主流条件下两级式PN-ANAMMOX工艺的高效能脱氮过程

High-rate Nitrogen Removal in a Two-stage Partial Nitritation-ANAMMOX Process Under Mainstream Conditions

中低温条件下采用两级式PN-ANAMMOX工艺对低浓度NH_4^+-N(50 mg·L^(-1))污水进行高效脱氮过程研究.结果表明,20~14℃范围内PN-ANAMMOX工艺的脱氮负荷和TN去除率可分别维持在0.6 kg·(m^3·d)^(-1)和80%以上;两级式PN-ANAMMOX工艺在限NO_2^--N和限NH_4^+-N两种模式下均可保持稳定运行,其中限NH_4^+-N运行模式为污水极限脱氮需求奠定了良好基础.当温度降至12℃时,PN-ANAMMOX工艺的脱氮负荷下降至0.5 kg·(m^3·d)^(-1)左右,低温使得ANAMMOX反应成为工艺脱氮的限速步骤而对PN无明显影响.ANAMMOX污泥比PN颗粒污泥具有更高的温度敏感性,二者活性的温度系数分别为1.056和1.172.综上可知,对于低温条件下运行的两级式PN-ANAMMOX工艺,ANAMMOX菌体数量及活性是决定工艺脱氮负荷的步骤,而PN出水中基质组成(即NO_2^--N/NH_4^+-N之比和NO_3^--N浓度)是控制工艺脱氮效果的环节.基于上述结果,提出两级式PN-ANAMMOX工艺主流条件下实现高效能脱氮的分级分离式调控策略.

A two-stage partial nitritation （PN）-ANAMMOX process was successfully carried out for low-strength NH4＋ -N （50 mg. L- ~ ） wastewater treatment at ambient/low temperatures. The results show that an average total nitrogen removal rate and removal efficiency above 0. 6 kg. （ m3 .d） -1 and 80% could be maintained, respectively, at temperatures between 20℃ and 14℃. The two-stage PN- ANAMMOX process was successful both under NO2-N-limited and NH4^＋-N-limited conditions. When the two-stage PN-ANAMMOX process was operated under NH4^＋ -N-limited conditions, the ＂limit of technology＂ for nitrogen removal （ TN 〈 3 mg·L^-1 ） could be easily achieved by following anoxic denitrification. Lowering the temperature to 12℃ resulted in the reduction of the total nitrogen removal rate to -0.5 kg· （m^3·d） ^-1 Due to the low temperature, the anammox reaction became the rate-limiting step for nitrogen removal, while the PN reaction was not impacted. In the temperature range of 10-20℃ , the activity -temperature coefficients （0） of the PN granules and ANAMMOX sludge were 1. 056 and 1. 172, respectively, suggesting that the anammox bacteria have a higher temperature sensitivity than the ammonium oxidizing bacteria （AOB）. Overall, the results clearly indicate that the nitrogen removal loading rate of the two-stage PN-ANAMMOX process is mainly controlled by the activity and quantity of anammox biomass. In contrast, the process nitrogen removal efficiency mainly depends on the performance of the first-stage PN （ i. e. , effluent NO2^ -N/NH4^＋ -N ratio and NO3^- -N concentration） under a constant nitrogen removal loading rate （no overload）. Based on these results, a hierarchically separate control strategy was proposed to obtain a high-rate nitrogen removal during the two-stage mainstream PN-ANAMMOX process.