Impact of sodium silicate on lead release and colloid size distributions in drinking water

Li, Bofu; Trueman, Benjamin F.; Munoz, Sebastian; Locsin, Javier A; Gagnon, Graham A.

doi:10.1016/j.watres.2020.116709

Cited by 32 publications

(35 citation statements)

References 68 publications

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“…While variation in equilibrium lead solubility probably explains at least some of the difference between October and February point-of-use lead levels, particle-generating mechanisms are also likely to be important, including partitioning of lead to particulate (>0.45 µm) or colloidal (<0.45 µm) aluminum. 20,54,55 Particulate aluminum was seasonal in the distribution system we studied, with the median concentration in October less than half that in February (20 and 48 µg L -1 , respectively, Figure 4b). The particulate fraction of total aluminum ranged from 16% in August to 35% in February, as estimated from the cyclic cubic regression splines shown in Figure 4b.…”

Section: Colloidal Aluminum and Lead In The Distribution Systemmentioning

confidence: 93%

“…This is consistent with previous work documenting adsorption of lead to aluminum hydroxides [56][57][58] or mixed iron/aluminum (oxyhydr)oxides, 59 and with previous studies reporting occurrence of lead and aluminum in a common colloid size fraction. 20,54,55 The presence of aluminum, iron, and lead in distinct but overlapping colloid populations, however, cannot be ruled out completely. Moreover, these data do not provide a complete picture of colloid composition; the role of phosphorus, for example, is not clear.…”

Section: Colloidal Aluminum and Lead In The Distribution Systemmentioning

confidence: 99%

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Seasonal lead release to drinking water and the effect of aluminum

Trueman

Bleasdale-Pollowy

Locsin

et al. 2021

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Monitoring lead in drinking water is important for public health, but seasonality in lead concentrations can bias monitoring programs if it is not understood and accounted for. Here, we describe an apparent seasonal pattern in lead release to orthophosphate-treated drinking water, identified through point-of-use sampling at sites in Halifax, Canada, with various sources of lead. Using a generalized additive model, we extracted the seasonally-varying components of time series representing a suite of water quality parameters and we identified aluminum as a correlate of lead. To investigate aluminum’s role in lead release, we modeled the effect of variscite (AlPO4 · 2H2O) precipitation on lead solubility, and we evaluated the effects of aluminum, temperature, and orthophosphate concentration on lead release from new lead coupons. At environmentally relevant aluminum and orthophosphate concentrations, variscite precipitation increased predicted lead solubility by decreasing available orthophosphate. Increasing the aluminum concentration from 20–500 µg L-1 increased lead release from coupons by 41% and modified the effect of orthophosphate, rendering it less effective. We attributed this to a decrease in the concentration of soluble (<0.45 µm) phosphorus with increasing aluminum and an accompanying increase in particulate lead and phosphorus (>0.45 µm).

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Section: Colloidal Aluminum and Lead In The Distribution Systemmentioning

confidence: 93%

Section: Colloidal Aluminum and Lead In The Distribution Systemmentioning

confidence: 99%

Seasonal lead release to drinking water and the effect of aluminum

Trueman

Bleasdale-Pollowy

Locsin

et al. 2021

Preprint

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“…The SiO2 residual target was increased to 48 mg L -1 in the final stage of the experiment to investigate the effect of sodium silicates on biofilm formation at higher doses. Further information about the model distribution system and a graphical water quality summary of this system can be found in Li et al 14 .…”

Section: Pipe Loop Systemmentioning

confidence: 99%

“…While sodium silicates are mostly used for sequestration of iron and coagulation applications, they have been studied for lead release control applications. [14][15][16] Sodium silicates may also inhibit the oxidation of ferrous iron, particularly in the pH range of 6.0 -7.0, 17 and they may reduce color and water turbidity. 18 While some focus has been directed to understanding sodium silicates as corrosion inhibitors, their impact on biofilm formation has not been documented in detail.…”

Section: Introductionmentioning

confidence: 99%

Effect of sodium silicate on drinking water biofilm development

Munoz

Trueman

et al. 2021

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Sodium silicates have been studied for sequestration of iron, coagulation, and corrosion control, but their impact on biofilm formation has not been documented in detail. This study investigated the impact of sodium silicate corrosion control on biomass accumulation in drinking water systems in comparison to orthophosphate, a common corrosion inhibitor. Biofilm growth was measured by determining ATP concentrations, and the bacterial community was characterized using 16S ribosomal RNA (rRNA) sequencing. A pilot-scale study with cast-iron pipe loops, annular reactors (ARs), and polycarbonate coupons demonstrated significantly lower biofilm ATP concentrations in the sodium silicate-treated AR than the orthophosphate-treated AR when the water temperature exceeded 20°C. However, an elevated sodium silicate dose (48 mg L-1 of SiO2) disturbed and dispersed the biofilm formed inside the AR, resulting in elevated effluent ATP concentrations. Two separate experiments confirmed that biomass accumulation was higher in the presence of orthophosphate at high water temperatures (20°C) only. No significant differences were identified in biofilm ATP concentrations at lower water temperatures (below 20°C). Differences in bacterial communities between the orthophosphate- and sodium silicate-treated systems were not statistically significant, even though orthophosphate promoted higher biofilm growth. However, the genera Halomonas and Mycobacterium—which include opportunistic pathogens—were present at greater relative abundances in the orthophosphate-treated system compared to the sodium silicate system.

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“…Lead concentration/lead release per unit surface area used to calculate the ratios in Figure 4 (rows represent comparable water quality conditions; units are consistent with the corresponding paper). [4][5][6][7][8][9][12][13][14] x$ph, dic = .x$dic, phosphate = .x$po4, phase = .x$phase, buffer = "HCl", Na = .5, Cl = .5, element = "Pb"…”

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confidence: 99%

Effectiveness of Sodium Silicates for Lead Corrosion Control: A Critical Review of Current Data

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Impact of sodium silicate on lead release and colloid size distributions in drinking water

Cited by 32 publications

References 68 publications

Seasonal lead release to drinking water and the effect of aluminum

Seasonal lead release to drinking water and the effect of aluminum

Effect of sodium silicate on drinking water biofilm development

Effectiveness of Sodium Silicates for Lead Corrosion Control: A Critical Review of Current Data

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