The Lowdown on Lead
The challenges of creating a lead removal certification protocol
In 2011, the Water Quality Assn. (WQA) reported in Water Quality Products on the history of lead in drinking water and the difficulties of testing for it.
Lead has continued to be a topic of discussion in the U.S. for the past few years, as we see periodic reports of lead problems in drinking water systems. As these systems continue to age, the breakdown of components containing lead will make it more necessary to have final barrier treatment options. Furthermore, individual homeowners who test their water are becoming increasingly aware and vigilant of the dangers of lead and other metal contaminants.
This is a good thing for our industry — it forces us to deal with an ever-widening problem in our current drinking water systems and find solutions to the problems that our customers want resolved. As consumers become more knowledgeable, they rightly demand more options for their treatment needs, and with that come the problems of lead treatment technologies.
Products wishing to make a lead claim must conform to NSF/ANSI Standard 53. This performance standard sets the minimum criteria for health claims, of which lead is one of the many available. It requires that products be challenged with influent water containing approximately 150 ppb of lead and reduce it to less than 10 ppb.
The 150-ppb level was chosen as the target influent due to data available from the U.S. Environmental Protection Agency at the time. Even though a vast majority of homeowners would never see lead levels of 150 ppb in their homes, it was decided that the challenge water had to encompass up to 150 ppb to ensure that as many homeowners as possible could be confident in the treatment product they choose to reduce any amount of lead they may have in their water. This may sound simple, but the difficulty is in the details.
NSF/ANSI Standard 53 requires a combination of ionic (soluble) and particulate (insoluble) lead, with the particulate further being divided into course particulate and fine particulate. The lead for each of the requirements is calculated using three samples: the total lead sample, a sample after the influent is run through a 1.2-µ filter, and a sample after the influent is run through a 0.1-µ filter.
The issue of certifying lead removal treatment products comes down to the difficulty in creating a proper testing environment to challenge them. The tolerances allow for as much as 90 ppb of particulate lead in the water, and another 90 ppb in ionic form; however, the tolerances also allow for as little as 18 ppb of particulate lead and 162 ppb of ionic lead. Because the ranges are so large, they permit the lab to allow the levels to drift from one extreme to the other, therefore requiring the product being tested to be able to handle both extremes.
The stability of the pH-8.5 water with this combination is not good, because the lead comes in and out of solution easily, which can cause the challenge water to be different from day to day in the same lab, and from lab to lab. This is what creates problems for most manufacturers when developing and testing their products. The issues of creating stable and reproducible lead challenge water at pH 8.5 caused the industry to gather a task force to come up with solutions to the lead testing problem.
The repercussions of the lead discussion are far reaching. The best way to consistently pass the current standard is to ensure there is enough media to handle the ionic lead, while also having enough carbon to handle the particulate lead. Adding too much of either, however, slows the flow rate, which may be unacceptable to consumers. It also increases the size and cost of the filter to an extent that it would be unworkable in most systems. Even if a product is able to handle these extremes, most companies are not willing to attempt the lead claim due to the high risk of failure, which adds cost and time to the certification process.
To help resolve these problems, the task force explored all of the variables in the lead testing and reported those results. Over the past few years, issues such as pH, alkalinity, temperature and tank material were explored. The task force attempted to determine which, if any, factors would lead to more lead stability within the tank. After years of study, the task force could not reach any definitive conclusion — it only determined that the stability issues seem to have been worked out at each individual lab to the point that influent criteria are met at each lab.
It is suspected that each lab has found a “sweet spot” where the procedure that it runs allows for the challenge water to come out correctly for it based on the unique quality of the water it receives from its local water source. Through continued research into the topic, WQA noticed that if the pH deviates even a small amount from 8.5, then the tank becomes unstable and the particulate percentages do not work. This has caused the association to tighten its internal controls over some parameters, such as pH, to the point that it is confident it can maintain the correct values for lead testing according to the current NSF/ANSI Standard 53.
With the knowledge gained from the task force and its own internal testing, WQA will embark on a new round of research that hopefully will lead to a more confident industry and produce an environment in which manufacturers are willing to test their products for the lead claim.