Waste nutrients harvested: Design and evaluation of nitrogen and phosphorus recovery processes utilizing membrane contactor and adsorption techniques

Research output: ThesisDoctoral ThesisCollection of Articles

Abstract

Global food production relies on industrial fertilizers. The explosive growth of the human population would not have been possible without processes that bind nitrogen from the atmosphere to ammonia and mined phosphate rock to easily soluble products. However, the linear consumption pattern (as opposed to circular) has backfired on us. As a result, the nutrient systems we rely on consume significant amounts of energy and create an array of environmental problems. This dissertation focuses on the question: 'How can we close the nutrient loop?' Furthermore, special attention is paid to managing nutrient recycling in an environmentally and economically sustainable way. There is a vast quantity of nutrients available in different concentrated waste streams. However, these nutrients are not recycled efficiently because it is economically unfeasible or there are concerns about pollutants. These concerns apply to both liquid and solid waste streams. This dissertation is built around NPHarvest, a nutrient recovery technology developed at Aalto University. NPHarvest recovers both nitrogen and phosphorus from liquid waste streams with high efficiency. The end products are clean ammonia salt and solid material that contains phosphorus, calcium and carbon. The dissertation found that NPHarvest as a technology is economically competitive. The recovery process's novelty is how well it is designed to tolerate suspended solids in a wastewater environment and operate with low energy consumption, which decreases operational costs. Upon studying the life cycle assessment of the process, NPHarvest environmental performance was found to be positive or neutral in most impact categories. The process has the potential to be climate-positive (carbon-negative) with further optimization. Additionally, this dissertation examines P recovery from chemically precipitated sludge. It is technically possible, but not feasible enough, to be implemented on a large scale with currently available technologies. Waste-based biosolid materials proved to be a suitable pathway to capture phosphorus after acidleaching. The phosphorus-loaded biosolid can function as organic fertilizers. Finally, the dissertation reflects on the implications of systemwide nutrient recovery. Nutrient recovery is a shift towards transforming treatment plants to resource recovery plants, in addition to enabling the facilities to reach better cost-effectiveness. Furthermore, nutrient recovery enables decentralized treatment systems should they be desired. To finish the discussion, the true meaning of sustainable technology is discussed.
Translated title of the contributionJäteravinteet talteen: Typen ja fosforin talteenoton suunnittelu ja evaluaatio käyttäen kalvo- ja adsorptiotekniikkoja
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Mikola, Anna, Supervising Professor
  • Al-Juboori, Raed, Thesis Advisor
Publisher
Print ISBNs978-952-64-1136-1
Electronic ISBNs978-952-64-1137-8
Publication statusPublished - 2023
MoE publication typeG5 Doctoral dissertation (article)

Keywords

  • wastewater treatment
  • nutrient recovery
  • circular economy
  • NPHarvest

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