Biological degradation of a light crude dispersed in sea water by a surfactant produced by an hydrocarbon degrading microorganism has been monitored in laboratory tests. Oligotrophic natural sea water was used with no additions. Results showed that the oil dispersed by the biosurfactant was more easily degraded than chemically dispersed oil. In adhesion tests it has been found that the number of microbial cells adhering to a water/hexadecane interface increases in presence of the biosurfactant. It is suggested that the biodegradation enhancement may be linked to a promoting action carried by the biosurfactant on the adhesion of degrading microorganisms onto the surface of the oil.

A process for anaerobic digestion of agroindustrial wastes containing mainly soluble pollutants has been developed utilizing fixed-bed reactors. A pilot plant at a sugar refinery with two reactors in parallel, respectively of 10 and 50 m3 operating volume, has functioned successfully in treating wastes produced in regenerating ion-exchange columns used to purify the sugar juices. With an hydraulic retention time (HRT) of less than one day, a maximum gas production of 11.5 volumes per operating volume of reactor per day was obtained together with a reduction of up to 80% of the biological oxygen demand for five days (BOD5), and volatile solids and up to 70% of the chemical oxygen demand (COD). The gas contained from 70 to 75% methane. On the basis of these results, a full-scale industrial plant was built which has produced up to 7500 m3 a day of biogas. The process has been found suitable for a large number of industrial wastes, especially when plants are seasonally operated.