THE DYNAMIC BEHAVIOR OF NITRIFYING ACTIVATED-SLUDGE SYSTEMS INFLUENCED BY INHIBITING WASTE-WATER COMPOUNDS

More or less severe nitrification inhibition was observed in several p ilot and full-scale activated sludge plants treating industrial wastew aters. In order to control the treatment process under inhibiting cond itions, extended nitrification models have been developed on base of t he 'Activated sludge model No. 1'. In the case of temperatures between 25 and 30 degrees C, the nitrification process has been expressed as a two-step reaction with nitrite as intermediate. Model elements for c ompetitive and non-competitive inhibition as well as for biodegradatio n of the inhibitor were added if required. The dynamic behaviour of th e investigated activated sludge systems indicates that there are biode gradable non-competitive inhibitors. Operational as well as simulation results show that nitrifying activated sludge plants may become accli matized to inhibitory compounds but have to be protected from peak loa ds of both nitrogen and inhibitory compounds.