A pilot-scale study on nitrogen removal from dry-spun acrylic fiber wastewater using anammox process

Abstract

Dry-spun acrylic fiber wastewater (DAFW) is one kind of toxic refractory petrochemical wastewater. The results of GC–MS qualitative analysis demonstrated that the residual organic compounds in DAFW after the biotreatment are non-biodegradable and hardly available for traditional nitrification–denitrification processes. First, the batch test indicated that there was no obvious inhibition or toxicity of DAFW to anaerobic ammonium oxidizing (anammox) bacteria. A pilot test was then carried out to evaluate the feasibility and efficiency of biological nitrogen removal by the anammox process. A rapid start-up was achieved by inoculating enriched anammox sludge to a biofilm system with low inoculated sludge concentration. The pretreatment for anammox process was necessary because DAFW contains high SS which affected the nitrogen removal efficiency. By controlling the reactor temperature and SS content in influent, the removal efficiencies of ammonium and nitrite were 85% and 90%, respectively. The stoichiometric ratios of ammonium conversion, nitrite removal and nitrate production were 1:(1.29):(0.24) for synthetic wastewater and 1:(1.26):(0.22) for DAFW. After 180days of operation, there was a diverse change of the anammox consortium bacteria. Compared with the inoculated sludge (single Brocadia anammoxidans sp.), Kuenenia sp. became the predominant bacteria, with a small amount of Jettenia sp. and B. anammoxidans sp. The results demonstrated that ammonia in effluent of DAFW after two-stage biotreatment could be removed efficiently by the anammox process.