Engineering Inc. - May/June 2007 - 23

MULTI-PROJECT FEATURE Earth Tech K. Friese & Associates, Inc. Kennedy/Jenks Consultants SaveS Money and IS eco-FrIendly T reating wastewater in the Nashville, Tenn., area has long been an expensive proposition, in part because the region’s water utility must truck sewage sludge—70 percent of which is water—to landfills for disposal. But a new biosolids facility designed by Long Beach, Calif.-based Earth Tech is about to change that. Earth Tech, a unit of Tyco International Ltd., has designed sludge thickening, digesting, dewatering and heat drying facilities that will convert sewage sludge into biosolids pellets. With the new project, the Department of Water Services of Metropolitan Nashville and Davidson County is expected to offset its operational costs Earth tEch by selling the pellets, which can be used as a soil enhancer and low-grade fertilizer. “Communities like the Nashville metropolitan area face simultaneous challenges: how to efficiently dispose of sanitary system byproducts while meeting changing federal regulations,” said Alan Krusi, Earth Tech’s president. “We are designing a technically advanced solution that addresses these issues and closes the environmental loop by producing a useful nontoxic byproduct.” The three-year, $117 million project aims to reduce the volume of sludge that requires treatment, largely by a series of steps designed to remove water from the sludge. The biosolids facility will use Dissolved Air Flotation Thickeners to remove excess water from the sludge. The thickened sludge will then be pumped to anaerobic digesters, which break down the sludge’s organic matter to reduce the volume and to produce methane gas. The methane gas is used in part to heat the sludge in the digesters at a controlled temperature of 95 degrees Fahrenheit for a month. After that, the digested sludge is put into centrifuges that remove even more water. Heat for the drying process comes mainly from the methane gas produced by the digesters, allowing for efficient use of energy. The sludge coming out of the centrifuges is 77 percent Alan Krusi water and 23 percent solids. From the centrifuges, the sludge is sent to dryers that produce the pellets of sludge. Pellets leaving the dryer are 95 percent solids and 5 percent water. The facility will have a maximum capacity of 137 dry tons of sewage solids per day. Almost two-thirds of the construction is finished, with startup and commissioning expected to begin this June. MAY / JUNE 2007 ENGINEERING INC. 23

Engineering Inc. - May/June 2007

Table of Contents for the Digital Edition of Engineering Inc. - May/June 2007

Table of Contents
From ACEC to You
News & Notes
Market Watch
Legislative Ac tion
Interview with Congressman James Oberstar
Port Security
Water: Managing our Precious Commodity
Engineering Excellence Awards
“Smart” Concrete
Business Insights
Members in the News
One on One
Engineering Inc. - May/June 2007 - Cover1
Engineering Inc. - May/June 2007 - Cover2
Engineering Inc. - May/June 2007 - Table of Contents
Engineering Inc. - May/June 2007 - From ACEC to You
Engineering Inc. - May/June 2007 - 3
Engineering Inc. - May/June 2007 - News & Notes
Engineering Inc. - May/June 2007 - 5
Engineering Inc. - May/June 2007 - Market Watch
Engineering Inc. - May/June 2007 - 7
Engineering Inc. - May/June 2007 - Legislative Ac tion
Engineering Inc. - May/June 2007 - 9
Engineering Inc. - May/June 2007 - Interview with Congressman James Oberstar
Engineering Inc. - May/June 2007 - 11
Engineering Inc. - May/June 2007 - 12
Engineering Inc. - May/June 2007 - 13
Engineering Inc. - May/June 2007 - Port Security
Engineering Inc. - May/June 2007 - 15
Engineering Inc. - May/June 2007 - 16
Engineering Inc. - May/June 2007 - 17
Engineering Inc. - May/June 2007 - 18
Engineering Inc. - May/June 2007 - 19
Engineering Inc. - May/June 2007 - 20
Engineering Inc. - May/June 2007 - 21
Engineering Inc. - May/June 2007 - Water: Managing our Precious Commodity
Engineering Inc. - May/June 2007 - 23
Engineering Inc. - May/June 2007 - 24
Engineering Inc. - May/June 2007 - 25
Engineering Inc. - May/June 2007 - Engineering Excellence Awards
Engineering Inc. - May/June 2007 - 27
Engineering Inc. - May/June 2007 - 28
Engineering Inc. - May/June 2007 - 29
Engineering Inc. - May/June 2007 - 30
Engineering Inc. - May/June 2007 - 31
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Engineering Inc. - May/June 2007 - 33
Engineering Inc. - May/June 2007 - 34
Engineering Inc. - May/June 2007 - 35
Engineering Inc. - May/June 2007 - 36
Engineering Inc. - May/June 2007 - 37
Engineering Inc. - May/June 2007 - “Smart” Concrete
Engineering Inc. - May/June 2007 - 39
Engineering Inc. - May/June 2007 - Business Insights
Engineering Inc. - May/June 2007 - 41
Engineering Inc. - May/June 2007 - Members in the News
Engineering Inc. - May/June 2007 - 43
Engineering Inc. - May/June 2007 - 44
Engineering Inc. - May/June 2007 - 45
Engineering Inc. - May/June 2007 - 46
Engineering Inc. - May/June 2007 - 47
Engineering Inc. - May/June 2007 - One on One
Engineering Inc. - May/June 2007 - Cover3
Engineering Inc. - May/June 2007 - Cover4
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