New stricter nitrogen effluent standards and increasing influent loads require existing wastewater treatment plans (WWTPs) to extend or optimize. At WWTPs with limited aeration capacity, limited denitrification capacity or shortage of aerobic sludge age, implementation of SHARON to improve nitrogen effluent quality can be a solution. SHARON is a compact, sustainable and cost-effective biological process for treatment of nitrogen-rich rejection waters. At WWTP Rotterdam-Dokhaven and WWTP Utrecht a SHARON has been in operation for several years. For both WWTPs the effect of SHARON on the nitrogen effluent quality has been evaluated. WWTP Rotterdam-Dokhaven has limited aeration capacity. By implementation of SHARON, the ammonia load of the effluent was reduced by 50%. WWTP Utrecht had limited denitrification capacity. The implementation of SHARON improved the effluent nitrate load by 40%. The overall TN removal efficiency increased from 65% to over 75% and strict nitrogen effluents standards (TN = 10 mg N/l) could be reached. Through modelling and supported by full scale practice it has been shown that by implementation of SHARON in combination with enhanced influent pre-treatment, the aerobic sludge age can be extended to maintain total nitrogen removal at lower temperatures.

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