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CONSIDERATIONS IN BIOLOGICAL TREATABILITY STUDIES FOR INDUSTRIAL WASTEWATERS Robert G. Kunz, Senior Environmental Engineer John G. Landis, Scientific Systems Analyst Air Products and Chemicals, Inc. AHentown, Pennsylvania 18105 INTRODUCTION The purpose of a treatability test is to obtain design information on contaminant removal rates, sludge production and oxygen consumption. Over the life of an activated sludge plant, the loading conditions for the plant vary as a result of daily, seasonal or yearly influent variations. To test every plant operating condition in the laboratory is usually impractical; therefore, a mathematical model is used to translate the experimental results into predictions of plant performance under different operating conditions. Many conventional models are often inadequate because as operating conditions change the biokinetic "constants" must change in order to describe properly substrate removals, sludge production and oxygen consumption. Generally, the failure of the model predictions is a result of assumptions made to simplify the mathematical model for each application, in particular, the assumption that the active biological mass is equal to the mixed liquor volatile suspended solids (MLVSS) in the aeration basin. Aside from obvious experimental errors, scatter is frequently caused by the use of these simple models when evaluating treatability test data obtained under apparently identical conditions. This chapter explores, by way of several examples, the effect of sludge age on the rate of substrate removal and outlines a design model which distinguishes between active biological solids and suspended solids. The usefulness of this model is illustrated by comparing its predictions with experimental treatability data. SUBSTRATE REMOVAL EQUATIONS AS A BASIS FOR MODELING An equation for substrate removal as a function of substrate and microorganism concentration forms a realistic description of the biochemical reactions involved in waste treatment. The mathematical model allows for prediction of the performance of the waste treatment process beyond the actual conditions investigated. To accomplish this, the mathematical model must be detailed enough to reflect, however empirical, the results of the processes occurring on a microscopic level. By way of review, one model in general use is the MichaelisMenten equation, written as follows: ii  *SX (1) dt Ks + S where S and X are the concentrations of substrate and microorganisms respectively, t is the time, and k and Ks are constants representative of each particular system. The k represents the maximum rate of substrate utilization per mass of microorganisms and Ks, the MichaelisMenten or halfvelocity constant, is equal to that substrate concentration at which the rate of substrate removal is onehalf its maximum value. In many cases, the microorganism concentration changes are small during an experimental run so that the concentration can be considered to be a constant. Equation 1 attempts to represent in a single continuous formulation two separate regimes in waste stabilization: one at high substrate concentrations where substrate is not limiting, Equation 2; and the other at low substrate levels where removal is dependent on substrate concentration, Equation 3, i.e.. 1080
Object Description
Purdue Identification Number  ETRIWC197698 
Title  Considerations in biological treatability studies for industrial wastewaters 
Author 
Kunz, Robert G. Landis, John G. 
Date of Original  1976 
Conference Title  Proceedings of the 31st Industrial Waste Conference 
Conference Front Matter (copy and paste)  http://earchives.lib.purdue.edu/u?/engext,27048 
Extent of Original  p. 10801089 
Collection Title  Engineering Technical Reports Collection, Purdue University 
Repository  Purdue University Libraries 
Rights Statement  Digital object copyright Purdue University. All rights reserved. 
Language  eng 
Type (DCMI)  text 
Format  JP2 
Date Digitized  20090708 
Capture Device  Fujitsu fi5650C 
Capture Details  ScandAll 21 
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Color Depth  8 bit 
Description
Title  page 1080 
Collection Title  Engineering Technical Reports Collection, Purdue University 
Repository  Purdue University Libraries 
Rights Statement  Digital object copyright Purdue University. All rights reserved. 
Language  eng 
Type (DCMI)  text 
Format  JP2 
Capture Device  Fujitsu fi5650C 
Capture Details  ScandAll 21 
Transcript  CONSIDERATIONS IN BIOLOGICAL TREATABILITY STUDIES FOR INDUSTRIAL WASTEWATERS Robert G. Kunz, Senior Environmental Engineer John G. Landis, Scientific Systems Analyst Air Products and Chemicals, Inc. AHentown, Pennsylvania 18105 INTRODUCTION The purpose of a treatability test is to obtain design information on contaminant removal rates, sludge production and oxygen consumption. Over the life of an activated sludge plant, the loading conditions for the plant vary as a result of daily, seasonal or yearly influent variations. To test every plant operating condition in the laboratory is usually impractical; therefore, a mathematical model is used to translate the experimental results into predictions of plant performance under different operating conditions. Many conventional models are often inadequate because as operating conditions change the biokinetic "constants" must change in order to describe properly substrate removals, sludge production and oxygen consumption. Generally, the failure of the model predictions is a result of assumptions made to simplify the mathematical model for each application, in particular, the assumption that the active biological mass is equal to the mixed liquor volatile suspended solids (MLVSS) in the aeration basin. Aside from obvious experimental errors, scatter is frequently caused by the use of these simple models when evaluating treatability test data obtained under apparently identical conditions. This chapter explores, by way of several examples, the effect of sludge age on the rate of substrate removal and outlines a design model which distinguishes between active biological solids and suspended solids. The usefulness of this model is illustrated by comparing its predictions with experimental treatability data. SUBSTRATE REMOVAL EQUATIONS AS A BASIS FOR MODELING An equation for substrate removal as a function of substrate and microorganism concentration forms a realistic description of the biochemical reactions involved in waste treatment. The mathematical model allows for prediction of the performance of the waste treatment process beyond the actual conditions investigated. To accomplish this, the mathematical model must be detailed enough to reflect, however empirical, the results of the processes occurring on a microscopic level. By way of review, one model in general use is the MichaelisMenten equation, written as follows: ii  *SX (1) dt Ks + S where S and X are the concentrations of substrate and microorganisms respectively, t is the time, and k and Ks are constants representative of each particular system. The k represents the maximum rate of substrate utilization per mass of microorganisms and Ks, the MichaelisMenten or halfvelocity constant, is equal to that substrate concentration at which the rate of substrate removal is onehalf its maximum value. In many cases, the microorganism concentration changes are small during an experimental run so that the concentration can be considered to be a constant. Equation 1 attempts to represent in a single continuous formulation two separate regimes in waste stabilization: one at high substrate concentrations where substrate is not limiting, Equation 2; and the other at low substrate levels where removal is dependent on substrate concentration, Equation 3, i.e.. 1080 
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