Section 6.    PHARMACEUTICAL WASTES
SINGLE STAGE NITRIFICATION ACTIVATED SLUDGE PILOT
PLANT STUDY ON A BULK PHARMACEUTICAL
MANUFACTURING WASTEWATER
Richard T. Donahue, Jr., Senior Engineer
Merck & Co., Inc.
Rahway, New Jersey 07065
INTRODUCTION
A pilot plant study was conducted at the Merck & Co., Inc., Stonewall Plant in Elkton, Virginia,
to confirm the results of a laboratory scale design study and to produce adequate quantities of sludge
for sludge thickening and dewatering studies. This paper presents a summary of the pilot plant
treatability data. Among the major topics highlighted are: operating parameters and their relationship
to performance, the effect of high temperature wastewater on nitrification and BOD, removal efficiency, the growth and control of filamentous organisms, determination of the temperature correction
coefficient, 8, the effect of wastewater temperature on reaction rate, and oxygen requirements for carbonaceous and nitrogenous removal. The bench scale study results which were actually used for
design of a full scale system are presented for comparison to the pilot plant results.
PILOT PLANT OPERATIONAL AND
EQUIPMENT INFORMATION
Merck constructed and operated a pilot-scale treatment facility on-site for a period of 10 months,
but this paper is based primarily on the first 5 months of operation. The pilot plant was designed at a
scale of 1:225 in relation to the new activated sludge system design.
Prior to the pilot plant investigation, a bench-scale bioreactor design study was done to define
design criteria for the Stonewall Plant waste treatment plant expansion. The bench-scale study determined that a F/M ratio of 0.15-0.25 and a MLVSS level of 3,500 mg/l, resulting in a hydraulic retention of four days and a minimum DO concentration of 3.0 mg/l, were essential to consistently meet
the proposed effluent limits and maintain a viable, good settling sludge. These were the basic design
criteria used to size the pilot plant and the full scale system.
The old treatment plant consisted of an equalization basin, neutralization, primary sedimentation,
roughing biofilter, activated sludge system, and rock trickling filters with final clarifiers. The units up
to and including the roughing biofilter were used in the new system. The old activated sludge system,
rock biofilters, and final clarifiers were replaced by the new single stage nitrification activated sludge
system.
Roughing trickling filter effluent was pumped to the pilot plant aeration basin at a flow of 3.7
gpm, along with a daily spike of a concentrated fermentation waste stream. This waste stream was included in the design basis of the new plant but was disposed of offsite during the study. Mixing and
aeration (to 3.0 mg/l or greater of dissolved oxygen) was accomplished by Kenics static aerators.
Solids were settled in a secondary clarifier and either returned to the aeration basin or wasted from the
system. A schematic of the pilot plant is presented in Figure 1.
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