Assessing Nutrient Removal in Stormwater Runoff for Urban Farming with Iron filings-based Green Environmental Media

Abstract

Ensuring urban areas have access to clean drinking water, safe food supply, and uncontaminated water bodies is essential to the good health of millions of urban residents. This paper presents the functionality of Iron Filings-based Green Environmental Media (IFGEM) in terms of nutrient removal efficiencies to support water quality management and urban farming. IFGEM uses recycled materials such as tire crumb and iron filings to help remove nutrients with essential physicochemical properties. In this study, IFGEM were proven effective and sustainable through an isotherm study, a column study of reaction kinetics, and a microstructure examination under various inlet nutrient concentration levels. IFGEMs exhibited over 90% nitrate removal, as well as 50-70% total phosphorus removal, under most inlet conditions. These promising results make IFGEM suitable for treating stormwater runoff, wastewater effluent, and agricultural discharge via varying ex situ treatment units in flexible landscape environments. In addition, the byproduct of ammonia generation permits possible reuse of spent IFGEM as soil amendments in crop land, gardens and yards, and green roofs for urban farming. Findings may help secure urban food supply chains and harmonize nutrients, soil, water, and waste management in different urban environments. Globalization and urbanization have reshaped human society, producing a set of complex, interdependent, and interrelated problems in a food-energy-water-waste nexus under the constraint of limited natural resources 1. One of the issues facing sustainable development is the contradiction between nutrient (nitrogen and phosphorus) depletion in agricultural production 2 and nutrient contamination from stormwater runoff, wastewater effluent, and agricultural discharge 3,4. Undesired nutrient loads to natural systems and the built environment create environmental sustainability concerns in terms of ecosystem degradation due to eutrophication and loss of biodiversity 5,6. On the other hand, the rapid growth of the global population constantly increases demands for food production, and modern agriculture largely relies on mining-based fertilizers, which are facing a depletion issue, particularly for phosphorus 7. Through consideration of these intertwined situations, the Environmental Protection Agency 8 promulgated regulatory standards for remediating the impacts from the non-point source pollution 9,10 and resolving the contradictory situation in nutrient management. Best management practices (BMPs) such as filtration basin, grassed swale, green roof, etc., have been used to remediate non-point pollution for decades 11,12. However, existing BMPs are becoming less effective due to increased nutrient concentrations and runoff volumes, as well as soil contamination via rapid urbanization 13,14. One solution is to use green sorption media (i.e., media with the inclusion of recycled materials), designed for enhancing nutrient removal both sustainably and cost effectively. However, there are some design complications ...