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Warm concentrated industrial wastewaters are preferably treated in an anaerobic reactor for reasons of energy generation and low surplus sludge production. Problems to be solved in the practical application concern a low growth rate of the micro-organisms, their low settling rate process instability, and the need for after-treatment of the noxious anaerobic effluent which often contains NH4+ and HS−. The use of biomass immobilized on small suspended carriers (< 0.5 mm) has proven to be a suitable mean to overcome most of these problems. Results are presented on–pilot and full-scale pretreatment of industrial wastewater in an anaerobic 2-stage fluidized bed reactor for CH.-production.–laboratory and pilot scale post-treatment of the anaerobic effluent, which contains NH4+. and HS2− in an aerobic air-lift suspension reactor for the production of NO3− and SO4−.

Warm concentrated industrial wastewaters are preferably treated in an anaerobic reactor for reasons of energy generation and low surplus sludge production. Problems to be solved in the practical application concern a low growth rate of the micro-organisms, their low settling rate, process instability and the need for aftertreatment of the noxious anaerobic effluent which often contains NH:and HS-. The use of biomass immobilized on small suspended carriers (< 0.5 mm) has proven to be a suitable means to overcome most of these problems. Results are presented on pilot and full-scale pretreatment of industrial wastewater in an anaerobic 2-stage fluidized bed reactor for CH,-production and laboratory and pilot scale post-treatment of the anaerobic effluent, which contains NH; and HSin an aerobic air-lift suspension reactor for the production of NO; and SO: -* Paper presented by J.J. Heijnen at the GVC-VDI Congress "Verfahrenstechnik Abwasserreinigung", Baden-Baden, October 17 to 19, 1988.

A new aerobic treatment concept for the aerobic oxidation of COD, ammonia and sulphide has been developed. The concept is based on the formation of biofilms on small suspended particles in an air-lift reactor. This reactor concept enables to combine a low sludge loading with a high volumetric loading. This makes the reactor especially useful for e.g. nitrification processes. It is also feasible to operate under conditions of marginal sludge production. In this article the scale up aspects of such a process are discussed.