Statistical procedures for corrosion studies

Wysock, Barbara M.; Sandvig, Anne; Schock, Micheal R.; Frebis, Christopher P.; Prokop, Boris

doi:10.1002/j.1551-8833.1995.tb06397.x

Cited by 15 publications

(23 citation statements)

References 1 publication

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“…Figure is a dot plot comparing the performance of different orthophosphate doses. In addition to visual observations, one can apply appropriate statistical procedures to compare the data (Wysock et al ). The coupon studies in Figure were conducted for approximately one year, with the data in Figure , part A, representing the results from day 28 to 49, which is a typical period for the coupons to reach steady state and after which time a decision based on the coupon study would be made.…”

Section: Example Resultsmentioning

confidence: 99%

Coupon Procedures for Evaluating Lead and Copper Solubility

Cornwell¹,

Wagner²

2019

Journal AWWA

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Section: Example Resultsmentioning

confidence: 99%

Coupon Procedures for Evaluating Lead and Copper Solubility

Cornwell¹,

Wagner²

2019

Journal AWWA

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“…Associated normal distribution methods are therefore not valid. USEPA recommends Wilcoxon nonparametric methods for analysis (Wysock et al, 1995). However, the Wilcoxon methods assume that the samples are obtained randomly.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…Data were analyzed using the Wilcoxon statistical method suggested by USEPA (Wysock et al, 1995). An alternative linear regression method was used to double‐check the conclusions.…”

mentioning

confidence: 99%

Effect of chlorine on corrosion in Drinking Water Systems

Cantor¹,

Park²,

Vaiyavatjamai³

2003

Journal AWWA

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The federal Ground Water Rule may require some water utilities that do not use disinfection to begin doing so. A common method of disinfection is to add chlorine to the water. A study was performed to investigate the corrosive effects of chlorine in drinking water systems out of concern for staying in compliance with the corrosion control stipulations of the Lead and Copper Rule. Comparative corrosivity experiments using pipe loops were performed at two test sites. In this study, iron appears to be the most affected by free chlorine addition, followed by copper, followed by lead, which may or may not experience increased corrosion.Elevating the pH of the water at one site (originally at a pH of 7.8, 140 mg/L as calcium carbonate [CaCO 3 ] total alkalinity, 6 mg/L dissolved oxygen) was beneficial in counteracting the corrosive effect of chlorinated water on iron. However, in this case, the elevation of pH was not beneficial in controlling corrosion of lead or copper. Adding orthophosphate decreased corrosion of lead and iron in contact with chlorinated water at the other site (original pH of 7.4, 290 mg/L as CaCO 3 total alkalinity, 11 mg/L dissolved oxygen). However, copper corrosion appeared to reach an increased level in the long term.

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“…Nonlinearity can also make it difficult to identify a stable phase, as typical guidance for analyzing pipe loop study data suggests. 3 The most common models for pipe loop data are usually inadequate to describe complex nonlinear variation. 4…”

Section: Non-linearitymentioning

confidence: 99%

Comparing corrosion control treatments for drinking water using a robust Bayesian generalized additive model

Trueman

James

Shu

et al. 2022

Preprint

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Pipe loop studies are used to evaluate corrosion control treatment, and updated regulatory guidance will ensure that they remain important for water quality management. But the data they generate are difficult to analyze: non-linear time-trends, non-detects, extreme values, and autocorrelation are common attributes that make popular methods, such as the t- or rank-sum tests, poor descriptive models. Here, we propose a model for pipe loop data that accommodates many of these difficult-to-model attributes: a robust Bayesian generalized additive model with continuous-time autoregressive errors. Our approach facilitates corrosion control treatment comparisons without the need for imputing non-detects or special handling of outliers. It is well-suited to describing nonlinear trends without overfitting, and it accounts for the reduced information content in autocorrelated time series. We demonstrate it using a four-year pipe loop study, with multiple pipe configurations and orthophosphate dosing protocols, finding that an initially high dose of orthophosphate (2 mg P L-1) that is subsequently lowered (0.75 mg P L-1) can yield lower lead release than an intermediate dose (1 mg P L-1) in the long term. Water utilities face difficult tradeoffs in applying orthophosphate for corrosion control, and better models of pipe loop data can help inform the decision-making process.

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Statistical procedures for corrosion studies

Cited by 15 publications

References 1 publication

Coupon Procedures for Evaluating Lead and Copper Solubility

Coupon Procedures for Evaluating Lead and Copper Solubility

Effect of chlorine on corrosion in Drinking Water Systems

Comparing corrosion control treatments for drinking water using a robust Bayesian generalized additive model

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