Energy Efficiency in Wastewater Treatment in North America: A Compendium of Best Practices and Case Studies of Novel Approaches: A Compendium of Best Practices and Case Studies of Novel Approaches

Abstract

The Water Environment Research Foundation, a not-for-profit organization, funds and manages water quality research for its subscribers through a diverse public-private partnership between municipal utilities, corporations, academia, industry, and the federal government. WERF subscribers include municipal and regional water and wastewater utilities, industrial corporations, environmental engineering firms, and others that share a commitment to cost-effective water quality solutions. WERF is dedicated to advancing science and technology addressing water quality issues as they impact water resources, the atmosphere, the lands, and quality of life.For more information, contact: Water Environment Research Foundation

Enhancing the Energy Efficiency of Wastewater Treatment Plants through Co-digestion and Fuel Cell Systems

“…The report pointed out that most impacting elements in the energy consumption of a conventional WWTP are the aeration of mixed liquor (55-70%), primary and secondary settling with sludge pumping (15.6%) and sludge dewatering (7%). These data are also confirmed by WERF report (Crawford and Sandino, 2010). Shen et al (2015), while analyzing the US WWTP sector, underlined that electric energy accounts for over than 30% of the total operation and maintenance cost and up to 80% of the GHG emission.…”

“…One of the available report mentions that more than half of energy consumption is linked to aeration process (54.1%), confirming data shown in Table 1 (Crawford and Sandino, 2010). Furthermore, 14.3% of energy consumption is related to pumping systems and another 14.2% to anaerobic digestion mixing.…”

“…Around 4-13% of US electricity generation is linked to water-related energy use, with peaks of 19% in California (Daw et al, 2012). The data is confirmed by the Water Environment & Reuse Foundation (WERF) report, where is mentioned that the 16,000 publicly owned US WWTP are consuming 1 to 4% of total energy production (Crawford and Sandino, 2010). Shen et al also mentions that 3-4% of the national electrical demand goes for WWTP, corresponding to 30.2 billion kWh per year and more than 21 million metric tons of GHG emission (Shen et al, 2015).…”

“…The WERF report for North America WWTP states that anaerobic digestion can recover approximatively 30-40% of the overall current energy consumption through a CHP system (Crawford and Sandino, 2010). However, according to Shen et al (2015), less than 10% of WWTPs in the US are producing biogas for energy production.…”

“…Use of oversized available digesters (more efficient digester volume utilization) Crawford and Sandino, 2010;Shen et al, 2015 Additional facilities requirement (waste collection and treatment line, mixers, pipelines), retrofitting of existing WWTP Shen et al, 2015 Improve in nutrient balance (C:N:P), keep a reasonable mix of minerals (Na, K, Mg, Mn) = stable and reliable anaerobic digestion, good fertilizer quality of digestate Braun et al, 2002 Risk of digestion instability due to high variability of co-digestion feedstock properties (composition and volume) and related pH fluctuations Shen et al, 2015 Improvements in fluid dynamics of solid aggregated wastes.…”