New and broader applications of anaerobic digestion

The general performance of anaerobic digesters and the diversity of wastes that these can treat have been increasing steadily during the last decade a s a result of new reactor designs, operating conditions, or the use of spec ialized microbial consortia. This article illustrates a few examples of new or broader applications of anaerobic digestion to the treatment of sewage, slurries, industrial wastewater, and solid wastes. In the case of domestic sewage, the sustainability of the overall process is much improved by the adoption of an anaerobic pretreatment step, for example, an upflow sludge b lanket (USB) reactor. New methods for nutrient removal need to be coupled w ith anaerobic digestion. These may include, for example, anaerobic ammonium oxidation (anammox) and chemical P precipitation. In terms of industrial w astewaters, new additives are being developed that help the anaerobic sludg e deal with unbalanced or toxic wastewaters. Engineering of anaerobic sludg e granules is a new area of research that serves the purpose of expanding a nd rechanneling the catabolic capabilities of the sludge and of shortening the length of the adaptation period of the microbial consortia to xenobioti cs. New biotechnologies are also being marketed for the anaerobic removal o f sulfate and heavy metals in liquid and gaseous wastes. The new 'high-soli ds' fermentation technology used to treat solid wastes in industrialized re gions is being expanded to suit specific needs of regions with other priori ties such as the presence of nonbiocompatible solid wastes or the occurrenc e of fuel shortage.