Jeffrey Parks

Boron in the Environment

Boron has recently come to the attention of the U.S. Environmental Protection Agency as a possible contaminant worthy of regulation, but questions must still be addressed before a regulatory determination can take place. This article reviews current knowledge about boron as it pertains to water treatment and the environment so that informed decisions can be made regarding regulations and direction of future research. Specifically, this article summarizes boron chemistry, boron occurrence, health effects of boron, existing guidelines and regulations concerning boron, and methods for removing boron from drinking water.

Impact of Water Chemistry, Pipe Material and Stagnation on the Building Plumbing Microbiome

A unique microbiome establishes in the portion of the potable water distribution system within homes and other buildings (i.e., building plumbing). To examine its composition and the factors that shape it, standardized cold water plumbing rigs were deployed at the treatment plant and in the distribution system of five water utilities across the U.S. Three pipe materials (copper with lead solder, CPVC with brass fittings or copper/lead combined pipe) were compared, with 8 hour flush cycles of 10 minutes to simulate typical daily use patterns. High throughput Illumina sequencing of 16S rRNA gene amplicons was employed to profile and compare the resident bulk water bacteria and archaea. The utility, location of the pipe rig, pipe material and stagnation all had a significant influence on the plumbing microbiome composition, but the utility source water and treatment practices were dominant factors. Examination of 21 water chemistry parameters suggested that the total chlorine concentration, pH, P, SO4 2- and Mg were associated with the most of the variation in bulk water microbiome composition. Disinfectant type exerted a notably low-magnitude impact on microbiome composition. At two utilities using the same source water, slight differences in treatment approaches were associated with differences in rare taxa in samples. For genera containing opportunistic pathogens, Utility C samples (highest pH of 9–10) had the highest frequency of detection for Legionella spp. and lowest relative abundance of Mycobacterium spp. Data were examined across utilities to identify a true universal core, special core, and peripheral organisms to deepen insight into the physical and chemical factors that shape the building plumbing microbiome.

Rapid free chlorine decay in the presence of Cu(OH)2: Chemistry and practical implications

A rapid reaction between free chlorine and the cupric hydroxide [Cu(OH)2] solids commonly found on pipe walls in premise plumbing can convert free chlorine to chloride and rapidly age Cu(OH)2 to tenorite (CuO). This reaction has important practical implications for maintaining free chlorine residuals in premise plumbing, commissioning of new copper pipe systems, and maintaining low levels of copper in potable water. The reaction stoichiometry between chlorine and Cu(OH)2 is consistent with formation of CuO through a metastable Cu(III) intermediate, although definitive mechanistic understanding requires future research. Natural levels of silica in water (0-30 mg/L), orthophosphate, and higher pH interfere with the rate of this reaction.

Effects of Bulk Water Chemistry on Autogenous Healing of Concrete

Autogenous healing can occur when hairline cracks in concrete repair themselves through reactions with water and/or constituents in water. The chemistry of water contacting the cement affects whether the crack heals autogenously or propagates until leaks occur. The strength testing on concrete specimens demonstrates that appreciable healing can occur at a pH of 9.5 when there is sufficient magnesium and silicon in the water. Scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) analyses indicate that a magnesium silicate material is present within the crack surfaces when higher strength healing has occurred. Calcium does not appear to promote the sealing of cracks. A carbonation of internal concrete surfaces was not detected when cracks were sealed via autogenous healing. Chloride diffusion rates do not return to levels seen in virgin concrete when cracks are autogenously healed. However, the water permeability and chloride diffusion are impeded by any filling of cracks regardless of the strength attained.

Evaluating Water Lead Levels During the Flint Water Crisis

In April 2014, the drinking water source in Flint, Michigan was switched from Lake Huron water with phosphate inhibitors to Flint River water without corrosion inhibitors. The absence of corrosion control and use of a more corrosive source increased lead leaching from plumbing. Our city-wide citizen science water lead results contradicted official claims that there was no problem- our 90th percentile was 26.8 μg/L, which was almost double the Lead and Copper Rule action level of 15 μg/L. Back calculations of a LCR sampling pool with 50% lead pipes indicated an estimated 90th percentile lead value of 31.7 μg/L (±4.3 μg/L). Four subsequent sampling efforts were conducted to track reductions in water lead after the switch back to Lake Huron water and enhanced corrosion control. The incidence of water lead varied by service line material. Between August 2015 and November 2016, median water lead reduced from 3.0 to <1 μg/L for homes with copper service lines, 7.2-1.9 μg/L with galvanized service lines, and 9.9-2.3 μg/L with lead service lines. As of summer 2017, our 90th percentile of 7.9 μg/L no longer differed from official results, which indicated Flints water lead levels were below the action level.

Effectiveness of Prevailing Flush Guidelines to Prevent Exposure to Lead in Tap Water

Flushing tap water is promoted as a low cost approach to reducing water lead exposures. This study evaluated lead reduction when prevailing flush guidelines (30 s–2 min) are implemented in a city compliant with lead-associated water regulations (New Orleans, LA, USA). Water samples (n = 1497) collected from a convenience sample of 376 residential sites (2015–2017) were analyzed for lead. Samples were collected at (1) first draw (n = 375) and after incremental flushes of (2) 30–45 s (n = 375); (3) 2.5–3 min (n = 373), and (4) 5.5–6 min (n = 218). There was a small but significant increase in water lead after the 30 s flush (vs. first draw lead). There was no significant lead reduction until the 6 min flush (p < 0.05); but of these samples, 52% still had detectable lead (≥1 ppb). Older homes (pre-1950) and low occupancy sites had significantly higher water lead (p < 0.05). Each sample type had health-based standard exceedances in over 50% of sites sampled (max: 58 ppb). While flushing may be an effective short-term approach to remediate high lead, prevailing flush recommendations are an inconsistently effective exposure prevention measure that may inadvertently increase exposures. Public health messages should be modified to ensure appropriate application of flushing, while acknowledging its short-comings and practical limitations.

Elevated Lead in Water of Private Wells Poses Health Risks: Case Study in Macon County, North Carolina

Recent research has indicated that lead in water of private wells is in the range of that which caused problems in Flint, Michigan. However, there is limited understanding of the mechanisms for water lead release in these systems. We evaluated water lead at the homes of two children with elevated blood lead in Macon County (North Carolina), which did not have identifiable lead paint or lead dust hazards, and examined water lead release patterns among 15 private wells in the county. Water lead release patterns differed among the 15 private wells. Problems with lead release were associated with (1) dissolution of lead from plumbing during periods of stagnation; (2) scouring of leaded scales and sediments during initial water use; and (3) mobilization of leaded scales during continued water use. Accurate quantification of water lead was highly dependent on sample collection methods, as flushing dramatically reduced detection of lead hazards. The incidence of high water lead in private wells may be present in other counties of North Carolina and elsewhere in the United States. The underestimation of water lead in wells may be masking cases of elevated blood lead levels attributed to this source and hindering opportunities to mitigate this exposure.