The fate of antimicrobials entering the aquatic environment is an increasing concern for
researchers and regulators, and recent research has focused on antimicrobial
contamination from point sources, such as wastewater treatment facility outfalls. The
terraccumulation of antimicrobials and mobility in diffuse pollution pathways should not
be overlooked as a contributor to the spread of bacterial resistance and the resulting threat
to human drug therapy. This review critically examines recent global trends of bacterial
resistance, antimicrobial contaminant pathways from agriculture and water treatment
processes, and the need to incorporate diffuse pathways into risk assessment and
treatment system design.
Slow sand filters are used in rural regions where source water may be subjected to
antimicrobial contaminant loads from waste discharges and diffuse pollution. A simple
model was derived to describe removal efficiencies of antimicrobials in slow sand
filtration and calculate antimicrobial concentrations sorbed to the schmutzdecke at the
end of a filtration cycle. Input parameters include water quality variables easily
quantified by water system personnel and published adsorption, partitioning, and
photolysis coefficients. Simulation results for three classes of antimicrobials suggested
greater than 4-log removal from 1 ��g/L influent concentrations in the top 30 cm of the
sand column, with schmutzdecke concentrations comparable to land-applied biosolids.
Sorbed concentrations of the antimicrobial tylosin fed to a pilot filter were within one
order of magnitude of the predicted concentration.
To investigate the behavior of antimicrobial contaminants during multi-stage filtration,
five compounds from four classes of antimicrobials were applied to a mature slow sand
filter and roughing filter fed raw water from the Santiam River in Oregon during a 14-day
challenge study. Antimicrobial removal efficiency of the filters was calculated from 0.2
mg/L influent concentrations using HPLC MS/MS. and sorption coefficients (K[subscript d], K[subscript oc],
K[subscript om]) were calculated for schmutzdecke collected from a mature filter column.
Sulfonamides had low sorption coefficients and were largely unaffected by multi-stage
filtration. Lincomycin, trimethoprim, and tylosin exhibited higher sorption coefficients
and limited mobility within the slow sand filter column. The lack of a significant
increase in overall antimicrobial removal efficiency indicated biodegradation is less
significant than sorption in multi-stage filtration. / Graduation date: 2004
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/30575 |
| Date | 07 May 2004 |
| Creators | Rooklidge, Stephen J. |
| Contributors | Moore, James A. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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