United States National Sewage Sludge Repository at Arizona State University--a new resource and research tool for environmental scientists, engineers, and epidemiologists

Abstract

Processed municipal sewage sludges (MSS) are an abundant, unwanted by-product of wastewater treatment, increasingly applied to agriculture and forestry for inexpensive disposal and soil conditioning. Due to their high organic carbon and lipid contents, MSS not only is rich in carbon and nutrients but also represents a "sink" for recalcitrant, hydrophobic, and potentially bioaccumulative compounds. Indeed, many organics sequestered and concentrated in MSS meet the US Environmental Protection Agency's definition of being persistent, bioaccumulative, and toxic (PBT). In a strategic effort, our research team at the Biodesign Institute has created the National Sewage Sludge Repository (NSSR), a large repository of digested MSSs from 164 wastewater treatment plants from across the USA, as part of the Human Health Observatory (H2O) at Arizona State University (ASU). The NSSR likely represents the largest archive of digested MSS specimens in the USA. The present study summarizes key findings gleaned thus far from analysis of NSSR samples. For example, we evaluated the content of toxicants in MSS and computed estimates of nationwide inventories of mass produced chemicals that become sequestrated in sludge and later are released into the environment during sludge disposal on land. Ongoing efforts document co-occurrence of a variety of PBT compounds in both MSS and human samples, while also identifying a large number of potentially harmful MSS constituents for which human exposure data are still lacking. Finally, we summarize future opportunities and invite collaborative use of the NSSR by the research community. The H2O at ASU represents a new resource and research tool for environmental scientists and the larger research community. As illustrated in this work, this repository can serve to (i) identify and prioritize emerging contaminants, (ii) provide spatial and temporal trends of contaminants, (iii) inform and evaluate the effectiveness of environmental policy-making and regulations, and (iv) approximate, ongoing exposures and body burdens of mass-produced chemicals in human society.

Fig. 1

MSS sampling locations of U.S. EPA's 2001 National Sewage Sludge Survey (NSSS) and the 2006/7 Targeted NSSS (TNSSS). Samples are currently housed in the NSSR maintained as part of the larger Human Health Observatory (H2O) at the Biodesign Institute at Arizona State University.

Fig. 2

Photographs of exemplary MSS samples archived at -20°C at Arizona State University in the NSSR as part of the larger Human Health Observatory (H2O).

Fig. 3

Rank order plot of mean concentrations of (a) pharmaceuticals and personal care products (PPCPs) [Source:(Chari and Halden 2012)], (b) alkylphenol and their ethoxylates (AP & APEOs) – 4-nonylphenol (NP); 4-nonylphenol monoethoxtlate (NP1EO); 4-nonylphenol diethoxylate (NP2EO) [Source: (Venkatesan and Halden 2013a)], (c) perfluorinated compounds (PFCs) - perfluorobutanoate (PFBA); perfluoropentanoate (PFPeA); perfluorohexanoate (PFHxA); perfluoroheptanoate (PFHpA); perfluorooctanoate (PFOA); perfluorononanoate (PFNA); perfluorodecanoate (PFDA); perfluoroundecanoate (PFUnDA); perfluorododecanoate (PFDoDA); perfluorobutane sulfonate (PFBS); perfluorohexane sulfonate (PFHxS); perfluorooctane sulfonate (PFOS); perfluorooctane sulfonamide (PFOSA) [Source: (Venkatesan and Halden 2013b)], and (d) brominated flame retardants (BFRs) – polybrominated diphenylethers (PBDEs); polybrominated biphenyls (PBBs); hexabromocyclododecane (HBCDD); decabromodiphenyl ethane (DBDPE); 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE); hexabromobenzene (HBB); pentabromoethylbenzene (PBEB) [Source: (Venkatesan and Halden 2014a)], detected in MSS composite samples from the U.S. EPA's 2001 NSSS. Error bars represent minima and maxima (n = 5).

Fig. 4

(a) Relative abundance of CECs in MSS samples from the 2001 NSSS. The number above the bar represents the number of chemicals detected in each chemical group. (b) Classification of 123 chemicals detected in NSSR samples based on abundance in MSS and on n-octanol water partition coefficient (K_OW). Dashed horizontal line represent the criteria for chemical bioaccumulation potential (Log K_OW = 5). Data source: (Venkatesan and Halden 2014b).