Monitor and Control Systems for Aquatic Housing in the Laboratory

danio lab
danio lab
Apr 13, 2017 · 8 min read

When it comes to monitor and control systems for aquatics housing, there is a great difference between the systems on the market, the way they operate, and their capabilities. Depending on the budget, the size of the system, and the level of monitor and control required, vendors should be able to specify the appropriate system.

It is best to clarify needs and expectations with any vendor on the specific requirements for monitor and control. If one is not sure about what is available and/or required, be ready to learn as much as possible about this equipment, because it will eventually become an integral part of the aquatics system. Their importance cannot be overstated, as the success of the laboratory and research running smoothly depends a great deal on the notifications that monitoring systems can provide.

The easiest way to monitor an aquatics system is to manually measure pH and conductivity, as well as the concentration of ammonia, nitrites and nitrates. The water chemistry can then be adjusted manually by adding fresh Reverse Osmosis Water (R.O. Water) or by adding chemicals such as a base or acid, and salts to achieve your desired result. While this is the least expensive way to monitor a system without having to buy costly equipment, the labor involved can quickly outpace the cost of an automated system. The monitor and control of the system is then limited to when laboratory personnel are working, 9–5, which leaves 16 hours of the day without monitoring of the system. Depending on the size of the system and the research, this might be sufficient. As the research and aquatics system grow, it is usually more cost efficient and more dependable to purchase an automated system.

The simplest system will monitor either pH or conductivity or both. Another term often used for conductivity is salinity. Basic systems usually include a meter and a probe that displays the value of the parameter being monitored, but still requires manual dosage of chemicals and manual water changes. The probes also require scheduled calibrations to maintain their effectiveness. While usually effective, there is still a chance that something could fail during the time that no laboratory personnel are present.

A more sophisticated system can control the water chemistry automatically. This is accomplished by adding a peristaltic pump that is controlled by a relay on the pH or conductivity meter to dose a chemical solution to your system. With proper setup and maintenance, these systems are very dependable in their operation. Proper maintenance of monitor and control systems is critical. We need to remember that animals’ lives and validity and accuracy of scientific results are depending on these systems. Most systems will give the user many years of service with proper maintenance and care, including cleaning and replacing worn out probes, hoses, and other various components. Developing a separate SOP for the monitor and control system and strictly following it will insure the success of the entire system.

Monitoring Systems
There are many different aspects of water quality that need to be verified on a daily and/or weekly basis. Depending on the budget, a monitoring system can be employed to cover most of these factors. The typical aquatics laboratory should be monitoring pH, conductivity, temperature, Dissolved Oxygen (D.O.), and water level on a constant basis. Ammonia, nitrites, and nitrates cannot be feasibly monitored with electronics, and once a system is biologically acclimated, we suggest once a week manual measurements.

The pH, conductivity, D.O., and water temperature measurements are all taken from probes usually mounted in the main system sump tank. Probes can also be mounted in an in-line system piping to get a constant flow of water across them; however, this set up makes maintenance more difficult unless the probes are properly installed on a bypass loop to shut the flow of water off from the main water supply lines. It is crucial to follow the manufacturer’s instructions on probe maintenance. This maintenance should be done at least once per month, but check with the manufacturer for specific details on your equipment.

Another option would be to monitor the mechanics of the aquatics system. This includes filter pressures, room temperature, water level, and power. Filter pressure readings from a pressure gauge are usually sufficient, and it only takes a minute for a technician to verify and record. If a filter was to clog, or a pump to fail in the middle of the night, the users can be notified with a pressure sensor connected to an alarm system. Water level sensors are also critical during an emergency situation. Although it is not necessary to know the exact sump tank water level at all times, it is crucial that the water remains at a minimal level. Otherwise, air can be introduced into the system through the pump intakes, creating micro bubbles in the water. This results in super saturation and gas bubble related diseases in aquatic species. A float switch that shuts down system pumps and UV sterilizers due to low water levels is also a good back-up to prevent damage to the equipment. Monitoring power is also important since power outages can be detected and alarmed. It is good practice to connect electrical circuits to emergency power if the facility is equipped with it. Power outages can result in many catastrophic situations in any laboratory especially when animals are present.

Although monitor and control systems can take care of most parameters, the ability to be notified in emergency situations is critical to the animals’ lives and thus the research being conducted. A simple telephone auto-dialer with normally open relay contacts is the least expensive way to get alarm notifications to your telephone. However, this does not always give a good picture of what is occurring and how urgent the situation is. More complex auto-dialers and Programmable Logic Controllers (PLCs) can read actual signal outputs from probes and meters and report that data via a phone line, email, text message, page, or fax. Although appearing complex, these systems are usually not that much more expensive than their cheaper alternatives and once set-up, usually do not require any additional maintenance. It is also a good idea to integrate a back-up battery to keep monitoring and alarming operational during power outages.

