Ammonia oxidation is a critical process during nitrogen removal, while the activity of ammonia oxidizing bacteria (AOB) might be impacted severely in disposing high-salinity nitrogen-containing wastewater. To protect AOB in high saline medium, layer-by-layer self-assembly using graphene oxide (GO) and poly(diallyl dimethyl ammonium chloride) (PDDA) was applied to immobilize enriched AOB. By mixing GO and AOB, it was found that 30 mg/L GO showed the best promotion on the ammonia oxidation capacity of AOB. After coating, AOB with PDDA/GO showed higher absolute value of zeta potential of −20.1 ± 1 mV and compact structure. Comparing with uncoated AOB, although NH₄⁺-N consumption process was slightly inhibited by the PDDA/GO composite materials under low-salinity conditions (0–2 % NaCl), they presented great effective protection on the capacity of AOB in a 3 % NaCl solution. The consumption ratio of NH₄⁺-N was 1.34 times that of uncoated AOB, and the accumulation ratio of NO₂⁻-N of the former one was 1.40 times that of the latter. It inferred that the inhibitory to mass transferring caused by immobilizing materials was less than its positive promotion of AOB protection at 3 % NaCl concentration, and the protection of PDDA/GO composite materials was better than GO. This finding has some certain guiding significance for ammonia oxidation in high salinity.

氨氧化是脱氮过程中的关键过程，而氨氧化细菌（AOB）的活性可能会在处理高盐度含氮废水时受到严重影响。为了在高盐介质中保护 AOB，采用氧化石墨烯 (GO) 和聚二烯丙基二甲基氯化铵 (PDDA) 的逐层自组装来固定富集的 AOB。通过将GO和AOB混合，发现30 mg/L GO对AOB氨氧化能力的促进效果最好。涂覆后，具有PDDA / GO的AOB显示出更高的-20.1±1 mV的zeta电位绝对值和紧凑的结构。与未涂层的 AOB 相比，虽然 NH ₄ ⁺PDDA/GO复合材料在低盐度条件下（0-2% NaCl）对氮的消耗过程有轻微抑制作用，它们对AOB在3% NaCl溶液中的容量有很好的保护作用。_{NH 4} ⁺ -N的消耗比是无涂层AOB 的1.34 倍，NO ₂ ^- -N 的积累比是后者的1.40 倍。推测在3 % NaCl浓度下，固定化材料对传质的抑制作用小于其对AOB保护的积极促进作用，并且PDDA/GO复合材料的保护作用优于GO。这一发现对高盐度氨氧化具有一定的指导意义。