Sorption behavior of a synthetic antioxidant, polycyclic musk, and an organophosphate insecticide in wastewater sludge

Abstract

Emerging contaminants (ECs) are chemicals that are currently unregulated due to limited understanding of health effects and limited data regarding occurrence. Wastewater treatment plants (WWTP) receive many ECs as components of influent waste and the removal of organic contaminants, such as ECs, occurs primarily by sorption to sludge. Therefore, it is important to develop measures of sorption behavior by ECs to sludge. This study evaluates sorption of three ECs: 3-tert-butyl-4-hydroxyanisole (BHA) a synthetic antioxidant, 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethyl-cyclopenta(g)-2-benzopyrane (HHCB) a polycyclic musk, and chlorpyrifos a organophosphate insecticide. Twenty-four hour laboratory-scale sorption experiments were conducted for each compound individually and then in combination, which allowed the quantification of sorption onto wastewater sludge and the affects of multiple compounds. ECs in both the liquid and solid phases were analyzed using a gas chromatograph with flame ionization detector (GC/FID). Isotherms of individual sorption behavior followed a linear trend (R2 > 0.9) for individual ECs, while K(d) averaged 2,689 L kg(-1), 27,786 L kg(-1) and 31,402 L kg(-1) for BHA, chlorpyrifos and HHCB, respectively. Sorption behavior for BHA was linear during combined studies with K(d) of 1,766 L kg(-1) or a decrease of 34%, while HHCB and chlorpyrifos followed non-linear isotherm models. Synergistic effects were observed with spike concentrations > or =25 mg L(-1) for HHCB and > or =20 mg L(-1) for chlorpyrifos. K(d) values ranged from 16,984-6,000,000 L kg(-1) for HHCB and 19,536-3,000,000 L kg(-1) for chlorpyrifos. These distribution coefficients differed substantially from previously published values, mainly because few studies used sludge as the sorption media. Results suggest that HHCB and chlorpyrifos may be contained in the sludge unlike BHA, which is more available in the aqueous phase. Future investigations should evaluate WWTP processes for degrading ECs to harmless products and releases of ECs from sludge.

Levels and distribution of synthetic musks and polycyclic aromatic hydrocarbons in sludge collected from Guangdong Province

“…[5] Due to their low water solubility and high hydrophobicity, PAHs and synthetic musks tend to be adsorbed onto particulates and transferred into sludge during the wastewater treatment process, which causes elevated loads in sludge. [6][7][8] Thomas et al [9] further verified that synthetic musks tended to be adsorbed onto sludge during the wastewater treatment processes in laboratory-scale sorption experiments using HHCB as a representative compound.…”

Treatment of Municipal Wastewater Treatment Plant Effluents with Modified Photo-Fenton As a Tertiary Treatment for the Degradation of Micro Pollutants and Disinfection

“…are unregulated and released constantly into the environment, as they do not undergo any significant degradation in conventional wastewater treatment plants. , Sewage sludge has a tendency to absorb nonpolar compounds such as synthetic fragrances (Galaxolide, Musk Xylene, Tonalide, etc. ), which then have to be removed from the aquatic compartment, only to be released later if the sludge is applied as fertilizer in agriculture. − Polar compounds, like most pharmaceuticals, are unaffected as they pass through the treatment plant, and reach rivers and aquifers where they may affect aquatic organisms, or crops and other plants when water is used for irrigation. , These contaminants must therefore be removed, because, although their individual concentration may seem low, their sheer numbers can pose serious problems in the environment. − There are a number of possibilities for removing these substances, among which are the advanced oxidation processes (AOPs), defined as processes which produce hydroxyl radicals (HO • ), one of the most oxidizing species known (2.8 V versus normal H electrode), second only to fluoride, and able to oxidize almost any organic molecule, yielding only inorganic ions and CO 2 , , and therefore of particular interest. One of the most potent AOPs is photo-Fenton, which produces radicals by homogeneous photocatalysis with Fe­(II/III), UV–vis light, and H 2 O 2 .…”