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Baffle Curtain - Waste Water Treatment Plant

To increase hydraulic retention times for effective water treatment a design often employs a fixed or floating baffle system.

Baffles are used as vertical walls which redirect flowing water through determined paths to increase the time water is exposed to treatment chemicals or processes.  A baffle system typically includes a high performance flexible geomembrane, stainless steel cables and mounting hardware.

This type of baffle system, probably the longest floating geosynthetic baffle curtain used in a wastewater application in New Zealand, was recently installed in Ngaruawahia, Waikato District. Permathene Ltd, located in Auckland, supplied and installed this baffle system.

The Waikato District Council provide eight localised wastewater networks that service areas of the Waikato district in order to ensure wastewater quality meets environmental standards. The Huntly and Ngaruawahia Wastewater Treatment Plants are using an Oxidation pond system which is currently being upgraded.

The latest stage of the plant upgrade included the removal of sludge and other deposits from the sewage treatment pond.  The sludge had to be dewatered and permanently deposited in a designated area of the treatment plant’s wetlands. A temporary dewatering pond was commissioned for this part of the project and Permathene supplied 3,250 m² of Permaliner 0.5mm Flexible Polypropylene for the lining of the excavation.  This liner was factory fabricated in three separate panels which were welded together on-site at the time of installation.  Dewatered sludge was placed in this area as a primary stage of the dewatering process.

Five new floating baffle curtain walls were fabricated and installed into the treatment pond.  This new system creates an extended flow path through the pond and separates the pond into a facultative and four maturation zones.  Baffles 1, 2, 5, and 6 have a range of square openings, which allow a controlled water flow throughout the four maturation zones towards the outlet.

This work significantly improves the performance of the treatment pond and prepared the pond for future upgrades.

Case Study for this can be found here (pdf).

waste water treatment pond baffle curtain