he says in 45 minutes, this sewage water will be drinkable. >> mike markus: you'll love it. >> stahl:hink i'm going to drink that water? >> markus: yes, you will. >> stahl: they put the wastewater through an elaborate three-step process-- suck it through microscopic filters, force it through membranes blast it with u.v. light. by the end, markus insists it's purer than the water we drink. but it doesn't go straight to the tap. they send it to this basin, and then use it to replenish the groundwater. >> famiglietti: it's amazing. because of recycling of sewage water, they've been able to arrest that decline in the groundwater. >> stahl: all right, i'm going to do it. all that was left was to try it. to tell the truth, it wasn't bad. i can't believe how brave i am. 45 minutes ago, this was sewer water. >> markus: and now, it's drinkable. >> stahl: he says it's a great model for big cities around the country. but it's not the answer for areas like the central valley, which is sparsely populated and therefore doesn't produce enough waste. so, at least for now, it's continuing withdrawals