Date of Award
Summer 2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Civil, Construction, and Environmental Engineering
First Advisor
Anthony Parolari
Second Advisor
Brooke Mayer
Third Advisor
Walter McDonald
Fourth Advisor
Kaushik Venkiteshwaran
Abstract
Phosphorus (P) is a life-essential element aiding the deterioration of water quality. Stormwater runoff transports nonpoint source P pollution to waterbodies, contributing to excessive P loading which may result in eutrophication. Green infrastructure (GI) is implemented to solve stormwater runoff pollution, but the P removal performance of these systems is variable. Moreover, P is arguably being unsustainably mined for fertilizer production and animal feed supplements to support demand from increasing global populations. This dissertation explored advancing the circular P economy utilizing additive manufacturing and GI soil amendments to remove and recover P from stormwater runoff. Laboratory-scale batch experiments were used to gather data for all objectives. First, the P removal and recovery potential of a 3D-printed iron-embedded polylactic acid composite was investigated. In solution at pH 5, 7, and 9 and 23 ℃, the composite’s maximum P adsorption capacity (qmax) was 1.90, 1.57, and 1.83 mg-P g-media-1, respectively. In solution at pH 7 and temperatures 15, 23, and 36 C, the qmax was 2.24., 1.57, and 1.85 mg-P g-media-1, respectively. The qmax decreased by 48% in solution with competing ions. In bioretention effluent, the composite removed 94% of P within 48 hrs. Solution at pH 12.3 facilitated the recovery of 69% of adsorbed P. Second, P recovery from GI soils was explored. Desorption solutions at pH 12.3 and 2 resulted in the recovery of 43% and 98% of the P mass (mg-P g-media-1) originally removed using iron- and slag-amended soils, respectively. When testing media reuse for P recovery, the mass of P recovered (mg-P g-media-1) decreased from 60% to 18% and 230% to 0% from cycles 1 to 5 for iron- and slag-amended soils, respectively. Lastly, native adsorbed P (NAP)-adjusted isotherm equations were used to model the equilibrium P adsorption data of iron- and slag-amended soils. NAP-adjusted equations fit the data better than traditional equations when P leaching was observed in solutions with initial P concentrations < 1.0 mg L-1. Additionally, adsorption capacities were higher at these concentrations (ranging from 0.01 – 1.1 mg-P g-media-1) using traditional versus NAP-adjusted model parameter estimates, indicating that traditional models may overestimate P treatment.