老帕讲堂：选择循环水系统时你需要知道的八件事（上）

昵称29757931 2017-09-19

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Starting new business in aquaculture would require more and more knowledge about systems that can be used to achieve profitable and sustainable aquaculture. Facing the multiplicity of offers on market from more and more suppliers, it becomes important to try to set up some key numbers or key ideas to help how to choose a RAS.

在水产养殖领域投资，如果想实现可盈利，可持续的养殖模式，对养殖系统认知和知识的储备显得越来越重要。面对市场上各种循环水供应商提供的方案，想知道如何选择适合自己的循环水系统，设定几个核心参数和核心条件是十分关键的。

In general, it is important to be aware that a system is designed to accomplish specific goals. Flexibility is NOT a criteria for RAS. The choice of a RAS should be driven by the operational costs it will generate versus the capacity it can fulfil. Choosing a RAS that does not specifically fit the requirement of one fish may lead in increasing operation cost.

总体来说，很重要的一点要认识到，循环水系统通常是为了实现指定养殖品种和养殖模式而订制设计的，所以不要把系统什么都能养这一点放到首位。循环水系统方案的规划取决于系统的运营成本和满负荷时的产能。各种鱼有不同的生长需求，不是按照特定生长需求设计的系统，可能会导致运营成本的增加。

The three main parameters commonly taken in consideration are:

在选择系统时，大部分人通常会考虑到三个主要参数：

Density 养殖密度

System water volume 系统总水量

Oxygen level 供氧含量

Therefore, they will be of the most mentioned parameters to describe a system. But are these parameters the ones that must be really considered to understand how efficient is a system? What would it mean of having a system handling 20kg/m3 compare to a system handling 50kg/m3? What are the main differences? Density and system water volume are the key numbers to give an idea of how much biomass could be produced in a system. But are these numbers relevant to understand if a system is well designed?

CERTAINLY NOT !!!!

这三个参数应该是描述一套系统最经常涉及的参数了，但是在衡量一套循环水系统的效率时，只考虑三个参数就足够了吗？一套可以承载每立方20公斤鱼的系统和每立方50公斤鱼的系统分别意味着什么呢？最主要的不同点在哪里呢？

密度和系统水量可以帮我们估算出系统承载的最大生物量，但是通过这两个参数就能判断循环水的设计是优秀的吗？

肯定不是！！

Directly linked to the density is:

密度直接关联的是

Feeding load 投喂量

(form which result the production of ammonia 通过投喂量可以计算出产生的氨氮)

Few farmers will ask for this parameter whereas it is probably one the most important parameter that will tell engineers with more precision how efficient should be a system.

很少有养殖户在寻求系统设计时会谈到投喂量，然而投喂量是能帮助循环水设计师设计一套优秀高效的养殖系统的重要参数之一。

The four previous parameters cited are numbers to quantify a system

上述提到的四个关键点事实上是确定循环水系统的体量：

How big is the system 系统的规模有多大?

How much fish I have in the system 系统中养多少鱼?

How much oxygen I have in the water 系统中的氧含量是多少?

How much feed I have to give 我要投喂多少饲料?

But, in no way they explain the functions of the system. A system is designed according functions it must achieve

但是，他们并不能说明循环水的处理功能。设计循环水系统时，必须实现的功能

The different functions are:

TSS removal 固体颗粒物的去除

Oxygen supply 氧气供给

Ammonia, nitrite removal 氨氮, 亚硝酸盐去除

pH control pH 控制

CO2 removal 二氧化碳去除

Bacteria control 细菌控制

Temperature control 温度控制

Nitrate removal 硝酸盐去除

To connect all these functions there is one unit that is the core of the system: THE PUMP. RAS system can be seen as a body. The main vital organ is above all, the heart.

能将所有处理功能联系到一起的设备，水泵，是循环水系统的核心。如果把循环水系统比作人体的话，水泵就像是人体最主要的维生器官，心脏。

The body is designed to respond to drastic changes in nutrients request. If muscle exercise increase (the need of cells in oxygen and energy) the only way to deliver the needed nutrients is then by accelerating the heart. There is no emergency oxygen supply in each organ and the blood (the flow) is the only way to bring oxygen. So, the heart (the pump) must accelerate to deliver more oxygen if needed. As for a body the higher the load of exercise the faster the heart. What must be considered in RAS then is how to deliver Oxygen and remove wastes like in a body. In that sense RAS and body are similar.

