Global Waste Management Symposium 2016 Abstract

Model Calibration for Biological Process Modeling of Landfill Treatment System

Sara Arabi1, Mehran Andalib1, Christopher Bye2, Andrew Lugowski3

1 Environmental Operating Solutions, Inc. (EOSi), Bourne, MA 02532, [email protected] 2 EnviroSim Associates Ltd., Hamilton, ON, Canada 3 GHD, Waterloo, ON, Canada

1.0 Introduction: Although BioWin® is widely used for municipal and industrial treatment simulation, the library of studies demonstrating the experiences of model calibration for a leachate treatment system is relatively inconspicuous. In order to use simulation packages such as BioWin® for landfill leachate process design, default parameters in BioWin® needs to be altered to provide valuable information on the performance and process design of leachate treatment systems. Respirometry and bench scale studies may be required in order to obtain the site specific stoichiometric and kinetic parameters for model calibration.

2.0 Objectives: Modeling and optimization of a biological leachate treatment process faces two major challenges. The first one is related to the leachate quality data due to site specific characteristics of landfill leachate and also the temporal nature of the landfill leachate generation process which significantly impacts the quality. The second challenge is the calibration of the process models. The goal of this paper is to increase our knowledge and understanding of the process modeling for landfill leachate using BioWin® simulation package using model calibration.

3.0 Data Analysis: In this paper, a database was prepared based on leachate characteristics information from 19 landfills in North America to cover young (1-10 years) and medium- strength (10-15 years) leachate in both cold and warm climates. Soluble and total fractions of organics and nutrients and inorganics are analyzed to obtain the leachate fractionation characteristics as an input to BioWin® (Table 1). Key stoichiometric and kinetic parameters information from four landfills are also recorded for sensitivity analysis. Statistical analysis for the data presented in Table 1, resulted in the fractionation presented in Table 2. Table 3 summarizes the stoichiometric and kinetic parameters for the landfill used for the modeling effort presented in Section 4.0.

4.0 Model Development and Calibration

Relatively high organics concentration, high non-biodegradable organics and nitrogen fraction, low , and inhibitory impact of leachate on kinetics of biological processes makes it necessary to use a calibrated model for treatment evaluation or design purposes. Landfill leachate database is considered to verify the predictability of the BioWin® model with site specific reliable influent characteristics. Changes to the default parameters were made to minimize the differences between the model predicted and actual leachate characteristics. Table 4 shows an example of the model input using default characteristics for influent TSS. Leachate generally contains low TSS and using the default parameters, the model over predicts the influent TSS which subsequently impact the modeled TSS or VSS in the biological system (an important design consideration). Calibrated model values which results in matching all the model calculated parameters and actual measurements are presented in Table 5. In case the leachate is inhibitory to hetrotrophic biomass or nitrifiers, site specific growth parameter biomass-specific nitrification rate should be considered in the design of a leachate treatment system. The process of model development and calibration for influent fractions and growth and decay parameters are presented.

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Global Waste Management Symposium 2016 Abstract

Table 1: Summary of Landfill Leachate Characteristics (19 Landfills)

Concentration (mg/L) Parameter Range Average Ammonia 200 – 1,200 700 Biological Oxygen Demand (BOD) 100 – 2,000 1,000 Soluble BOD (SBOD) 50 – 1,600 800 1,000 – 4,500 3500 Soluble Chemical Oxygen Demand (SCOD) 900 - 4,000 3,100 Total Kjeldhal Nitrogen (TKN) 250 – 1,500 900 Total Phosphorous 1 - 10 3 Total Suspended Solids (TSS) 50 - 200 100 Volatile Suspended Solids (VSS) 25 - 100 50

Table 2: General Leachate Fractionation Value Parameter

SBOD/BOD 0.5 - 0.8 SCOD/COD 0.9 – 0.7 Ammonia/TKN 0.8 Non-biodegradable Influent COD/Total influent COD 0.2 – 0.6

Table 3 – Kinetic and Stiochiometric Parameters used for Modeling

Parameter Unit Default Value -1 Maximum Specific Growth rate , heterotrophs , µmax d 3.2 2.7 ± 0.71 Monod half saturation coefficient , KS mg COD/L 5 185 ± 25 Biomass Yield (heterotrophic), YH g COD/g COD 0.66 0.48 ± 0.03 -1 Decay Rate bH d 0.62 0.67 ± 0.03 Slowly biodegradable substrate XS mg COD/L 90 -1 Hydrolysis rate constant, Kh d 2.1 0.95 ± 0.05 Maximum Specific Growth rate – Ammonia Oxidizers d-1 0.9 0.75

Table 4 – Comparison of the Actual vs. Modeled parameters using Default Fractionation

Parameter Actual (mg/L) Modeled using default Fractionation (mg/L) COD 3,500 3,500 TSS 200 1,330 VSS 100 1,100

Table 5 – Calibrated Model Parameters Compared with Default Parameters

Parameter Unit Default Value Fbs- Readily biodegradable g COD/g tot COD 0.160 0.136 Fus Un- biodegradable soluble g COD/g tot COD 0.05 0.721 Fup Unbiodegradable particulate g COD/g tot COD 0.13 0.018 Fzbh Non-poly P heterotrophs g COD/g COD 0.02 0.017 Fxs Slowly biodegradable fraction of COD g COD/ g tot COD 0.640 0.108 Fxsp Non colloidal slowly biodegradable g COD/g of slowly degradable 0.75 0.008 Fna - Ammonia g NH3-N/ g TKN 0.66 0.8

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