The recent alligator attack at Disneyworld made me wonder if there were such a thing as a chemical deterrent to alligators. The simplest thing that occurred to me was to simply salinate the water – to turn a freshwater body of water into a brackish or fully-fledged saltwater body of water.
The GQs are: (a) is this ever done, especially for recreational purposes, and (b) if it’s not done, is it feasible? Affects on the nearby fish and plant life are understood – basically, I’m asking about turning a natural body of fresh water into a virtual saltwater swimming pool.
A piggyback GQ: if salination is too problematic to attempt, are there known agents that can be added to freshwater that would repel alligators but be generally safe for humans?
The problem in the Disney case is that the lagoon in question, while man-made, is fed from and drains to the local environment. It is not a closed system like a water park (like Typhoon Lagoon). There is no way that the state of Florida would allow the water in the lagoon (or anywhere else on the Disney property, other than swimming pools and equivalent) to be treated in a way which would, by definition, be harmful to the ecosystem.
This tragedy might have been avoided by either better signage or a fence to keep kids out of the water. They knew that alligators can move from one body of water to another with relative ease, and that something like this was a real possibility. Someone insures Disney properties, and they must have felt the risk was low enough to warrant a small sign, which of course, 3 year olds can’t read. Now they know better. Expect an attractive nuisance lawsuit, followed by a quiet settlement, in the upcoming months.
Also: could this lagoon be effectively closed off and made into the world’s biggest swimming pool? As an engineering challenge, that is – assume for this exercise that all environmental concerns are ignored.
Don’t aquaria usually mix their own salt water so they can keep it free of potentially harmful bacteria and algae and so forth? I haven’t been to the Long Beach aquarium in a while but I vaguely remember some information about how they mix their own and filter and recycle it.
Yep, not only to keep micoorganisms out of it, but because a lot of marine life needs very specific levels of pH, salinity, calcium and other minerals and it’s way easier to keep all that in check by using a salt mix of known composition instead of sea water, where the composition can vary quite a lot depending on environmental factors.
Once the salt was in, it would stay in unless you took it out. The salt level would stay fairly stable if topped up with fresh water to compensate for evaporation.
The main problem with a big artificial saltwater pool is that the salt would corrode the plumbing and concrete, and water splashing out or overflow due to rain would kill plants around it.
That said, there may be some specialty exhibits with particularly difficult critters to culture, or isolation tanks for sick critters where the saltwater is mixed on small-scale from DI water.
We know, but the OP isn’t concerned with that. Can you build a saltwater pool, pond or lake? Yes. Just add salt.
I just learned that salt water pools are a thing now. The salt levels are only 1/10th that of seawater, but I guess it’s easier to use the chloride from the salt to make your own chlorine than to dump lots of pool chemicals in.
Correct on the levels of salt being fairly stable. About concrete and plumbing, not so much. Concrete degradation has more to do with the calcium and ph levels and much less than the salt level. Also, you get around the plant issue by ensuring you place salt tolerant flora around the pool. Even plants that are not on the list of being salt tolerant tend to do ok with the low levels of salt found in a salt water pool. You get around the plumbing problem by using pvc plumbing, which is almost used exclusively in modern pool plumbing. You might find some copper if running a pool heater, but then again, the salt does not really matter all that much. Improper ph will do far more damage than the salt ever could.
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Yes, saltwater pools get points for being convenient, but the only chemical it eliminates having to add is chlorine. Besides, you should never have to add “lots of chemicals” to any well maintained pool.
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