Most systems on the market offer data-logging of all parameters being monitored. The ability to download the data into a spreadsheet and view it graphically can help to pinpoint specific instances in water quality or system mechanics. These data trends might show what could lead to a decreased egg lay in Zebrafish. Although it is important to contact your facility veterinarian whenever the animals develop symptoms of abnormal behavior, any data you can produce for the veterinarian will be helpful. Daily reports sent by fax or email are also helpful especially while away from the laboratory or vivarium. Supervisory Control and Data Acquisition (SCADA) systems are ideal for aquatics housing systems. They can be integrated into equipment that has industry standard communications protocols, perform all alarm functions, and download data manually or automatically to a user’s computer.

Control Systems
Control Systems can differ in many different ways. They can be simple digital timers that control water exchange pumps or be fully integrated into an Aquatics Housing System SCADA. Typically, peristaltic pumps are used to control pH and conductivity levels in the water, activated by relays builtin to the pH and conductivity meters. Set-points and hysteresis values can be defined right in the meter, or programmed into the SCADA system. There are also more complex industrial control systems available like PLC’s, however, they need to be custom engineered and programmed for each application. They do have an advantage in that they are extremely modular from the most basic system to the more complex ones. PLC’s are very simple to upgrade for future expansion.

Control systems can also perform automatic water exchanges, backwash filters, and pump control. An ideal situation would be a controller that can actuate valves as needed, monitor the pressure of the filter and the flow of water going to the system, and drain during all phases of a backwash cycle. Even advanced R.O. water makers have the capability to perform these functions automatically.

As with everything in science and husbandry, a proper SOP is necessary to maintain this specialized equipment. This includes all of the monthly probe checks, cleanings, and calibrations when needed and testing back-up pumps for proper flow and operation.

The probes, particularly pH, need to be cleaned and calibrated much more often than a conductivity probe. This usually includes soaking in a slightly acidic solution for a few minutes to remove bio-film and then rinsing with R.O. water. A two-point calibration procedure is standard for many systems. D.O. probes typically need to have membrane changes and the electrode scrubbed. However, recent technology has yielded newer D.O. probes that require much less maintenance. Conductivity probes need to have the bio-film cleaned off with a gentle wipe. They usually do not need to be re-calibrated, but verifying an adequate value of the probe in a standard solution is always recommended. The pH and conductivity probes should always be temperature calibrated, since the values will vary at different water temperatures. Most water temperature probes do not need calibration, but manual verification for any offset values with a mercury thermometer is a good idea. New, un-opened buffer solutions should always be used with probe calibration. Buffers do age and become contaminated over time which will affect the calibrated value.

The most important part of all these systems is scheduled testing of the equipment. All functions should be checked on a regular basis to know that they will work when they need to. Testing the alarms for proper notification will insure that they work during an emergency situation. This is just as important as calibrating the probes and sensors on a monthly basis. Systems that are phone line based might be vulnerable to modern PBX style phone systems often installed in newer buildings. Maintaining the phone line is a simple task, yet often overlooked. Adding this to the SOP should help prevent these problems from arising.

As regulations continue to evolve in aquatics housing, we will likely see more of a need for systems that monitor and control the environmental parameters of aquatic housing systems. Systems that could ideally be integrated into every “stand alone” product or centralized system and report back to the animal care staff, veterinarians, facilities, and researchers will play an important role in aquatics housing becoming mainstream. The ability to smoothly integrate into existing networks with standardized protocols will also greatly improve the aquatics housing industry. This will also allow the staff to be more comfortable with the equipment and where their duty lies when something goes wrong. Ideally, water quality alarms could be sent to animal care staff, mechanical failures to facilities staff, and in the event of a more catastrophic event, the veterinarians and researchers would be alarmed as well. Institutions that are ready to adopt aquatics as part of their core facility can easily dispatch and handle these functions. As researchers, husbandry experts, and regulators evolve what is necessary for aquatics housing, the vendors will need to respond with the proper equipment that meets these needs. There are currently many great products available from aquatics housing manufacturers, but they all have their advantages and disadvantages. Looking back at what has been developed in the last ten years of aquatics housing solutions makes the next five years look very exciting in system development. The industry will need to come together to ensure the success of these systems and the research that depends on them.

This article originally appeared in the January 2009 issue of ALN Magazine;

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