Application – Aquaculture

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SENECT control technology in aquaculture

In professional aquaculture, the use of decent technology is nowadays indespenseable. For example, the aeration and, in case of higher fish densities, the use of pure oxygen became standard in modern trout farming. Also, automatic feeding with fish feeders grew to the standard method which saves the farmers labour and increases the feed conversion rate - therefore it saves additional costs. 

Futher intensification lead to a partial or full water treatment in so-called (partially) recirculating aquaculture systems. There, the removal of the particle load - in moste cases by drum filters - is the first technologicial step. The next step is the degradation of ammonia in so-called biofilters. There, the relative toxic ammonia is converted in two steps to the relatively untoxic nitrate. Where water is scarce, also biological denitrification filters are used to degrade the accumulated nitrate. For a reduction of the bacterial load (and sometimes due to other reasons), UV-C lamps or ozonation is used to treat the circulating water.

Most of these water treatment or automatization steps need - to be effecitve and reliable - the proper control. Here, the technology of SENECT comes into play. Some examples may highlight this:

 

Example 1: Oxygen measurement and dosing

If pure oxygen is transferred into the water, for example via low-head oxygenation systems or ceramic diffusors,  it is necessary that the oxygen level in the water is controlled to avoid over- and undersaturation. The underlying reason for a dynamic control is that the oxygen demand is changing during the day and therefore, different amounts of oxygen are needed to achieve the optimal concentration.

The SENECT control units measure the dissolved oxygen concentration with the optical O2S oxygen sensor and add only as much oxygen as needed to achieve the desired concentration, e.g. 100% a.s. The addition of oxygen is typically made by opening solenoid valves or by switching on an oxygen production device, e.g. via the PowerSwitch.

Example 2: Controlling automatic feeders

Moste automatic fish feeders can be controlled directly by electrical signals, e.g. via 24 V DC or 230 V AC. Is the voltage switched on, the feeder starts to feed. Since the feeder should be activated only for short time periods dispersed over the day, a temporal control of the feeders is necessary. To feed the optimal amount, the mass of feed per day should increase with the increase of the fish biomass and the feed amount should be adjusted depending on the temperature. It is also reasonable, to stop feeding when oxygen levels are low or - even better - to increase the oxygen concentration prior to feeding to avoid critical situations. This balances the extra oxygen consumption during digestion and leads to a better feed-conversion-rate.

The SENECT control units allow the temporal control of feeding either by the input of intervals (e.g. every hour between 7 a.m. and 7 p.m. for 20 s) or by the input of distinct times (e.g. at 7 a.m., 12 a.m., 3 p.m. and 6 p.m. for 20 s). Additional functions like a daily increase, the temperature-dependend feed amount correction or skipping the feed portion if the oxygen level is too low and the calibration of feeders make the feeder control of SENECT to a powerful tool to feed optimal.

Example 3: Controlling drum filters

The first step towards a recirculation system is the removal of supended particles by a drum filter. Theses filters fulfill this task completely automatized, therefore the backwashing process must be controlled.

All large SENECT control units (AQUACULTURE|CONTROL, FILTER|CONTROL) can control drum or belt filters. By using water level information measured with the SENECT water level probe PS, the backwashing is only induced, when the filter mesh is clogged. Therefore, unnecessary wear-out, waste of water and energy can be avoided.

Many useful functions like soft-start, intensive cleaning programme, EcoMode or emergency pump switch off lead to a reliable filter operation which simultanously elongate maintenance intervals.

Another advantage: the SENECT AQUACULTURE|CONTROL is able - beside the drum filter control - to fulfill other tasks, e.g. the control of oxygenation, pH mesurements or the control of fish feeders. All these functions are possible with only one control unit!

Fish farms have often a long history, where components are already bought. This is no problem for the SENECT control units, since many external components from third party suppliers can still be used. Therefore, the modernisation is possible even without exchanging all components.

Thanks to its modular architecture, also only parts of the aquaculture system can be controlled "new" and the control system can be extended step-by-step. The consequent use of plugs make it easy to install the control units and sensors. This brings an enormous flexibilty and saves additionally installation costs.

All SENECT control units can be connected to a WLAN network. With that, you have access to all current measurement values and the status of output ports or you can display graphs of the recorded data on your smartphone, tablet or PC. Additionally, you can receive alarm messages on your smartphone so that you are informed instantanously!