Of all the contaminants that end up in our water, few are as emotive as lead.  This dense metallic element has been linked to a number of issues in children, including delayed development, reduced IQ scores, behavioural problems, and attention disorders.  In addition, lead may also have adverse effects in adults including high blood pressure, kidney problems, and cardiovascular issues. Plainly, lead is a dangerous addition to water but gets in unintentionally so is difficult to control.

Lead becomes dissolved in water primarily through corrosion.  Water can have a slight acidic, depending upon mineral content, and that can lead to concentrations of lead building up in water, particularly in fast moving systems, which create significant agitation against the sides of the pipes.  Prior to the 1970’s, many houses had lead pipe water systems as it was a relatively cheap (at the time) and easily workable material.  It could be formed into shapes and joined with ease.  Obviously, even though it is not permeable to water, the flow still corroded the lead and picked up small amounts of it.  

The 1970’s marked a mass-change to copper piping in new houses and a huge reduction in lead piping.  Health implications should have been much reduced at that point, were it not for the continued use of lead-based solder to join the copper pipes.  Because there was a significant amount of lead already within the water system, and it continued to be supported by the solder issue, lead has continued to be a problem in some supplies, and removal is paramount.

The American Centre for Disease Control and Prevention (CDCP) recommend several methods of water filtration for lead removal, including distillation, carbon filtration, and reverse osmosis, but one of the most effective means and one that is gaining increasing interest is that of adsorption.  Lead reduction by passing the water through an adsorbent is seen as a new and efficient way of removing this difficult and dangerous substance, while retaining a strong air of reusability and green credentials.  And the actual adsorbents are more surprising than you may think.

Academic studies have found a number of different products that work surprisingly well as adsorbents for heavy metals and lead in particular.  Studies have found that kaolinite, the clay-based mineral sedimentary rock, and its related its aluminium phyllosilicate clay, bentonite, are almost as effective as activated carbon at removing lead from water.  And the good news is that they are highly abundant and easy to extract, making them a cost-effective solution. On a much lower level, both blast furnace slag and fly ash – a pulverised coal-consumption by-product – are similar in adsorbent abilities but are in shorter supply so are not considered a real alternative.  Clays like kaolinite and bentonite can be dried and formed into a matrix within a filter cylinder through which the lead-contaminated water can be driven, resulting in cleaned water out of the exit pipe.  The beads can be dried and reused, making it an efficient system.

The lead pipe issue and aging infrastructure of our municipal water systems will take time and money to remedy. It’s estimated that water suppliers need to spend more than 250 Billion dollars to repair this problem–and this will not happen very quickly.  This means that we are going to have remove it from our water for some years to come, and adsorbents offer an increasingly cost effective and efficient way of doing that.