Abstract
A laboratory-scale two-stage moving bed biofilm reactor was used to remove medium-strength ammonium (50–400 mg NH4+-N/L) from synthetic wastewater and pretreated monosodium glutamate wastewater, respectively. The reactor was operated at a temperature of 23–29°C and a dissolved oxygen of 2–3 mg/L. The results indicated that the ammonium removal efficiency was as high as 99% for the synthetic wastewater and the effluent ammonium concentration was below 1 mg NH4+-N/L. Even though the influent ammonium concentration was increased to 400 mg NH4+-N/L corresponding to the ammonium volumetric loading of around 0.6 kg NH4+ -N/m3/day, the removal efficiency still maintained over 95%, whereas the ammonium removal efficiency decreased slightly for the monosodium glutamate wastewater and the effluent ammonium concentration was 11.3 mg NH4+-N/L on an average. It was also found that the pH value in the range of 8.0–9.0 was favorable for ammonium removal. In addition, the composition of oxidized nitrogen (NOx−) was influenced greatly by free ammonia, and nitrite was built up remarkably when the concentration of free ammonia was higher than 2.5–3.0 mg/L. Microscopic examinations illustrated that the main bacteria cultures in the biofilm were filamentous bacteria and zoogloea.
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