Treatment of semiconductor wastewater using single-stage partial nitrification and anammox in a pilot-scale reactor

Abstract

Start-up of pilot scale reactor to treat real semiconductor wastewater is reported in this study. Semiconductor industrial wastewater stream was characterized as highly alkaline (pH 10) and contained high concentration of H2O2 of 311 ± 505mg/L, ammonium nitrogen of 318 ± 122 NH4+-Nmg/L and negligible COD of <10mg/L. H2O2 was removed by adding enzyme “REYONET F-35” and H2SO4. Before the H2O2-free wastewater is fed to the biological reactor, the pH is adjusted to ∼7.0. Completely autotrophic nitrogen removal over nitrite (CANON) process was cultivated in a 1.0m3 pilot-scale sequencing batch reactor by using enzyme pretreated semiconductor wastewater without temperature control. The nitrogen loading rate was increased step-wise from 94 to 665g NH4+-N/m3d. The average NH4+-N and total nitrogen removal efficiencies were 85.5 and 75.7%, respectively at NLR of 665g NH4+-N/m3d and HRT of 4d. The pilot reactor was successfully started up and operated for more than 550d. The CANON was evidenced by the ratio of the effluent nitrite and nitrate to ammonium ratio (η) of 0.076 during the steady state operation period. PCR results also confirmed the presence of AOB (aerobic ammonia oxidizing bacteria) and anammox (anaerobic ammonia oxidizing) bacteria in the reactor.