在人类进化的过程中，我们的身体在应对外界条件变化时，可以及时对我们的身体机能做出调整。如果你的肌肉在某种条件下需要做更多的工作，那么唯一的方式就是心脏加速跳动，通过血液带给肌肉更多的工作要素（氧气和能量）。因为身体器官本身没有应急供氧功能，只有血液（相比水流）才能带来氧气。所以心脏（相比水泵）必须加速工作，以确保足够的氧气供给。所以身体机能的负荷（循环水系统负荷）越多，心脏（水泵）就要跳动的越快。在循环水系统中，如何将氧气带到鱼池，将废物带出鱼池，与我们身体的运行机理十分相似。

This article will give “rules of thumbs” to evaluate functions of a RAS. Each of these functions will be later describe in future articles.

我会在今后的一系列文章中，为大家带来关于循环水功能的“经验法则”。

TSS REMOVAL 悬浮颗粒物的去除

Faeces are the primary waste produced by fish. It will be found into the water on the form of suspended solids. All particles in water should be dealt with to avoid accumulation of them and consequently, a degradation of the water quality.

粪便是鱼类产生的首要污染物，在水中以固体悬浮物的形式存在。水中所有的颗粒物都应该有效分离，避免其积累，最终污染水质。

From 0.001 microns to few millimeters particles, it is the first challenge that a system must accomplish. the predominant particle sizes in the outlet water from tanks are less than 30–40μm. For those particles, simple mechanical filtration will be ineffective. As an understanding 60 to 90% of the particles, size might be under 30μm. Drum filters are usually designed to catch particles over 60μm if not 90μm.

循环水系统最先要完成的挑战就是如何去除各种大小的颗粒物，小到0.001微米，大到几毫米。鱼池出水口的主要颗粒物尺寸一般小于30到40微米，对于这些颗粒物，简单的机械式过滤工艺并不是十分有效。根据经验，60%到90%的颗粒物是小于30微米的。而转鼓式微滤机的设计精度一般是60微米或者90微米。

Therefore, it is important to understand if the raised specie is requiring high water quality and/or can tolerate particles in water. Check the size of the drum filter to understand if further filtration is needed. Higher water quality will require other or more efficient particles removal devices such as drum filter up to 20μm or specific filtration that can catch up to less in size such as protein skimmer, fixed bed, membrane filtration…

因此，对于养殖而言，一定要知道自己养殖的品种是否需要特别洁净的水体或者可以忍受水中的颗粒物。在确认微滤机过滤精度的同时，也要考虑是否需要进行更精细的过滤。如果想把水过滤的更加彻底，就需要更有效的过滤工艺，比如精度到20微米的微滤机或者能够去除更小尺寸颗粒物的蛋白分离器，固定生物床或者反渗透。

It is therefore, very important to understand which level of filtration is necessary to reach the necessary water quality for your fish. Tilapia or carps will definitely not need the same clarity of the water as flat fishes or trout.

“经验法则“：物理过滤的关键在于了解养殖品种对水质的耐受程度而选择不同级别的过滤工艺。鲆鲽类和鲑鳟类与对水的要求程度相对于罗非鱼，鲤鱼肯定是不相同的。

OXYGEN SUPPLY 氧气供给

The oxygen consumption is directly related to the consumption of feed and NOT TO THE DENSITY OF FISH. The more feed the more oxygen is needed. Consequently, In an RAS aiming to high density it is estimated that a safe value of oxygen needed is around 0.8 to 1kg O2/ kg feed/day.

氧气的消耗程度并不只是由养殖密度决定的，而且直接受投喂量的影响。投喂的越多，消耗的氧气就越多。

“经验法则“：通常来说，在高密度循环水养殖系统中，计算氧气需求量所采用的安全数值为每天每公斤饲料消耗0.8到1公斤的氧气。

AMMONIA 氨氮

The use of feed in aquaculture will result quickly in accumulation of ammonia which is the primary physiological waste produce by fish and which is excreted through gills. The content of feed in protein will directly impact the product ion of ammonia. The only way to remove ammonia is by biofiltration. Bacteria are responsible for biofiltration. They need space to grow and must be protected from physical abrasion and chemical toxicity.

