LEED in Vietnam

Given that this is an international project, I strongly suggest that you submit an inquiry to your LEED reviewer. Theoretically, the LEED standards are to be applied consistently throughout the world as it's adopted in other countries. However, this may be infeasible in certain cases but only GBCI can make that determination. My bias would be to agree with you because the water is treated to tertiary standards of the local governing agencies for the intended use (landscaping) and as long as you meet the overall goal of treating 50% of wastewater on site and reuse it or let it infiltrate you meet the intent of the credit, and this reuse would also contribute to WEc1.1 and 1.2, if you use no potable water for irrigation.