The safety of our drinking water supply is a serious matter. By now everyone is familiar with the tragic situation in Flint, Michigan, where a decision to switch the municipal water system led to massive lead contamination in the drinking water. The Flint tragedy had numerous causes, but one lesson to be learned is that regular inspection of the physical water system is critically important. If the infrastructure of the Flint system had been adequately inspected, it is possible that officials would have been aware of the problem at an earlier date. When it comes time to inspect a water system – whether a giant municipal potable water supply or a small private tank like a facility storage tank – remote operated vehicles (ROVs) offer a number of advantages over other methods.
In the pre-ROV era, tank inspections meant either sending a human diver into the tank (posing risks to the safety of both the water supply and the human diver) or draining the whole tank and inspecting it dry. Both of these approaches have serious drawbacks. Using ROVs as the centerpiece for a tank inspection strategy has some enormous advantages over the older method.
The Tank Doesn’t Need to be Drained
Draining a water tank is a wasteful and expensive process. A municipal potable water supply tank can be millions of gallons of water – even tens of millions of gallons. It’s rare for there to be any productive use for all that water being drained at once – it literally flows out into the sewers and is gone. Not only that, but the water system the tank was supporting is then left high and dry while the inspection takes place. ROVs permit the tank to be left filled and in service while the inspection is taking place, saving both time and money.
No Risk to Human Divers or the Water System
Human divers cost a lot of money. Training, equipment, insurance – the list goes on. If there’s a safety incident, the financial cost alone can be huge, to say nothing of the human cost. In addition, to send a human diver into a potable water system, the diver must be sterilized – a difficult, unwieldy and unpleasant process, and one which if done improperly can compromise the safety of the entire water system.
ROVs, on the other hand, are relatively inexpensive and, compared to a human life, completely expendable. Because they are small and mechanical, they are much easier to sterilize for use in a potable water environment. Best of all, ROVs don’t charge extra for working a long shift!
Low Barrier to Entry
Certified divers are skilled professionals and scarce in some locales. By comparison, becoming proficient in operation of the Aquabotix ROV is a matter of three days of practice with the vehicle. Divers require support teams, so a minimum of two people are going to be on the job site, but an ROV is a one-person operation. Aquabotix ROVs come complete with recording capability (allowing the operator to take video footage, snap photographs, and record data from onboard instrumentation) and can operate on battery power alone.
Built-In Data Gathering
Every measurement a human diver takes requires them to carry (and learn the operation of) another sensor or instrument. ROVs, on the other hand, can carry built-in sensor suites that have all of the needed data-gathering equipment for any given inspection mission. For example, thermal stratification (water forming temperature layers or clines) can prevent mixing of water in a tank, which can reduce the efficacy of chlorine or chloramines in disinfecting the water. ROVs carry temperature and depth sensors which will automatically record and report the temperature and depth throughout the vehicle’s inspection cruise, automatically producing an easily-read report showing problem areas. There are many other environmental sensors available for ROVs which can quickly collect enormous amounts of data that would take a human diver multiple dives, at great expense, to gather. For example, ROVs can carry a Cygnus NDT metal thickness gauge, allowing the vehicle to test the thickness of the tank wall at hundreds or even thousands of points during an inspection.
Increased Frequency of Monitoring
As become sadly evident in the case of Flint, a water system can develop problems very quickly. Because ROV-based inspections are so much less expensive and so much more convenient than diver or draining inspections, they can be performed at much shorter intervals. That means, for example, that a problem like Flint’s (which is expected to cost hundreds of millions of dollars to fix) might instead have been caught when it could have been fixed for a few million. Frequent inspections greatly increase the chance of catching minor problems while they are still minor.
ROV-based inspections of water systems, particularly water tanks, save water and money, reduce the risk to human life, increase the safety of the water supply, are easier for small municipalities and operations to do for themselves, and collect valuable data at a lower cost than other options. There will continue to be need for human divers in some applications, but ROVs greatly expand our ability to inspect, and to keep safe, our water systems.