Water treatment company Va Tech Wabag (WABAG) has bagged a Rs 4,400-crore seawater reverse osmosis project in Tamil Nadu which after completion would be the largest sea-water desalination project in the South East Asia region. The project has been bagged in a joint venture with Metito Overseas Ltd and will be implemented on a design, build, operate (DBO) model, the Chennai-based company said in a statement on Friday.