2010 Issue

21 in employing one or more of the methods discussed in this paper. In an economy with steadily increasing operating costs, engineers face new challenges in maintaining not only the stability of these systems but their sustainability as well. Engineers also face the challenges as- sociated with designing systems with higher levels of complexity. Many solids pretreatment methods have yet to be established at full scale and first require further investigation at pilot scale. Additionally, advanced treatment methods require that increased attention be paid to these systems and a higher level of operator expertise that, of course, can increase operation and maintenance costs. Many codigestion processes have been observed in solids digesters, and rates of commercial and industrial waste loadings that can be maximized as reliable methods for determining digester capacity have emerged. Further, the efficiency with which biogas is utilized as an energy source can be maximized through efficacy and cost analyses of the energy recovery systems. In recent years, there has been heightened awareness of the need to develop sustainable sources of energy in order to supplant nonrenew- able sources of energy. There is a worldwide concern about the impact of fossil fuels on the climate due to global warming. This compounded with increasing power and natural-gas utility costs make the case for increas- ing self-generated energy more compelling. In fact, some facilities have achieved energy independence through a combination of decreasing energy demand and increasing energy output. Typically, this has been achieved through a combination of energy conservation, implementing more energy efficient systems, and creating renewable energy. Generally, renewable energy creation is achieved by a combination of utilization of anaerobic digestion biogas supplemented with solar, wind, and so forth, at the wastewater facility. With a new emphasis on renewable energy in the U.S. and globally, the change will likely be rapid in the first half of this century. Hence, the goal of wastewater facilities achieving energy independence is a worthy one and consistent with the current progression to sustainable systems. Tolearnmoreaboutthispaper,pleasecontactDruryWhitlock (Drury.Whitlock@ch2m.com ),Julian Sandino (Julian.Sandino@ch2m.com) ,TimShea (Tim.Shea@ch2m.com) ,orPeterBurrowes(Peter. Burrowes@ch2m.com ).DruryWhitlock,SaltLakeCity,Utah;JulianSandino,KansasCity,Missouri;Tim Shea,Chantilly,Virginia;andPeterBurrowes,Kitchener,OntarioareaffilitatedwithCH2MHILL.