Wastewater plants extract nutrients from sewage_美文

Wastewater plants extract nutrients from sewage

Sludge power

Engineer Chris Peot heads the solid waste program at Blue Plains, which is working on making better use of the mud-like sludge components of the wastewater stream.

He says by 2012 the four huge digesters now under construction will cook the sludge.

“The microbes in the digesters are methanogens and they help break down the organic matter and convert it into methane which can be collected and burned in a turbine which turns and creates electricity.”

The process will make enough methane gas to supply about one-third of the treatment plant’s electric power needs, a great savings given that Blue Plains is the city’s biggest electricity user.

The other half of the digested wastewater bio-solids will be sold as a nutrient-rich soil additive.

“If we blend it and make it look like a top soil we can market it to the public," Peot says. "It can certainly be a source of revenue, a source of good clean soils for restoration projects, for reducing run-off for tree planting.”

Ghana's green factory

Other sewage treatment plants in the United States and other developed countries have adopted this by-product technology, or are considering doing so. The idea is also generating interest in developing countries.

Amit Pramanik is an environmental engineer with the Water Environment Research Foundation. In a recent trip to Ghana, West Africa, he visited Kumasi, the nation’s second largest city, where only 10 percent of the residents are connected to a central sewer system.