg, Al, K, and Ca) metals from the used adsorbents was minor. The leached pollutants were all below the U.S. SPLP and TCLP criteria. A preliminary cost analysis was made for the SSDB coated wood mulch chips. The SSDB-coated mulch chips cost approximately $97/yd3, corresponding an increase of 62% to the price of raw wood mulch. The expense growth is ascribed to the use of mulch glue (86% of the price increase) and biochar (14% of the price increase).
4). Developing general principles.
Along with the project research, general principles are developed in two urban stormwater treatment and management scenarios. First, key aspects and principles for utilization of low-cost adsorbents for urban stormwater treatment were discussed. Various low-cost adsorbents (e.g., biochar, scrap tire, sawdust, zeolites, iron filings, and fly ash) were included. To determine whether a low-cost adsorbent is suitable for stormwater treatment, two aspects need to be carefully assessed, including: 1) its adsorption mechanisms and behaviors, which affect the binding strength, adsorption kinetics, and treatment capacity; and 2) unwelcome chemical leaching patterns influencing the extent of water quality degradation. Second, challenges of rainwater harvesting (RWH) for irrigation in urban agriculture were identified. Primary pollutants of irrigation concern in harvested urban rainwater were documented, followed by recognition of challenges, knowledge gaps, and research needs for RWH irrigation at urban farms. Five aspects are highlighted, i.e., the role of roof, nutrient management, development of RWH treatment tailored for urban crop irrigation, water quality monitoring, and the interactions between water, crops, and soil.
5) Education activities.
Multiple education activities were integrated into the project research, including: one economically disadvantaged Hispanic high school student from the Union City High School (Union City, New Jersey) participated in the project through her summer research intern; 2) PI delivered a seminar to approximately forty students from different U.S. northeast universities in the Green Team Program operated by the PSEG Institute of Sustainability Science in the summer of 2019. In the talk, the project findings and sustainable urban stromwater management were highlighted.
Conclusions:
Laboratory and pilot-scale on-site experiments demonstrate technical viability of sewage sludge-based biochar for alleviation of urban stormwater runoff pollution in this project. The adsorbent coated on mulch chips could effectively remove toxic metals and SOCs in urban runoff. Attention should be paid to initial chemical leaching from biochar. Certain constituents (e.g., P in this study) could be released from biochar to the environment during the initial application phase. However, the leaching would be lessened over time with the depletion of these chemicals. Therefore, the leaching may not be a major concern during a long-term implementation. If the short-term release of unwanted chemicals needs to be avoided, the biochar is suggested to be rinsed for removing leachable chemicals prior to the application. On the other hand, the overall cost of the adsorbent-based mulch chips is moderately increased in comparison with raw wood chips. The cost growth is principally ascribed to the use of mulch chip, followed by the biochar coating. Therefore, the exploration of new binding methods for adsorbent coating on mulch chips is recommended for further reduction of the material costs.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
Other project views: | All 6 publications | 2 publications in selected types | All 2 journal articles |
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Type | Citation | ||
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Deng Y. Low-cost adsorbents for urban stormwater pollution control. Frontiers of Environmental Science & Engineering 2020;14(5):1-8. |
SV839355 (2019) SV839355 (2020) SV839355 (Final) |
Exit Exit |
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Deng Y. Pollution in rainwater harvesting:A challenge for sustainability and resilience of urban agriculture. Journal of Hazardous Materials Letters 2021;2:100037. |
SV839355 (Final) |
Exit Exit |
Progress and Final Reports:
Original AbstractP3 Phase I:
Low-Cost Active Coating Mulch for Urban Runoff | 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.
Project Research Results
- 2020 Progress Report
- 2019 Progress Report
- 2018 Progress Report
- Original Abstract
- P3 Phase I | Final Report
2 journal articles for this project