Understanding the impact of chemical additives on struvite precipitation

Sim, Dong Hoon

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https://hdl.handle.net/2142/129942 Copy

Description

Title

Understanding the impact of chemical additives on struvite precipitation

Author(s)

Sim, Dong Hoon

Issue Date

2025-07-25

Director of Research (if dissertation) or Advisor (if thesis)

Cusick, Roland D.

Department of Study

Civil & Environmental Eng

Discipline

Environ Engr in Civil Engr

Degree Granting Institution

University of Illinois Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Struvite
• Calcium phosphate

Abstract

Although the use of struvite precipitation systems in water resource recovery facilities (WRRFs) is growing, these systems are frequently constrained by poor phosphorus recovery, fine particle losses, and inconsistent performance. Empirical precipitation models that overlook the impact of impurities and particle size on crystallization rates further limit reactor optimization. To comprehend the effects of supersaturation, organic additions (citrate and aspartate), and competing cations (calcium) on precipitation kinetics and particle dynamics, we conducted out a variety of struvite precipitation studies. Our findings demonstrate that supersaturation is important in particle dynamics in pure struvite growth solutions. After phosphorus removal stops, low supersaturation can extend the nucleation and growth phase before shifting to an aggregation dominating phase that continues to modify the particle size distribution. Citrate and aspartate experiments showed these additives promoted aggregation resulting in the formation of large (D > 500 µm) aggregates while also stabilizing smaller particles. The morphology of struvite changed from trapezoidal prisms to clusters of radially growing crystals that all emanated from a single central point when calcium was added. This observation is reinforced by the shift of the same peak to the right in the particle size distribution data, suggesting that struvite growth consistently centers around this nucleation point. Furthermore, amorphous calcium phosphate (ACP) starts to redissolve at around the 10-minute mark, according to calcium removal data, indicating that amorphous calcium that is not concentrated inside the struvite precipitants redissolve into the solution.

Graduation Semester

2025-08

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/129942

Copyright and License Information

Copyright 2025 Dong Hoon Sim

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