34    METHODS FOR UPGRADING AND RETROFITTING
INDUSTRIAL ACTIVATED SLUDGE PLANTS:
AN OVERVIEW AND CASE HISTORIES
Sam E. Shelby, Jr., Principal
Carl E. Adams, Jr., Principal
The ADVENT Group, Inc.
Brentwood, Tennessee 37027
INTRODUCTION
With increasingly stringent wastewater discharge regulations in the United States, particularly for
the organic chemicals industry, and a new emphasis on control of effluent toxicity, many industries
are faced with upgrading and retrofitting activated sludge plants. These upgrades may involve
increased removals of specific organics (i.e., phenol), improved winter performance, and reduced
effluent aquatic toxicity. This paper presents methods available to upgrade such systems, rationale for
process selection, and several case histories demonstrating these methods.
BACKGROUND
Most activated sludge systems encountered in industry today consist of a single-stage complete mix
aeration basin with final clarification system. The activated sludge system is often preceded by
equalization and pH control and, perhaps, TSS and oil and grease removal. Figure 1 schematically
presents the components of such a system. Single stage systems were selected in the past due to capital
cost effectiveness, resistance to shock loads, and operational ease. However, problems encountered,
especially with long detention time systems treating high-strength industrial wastes include the
following:
• Poor winter kinetic performance for BOD and ammonia-nitrogen removal due to basin
cooling (especially with surface aerators);
• The lack of selectivity or specificity for removal of priority pollutants and other toxic,
but degradable organics;
• Development of poor settling sludge; and
• The presence of effluent aquatic toxicity in some cases.
Poor dissolved oxygen control has also been observed in such systems. In order to upgrade these
systems to accommodate plant expansions or more stringent effluent limits, considerations should
AERATION BASIN
AL COMPLETE M'X BASIN
SURFACE AERATORS
LONG SLUDGE AGE
LOW F/M RATW
FINAL CLARIFIER
EQUALIZATION/ —
NEUTRALIZATION
^ =4<=.
RETURN SLUDGE
- WASTE SLUDGE
Figure   1.    Typical  industrial  activated  sludge
system.
45th Purdue Industrial Waste Conference Proceedings, © 1991 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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