ABSTRACT

The development work of a new type, in-depth oil filter -coalesces for the treatment of oily ballast waters is de- scribed. Reticulated polyurethane foams as the best filter-coalesces media affording bed fluxes in excess of 10 gpm/ft2 and simple regeneration via squeezing. Extensive separation tests in a 40 gpm unit with a variety of simulated, effluent of less than 30 ppm oil, can be separate produced from an influent containing on the average of up to several thousand ppm oil including oil slugs. Substantial retention of suspended solids was also noted without causing either irreversible clogging of the foam of reduction in the oil separation efficiency. A 400-gpm scale-up unit has been built and is now being evaluated in the field.

INTRODUCTION

Pollution of harbors, coastal waters or inland waterways by discharging oily ballast from watercraft has become a serious problem in the last decade as a result of a substantial increase in the petroleum cargo volume.

The Maritime Administration?s timely concern to preserve marine ecology has lent impetus to a program for the for the development of a unique, moving bed filter coalescertype oil separator, originally proposed by Gollan [I]. The system proposed, keyed to the separation of oil from oil-water suspensions, offered two clear advantages over other available oil separators. Firstly, being based on a moving bed in-depth filter-coalescer, it offered significant reduction in clogging susceptibility by particulate matter-a problem of major concern in the use of conventional filter-coalescers. Secondly, the system afforded several modes of operation, hitherto not available, and seemed easily adaptable to a variety of ballast water containing various types of oil suspensions.

The overall research plan called for a three-phase program, having as its ultimate objective the development of a practical device for scavenging oil from typical oily ballast and the establishment of basic engineering and system operational procedures for such separators. Phase I of the development effort was concerned with the screening and the evaluation of potential filter coalescing media which lend themselves to a moving bed type operation and simple regeneration procedures. At the end of this phase it was realized that the major objective of the program could actually be accomplished by a stationary BatchWise In-Situ Regenerated Separator (BIRS), employing open-structured polyurethane foam as a filter-coalescer, and a simple aqueezing operation for regeneration. Consequently, a 40 gpm BIRS, bench scale system, was selected for the studies in Phase II; and its separation efficiency for various simulated oiI-water suspensions was evaluated. The third phase of the program involved the design and construction of a 400 gpm demonstration oil/water separator. This system is presently undergoing extensive field tests.

A significant fallout of this program was the development of. a photographic method for the determination of oil droplet size and distribution found in ballast water, as well as a basic approach to the determination of oil concentration. Description and discussion of these methods have been presented elsewhere [2].

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