A Proposed Approach for Modeling Sludge Reduction Technologies

Abstract

Sludge reduction technologies have gained popularity as solids handling and disposal become an increasingly costly portion of a wastewater treatment plant. The technologies are implemented within the liquid processes for waste activated sludge minimization, or as pre-treatment to anaerobic digestion to enhance digestion and reduce biosolids. Biological, chemical, and/or physical procedures are used and achieve varying level of success, but the underlying mechanisms are not well understood and modeled. The paper presents a general framework -via the WERF project 05-CTS-3, Evaluation of Processes to Reduce Activated Solids Generation and Disposal -for simulating representative sludge reduction technologies, including Cyclic Metabolic Environments (e.g. Siemens' Cannibal (biological)) and Ozonation (chemical), as well as the Thermal Hydrolysis (Cambi, Veolia) and Pressure Release (Siemens' Crown (physical)) digestion pre-treatment technologies. Non-proprietary ASM 2d model was implemented for activated sludge processes and ADM1 model for anaerobic digestion, with modifications to reflect potential solids reduction mechanisms. The models were calibrated to existing installations where adequate process data are available, or compared with reported performances otherwise. The modeling framework generally resulted in predictions consistent with plant records or reported performance for selected sludge reduction technologies, suggesting successful capture of key mechanisms and parameters.

Investigation of the Impacts of Thermal Activated Sludge Pretreatment and Development of a Pretreatment Model

“…A few research groups have proposed approaches for modeling WAS pretreatment technologies and an even fewer number have published stand-alone pretreatment models. Lei et al (2010) Lei et al (2010), the original plant-wide model was adjusted to fit the data measured after pretreatment implementation by increasing the anaerobic disintegration rate and transforming inert decay products to biodegradable COD. The authors demonstrated that the measured ammonia increase after digestion due to the HPTH pretreatment could only be explained by a complete degradation of decay products.…”

Investigation of the Impacts of Thermal Pretreatment on Waste Activated Sludge and Development of a Pretreatment Model

“…A generally accepted means of characterizing and comparing the impact of pretreatment processes on these responses does not exist. A few research groups have presented approaches for modeling WAS pretreatment technologies (Lei et al, 2010;Phothilangka et al, 2008;Frigon and Isazadeh, 2010;Musser, 2009). However, in these studies, assumptions about the WAS COD fractionation were required because of the complex nature of the biomass.…”

Modeling, Instrumentation, Automation, and Optimization of Wastewater Treatment Facilities

“…The application of ASM2d-ADM1 modeling of digestion processes with sludge pre-treatment for improved digestibility was discussed Lei et al, 2010) (2010b) provided a consensus report on the state-of-the art, areas of uncertainty, and future needs for advancing the use of biofilm models in engineering design. A pilot-scale fixed-biofilm reactor (FBR) was established by Lin (2010) to treat textile wastewater to evaluate the feasibility of replacing conventional treatment processes that involve activated sludge and coagulation units.…”