The NFP reactors can either be operated manually, semi automatically or fully automatically.
This will depend on the application and level of sophistication that you want to go to. The first part of these instructions describes the operation of the unit without the need for any supplementary equipment other than a reliable high sensitivity nitrate test kit which is not supplied with the unit.
FULLY-AUTOMATIC METHOD OF OPERATION
This method is suitable for all sizes of reactor and is covered by a separate diagram which is under downloadable files.
For this method you will require the following items of equipment;
1 - The NFP Nitrate Reactor.
2 - A redox controller, probe and calibration solutions.
3 - A solenoid valve which is suitable for salt water (can be ordered with your Deltec reactor).
4 - A peristaltic pump and timer, (timer capable of controlling down to second intervals), to supply the Nitrate Fluid.
Operation of the NFP reactor follows the same principles as has already been explained in the manual and semi automatic sections. These should be read and understood before moving on.
Supply of Nitrate Fluid to the Nitrate Reactor.
Either of the two methods described under ‘Semi-Automatic Method of Operation' for feeding the reactor with nitrate fluid can be used however for optimum output or with the larger reactors it will be necessary to use the peristaltic pump option.
The same ratio of daily Nitrate Fluid addition to media area applies as in the manual section and an indicative starting level for each reactor is given in the table at the top of the introduction page.
Supply of water to the Nitrate Reactor
This is where the fully automatic operation of the Nitrate Reactors varies from the other two methods described.
With this method we use a controller ‘B' and probe ‘A' to ensure that the redox within the unit is maintained at the correct level of oxygenation, or deoxygenation, for the denitrification process to operate at its optimum level.
As we can see from the diagram there are two feeds to the reactor, both with control taps 'D' & 'E'. The supply for these two feeds can come from a common pump which can be split with a T or Y connector at ‘F'.
One of the water feeds is fitted with a solenoid ‘C' which will be actuated by the redox controller to switch the flow off and on. This solenoid must be salt water safe if used on a saltwater tank and not one of the general units used for CO2 or fresh water. The special solenoid can be ordered at the time of ordering the Nitrate Reactor.
The redox controller and probe must be calibrated prior to use and will require regular recalibration as they tend to drift with time towards a more positive value. Note that it can take several days for a new probe to settle down and to start reading the correct value when first installed and calibrated.
Operating the Fully-Automatic System
1 - Fill and check the reactor as described earlier, fit the redox probe and controller, switch on the recirculation pump and then close off both water feeds for 3 days.
2 - From day 1; set the timer on the peristaltic pump ‘G' to supply the correct dose of Nitrate Fluid as shown in the table for the particular model of reactor. Add this volume split into 2 or 4 doses over the period of the day controlled by the digital timer.
3 - After 3 days open tap ‘E' gradually until you achieve 1 drip every 3 seconds and then follow the instructions for testing and adjusting the water flow over a period of days and weeks as described in the manual operation section.
At this initial stage the only tap that will be adjusted will be tap ‘E'. We will start to use the second water feed through the solenoid and tap ‘D' once the reactor starts to mature by a couple of weeks.
The redox in the unit will start off at a positive value and will slowly move to zero and then to a negative reading as the oxygen in the system is used up by the bacterial culture. Remember that we want to control the redox at about minus 170mv.
4 - Now that the reactor has been running for a few weeks and the redox has fallen we can start to use the redox controller to add more water to the system to increase the flow through the reactor when required which will maintain the redox at the optimal level for denitrification.
When the redox level reaches minus 170mv the controller should be set to activate the solenoid. This will allow additional water into the reactor which will subsequently reduce the redox and will switch the solenoid off again.
To ensure that the volume of water that we add via this secondary water supply is not too high, thus bringing the redox down too far, we set tap ‘D' so that there is only a low flow rate going into the reactor. The rate of flow will depend on the size of the reactor, in the order of drips for the small reactors and a slow dribble for the larger ones. It is better to control in regular small stages than to add the water in one large amount and to drop the redox down too far below its optimal level.
Note that the redox will fall every time you add food to the system therefore small regular doses will give a more stable reactor.
Balancing and optimising the Reactor
Once the reactor has been running for several weeks we will find that the flow rate through the reactor has increased many fold and the nitrate level with in the aquarium or system is starting to fall.
At this point we have 3 controls to adjust to optimise the performance of the reactor.
The Nitrate Fluid (food) volume.
The main water flow.
The secondary redox controlled water flow.
All 3 are in equilibrium and if we adjust one then we must adjust the others to bring it back into balance.
If we increase the volume of Nitrate Fluid then the amount of bacteria within the reactor will be allowed to increase and the redox level will fall, (become more minus). At this point the redox controller will open up the solenoid valve to allow more water through tap ‘D' to bring the redox back to below 170mv. If we find that the redox still stays high or that the solenoid is open all the time then we should increase the flow rate through tap ‘E' to bring the system back into balance.
If we increase the flow rate through the main water supply tap ‘E' by too much then we will see that the redox will start to rise, (less negative), and the solenoid will not open at all. At this point we must increase the amount of Nitrate Fluid supplied to bring the system back into balance or reduce the flow rate through tap ‘E' back to a level that the existing food and bacterial level will support.