Practical considerations optically sensing rhodamine WT in water impacted by municipal biosolids

Abstract

Rhodamine WT (RWT) is an adsorptive flourescent dye tracer that is used in hydrological and hydrogeological studies. Municipal biosolids (sewage) are rich in organic matter and have a variety of chemical constituents that can interact to confound optical sensing of RWT florescence in water (e.g., quenching, interference, adsorption). Laboratory studies were conducted to evaluate optical sensing constraints associated with quantifying known RWT concentrations in a suite of RWT-spiked distilled water/liquid municipal biosolid (LMB) mixes. RWT flourescence decreased with an increase in LMB total suspended solids (TSS) in decay function form (R2=0.98). A method was then described to correct the undersensed RWT readings based on knowledge of TSS and/or turbidity. This study also found that, for samples agitated by stirring, RWT readings increased in logarithmic form over time. In addition, sample agitation augmented the undersensing of known RWT concentrations, but when agitation ceased, optical readings immediately approached more closely the known RWT values. Studies that use RWT as a tracer to assess the fate and transport of biosolid impacted water in hydrological environments should be aware of some of the optical sensing limitations identified here.

Quantitative Campylobacter spp., antibiotic resistance genes, and veterinary antibiotics in surface and ground water following manure application: Influence of tile drainage control

“…This percentage likely reflects the tendency for RWT to sorb to the solid phase of the manure (Edwards et al, 2011). Both the liquid and solid components of the LSM were analyzed for 15 antibiotic compounds (Table 2), of which two are parent compounds (TY and CTC) administered in the feed.…”