Other learned colleagues have ...
Published by David Boggs, Director of Environmental Services
Other learned colleagues have commented on this adequately. It really depends on the end use for the "raw" water. If it is for use as potable, 500-600mg/l should be the upper limit (per WHO). Conventional water treatment does not reduce TDS, but likely increases it due to coagulation and chemical addition. So a feed water for potable, would ideally be less than 500. Other industrial process waters or irrigation users may be able to tolerate higher TDS, in fact some halophyte plants can tolerate or even thrive on high TDS water above 100 mg/l.