水产养殖中，饲料的投喂将在短时间引起氨氮的积累。氨氮是鱼类通过鳃排除的首要生理废物。饲料中的蛋白含量直接关系到氨氮的排放量。去除氨氮的唯一方法是生物处理。这个处理过程会由硝化细菌完成。这些硝化细菌需要空间生长，同时要避免受到物理方式或是化学方式的破坏。

The most efficient biofilter so far is a MBBR (Moving Bed Biofilm Reactor). The principle is to keep in movement into the water highly designed pieces of plastic that ensure the bacteria to have a lot of protected space. These plastic called biomedia are specified by a number: the specific area expressed in m2/m3. Commonly find biomedia of 200 to 800m2/m3.

目前最有效的处理方式是移动生物床。移动生物床通过在水中移动的特殊设计的填料，确保细菌有充足的空间生长繁殖。这种填料叫做生物填料，描述生物填料特性的单位为m2/m3，我们称作比表面积。一般来说，生物填料根据设计不同，比表面积在200到800m2/m3之间。

A safe rule of thumb in designing biofilter is that a 1 m3 of biomedia with a specific area of 100m2/m3 can treat 1 kg of feed (50% protein). Commonly K5 (kaldnes 5, a type of biomedia available on market) has a specific area of 800m2/m3 can treat easily 8 kg feed /m3/day. This value is an indicative value. By choosing this as a reference then it is quite safe but it is discussable. This will be developed in a future article.

Beside ammonia removal, it is important to understand one thing: Ammonia removal is NOT NEUTRAL on water parameters. This HAVE TO BE TAKEN IN ACCOUNT WHEN RUNNING RAS.

This is the purpose of the next point.

“经验法则“：在设计生物床时，比较安全的计算方式是，1立方比表面积为100m2/m3的生物填料可以处理1公斤的饲料（蛋白含量为50%）。比较常用的填料型号K5（Kaldnes公司的5号填料，是市场上的常见型号）拥有接近800m2/m3的比表面积，每立方填料的处理能力可以达到每天8公斤的鱼饲料。这个数值是理论值，按照这个比例计算虽然比较安全，但是值得讨论的地方也很多。我们会在以后的文章中详细说明。

关于氨氮去除，还有一件事十分重要：去除氨氮对水质参数的影响并不是独立的！在循环水运转的同时，所有的水质参数都是相关联的，比如我们要下面要讲到的第四点.

pH CONTROL pH调节

In biofiltration, the pH plays an important role. Why the pH varies in a system? It is the result of two mains processes:

在生物处理中，pH扮演了一个十分重要的角色，系统中的pH为什么会产生变化呢？是由于两个反应过程造成的结果：

Biofiltration will produce H+ which acidifies water whereas it consumes carbonates. 硝化处理过程会消耗碱度，产生氢离子，使水酸化

Respiration will produce CO2 which also acidifies water. 生物呼吸过程会产生二氧化碳，使水酸化

Two ways of controlling the pH:

By exchanging water. The water to be exchanged will be proportional to the density (in other terms, the feed load). The higher of the feed load, the higher the exchange rate. To give an idea at 25kg/m3, pH can be maintained with a minimum exchange of 30% of the total volume (indicative value). By adding some chemical (carbonates) that will change the PH. The relation is typically between 0.15 to 0.25kg/kg feed / day.

“经验法则“：通常由两种方式调节pH：

第一种是通过换水调节pH，换水量通常是与养殖密度正相关的（实际上是投喂量），密度越大，换水量越多。我们来举个例子，比如养殖密度是每立方水体25公斤，想要保持pH恒定的最小换水量为30%。

第二种是通过添加化学试剂（碱性试剂）调节pH

通常来说添加的碱性试剂与投喂量的关系为每公斤饲料每天投放0.15到0.25公斤的碱性试剂。（根据试剂的不同，水质的条件不同，需要计算合适的计量）。

To be continued

未完待续

翻译：小梁

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