sump - a pit, tank, etc. for collecting liquid, specif. one into which waste or excess liquid drains and from which it is evacuated mechanically

https://www.yourdictionary.com/sump

Sump recovery system, is a system that sumps water, or oil, or whatever needs to be filtered later, and recycles it, so that it's products can be used again. It is used for filtering of contaminated wells, were it serves to stop contamination, or unauthorized discharge. Or oil spills or similar disasters...

Contingency plan, is a plan of actions in some unexpected, unusual, exceptional, unwanted situations. It is a part of risk management.

https://es.wikipedia.org/wiki/Plan_de_contingencias

So this system of water, fuel, waste or whatever is in question, recovery being a part of contingency plan, means that it serves as a system that is employed when something hazardous or unexpected happens, and tries to minimize the damage, or waste...

http://www.americanenvironmentalaviation.com/sump-recovery-u...

https://www.aviationpros.com/home/article/12384250/to-reclai...

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Note added at 2 hrs (2019-03-18 13:14:27 GMT)
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system of tanks7pits/collectors, for collecting waste water/fuel/liquid and recycling it from there

not 7, it's typo... should be:

system of tanks/pits/collectors, for collecting waste water/fuel/liquid and recycling it from there

A collection of equipment for cleaning 'dirty' fuel samples drained from an aircraft, so that they can be returned back to the aircraft's fuel tank.

The 'cleaning' technology varies, and could involve filtration ...
"The Sump Recovery System is a closed circuit system for clean and bright fuel testing that allows the tested fuel to be conserved, filtered, and circulated back into the fuel supply."
http://fischer-robertson.com/downloads/Velcon/Fuel/2009/Sump...

... or sedimentation/settling ...
"Operating an Aviation fuel system requires that about 5 gallons of fuel be “sumped” from the tank and the fuel filter vessel daily into a bucket for examination. With a sump fuel recovery unit the good fuel can be recovered and returned to storage instead of the old way of putting it in drums and paying a Haz Waste company to haul it off site. [...] How it works: sumped fuel is poured into the 20 gallon tank and left to settle."
http://fueltech.com/fuel-recovery-systems/

... or some other mechanism(s).

The system may also incorporate testing equipment, as testing the fuel appears to be the main reason for draining some fuel — i.e. collecting samples — in the first place.
"Draw a generous sample of fuel from each sump and screen drain into a transparent container. Check for the presence of water, dirt, rust or other contaminants. Unless you have the proper kind of fuel tester (e.g., GATS jar with intact fuel strainer), do not attempt to save the fuel drained from the sumps by pouring it back into the tank."
https://aviation.stackexchange.com/questions/1141/what-shoul...

In the aviation industry, the "sumps" are the drains for the fuel system ...
"[...] the pilot normally takes samples from fuel system drains (a.k.a. “sumps”) [...]."
https://www.nap.edu/read/22343/chapter/1
... of which each aircraft could have several
"[...] those post-1997 Cessna singles with the 13 drains."
https://forums.jetcareers.com/threads/sumping-fuel-tanks.768...

The cleaned fuel is classified as "recovered", and can then safely be returned to the aircraft's fuel tank.
The process of 'cleaning' would also generate a separate 'waste' byproduct.

Although in principle a sump could appear in lots of industries, and could be relevant to things like wastewater, in practice I couldn't find many references to the requested term (or similar variants) outside of the narrow usage in aviation described above.
Compare the following:
https://www.bing.com/search?q=+"sump recovery" system fuel
https://www.bing.com/search?q=+"sump recovery" system wastew...

FWIW, here is one exception:
"Ground Water Sump Recovery. Some buildings on campus sit two or three stories below ground level and, as a result, ground water must be removed from these foundations to prevent building flooding."
https://www.epa.gov/sites/production/files/2017-01/documents...