Remaining nitrogen elimination of already treated wastewater in a bypass - a modified process using MBBR technology

Abstract

A proven process was modified for retrofitting large-scale WWTPs with increased nitrogen requirements. Remaining nitrogen elimination in a downstream stage occurs in a downstream stage of the already treated wastewater in a bypass using MBBR technology. Nitrate nitrogen concentrations of 10 mg/l in the influent to the downstream stage are eliminated by up to 90% (= 1 - 2 mgNO₃-N/L in the effluent). Based on four years of operation of a pilot plant and several laboratory plants at semi-industrial scale, the process has been further developed and tested. The present study focuses on the influence of hydraulic retention time on targeted remaining nitrogen elimination and its effect on remaining COD concentrations in the effluent. The results provide important insights for the practical application of the modified process for efficient wastewater treatment and give indications for the dimensioning of corresponding plants for use in the effluent of large wastewater treatment plants.