As example "Spruce Creek". Many residents own private aircraft and can fly anytime they want. Do they have an separate air traffic controller? How is this high amount of air traffic managed?
How is this high amount of air traffic managed?
Air traffic is managed at many levels by many people and is heavily dependent on the airports specifics when it comes to GA. First off not every airplane in the sky is talking to or under control of ATC, for that mater in some airspaces you don't even need a radio on board. The following is pursuant to US FAA regulations, other countries may handle air traffic differently.
The first level of traffic management is the pilot, its the job of every pilot to "see and avoid" other traffic, this goes for both commercial and general aviation traffic. Even if issued a command by ATC you can deviate to avoid an emergency (i.e. hitting another plane).
The next level of traffic management is the various FAA regulations on both ground and air flight operations. These regulations (like traffic rules) are laws and must be followed. They are designed to mitigate traffic in certain areas and will also force you in some areas to at least be on the radio with ATC (e.g. class B airspace). You can read up on the full regs here and you will find most of what you are looking for under "flight rules". Much of the country (below 18,000Ft and above 1200ft generally) is actually class E airspace which does not require ATC communications. This is where most GA traffic lives although small turbo props and the boldest of piston singles can now make it into the levels, most GA planes cant. There are also pre set cruising altitude intervals for VFR and IFR traffic to help keep separation.
Above that you will have ATC who is controlling all IFR traffic, traffic in Class A, B, C, and D airspace and will provide limited radar services to VFR traffic when load permits. When flying under VFR (depending on where you are) you may not need to ever talk to ATC. It is possible to depart an un-towered airport in class G or E airspace, fly around and return with out ever having contacted an ATC facility.
On the ground control depends on the airport. At an uncontrolled field (lots of smaller general aviation airports) the pilots decide. Taxing around is much like driving a car and there are pre determined radio calls to enter the traffic pattern and use the active runway. At a towered airport ground control will monitor and control the flow of traffic on the ramp and the tower will control the traffic from the runway thresholds until the plane departs its airspace.
The only exceptions to the rules here in the US are 5 airports (LaGuardia, Newark, O'Hare, Ronald Reagan National, and John F. Kennedy) which are subject to the FAA's high density airport rules (specific to the airports) generally speaking the operations are the same in terms of how ATC will handle a given aircraft but departures and arrivals are limited and must be reserved ahead of time.
Another note on IFR operations, ATC will treat all planes the same and will only give priority to a plane in an emergency. Your little Cessna 172 on an IFR flight will receive the same services as a 747 30,000ft above you.
Do they have an separate air traffic controller?
No. See above but for what its worth the big planes contact the same ATC facilities as the little guys.
For what its worth Spruce Creek sits under a Class C shelf as you can see on the sectional here.
Departing from RW 5 and staying below 1200 puts you right between the Daytona Class C and New Smyrna Beach Class D so you may find your self contacting ATC on departure depending on your route you are somewhat boxed in there. Even departing from 23 you may find your self contacting Daytona approach to punch into the Class C there. Technically you can get out of there with out contacting ATC but you may find your self needing to depending on the situation.
At untowered airfields, like Spruce Creek there is no "ATC," the pilots self organize.
Generally speaking, the way this works is that as you approach you announce your arrival on the common frequency used by the airfield, 122.975 in the case of Spruce Creek. This frequency is listed both on aeronautical charts and in the FAA airport directory. So, for example, you might say something like this:
Spruce Creek, November niner seven six five four, Cessna one seven two, three miles out on one eight zero, request runway, Spruce Creek
Other pilots at the airfield will hear you and react appropriately. As you get closer you repeat your announcement and intentions. For example, the pilot might say:
Spruce Creek, November niner seven entering downwind for two three, traffic in sight, Spruce Creek
If the traffic is so heavy that you cannot enter the landing pattern, then you bear off and do a circle or racetrack pattern away from the airfield and try to approach again later. Often registrations will be abbreviated in various ways. For example, instead of saying "November niner seven six five four" every time, if you are the only Cessna, you can just say "Cessna", and the other pilot, say it is an Archer or Cherokee, will just say "Archer" or "Cherokee".
ATC is responsible for all aircraft, not only commercial IFR, but also general aviation IFR and VFR. Some airports may have restrictions (EDDM - Munich does not accept VFR below 2to MTOM), but in most other cases VFR general aviation is sequenced between IFR commercial.
Enroute VFR traffic may not necessarily be on the same frequencies, some countries offer own Flight Information Services for VFR traffic, where separation is not required, some airspaces that are shared require separation and will have both aircraft on the same frequency.
In the case of Spruce Creeks, there is a listed CTAF frequency, on which aircraft will be in the vicinity of the airfield. Leaving the airfield vicinity, they will join the regular frequencies for the services they require enroute.