Project Detail
Located about 125 kilometers (78 miles) west of Mexico City lies the municipality of Villa de Allende, home of Mexico’s largest potable water treatment plant. In 2010, Conagua decided to replace the nozzle underdrain system at Los Berros. The plant had experienced poor backwash water distribution as well as frequent nozzle breakages. This caused significant loss of sand media, which usually ended up in the sedimentation tanks. Replacing the lost media and emptying the sedimentation tanks, which wasted vast amounts of valuable water, had become a costly proposition. Conagua decided that refurbishment of the filter underdrain and replacement of the media were required. In searching for a new filter underdrain system, the agency sought a more reliable solution that would provide for better air and water distribution during the backwash operation and would not require frequent parts replacement.
After investigating a number of filter underdrain systems, Conagua selected the TETRA LP Block low-profile dual parallel lateral filter underdrain blocks with the GroutGrip design from De Nora Water Technologies. The installation also included sludge collectors and fiberglass reinforced plastic troughs for eight sedimentation basins and eight new double-bay filters. A total of 96 new filters were installed, providing 7,834 sq meters (25,696 sq ft) of filtration capacity.
The LP Block provides superior distribution for both water and air, sequentially or concurrently. The blocks cover the floor of the gravity filters, supporting the filter media. Air is distributed evenly across the entire filter bottom area to scour the media and to provide an air lift which, with the water, removes the released solids from the media. This dual backwash action provides intense and extremely effective backwashing of the filter media. Importantly, the nozzleless design ensures there are no blockages that could potentially affect the performance of the filter. And the system’s absence of moving parts eliminates wear and tear.
“The LP block is about 13 cm [8 in.] lower than the plant’s previous underdrain system, which prevents the loss of media during backwash. The lower profile also increases hydraulic head during filtration. The system does not require pumps or elevated tanks often needed with some other systems, so it requires less power for operation. With the TETRA LP Block technology, we believe we have made the best choice in terms of performance and cost and based upon the structural requirements and functionality of the Los Berros plant,” said Virgilio Martinez, regional manager for De Nora Water Technologies.
