EVALUATION OF CHLOROFORM REMOVAL IN A BIOLOGICAL
TREATMENT SYSTEM TO MEET BAT LIMITS
Yerachmiel Argaman, Professor
Department of Civil Engineering
Technion—Israel Institution of Technology
Haifa, Israel
John H. Koon, Regional Manager
Post, Buckley, Schuh, & Jernigan, Inc.
Nashville, Tennessee 37215
INTRODUCTION
Issuance of second-round NPDES permits includes evaluation of Best Available Technology
(BAT) requirements for "priority" or toxic pollutants. In many cases, effluent guidelines are not
available that apply to all manufacturing processes at complex industrial facilities, and permit
discharge limitations for priority pollutants must be developed on a plant-by-plant basis. This is particularly true in the chemicals industry where a wide range of products produced results in highly
variable waste loads.
Eight alternative treatment methods for removing chloroform from a chemical plant wastewater
were evaluated to determine which would be appropriate for meeting BAT technology requirements.
A predictive steady state model describing the stripping of chloroform from water developed by
Roberts et al [1] was used to assist in determining effluent chloroform levels from a biological treatment system. The cost of each treatment option was also determined. Actual chloroform removal was
monitored in a full-scale biological treatment system using surface aeration and in a pilot-scale system
using diffused aeration.
DESCRIPTION OF EXISTING FACILITIES
A schematic of the existing biological treatment system (Outfall 001) is presented in Figure 1.
Following equalization, clarification, and neutralization, the wastewater is treated in an activated
sludge system which consists of three parallel, 5 mg aeration basins followed by three parallel secondary clarifiers. At the time this evaluation was conducted, only two of the aeration basins were in use.
Each aeration basin contained ten low-speed surface aerators. Basin No. 1 contained 1,000 hp of
aerated capacity, while Basin No. 2 contained 950 hp.
At the time this evaluation was conducted, plans were to retrofit the biological system with static
aerators in order to have a more energy efficient treatment system and provide maximum heat retention during winter months. This system is to have the capacity to supply 35,000 scfm of air to the aeration basin. The company projected that the additional heat retention capabilities of these aerators
would eliminate the need for steam during cold winter months which has been necessary to maintain
the biological system at a proper operating temperature.
In order to evaluate performance of the biological system with only one basin in operation, a pilot
plant was constructed at the treatment facility and operated during the winter of 1981-82 using subsurface aeration. A schematic illustration of this system is shown in Figure 2. The pilot system was
operated at an F/M ratio which would be experienced if the full-scale system was operated with only
one aertion basin in service. The pilot aeration basin had an inside diameter of 11 ft, a water depth of
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