Some white granular stuff in leek seed powder infused water may be due to the following two reasons:

1. It may be the unground chunks in the leek seeds, because leek seeds are irregular in shape and relatively small, which may produce small white granules in infused water.

2. There may be some insoluble impurities or precipitates present in the leek seeds, as the leek seeds may not be able to completely remove all the impurities during the grinding process.

These white granular substances are usually harmless, but can be properly strained if you mind.