There already are low-cost, natural water filtration techniques being used across the world that produce clean water at a higher rate, like biosand filters. For water projects i have previously worked on, how quickly water is purified has been a significant practical concern for the folks who would benefit from the project. That was the reason that solar stills were dismissed, for example; they require more effort and materials to construct, but even then have a higher flow rate than the xylem filter. Also, how often the filter must be replaced is another big practicality issue.