EFFECTS OF COPPER AND ZINC ON SEQUENCING
BATCH REACTORS
Christine Goldman Robinson, Project Engineer
Montgomery Watson Americas, Inc.
Metairie, Louisiana 70002
Dennis D. Truax, Professor
Adnan Shindala, Professor
Dept. of Civil Engineering
Mississippi State University
Mississippi State, Mississippi 39762
ABSTRACT
This chapter will focus on the effects of copper and zinc, acting individually, in bench-scale
sequencing batch reactors which were studied at different mean cell retention times (MCRTs).
Results indicate that MCRT and the metal mass to biological mass ratio present are the major
factors in determining the impacts of the copper or zinc on the treatment process. Organic removal efficiency and suspended solids levels were observed to be indicators of potential inhibition.
INTRODUCTION
Municipal solid waste landfills (MSWLFs) and hazardous waste landfills (HWLFs) produce
leachate that must be treated in accordance with Subtitle D of the Resource Conservation and
Recovery Act or the Hazardous and Solid Waste Amendments of 1984. Leachate composition is
highly variable and may contain significant heavy metal constituents as well as the more common high concentrations of biodegradable organics. Because of the high organic content, biological treatment systems, such as those found at publicly-owned treatment works (POTWs) and
used for the treatment of municipal sewage, have been demonstrated effective for the treatment
of leachate from HWLFs12 and MSWLFs.3-4 Copper and zinc are two heavy metals that are
found consistently in MSWLF and HWLF leachates, due to the high occurrence of their use in
many industries. This study was conducted using bench-scale Sequencing Batch Reactor (SBR)
activated sludge systems to research the independent effects of copper and zinc on the treatment
systems and trace the fate of each metal through the system.5 Emphasis was placed on relating
the effects of each metal to the MCRT of the biomass. To meet the above goals, the following
objectives were pursued in this research:
1. Determine the concentration of copper and zinc at which each can be present in the
feed to the treatment process without significantly inhibiting biomass synthesis.
2. Evaluate the effects of varying levels of copper and zinc on the organic removal efficiency of the biomass, noting differences over the range of MCRTs studied.
3. Evaluate the relationship between metals removal and MCRT for each metal and
note any differences between the two.
PRIOR RESEARCH
Hannah et al.6 conducted a pilot plant study comparing the capabilities of five less-than-sec-
ondary treatment processes to the conventional activated sludge system for removal of priority
52nd Purdue Industrial Waste Conference Proceedings. 1997. Ann Arbor Press, Chelsea, Michigan 48118. Printed in
U.S.A.
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