Wastewater anionic surfactant concentrations

Using a clean 25-mL graduated cylinder, place 10 mL of an aqueous sample whose anionic surfactant concentration is to be determined into a 50-mL beaker. The aqueous sample could be a blank (i.e., a sample with all reagents added except for the analyte of interest), calibration standard, ICV, fortified (i.e., spiked) sample, or an actual unknown wastewater effluent sample. 

AES are typically measured in environmental matrices by nonspecific colorimetric analyses (MBAS) that collectively measure LAS, AS, and naturally occurring anionic surfactants. Alternatively, a specific gas chromatographic method for AES, developed by Neubecker (55), was employed to measure AES concentrations in influent and effluent from STPs and river water. Total AES measured in influent wastewater to a STP was 1.88 mg/L. AES removal of 94-100% was measured during actual sewage treatment by activated sludge the resulting effluent concentration was 0.06 mg/L. Total AES levels in river water were less than 0.01 mg/L. AES accounted for 6-13% of MBAS measured in natural water. 

In a wastewater stream, cationics are often present together with anionic surfactants. In such cases, only the excess of one or the other is available for determination by the standard method the balance can be considered to already be titrated. Prior to analysis, the sample must be treated with ion exchange resin to remove either anionic or cationic surfactants. If, for example, cationics are removed and two titrations of anionics are performed, one with and one without cationic removal, the difference is equivalent to the concentration of cationics (100). 

Emulsion Formulation. The emulsion consists of two separate phases the membrane (oil) phase and the internal stripping phase. The membrane phase encapsulates the aqueous internal phase, separating it from the low concentration stream of wastewater being treated (the external phase). The membrane phase is composed of a complexing agent, a surfactant, a solvent, and a co-solvent. The solvent is kerosene. The co-solvent is n-decanol. Both the complexing agent and the surfactant are proprietary materials. The extractant complexes with the anionic... 

Discussion The elimination of interferences is aimed at making the methylene blue method more nearly specific for the chief surfactant component of municipal wastewater LAS. The acid hydrolysis destroys alcohol sulfate surfactants, for example, which in a specific application may or may not be considered an interference to be eliminated. Acid hydrolysis also aids the recovery of LAS adsorbed onto solids. The main contribution of the anion exchange step is the elimination of cationic materials which would complex with LAS to give low results. The XAD-2 concentration step effectively removes inorganic materials from the system. 

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