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Abstract
Abstract Supply water is an important source of human exposure to heavy metals through the oral pathway. Due to stagnation of water in plumbing systems, exposure concentrations of heavy metals from tap water can be higher than water distribution systems (WDS), which is often ignored by the regulatory agencies. In this study, concentrations of a few heavy metals (arsenic (As), chromium (Cr), copper (Cu), mercury (Hg), manganese (Mn), magnesium (Mg), zinc (Zn) and iron (Fe)) and water quality parameters were monitored in WDS, plumbing pipe (PP) and hot water tanks (HWT). Multiple models were trained for predicting metal concentrations in PP and HWT, which were validated. Heavy metal concentrations in HWT were 1.2–8.1 and 1.4–6.7 times the concentrations in WDS and PP respectively. Concentrations of As, Cr, Cu, Hg and Zn were in the increasing order of WDS, PP and HWT. Concentrations of Cr and Fe were higher during summer while Cu and Zn were higher in winter. The models showed variable performances for PP and HWT (R2: PP = 0.61–0.99; HWT = 0.71–0.99). The validation data demonstrated variable correlation coefficients (r: PP = 0.45–0.99; HWT = 0.83–0.99). Few models can be used for predicting heavy metals in tap water to reduce the cost of expensive sampling and analysis.
Highlights
Few heavy metals are necessary for humans while an excess amount can pose elevated risks (ATSDR 2015; USEPA 2017, 2019)
The Dissolved organic carbon (DOC) in the water distribution systems (WDS), PP and hot water tanks (HWT) were in the ranges of 0.11–10.24, 0.24–3.98 and 0.30–4.49 mg/L, respectively (Kabir et al 2018)
The aggressivity index (AI) of water is a function of pH, alkalinity and calcium hardness, which is calculated as: AI 1⁄4 pH þ CH þ DA; where CH 1⁄4 Logarithm of calcium hardness; and DA 1⁄4 Logarithm of alkalinity
Summary
Few heavy metals are necessary for humans while an excess amount can pose elevated risks (ATSDR 2015; USEPA 2017, 2019). Drinking water is an important source of human exposure to heavy metals. Safe drinking water must not impose an elevated risk (WHO 2017). Natural and industrial processes generate wastes with heavy metals, which are mostly discharged into the environmental systems (Szefer et al 1999; Chowdhury et al 2016). The sources of industrial pollution include electroplating, metal smelting, chemical and mining industries and manufacturing processes (He et al 2008; Liu et al 2011, 2012). Treated industrial, domestic and agricultural wastewater often contains higher levels of metals, which are typically released into the environment (Gupta 2008). Several other sources were reported to pollute the environment and water sources (Wu et al 2014; Wang et al 2015; Chowdhury et al 2016)
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