Section 11. HAZARDOUS/TOXIC WASTES
BIOLOGICAL TREATMENT REQUIRED FOR CLEANUP OF
CONTAMINATED GROUND WATER AT A HAZARDOUS
WASTE DUMP SITE
Enos L. Stover, Vice President
Don F. Kincannon, President
T. S. Manickam,   Director
Treatability and Pilot Plant Studies
Environmental Engineering Consultants, Inc.
Stillwater, Oklahoma 74075
INTRODUCTION
The New Hampshire Water Supply and Pollution Control Commission has been directing efforts
to contain and cleanup the Gilson Road Hazardous Waste Site in Nashua, New Hampshire for several
years. Funding by the U. S. Environmental Protection Agency under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (Superfund) provided for a comprehensive containment and cleanup feasibility assessment which was completed in January 1982. A two
phased approach for management of contamination at the site was proposed. Phase one consisted of
installation of an impermeable surface cap and a bentonite slurry cut-off wall around the site. The second phase consisted of investigation, design, and building of a ground water treatment system to
reduce the ground water contamination to acceptable levels. Based on this second phase requirement,
Environmental Engineering Constants, Inc. (EEC) was retained by the primary consultant to participate in treatability studies and concept design investigations for developing the design requirements of
the ground water treatment system.
Contaminants found in several wells near the site included volatile organics, extractable organics,
and heavy metals. Several unit operations including air stripping, steam or high temperature air stripping, carbon adsorption, ozone treatment, chemical precipitation, biological treatment, and combinations of these unit processes were identified to be applicable treatment alternatives to one or more
groups of contaminants. ECC conducted preliminary laboratory-scale treatability studies of these
various unit processes to select the best unit processes and combinations of processes for more
detailed evaluations. These preliminary studies provided the necessary information for conducting
initial process design and cost estimates [1,2).
The results of this first phase treatability program indicated the combined unit processes of metals
removal by chemical precipitation with lime, steam or high temperature air stripping, and biological
treatment to be the most feasible treatment alternative. More detailed information was required prior
to the final design of this proposed treatment system to ensure an effective reliable design. Pilot-scale
studies were conducted on site to refine the final design of the high temperature air stripper and metals
removal process since metals removal was required prior to the stripping column for iron and
manganese removal. The results of these pilot scale studies have been presented previously [3]. These
two processes accomplished removal of the specific organics and heavy metals of primary concern;
however, the stripper extract remained high in TOC, BOD, and COD. The compounds remaining,
like alcohols and ketones, were very soluble in water and more difficult to remove by these processes.
The high concentrations of these types of compounds in the stripper extract could be effectively
removed by biological treatment, as established during the earlier laboratory-scale studies.
The stripper extract was subjected to biological treatment studies to define the biokinetic descriptive constants and the treatment performance reasonably achievable by biological treatment. These
studies consisted of activated sludge studies, aerated lagoon studies and rotating biological contactor
(RBC) studies. These systems were operated at different loading rates to provide the following information:
291