title: Acidification of In-Storage-Psychrophilic-Anaerobic-Digestion (ISPAD) process to reduce ammonia volatilization: Model development and validation.
abstract: In-Storage-Psychrophilic-Anaerobic-Digestion (ISPAD) is an ambient temperature treatment system for wastewaters stored for over 100days under temperate climates, which produces a nitrogen rich digestate susceptible to ammonia (NH3) volatilization. Present acidification techniques reducing NH3 volatilization are not only expensive and with secondary environmental effects, but do not apply to ISPAD relying on batch-to-batch inoculation. The objectives of this study were to identify and validate sequential organic loading (OL) strategies producing imbalances in acidogen and methanogen growth, acidifying ISPAD content one week before emptying to a pH of 6, while also preserving the inoculation potential. This acidification process is challenging as wastewaters often offer a high buffering capacity and ISPAD operational practices foster low microbial populations. A model simulating the ISPAD pH regime was used to optimize 3 different sequential OLs to decrease the ISPAD pH to 6.0. All 3 strategies were compared in terms of biogas production, volatile fatty acid (VFA) concentration, microbial activity, glucose consumption, and pH decrease. Laboratory validation of the model outputs confirmed that a sequential OL of 13kg glucose/m(3) of ISPAD content over 4days could indeed reduce the pH to 6.0. Such OL competes feasibly with present acidification techniques. Nevertheless, more research is required to explain the 3-day lag between the model results and the experimental data.
authors.affiliation: Department of Building, Civil and Environmental Engineering, Concordia University, 1455 de Maisonneuve, Montréal H3G 1M8, Canada.
authors.forename: Mahsa
authors.initials: M
authors.lastname: Madani-Hosseini
authors.affiliation: Department of Building, Civil and Environmental Engineering, Concordia University, 1455 de Maisonneuve, Montréal H3G 1M8, Canada. Electronic address: mulligan@civil.concordia.ca.
authors.forename: Catherine N
authors.initials: CN
authors.lastname: Mulligan
authors.affiliation: Department of Building, Civil and Environmental Engineering, Concordia University, 1455 de Maisonneuve, Montréal H3G 1M8, Canada.
authors.forename: Suzelle
authors.initials: S
authors.lastname: Barrington
mesh_terms: D000641:Ammonia / Q000032:analysis*; D000693:Anaerobiosis; D005232:Fatty Acids, Volatile; D008962:Models, Theoretical; D009584:Nitrogen; D014835:Volatilization; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D005232:Fatty Acids, Volatile; D000641:Ammonia; D009584:Nitrogen
keywords: Acidification; Ammonia; Anaerobic digestion; Organic load