File(s) under permanent embargo
Geochemical changes during recharge with tertiary-treated wastewater at a coastal sandfill
journal contribution
posted on 2009-01-01, 00:00 authored by Lloyd ChuaLloyd Chua, E Lo, T Lim, A Robertson, E Shuy, S TanResults of experiments investigating geochemical changes during artificial recharge of treated wastewater at a coastal sandfill, reclaimed with sand dredged from the seabed, are reported in this paper. Laboratory batch experiments were conducted using secondary effluent (SE) and SE treated with an additional ultrafiltration process (UF), and wastewater treated by reverse osmosis (RO) process, mixed with surface sand obtained from the sandfill. Experiments with RO showed a net increase of 0.41 meq/L, 0.12 meq/L and 0.31 meq/L for Ca(2 + ), Mg(2 + ) and HCO(3) (-), respectively. UF and SE also exhibited net increase in Ca(2 + ), Mg(2 + ) and HCO(3) (-) indicating carbonate mineral dissolution. All three waters were found to be over-saturated with respect to calcite. Carbonate dissolution reactions were observed in the field experiments. However, the presence of imported clays from the borrow source gave rise to ion exchange reactions where Na(+) attached to the clay particles were exchanged for Ca(2 + ) and Mg(2 + ) inducing mineral dissolution, driven by sub-saturation conditions. This resulted in an increase in pH with maximum values in excess of 9.0. It was also found that the sodium adsorption ratio remained high (>10) even after the groundwater had been diluted sufficiently to freshwater levels (ionic strength, I <0.015) indicating a potential for the dispersion of clay particles. This could have a deleterious consequence on porosity and hydraulic conductivity.
History
Journal
Water science and technologyVolume
60Issue
5Pagination
1273 - 1281Publisher
IWA PublishingLocation
London, Eng.Publisher DOI
ISSN
0273-1223Language
engPublication classification
C1.1 Refereed article in a scholarly journalCopyright notice
2009, IWA PublishingUsage metrics
Categories
No categories selectedKeywords
geochemical changeswastewaterwaterecologysodium absorbtionScience & TechnologyTechnologyLife Sciences & BiomedicinePhysical SciencesEngineering, EnvironmentalEnvironmental SciencesWater ResourcesEngineeringEnvironmental Sciences & Ecologyartificial rechargecalcite dissolutiongeochemicalion exchangesandfilltertiary treated wastewaterAQUIFER
Licence
Exports
RefWorks
BibTeX
Ref. manager
Endnote
DataCite
NLM
DC