Water Resources Research Act Program

Details for Project ID 2020DC137B

Impact of high strength wastes (HSW) co-digestion with sludges on the performance of lab-scale anaerobic digesters and biogas methane potential (BMP) assays with potential to generate H2.

Institute: District of Columbia
Year Established: 2020 Start Date: 2020-03-01 End Date: 2021-02-28
Total Federal Funds: $9,980 Total Non-Federal Funds: Not available

Principal Investigators: Hossain M. Azam

Abstract: Over the past decades, the importance of water-energy nexus has increased because of growing attention for climate change, energy saving, energy efficiency and energy alternative (Friedrich E et al., 2009; Dincer I; 2002). Water Resource Recovery Facility (WRRF) is one of the promising avenue for the nexus between water and energy. Water and wastewater systems consume approximately 3–4% of energy in the U.S. with total emis¬sions of more than 45 million tons of greenhouse gases (GHGs) annually (U.S. EPA, 2013). At a WRRF, the interaction between water and energy implies that a good effluent quality requires a significant input of energy (Yifan Gu et al., 2017). The challenge for all WRRFs is then to meet the strict effluent quality requirements without any major energy consumption (Rojas.J et al., 2012). One of the major ways to optimize water-energy nexus is employment of co-digestion in WRRFs. It is possible to utilize the technologies for sustainable buildings after major development of this technology at WRRF. There is significant potential for energy recovery from WRRFs via anaerobic digestion (AD) with biogas utilization. AD could save 628 to 4,940 million kWh electricity annually in the U.S. Co-digestion, a process utilizing food waste materials as substrate with primary sludge (PS) and waste activated sludge (WAS), allows to avoid the disadvantage of AD in terms of mono-digestion (J.Mata-Alvarez et al.,2014). Thus, co-digestion of high strength waste (HSW) with wastewater sludge increases biogas (CH4) production, decreases reliance on external power provider by beneficial use of biogas (if a combined heat and power (CHP) system is implemented), and provides a potential revenue stream from tipping fees. The success of co-digestion largely depends on the type of food wastes, along with the composition and the proportion of each food waste in the feed mixture. Therefore, it is necessary to select the most suitable food waste and blend ratio, pH, alkalinity, etc. to maximize the biogas production and maintain the quality of the digestate (Silvestre et al., 2011 ,Wang et al., 2016). It is necessary to avoid the inhibition of different components such as ammonia, volatile fatty acids (VFAs) and intermediate products to enhance the biogas production (Xie et al., 2017, Astals et al., 2014). Furthermore, most of the anaerobic co-digestion facilities are focused on generating methane. Currently, approximately 95% of the total energy produced is fossilâ€fuel based energy in the world. H2 is considered as one of the clean energy sources because of its renewability, high calorific value, and pollutionâ€free combustion (Zhitong et al., 2018). Producing H2 from sludge digestion can make this excess sludge innocuous and reduce its quantity as well as also can generate clean hydrogen energy (Zhitong et al., 2018). In this study, lab-scale anaerobic digester performance will be optimized to evaluate the anaerobic co-digestion of waste activated sludge (WAS), cheese whey (CW), fat, oil & grease (FOG), pulp fiber waste (PFW) and other relevant wastes with primary sludge (PS). Later, the co-digestion of WAS, CW, FOG, PFW will be further investigated in BMP assays for different substrate mixture condition to identify which substrate mixture or single substrate would be good candidate for co-digestion without any pretreatment in order to enhance methane potential. Furthermore, different factors (e.g. sludge characteristics, C/N ratio, pH value, temperature, metal ions etc) affecting clean energy such H2 will be evaluated. The effects of different food waste on biogas (CH4) & H2 yield will assist to determine the energy benefit that the treatment plant can target to achieve. While wastewater treatment process is moving forward with the application of advanced carbon and nutrient removal technology to make energy efficient WRRF, this study will further evaluate a comparative energy balance study between existing WRRF with co-digestion process with provision to generate H2 and different advanced technologies. Understanding the co-digestion process energy balance will provide any WRRF to select which feasible technology is best suited for full-scale application.