Traditionally, destruction of DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane] for environmental remediation required high-energy processes such as incineration. Here, the capability of powdered zero-valent iron to dechlorinate DDT and related compounds at room temperature was investigated. Specifically, DDT, DDD [1,1-dichloro-2,2-bis(p-chlorophenyl)ethane], and DDE [2,2-bis(p-chlorophenyl)-1,1-dichloroethylene] transformation by powdered zero-valent iron in buffered anaerobic aqueous solution was studied at 20 °C, with and without the presence of nonionic surfactant Triton X-114. The iron was successful at dechlorinating DDT, DDD, and DDE. The rates of dechlorination of DDT and DDE were independent of the amount of iron, with or without surfactant. The rates with surfactant present were much higher than without. Initial first-order transformation rates for DDT, DDD, and DDE were determined. For example, the initial first-order rate of DDT dechlorination was 1.7 ± 0.4 and 3.0 ± 0.8 day-1 or, normalized by the specific iron surface area, 0.016 ± 0.004 and 0.029 ± 0.008 L m-2 h-1, without and with surfactant, respectively. A mechanistic model was constructed that qualitatively fit the observed kinetic data, indicating that the rate of dechlorination of the solid-phase (crystalline) reactants was limited by the rate of dissolution into the aqueous phase.

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Two analytical methods were developed and refined for the detection and quantitation of two groups of endocrine-disrupting chemicals (EDCs) in the liquid matrixes of two pilot-scale municipal wastewater treatment plants. The targeted compounds are seven sex hormones (estradiol, ethinylestradiol, estrone, estriol, testosterone, progesterone, and androstenedione), a group of nonionic surfactants (nonylphenol polyethoxylates), and their biodegradation byproducts nonylphenol and nonylphenol ethoxylates with one, two, and three ethoxylates. Solid phase extraction using C-18 for steroids and graphitized carbon black for the surfactants were used for extraction. HPLC-DAD and GC/MS were used for quantification. Each of the two 20 L/h pilot-scale plants consists of a primary settling tank followed by a three-stage aeration tank and final clarification. The primary and the waste-activated sludge are digested anaerobically in one plant and aerobically in the other. The pilot plants are fed with a complex synthetic wastewater spiked with the EDCs. Once steady state was reached, liquid samples were collected from four sampling points to obtain the profile for all EDCs along the treatment system. Complete removal from the aqueous phase was obtained for testosterone, androstenedione, and progesterone. Removals for nonylphenol polyethoxylates, estradiol, estrone, and ethinylestradiol from the aqueous phase exceeded 96%, 94%, 52%, and 50%, respectively. Levels of E3 in the liquid phase were low, and no clear conclusions could be drawn concerning its removal.

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