Variability of trace organic chemical concentrations in raw wastewater at three distinct sewershed scales Jennifer Teerlink a , Amanda S. Hering b , Christopher P. Higgins a , Jo ¨rg E. Drewes a, * a NSF Engineering Research Center ReNUWIt, Department of Civil and Environmental and Engineering, Colorado School of Mines, Golden, CO 80401, USA b Department of Applied Mathematics and Statistics, Colorado School of Mines, Golden, CO 80401, USA article info Article history: Received 28 July 2011 Received in revised form 23 February 2012 Accepted 10 March 2012 Available online 22 March 2012 Keywords: Trace organic chemicals (TOrCs) Wastewater Variability Distributed systems Occurrence abstract The site-specific daily fluctuations and scale-dependent variability of influent water quality, particularly concentrations of trace organic chemicals (TOrCs), have not yet been well described. In this study, raw wastewater from three distinct sewershed scales was sampled including a centralized wastewater treatment facility in Boulder, Colorado (population w125,000) and two decentralized wastewater catchments in Golden, Colorado (clustered system population 400, and septic system population 32). Each site was sampled hourly for 26 h and samples were subsequently analyzed in triplicate for 32 TOrCs using liquid chro- matography with tandem mass spectrometry and stable isotope dilution. Detection frequency (DF) of the various TOrCs was positively correlated with sewershed size with the greatest DF of the targeted TOrCs at the Boulder site and with decreasing DF with decreasing sewershed size. Site-specific fluctuations were both scale and compound-specific. The 11 TOrCs detected greater than 75% of the time across all three sites were used to further investigate and quantify variability and to develop a statistical model to investigate the flow-dependence and time- dependence of TOrC variability. Sewershed scale was inversely correlated to variability with coefficients of variation ranging from 0.24 to 0.96, 0.39 to 2.22, and 0.32 to 3.93 for the Boulder, cluster, and septic sites, respectively. A significant linear relationship was observed between concentration and flow and concentration and the concentration at prior time points for most TOrCs at the Boulder site. This suggests less variable influent concentrations result from dispersion and mixing in the conveyance system and a larger number of discrete inputs. A notable exception was the chlorinated flame retardant TCPP, which is likely associated with a high concentration, low-flow industrial input. A significant linear relationship between flow and concentration and sequential time points was not common at the decentralized sites. Scientists and engineers developing decentralized treatment systems must consider a larger range of influent qualities, particularly with respect to TOrCs. ª 2012 Elsevier Ltd. All rights reserved. 1. Introduction In the past few decades, there has been great effort focused on understanding the occurrence of trace organic chemicals (TOrCs) in natural and engineered treatment systems, including raw wastewater from both centralized (Kimura et al., 2007) and decentralized (Conn et al., 2006; Matamoros et al., 2009) systems. TOrCs include a wide range of personal * Corresponding author. Tel.: þ1 303 273 3401; fax: þ1 303 273 3413. E-mail addresses: jdrewes@mines.edu, jorg.drewes@kaust.edu.sa (J.E. Drewes). Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/watres water research 46 (2012) 3261 e3271 0043-1354/$ e see front matter ª 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.watres.2012.03.018