Anaerobic Digestion of
Rum Distillery Wastes
WILLIAM C. HIATT, Engineer
Watermation, Incorporated
Cleveland, Ohio 44114
A.D. CARR, Professor and Head
Chemical Engineering Department
University of Cape Town
Rondebosch Cape, South Africa
JOHN F. ANDREWS, Professor and Head
Environmental Systems Engineering Department
Clemson University
Clemson, South Carolina 29631
INTRODUCTION
The production of rum in Puerto Rico is of major significance to the economy of the
island. Inherent in rum production, however, is a very large output of pollutants. This waste
stream, primarily the distillation residue, or slops, from the five operating distilleries on the
Island has a waste equivalent of 77 percent of the island's population. The rum slops are
characterized by low volatile solids, high BOD (30-60 gm/1) and COD (100-300 gm/1), a
dark brown color, and a high temperature (near boiling). The slops have a high ionic
strength, approximately that of sea water, and contain a high concentration of sulfate ions.
An extensive research effort is being conducted by the Bacardi Corporation to
determine the best method of waste treatment for rum slops. This work is partially financed
by a demonstration grant from the United States Environmental Protection Agency.
Earlier work at the Rum Pilot Plant, University of Puerto Rico (1), had indicated that this
waste might be amenable to anaerobic digestion; however, this research also indicated that
more extensive laboratory-scale work was required. In addition to the work at Bacardi,
research on anaerobic digestion of rum waste has also been conducted at Clemson
University and the University of Florida, among other institutions.
In considering a full-scale treatment facility, little was known about the start-up and
operational problems which might be encountered. Typical problems could be: the high
ionic strength, high sulfate concentration, intermittent distillery operation, and variations
in composition and concentration of the waste. A laboratory investigation, using rum slops
supplied by the Bacardi Corporation, was therefore carried out with the following
objectives in mind: 1) Establish that satisfactory pretreatment of this particular waste can be
obtained, on a sustained basis, by anaerobic digestion; 2) Determine whether the slops are
amenable to treatment at full strength or whether they must be diluted prior to treatment; 3)
Establish preliminary hydraulic and organic loading parameters for use in subsequent pilot
plant investigations; and 4) Investigate the special requirements for acclimitization of the
microorganisms during the start-up period and study certain control actions, such as
interruption or decrease of the feed rate, gas scrubbing to remove hydrogen sulfide, and
neutralization of the feed.
BACKGROUND
The Production of Rum
Rum is the end product of a complex manufacturing process, which includes biological
966