Toilets: Then and Now, Part 12: Sewage Treatment Plants with Vegetation

(using plants; such as, algae to clean up waste water)

Can vegetation provide a solution to the sanitation process of human wastes?

A description of primitive toilet conditions with a possible natural solution

This information is offered as another example of the dangerous hygienic situations many people are still living in because of primitive toilet conditions and as a reminder of how too many of us take our advantages for granted without any real appreciation for the progress that has been made in our "modern age".

  • Andile Tiyani wrinkles his nose in distaste as he points to a listing outhouse patched together from scraps of wood and corrugated metal.
  • The tiny shack, huddled among thousands of other slightly larger shacks that house the black residents of the Crossroads township outside of Cape Town, South Africa, is just large enough to accommodate a toilet seat mounted over a bucket.
  • The bucket is overßowing. "In better areas, they periodically take these buckets to the edge of town and dump them", Tiyani explains. "When the rains come, it all runs into the streams, where people wash their clothes, and it contaminates the groundwater, which lies just four meters below the surface here."
  • In five neighboring townships, home to some one million black South Africans, conditions vary only slightly.
  • In Harare, residents share pit toilets. Tiyani's house in the middle-class district of Guguletu is among the most hygienic around, because it has a septic tank.
  • Sanitation services are a public health priority, but can algae help?

  • Bringing basic sanitation services to the millions who lack them is a top public health priority for the new South African government. It is also a huge fiscal challenge.
  • As in so many other poor countries, expensive Western technologies are simply not an option.
  • One cheap Western technology may be, though. Nearly 500 miles to the east of Cape Town, Peter D. Rose of Rhodes University is adapting an American algae-based system to meet the needs of sub-Saharan Africa.
  • In a nearby pilot plant, due to be completed next year, the waste of 500 to 1,000 people will be pumped through 1,000 square meters of ponds and raceways full of Spirulina, a single-celled plant that thrives on salty, nutrient-rich sewage.
  • Exposed to sunlight and stirred gently, these algae ingest most of the waste.
  • A small remainder of heavy metals and other inorganic detritus sinks to the bottom of the pits.
  • Ponds containing algae have been used to treat waste for at least a century.
  • It is only in the past decade that advanced algal systems, in which just certain species are actively cultivated, have begun to challenge the activated-sludge techniques commonly used in industrial nations.
  • Advanced algal ponding processes now offer several advantages, says William J. Oswald of the University of California at Berkeley, who has worked on the technology since the 1950s.
  • The equipment and power used in conventional plants to mix incoming sewage with pressurized air and bacteria-rich sludge are avoided in algal systems, so the latter cost about one half as much to build and operate.
  • They can run on less water; important in arid climes such as South Africa's.
  • They produce far less sludge, which is generally trucked to landfills or dumped at sea.
  • In fact, the main product is tons upon tons of dead algae, which when dried makes a good fertilizer or additive for fish food, and because the plants produce lots of oxygen, they don't stink.
  • "We had a wine tasting not long ago at the [algal pond] plant in St. Helena," which processes 500,000 gallons of sewage a day in the heart of California wine country. "It was very picturesque," Oswald says.
  • For Rose, the technology holds a dual attraction.
  • The potential for improving community sanitation throughout the Third World is obvious

  • "But it has allowed us to do some very interesting fundamental research as well," Rose says, donning his biochemist's cap.
  • As South African science budgets are increasingly squeezed by a government facing more urgent needs, many scientists there are scrambling to find relevant applications to justify their basic research.
  • "One of the future beneÞts of the process is that once you have this algal biomass, you might be able to engineer it to produce by-products that are more valuable than just animal feed," Rose continued.
  • His team recently elucidated the biochemical mechanism by which another algae, Dunaliella salina, produces massive amounts of beta carotene (the nutrient used by the body to make vitamin A) when stressed by excessive salt or heat.
  • Rose has also demonstrated that Spirulina ponds can treat industrial waste, particularly from tanneries.
  • "The tanning industry is set to explode in Africa," says Randall Hepburn, Rhodes's dean of science. "The reason is simple: we kill 650 million sheep, goats, pigs and cows each year; but the hides of all but three percent of those are left to rot. That is going to change."
  • The possibility of a tanning boom worries some African environmentalists

  • "Tanneries produce some of the worst effluents of any industry: sulfides, ammonia, heavy metals," Rose says. "It's shocking stuff." So he was a bit surprised several years ago when he noticed giant blooms of Spirulina forming in a tannery's evaporation pond.
  • The discovery has led to test projects at tanneries near Cape Town, in Namibia, and in the Transvaal, where algal treatment systems are successfully (and inexpensively) squelching odors and reclaiming water that was previously wasted through evaporation.
  • "Rapid industrialization in Third World countries is very often done at the expense of the environment, because the costs of First World remediation technologies cannot be afforded simultaneously," Rose says.
  • "To come up with a low-cost method that turns waste into something not only safe but useful—well, that's the first prize in biotechnology."
  • —Compiled from information located in
    "Sewage Treatment Plants, Algae offer a cheaper way to clean up wastewater";
    written by W. Wait Gibbs; Scientific American, November, 1995.

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