The recirculating aquaculture system (RAS) is a land-based water treatment technology, which allows for farming aquatic organisms, such as fish, by reusing the water in the production (often less than 5%). This technology is based on the use of filters, either mechanical or biological, and can, in principle, be used for any species grown in aquaculture. Due to the low recirculation rate, ammonia accumulates in the system and must be converted into nitrate using nitrification reactors. Although less toxic for fish, nitrate can also be further reduced into nitrogen gas by the use of denitrification biofilters which may create several issues, such as incomplete denitrification, resulting in toxic substances, such as nitrite and nitric oxide, or a waste of carbon source in excess. Control of the added quantity of carbon source in the denitrification biofilter is then mandatory to keep nitrate/nitrite concentrations under toxic levels for fish and in accordance with local effluent regulations, and to reduce costs related to wasted organic carbon sources. This study therefore investigates the application of different control methodologies to a denitrification reactor in a RAS. To this end, a numerical simulator is built to predict the RAS behavior and to allow for the comparison of different control approaches, in the presence of changes in the operating conditions, such as fish density and biofilter removal efficiency. First, a classical proportional-integral-derivative (PID) controller was designed, based on an SIMC tuning method depending on the amount of ammonia excreted by fish. Then, linearizing and cascade controllers were considered as possible alternatives.

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循环水产养殖系统中的反硝化控制—模拟研究

循环水产养殖系统（RAS）是一种陆基水处理技术，可通过在生产中重复使用水（通常少于5％）来养殖水生生物，例如鱼类。该技术基于机械或生物过滤器的使用，并且原则上可以用于水产养殖中生长的任何物种。由于再循环率低，氨在系统中积聚，必须使用硝化反应器将其转化为硝酸盐。尽管对鱼类的毒性较小，但也可以通过使用反硝化生物滤池将硝酸盐进一步还原为氮气，这可能会产生一些问题，例如反硝化不完全，导致产生有毒物质（例如亚硝酸盐和一氧化氮）或浪费碳源。过量。因此，必须控制反硝化生物滤池中碳源的添加量，以使硝酸盐/亚硝酸盐的浓度保持在鱼类有毒水平且符合当地废水法规，并减少与浪费的有机碳源有关的成本。因此，本研究调查了不同控制方法在RAS中的反硝化反应器中的应用。为此，在操作条件（例如鱼的密度和生物滤池去除效率）发生变化的情况下，建立了一个数字模拟器来预测RAS行为并允许比较不同的控制方法。首先，根据鱼类排泄的氨量，基于SIMC调整方法，设计了一种经典的比例积分微分（PID）控制器。然后，