The performance of three drinking water treatment sequences found in small community systems in reducing disinfection by-product precursor concentrations and the corresponding disinfection by-product formation potential was evaluated. Raw water quality and its potential for effective removal were characterized by the specific ultraviolet absorbance (SUVA) components of absorbance of ultraviolet light at 254 nm wavelength (UV254) and dissolved organic carbon (DOC). The results demonstrate that, for the source water qualities tested (hydrophobic SUVA with moderate DOC content, 2.0 to 4.8 L/(mg.m) and 4.1 to 6.3 mg DOC/L), there was a tendency to produce a higher percentage of total trihalomethane (TTHM) over the five regulated species of haloacetic acid (HAA5). The treatment sequence and chemical selection play a critical role in the ability of a small community system operator to achieve compliance with the concentration of regulated disinfection by-products. For the waters tested ferric chloride coagulants perform better at reducing the higher molecular weight, hydrophobic organic precursors. Powdered activated carbon does not perform as well with these source waters unless its application is followed by a clarification process that effectively forms a sludge blanket. This research provides additional criteria for linking source water quality with treatment sequence for sustainable management of disinfection by-product (DBP) compliance.

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.