Clarifier Launder and Weir Resurfacing

The challenge

The concrete launder and weir trough around a clarifier carries the constant wash of water running over the lip and into the trough. Over time that surface spalled and roughened, and the weir lip lost its true line. Once the edge is no longer even, the water no longer spreads evenly across the weir, so the flow channels to the low spots and the wash concentrates there. That uneven flow keeps breaking the surface down, the spalling works back into the trough, and the launder can no longer carry an even overflow the way the clarifier was designed to run.

The Belzona approach

All the failed and spalled concrete is chipped out back to a solid base, and the launder and the weir lip are cleaned down to sound substrate. A cold-applied repair mortar then rebuilds the lost concrete in the launder and along the weir lip, bringing the section back to profile. The lip is reprofiled to a true, even edge so the water can spread across it the way it should. Once the substrate is sound and shaped, a coating that leaves a smooth surface lines the wetted launder against the water, so the trough carries an even overflow and stands up to the constant wash instead of spalling back open.

1. Assess and mapThe launder and weir are surveyed to map the spalled and roughened areas and check where the lip has lost its true line.
2. Chip out and cleanThe failed concrete is chipped out back to a solid base, and the launder and weir lip are cleaned down to sound substrate.
3. Rebuild with repair mortarA cold-applied repair mortar rebuilds the lost concrete in the trough and along the lip, returning the section to profile.
4. Reprofile the weir lipThe lip is reprofiled to a true, even edge so the water spreads evenly across the weir.
5. Line and return to serviceA smooth coating lines the wetted launder against the water, and the trough returns to service ready to carry an even overflow.