Prompted by the potential benefits of multi-phase anaerobic digestion, such as improved digester performance, increased process reliability, sludge dewaterability, and the potential to produce Class A biosolids, the City of Phoenix Water Services Department (WSD) initiated a study in January 2003 to evaluate the feasibility of converting the existing single-stage high-rate anaerobic digestion process at the 23rd Avenue Wastewater Treatment Plant (WWTP) to a multiphase digestion process. Accompanying a higher volatile suspended solids reduction, multiphase digestion can result in elevated ammonia levels in the digested sludge. Dewatered sludge centrate with elevated ammonia would be returned to the plant's liquid stream via a side stream recycle and potentially impact nitrification performance. To assess the impact of multi-phase digestion on liquid stream treatment and provide a basis for plant expansion, process modeling using Biowin32 was performed at steady-state and with diurnally varying influent loads.Plant historical records were evaluated to obtain influent wastewater characteristics, unit process performance, and plant operational configuration. 2-weeks of intensive sampling were conducted to supplement plant data for characterizing influent, establishing influent diurnal patterns, and the process response to dynamic loading, all of which was used to validate the Biowin model calibration. Due to the configuration of the plant's sampling systems, intensive sampling data were obtained almost exclusively on the primary effluent. A mass balance was performed to back-calculate the raw influent characteristics based on the plant's historical primary treatment efficiency. Both the steady state and the extended period dynamic modeling for the intensive sampling period resulted in predictions that closely match key plant measurements obtained during the same period, such as aeration basin mixed liquor suspended solids (MLSS) and volatile suspended solids (MLVSS), effluent NO 3 --N, TKN, and TSS.The calibrated model was then used to evaluate the maximum treatable flow and ammonia load, in order to determine the requirement for side stream treatment after the conversion to multiphase digestion. A set of limits was established to gauge acceptable plant operation and performance. At the winter average day maximum month (ADMM) condition, both steady state and dynamic modeling results indicate that the plant can produce satisfactory effluent while operating the existing process within the recommended limits at flow up to 63 MGD. At the rated flow, the hydraulic loadings of primary and secondary clarifiers, the BOD 5 loading on aeration basins, and the total oxygen transfer rate (OTR) at the corresponding peak day condition would exceed the recommended limits. At summer ADMM loadings with one aeration basin out of service for maintenance, the plant could treat up to 61 MGD with the hydraulic loadings of primary and secondary clarifiers, the BOD 5 loading on aeration basins, and the oxygen uptake rate (OUR) exceeding rec...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.