Safety Devices for basins

Hello, I am the safety officer for a wastewater treatment plant, and I am wondering what safety devices other facilities are using to rescue someone if they fall into a basin (e.g. clarifier, anoxic, and aeration tanks).

Currently, my facility has life rings, but over time the rope deteriorates and makes the life ring defective. This is likely caused by the sun, and the hot Florida heat. In response to that, we bought a few cases to contain the life rings, and they work great. However, each case costs about $500. I would like to know what other treatment plants are using that is effective and inexpensive. I will appreciate any feedback. Thanks.