[After Pruned’s unfortunately lost egg digester Flickr set, satellite photography of egg digesters heating and breaking down sludge on Deer Island, just outside Boston.]
[More egg digesters, this time at New York’s Newton Creek Wastewater Treatment Plant. A New York City press release describes the eggs:
“The digesters will process up to 1.5 million gallons of sludge everyday. Each egg, clad with low reflectivity stainless steel, is 145 feet high and 80 feet in diameter. The eight eggs were welded on site from pieces that were brought from Texas and fabricated by Chicago Bridge and Iron. It took three months to assemble each one. Although the weight for each egg is around 2 million pounds when empty; it is calculated that they may weigh up to 32 million pounds when processing sludge…
Digesters play a critical role in the wastewater treatment process. During the wastewater treatment process, organic material called sludge is removed from sewage. Sludge is “digested” and processed for beneficial use. Inside of digesters, bacteria break down this sludge into more stable materials. Heat, lack of oxygen, and time are all needed for this to happen. Much of the sludge is converted into water, carbon dioxide and methane gas. The remaining is called digested sludge. Digested sludge is then dewatered to form a cake, which, after additional processing, can be beneficially used as a fertilizer. The eggs are state of the art in digester design as the shape assists in concentrating grit at the bottom of the tank, mixing for improved digestion and the concentration of gas at the top of the tank. Each egg holds 3 million gallons of sludge.”
Image via Flickr user roboppy (CC BY-NC-ND 2.0).]
