Section Five
WASTE TREATMENT PROCESSES
C. CONTROL OF VOLATILE
ORGANIC CHEMICALS
43    CONCEPTUAL EVALUATION OF WASTEWATER
TREATMENT SYSTEM PERFORMANCE WITH
RESPECT TO CAPACITY EXPANSION AND
REGULATORY COMPLIANCE
Thomas D. DiStefano, Assistant Professor
The Pennsylvania State University, Harrisburg
Middletown, Pennsylvania 17057
Richard E. Speece, Professor
Vanderbilt University
Nashville, Tennessee 37240
INTRODUCTION
Many industrial wastewater treatment facilities operate routinely close to, or may occasionally
exceed effluent discharge limits. Industrial production and potential expansion, or development of
new product lines that would impose higher pollutant loadings, may be restricted due to the apparent
existing capacity of such treatment systems. Future regulatory requirements, such as the 1990 Clean
Air Act Amendments (CAAA), will require evaluation of ultimate treatment system capacity and
potential modifications to achieve compliance.
Treatment systems that employ aerobic biological treatment processes may experience noncompliance with conventional pollutant limits due to a multitude of operational problems such as
maintenance of excessive sludge age, nutrient limitations, low dissolved oxygen concentrations, or
high process wastewater temperatures. Restrictions in volatile organic compound (VOC) emissions
due to the CAAA must also be considered in evaluating treatment system capacity and future regulatory compliance. Various types of aeration systems must be considered based on advantages and
disadvantages with respect to heat transfer and VOC emissions as well as oxygen transfer and mixing.Furthermore, a comparison of pure-oxygen versus air-supplied activated sludge systems may be
warranted to examine future compliance with CAAA. Routine operation near effluent permit limits
may restrict manufacturing productivity by imposing limitations on expansion of processes that
would increase pollutant loads to the wastewater treatment system.
TREATMENT SYSTEM CAPACITY-BOD AND TSS
With respect to activated sludge systems that treat industrial wastewaters, long solids retention time
(SRT) and inadequate nutrient additions may represent the major factors that limit the organic
loading capacity and contribute to BOD and TSS permit violations.
Solids Retention Time
Solids retention time is the fundamental operating parameter of a suspended-growth biological
treatment system. Because SRT represents the average time that biomass is retained in the system, it
directly impacts BOD removal efficiency, and therefore, effluent quality. Long SRTs result in greater
removal efficiency of biodegradable organics and also improve the degradability of recalcitrant
compounds, thus producing effluent with lower concentrations of soluble COD.
49th Purdue Industrial Waste Conference Proceedings, 1994 Lewis Publishers, Chelsea, Michigan 48118. Printed in
U.S.A.
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