Enhancing Nitrogen Removal in Coking Wastewater Treatment by Activated Sludge Process: Comparison of Sodium Acetate, Methanol and Phenol as External Carbon Source for Denitrification

摘要

A lab-scale test for the treatment of coking wastewater mainly generated in coal carbonization and gas purification in Shanghai Baosteel Chemical Co. Ltd. was carried out by modification of its former anoxic-oxic (A/O) process into anoxic-oxic-anoxic-oxic (A/O/A/O). Three external carbon sources, namely sodium acetate, methanol and phenol, were investigated aiming for enhancement of denitrification purpose. The experimental results showed that total nitrogen could be lowered to 14.5 or 17.6 mg/L when adding sodium acetate (1875 mg/L) or methanol (880 mg/L) to the secondary modified anoxic zone and in both cases organic nitrogen contributed most to the residual total nitrogen in effluent. In contrast, phenol could not decrease total nitrogen in effluent effectively to less than 35 mg/L in its tested phenol dosage range (370-1200 mg/L) due to less efficiency in denitrification and therefore resulted in higher NO2.3-N residue in effluent. In conclusion the results strongly suggested that the modified A/O/A/O process with sodium acetate or methanol as external carbon source could successfully achieve the goal for total nitrogen removal based on the issued Shanghai Discharge Standard (DB31/199-2009).