Online control of biofilm and reducing carbon dosage in denitrifying biofilter: pilot and full-scale application

Abstract

Online control of DNBF was studied in the pilot-scale and full-scale experiments.

DNBF was controlled by the online monitored effluent nitrate and turbidity.

The effluent nitrate lower than 3 mg·L⁻¹ and saving 18% of carbon were both achieved.

Denitrifying biofilter (DNBF) is widely used for advanced nitrogen removal in the reclaimed wastewater treatment plants (RWWTPs). Manual control of DNBF easily led to unstable process performance and high cost. Consequently, there is a need to automatic control of two decisive operational processes, carbon dosage and backwash, in DNBF. In this study, online control of DNBF was investigated in the pilot-scale DNBF (600 m³·d⁻¹), and then applied in the full-scale DNBF (10 × 104 m3·d⁻¹). A novel simple online control strategy for carbon dosage with the effluent nitrate as the sole control parameter was designed and tested in the pilot-scale DNBF. Backwash operation was optimized based on the backwash control strategy using turbidity as control parameter. Using the integrated control strategy, in the pilot-scale DNBF, highly efficient nitrate removal with effluent TN level lower than 3 mg·L⁻¹ was achieved and DNBF was not clogged any more. The online control strategy for carbon dosage was successfully applied in a RWWTP. Using the online control strategy, the effluent nitrate concentration was controlled relatively stable and carbon dosage was saved for 18%.

Graphical abstract

Keywords

Reclaimed water treatment / Denitrifying biofilter / Carbon dosage / Backwash control

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