Spatial Models of Sewer Pipe Leakage Predict the Occurrence of Wastewater Indicators in Shallow Urban Groundwater

Abstract

Twentieth century municipal wastewater infrastructure greatly improved U.S. urban public health and water quality. However, sewer pipes deteriorate, and their accumulated structural defects may release untreated wastewater to the environment via acute breaks or insidious exfiltration. Exfiltrated wastewater constitutes a loss of potentially reusable water and delivers a complex and variable mix of contaminants to urban shallow groundwater. Yet, predicting where deteriorated sewers impinge on shallow groundwater has been challenging. Here we develop and test a spatially explicit model of exfiltration probability based on pipe attributes and groundwater elevation without prior knowledge of exfiltrating defect locations. We find that models of exfiltration probability can predict the probable occurrence in underlying shallow groundwater of established wastewater indicators including the artificial sweetener acesulfame, tryptophan-like fluorescent dissolved organic matter, nitrate, and a stable isotope of water (δO). The strength of the association between exfiltration probability and indicators of wastewater increased when multiple pipe attributes, distance weighting, and groundwater flow direction were considered in the model. The results prove that available sanitary sewer databases and groundwater digital elevation data can be analyzed to predict where pipes are likely leaking and contaminating groundwater. Such understanding could direct sewer infrastructure reinvestment toward water resource protection.

Is the Hyporheic Zone Relevant beyond the Scientific Community?

“…TrOCs typically enter surface waters via wastewater treatment plant effluents, since wastewater is most commonly only purified in treatment plants with respect to organic matter, phosphorus, and nitrogen [144], while many TrOCs are not, or only partially, degraded in wastewater treatment plants [145]. Furthermore, urban drainage, combined sewer overflow [146], or leaking water from sewer systems [147], onsite wastewater treatment systems [148], and landfills [149] reach the aquatic environment without undergoing human-induced purification processes. This means that a significant amount of TrOCs are discharged into rivers and streams [150].…”

Reactive and Mixing Processes Governing Ammonium and Nitrate Coexistence in a Polluted Coastal Aquifer

“…Nitrate (NO 3 − ) and ammonium (NH 4 + ) are often recognised as major contaminants in both surface water and groundwater [1][2][3]. The causes can be multiple, including fertilizers leaching in agricultural environments [4][5][6][7], storm and sewage water spillages in urban environments [8][9][10], natural elevated background concentrations [11,12] and spillages of complex chemical mixtures below industrial plants [13,14]. Moreover, the nitrification of NH 4 + into NO 3 − in oxic environments often leads to an increased NO 3 − concentration along the flow paths, up to values well beyond to the maximum water quality admissible levels [15].…”

Comparison of the colloidal stability, mobility, and performance of nanoscale zerovalent iron and sulfidated derivatives

“…Groundwater was obtained from a monitoring well in Santa Barbara, CA, and river water was collected from Upper Middle Creek in Malibu, CA. The characterization of all these waters have been presented in previous studies (Conway et al, 2015;Roehrdanz et al, 2017). All the waters were passed through 0.1 μm filters (Millipore, Ireland) and stored at 4°C prior to colloidal stability experiments.…”