Smart Chemistry Overcomes Costly Scale Build-Up

Key Takeaways:

• Issue: Severe scale buildup due to design and improper pH control in lime softening process
• Solution: Targeted CO₂ dosing to safely and gradually dissolve scale; polyphosphate feed point relocation
• Results: Lines cleared in under a month with minimal cost or disruption
• Collaboration: Worked with plant operations team to resolve complex issues caused by initial design choices

Location: Surface Water Treatment Plant – North Dakota

A newly constructed lime softening plant in North Dakota ran into serious issues just 18 months after opening. The plant, which treats surface water, was designed with primary and secondary softening basins. The design called for six basins instead of three, greatly increasing the building size and complexity.

Aqua-Pure Inc. recommended a simpler setup, but the consulting engineers insisted on the two-stage softening process. Unfortunately, the plant never fully used it as intended. Over time, a major problem developed. Calcium carbonate began to build up in the 72-inch pipe between the primary and secondary basins. The buildup reached nearly 8 inches thick.

Chemistry-First Thinking, Practical Solution

The plant’s Superintendent reached out to us for advice. He wanted to know how much acid it would take to clean the pipe. We explained that a full tanker might be needed, and even then, the pipe would be hard to fill due to flow patterns. Ventilation was also a concern. Using acid would release CO₂ and HCl fumes, and the space lacked proper airflow.

Instead, we offered a safer, easier approach. We suggested using the three basins in parallel. By lowering the pH in one basin at a time using CO₂, the calcium carbonate could dissolve naturally. We dropped the pH to around 5.0. While one basin cleaned itself, the other two ran with slightly higher pH levels to keep the system balanced.

This approach worked exactly as planned. Within a month, the scale was gone. There was almost no manual labor, downtime, or chemical cost. We also moved the polyphosphate feed point to the recarbonation chambers. Since then, the plant has run smoothly—for over 20 years.

At Aqua-Pure Inc., we solve treatment challenges with innovative, chemistry-driven strategies that extend system life, reduce costs, and improve water quality. Contact us to optimize your plant’s performance today.