Effect of boron on the recovery of nitrification efficiency after high ammonia nitrogen impact

Abstract

By increasing the concentration of ammonia nitrogen, the stable nitrification system was inhibited, and then boron was added to the reactor to improve the recovery of nitrification efficiency. The changes of the short-range nitrification system were characterized by the nitrogen conversion capacity, the activity of ammonia-oxidizing bacteria, the content of protein and polysaccharide, the morphology of sludge, and the particle size distribution of granular sludge. The results showed that the stable short-range nitrification system was affected by 800 mg/L ammonia nitrogen in a short period of time, and the stability of the sludge was weakened, and it could not be recover in the short term when the ammonia nitrogen concentration returned to 200 mg/L. Compared with the inhibition period, the removal rate of ammonia nitrogen increased from 50% to 95% during the recovery period. The accumulation rate of nitrite increased from 50% to 85%, the accumulation rate of nitrate decreased from 50% to 15%, and the specific ammonia nitrogen oxidation rate(SAOR) increased from 18.65 mg/(g·h) to 38.36 mg/(g·h). Specific oxygen consumption rate(SOUR) increased from 47.68 mg/(g·h) to 54.24 mg/(g·h), MLSS increased by 32% to 4.5 g/L, PN mass fraction in EPS increased by 23% and m(PN)/m(PS) increased by 35.96% compared with the inhibition stage. The concentration of the signal molecule AI-2 also increased from 0.021 ng/mL to 0.124 ng/mL. Therefore, this study illustrated that boron could promote the recovery of short-range nitrification system performance under the impact of high ammonia nitrogen concentration.

Keywords

• short-cut nitrification
• high ammonia nitrogen concentration
• boron