On Wired.com, Dave Bullock has an article and image gallery in New Purification Plant Answers California’s Water Crisis, which uses microfiltration and other technologies to treat sewage and pump it back into aquifers. Here are a few of Bullock’s excellent photographs:
, writing in The New York Times
before the plant went on-line:
the Orange County Water District will turn on what industry experts say is the world’s largest plant devoted to purifying sewer water to increase drinking water supplies. They and others hope it serves as a model for authorities worldwide facing persistent drought, predicted water shortages and projected growth.
The process, called by proponents “indirect potable water reuse” and “toilet to tap” by the wary, is getting a close look in several cities.
The San Diego City Council approved a pilot plan in October to bolster a drinking water reservoir with recycled sewer water. The mayor vetoed the proposal as costly and unlikely to win public acceptance, but the Council will consider overriding it in early December.
Water officials in the San Jose area announced a study of the issue in September, water managers in South Florida approved a plan in November calling for abundant use of recycled wastewater in the coming years in part to help restock drinking water supplies, and planners in Texas are giving it serious consideration.
“These types of projects you will see springing up all over the place where there are severe water shortages,” said Michael R. Markus, the general manager of the Orange County district, whose plant, which will process 70 million gallons a day, has already been visited by water managers from across the globe.
The finished product, which district managers say exceeds drinking water standards, will not flow directly into kitchen and bathroom taps; state regulations forbid that.
Instead it will be injected underground, with half of it helping to form a barrier against seawater intruding on groundwater sources and the other half gradually filtering into aquifers that supply 2.3 million people, about three-quarters of the county. The recycling project will produce much more potable water and at a higher quality than did the mid-1970s-era plant it replaces.
The Groundwater Replenishment System, as the $481 million plant here is known, is a labyrinth of tubing and tanks that sucks in treated sewer water the color of dark beer from a sanitation plant next door, and first runs it through microfilters to remove solids. The water then undergoes reverse osmosis, forcing it through thin, porous membranes at high pressure, before it is further cleansed with peroxide and ultraviolet light to break down any remaining pharmaceuticals and carcinogens.
The result, Mr. Markus said, “is as pure as distilled water” and about the same cost as buying water from wholesalers.
Recycled water, also called reclaimed or gray water, has been used for decades in agriculture, landscaping and by industrial plants.
And for years, treated sewage, known as effluent, has been discharged into oceans and rivers, including the Mississippi and the Colorado, which supply drinking water for millions.
But only about a dozen water agencies in the United States, and several more abroad, recycle treated sewage to replenish drinking water supplies, though none here steer the water directly into household taps. They typically spray or inject the water into the ground and allow it to percolate down to aquifers.
Namibia’s capital, Windhoek, among the most arid places in Africa, is believed to be the only place in the world that practices “direct potable reuse” on a large-scale, with recycled water going directly into the tap water distribution system, said James Crook, a water industry consultant who has studied the issue.
From Sewage, Added Water for Drinking, December 7, 2007.