OPERATION OF A 2-STAGE ACTIVATED-SLUDGE PACKAGE PLANT FOR HIGH-EFFICIENCY TREATMENT

A new two-stage package plant which is built in standard containers treats the effluents of a highway rest stop near Vienna (Austria). The plant is designed for a maximum daily flow of 110 m3 and a maximum daily load of 51 kg BOD5 in winter and 75 kg BOD5 during heavy holiday traffic in summer. The plant has been in operation for one year and was investigated during peakloading conditions in summer and under low loading conditions at very low outdoor temperatures in winter. In both cases full carbonaceous removal and complete nitrification of a high-loaded sewage was obtained. Although the nitrogen elimination amounts to 85% the nitrate concentration in the effluent can be as high as 60 mg NA due to the high concentration in the influent. In order to improve the denitrification even further a new treatment scheme (the Hybrid process) combining (mixing) the biocenosis from both stages was applied at the plant.