Title
Anoxic Iron Sulfides Formation: A Novel Approach for Iron Removal in Groundwater Treatment
Author
Holst, Tjark (TU Delft Civil Engineering & Geosciences)
Contributor
van Halem, D. (mentor) 
van Loosdrecht, Mark C.M. (mentor)
Goedhart, R.C. (mentor)
Degree granting institution
Delft University of Technology
Programme
Water Management | Sanitary Engineering
Date
2023-05-26
Abstract
Groundwater (GW) makes up roughly half of the global drinking water supply. Conventional iron removal in GW treatment produces approximately 10,000t/d of iron sludge. Iron sludge consists of low-density flocs with low to no commercial value and causes frequent energy intensive backwashing of the rapid sand filter. This study aimed to explore the novel concept of iron removal via iron sulfides formation. Iron sulfides are usually forming dense structures and offer a wider range of re-use applications.
To investigate this, an up-flow column reactor filled with pyrite seeding crystals was built and fed with iron and sulfide containing solutions. Flushed out formed solids were investigated with X-ray diffraction analysis and Raman spectroscopy. Seeding crystals were analyzed with scanning electron microscopy with energy dispersive X-ray spectroscopy.
This study observed rapid mackinawite formation after a few minutes. Mackinawite was likely retained by electrostatic adhesion on the pyrite seeding crystals. The molar ratio of removed iron to removed sulfide equaled up to 0.8 ± 0.2.
Mackinawite formation can present an interesting alternative to conventional iron removal, due to (i) its compact size, (ii) fast formation rates and (iii) possibly simple removal mechanism via electrostatic adhesion. Furthermore, in-situ formed mackinawite has the potential to simultaneously treat a wide range of pollutants ranging from toxic metals and metalloids such as arsenic over organic contaminants and nutrients such as nitrate and phosphate. Moreover, in-situ electrochemical dosing of sulfide by sulfate reduction might present a chemical-free solution for this approach. These potential synergies should be addressed in further investigations.
Subject
Groundwater
Iron
Sulfide
Water treatment
Anoxic
Mackinawite
Pyrite
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http://resolver.tudelft.nl/uuid:c346f0a2-6aa9-4656-931f-5628e8a32a7b
Embargo date
2024-05-26
Part of collection
Student theses
Document type
master thesis
Rights
© 2023 Tjark Holst