Granular Activated Carbon Filtration as a Lead Control Strategy

Area of Science:

• Environmental Science
• Water Treatment Engineering
• Materials Science

Background:

• Rising surface water organic carbon due to climate change challenges drinking water quality regulations.
• Water treatment processes can alter natural organic matter (NOM) and water chemistry, influencing lead release from plumbing systems.
• Understanding the interplay between treatment chemicals, filtration media, and lead solder is crucial for maintaining water safety.

Purpose of the Study:

• To compare the efficacy of different coagulants and filter types in managing natural organic matter (NOM) and mitigating lead release.
• To evaluate the impact of zinc-orthophosphate on lead release in a galvanic lead solder-copper system.
• To assess the performance of aluminum sulfate (alum), polyaluminum chloride (PACl), anthracite/sand, and granular activated carbon (GAC) in pilot- and bench-scale studies.

Main Methods:

• Pilot-scale testing of alum, PACl, anthracite/sand, and GAC filters for water quality and NOM removal.
• Bench-scale dump and fill experiments using treated water with varying zinc-orthophosphate concentrations (0-2 ppm).
• Evaluation of lead release, galvanic corrosion, and filter media performance (e.g., GAC exhaustion).

Main Results:

• Granular activated carbon (GAC) contactors significantly reduced organic carbon and demonstrated a strong protective effect against lead release.
• Polyaluminum chloride (PACl) showed slower GAC exhaustion rates compared to alum at equivalent aluminum doses, enhancing overall removal efficiency.
• PACl was associated with increased galvanic corrosion, while zinc-orthophosphate effectively mitigated lead solder corrosion.

Conclusions:

• Removing NOM is key to reducing lead release, with GAC being a highly effective filtration method.
• While PACl can improve NOM removal, its potential to increase galvanic corrosion requires careful consideration.
• Optimizing water treatment strategies, including coagulant choice and corrosion inhibitor application, is essential for ensuring drinking water quality and safety.