In this study, water quality and fish performance of traditional RAS with nitrifying biofilters were compared with systems operated under heterotrophic N assimilation (HET-N), a process where bacteria consume ammonium directly for growth and thereby remove dissolved N excreted from the fish, using three different modes of carbon addition. Using twelve identical pilot scale RAS, four treatment groups were established in triplicate: RAS with autotrophic biofilters (Control), RAS with autotrophic biofilters and acetate addition (BF RAS +Acetate), RAS without biofilter with acetate addition (BF RAS -Acetate) and RAS without biofilter and a biopellet reactor (Biopellet RAS). The nine RAS with carbon addition all had lower levels of nitrate and orthophosphate at the end of the trial compared to the three control RAS (approx. 70% less NO₃^- in the Biopellet RAS and 72% less PO₄^3- in BF RAS -Acetate). Without biofilters installed, both BF RAS -Acetate and Biopellet RAS maintained acceptable water quality parameters during their respective start-up phases and were fully developed in under 3 weeks. The addition of acetate to the water caused an expected formation of bioflocs in the systems, and a significant increase in bacterial activity and turbidity. Substantial feed spill was observed in RAS with acetate addition. The absence of bacterial accumulation and no increase in turbidity in the water in Biopellet RAS suggest that the processes primarily occurred within the reactor. The overall fish mortality was <1%, however, both types of RAS with acetate addition led to reduced fish growth (7.4–20%) compared to the control RAS and the RAS with biopellets. Biopellets were found to reduce dissolved N and P, and had a fast start up time without deteriorating water quality, thereby showing promising traits for use in RAS.

在这项研究中，将带有硝化生物过滤器的传统 RAS 的水质和鱼类性能与异养氮同化 (HET-N) 下运行的系统进行了比较，在异养氮同化 (HET-N) 下，细菌直接消耗铵进行生长，从而去除鱼中排出的溶解氮，使用三种不同的碳添加模式。使用十二个相同的中试规模 RAS，一式三份建立四个处理组：具有自养生物过滤器的 RAS（对照）、具有自养生物过滤器和添加乙酸盐的 RAS（BF RAS +乙酸盐）、不具有添加乙酸盐的生物过滤器的 RAS（BF RAS -乙酸盐）和不带生物过滤器和生物颗粒反应器的 RAS (Biopellet RAS)。与三个对照 RAS 相比，在试验结束时，添加碳的九个 RAS 的硝酸盐和正磷酸盐水平均较低（Biopellet RAS 中的 NO 3 - 减少约 70%，BF RAS 中的 PO 4 3-_减少^约72 _% ^） -醋酸盐）。在未安装生物过滤器的情况下，BF RAS -Acetate 和 Biopellet RAS 在各自的启动阶段均保持了可接受的水质参数，并在 3 周内完全开发完毕。向水中添加醋酸盐会导致系统中预期形成生物絮凝物，并显着增加细菌活性和浊度。在添加醋酸盐的 RAS 中观察到大量饲料溢出。Biopellet RAS 中没有细菌积累且水中浊度没有增加，表明该过程主要发生在反应器内。鱼类总体死亡率<1%，然而，与对照 RAS 和含有生物颗粒的 RAS 相比，添加醋酸盐的两种 RAS 均导致鱼类生长减少 (7.4-20%)。研究发现生物颗粒可以减少溶解的氮和磷，并且启动时间快，且不会恶化水质，从而显示出在 RAS 中使用的良好特性。