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This paper documents the energy intensity and environmental impacts from operation of waterand wastewater treatment systems through case studies in the United States. Life-cycleenergy and impact assessments were conducted for the Ann Arbor Water Treatment Plant(WTP) and Ann Arbor Wastewater Treatment Plant (WWTP) in Michigan. The framework forassessment was modified to assess the environmental burdens from Laguna WWTP in Californiaand Ypsilanti Community Utility Authority (YCUA) WWTP in Michigan.From the comparative assessment of the three WWTPs, it is found that the life-cycle energy forthe YCUA WWTP is the highest - 21 GJ/MG; out of which, 46% is from electricity used foroperation, 44% from natural gas used for the sludge incinerator and 10% from production ofchemicals used for treatment. For the Ann Arbor WWTP, electricity utilized accounts for 50%,natural gas used for 25%, energy for sludge-hauling for 16% and energy in the form of chemicalsused for 9% of the total life-cycle energy of 16 GJ/MG. The life-cycle energy for the LagunaWWTP is the lowest - 11 GJ/MG, as it meets the total requirement for natural gas and 40% of theelectricity required from methane produced upon anaerobic sludge digestion. Hence, 91% of thelife-cycle energy for Laguna WWTP is from electricity, 8% from chemicals and a mere 1% fromsludge-disposal.From the assessment of the Ann Arbor "water and wastewater" system, it is found that the AnnArbor "water and wastewater" treatment system accounts for 54% of the total electricity requiredby the Ann Arbor municipal government sector. Further, the life-cycle energy required for thesystem is 40 GJ/MG of clean water, out of which 60% is from the operation of the Ann ArborWTP. The system also generates 5,230 kg COsub2/sub eq. /MG clean water or 3.57 million kg COsub2/subequivalent per year. Electricity required for operation of the Ann Arbor WTP and WWTPcontributes significantly to the total life-cycle energy and emissions. Thus, energy conservation atthe plants, adoption of renewable energy and an anaerobic sludge digestion system coupled withco-generation unit would prove to be useful for reducing the total life-cycle energy andenvironmental burdens from the system. Includes 12 references, tables, figures.

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Edition: Vol. - No. Published: 11/01/2008 Number of Pages: 59File Size: 1 file , 1.2 MB