It seems to me the best ...

It seems to me the best people to answer this question are operators of water and wastewater facilities, especially those who have experienced more than one disinfection method. I've been involved with disinfection as a plant engineer, start-up engineer, and design engineer. Personally, I like chlorine and I believe it maybe the cheapest disinfection method though I have not seen costs for disinfection methods in recent years. There is a lot of hoopla about the dangers of chlorine and we know it can be dangerous. However, how many chlorine leaks have occurred at water and wastewater facilities in the last few decades. I as a young start-up engineer many years ago had to switch from an empty chlorine tank to a full one and found the disconnecting and reconnecting simple. Sodium hypochlorite has often been used in recent years to replace chlorine gas systems. One problem with NaOCl is that it weakens over time. With warm temperatures, it weakens faster. So if NaOCl has a long detention time in a storage tank, it could be significantly weaker by time the tank is nearly empty. UV has grown in popularity which I have heard operators praise and cuss at. The bulbs can be expensive to replace. I had a client who wanted UV put in on the back end of an AWT process and they eventually hated it and replaced it with NaOCL. A white film kept depositing on the bulbs causing the bulbs to prematurely burn out. I suspect the heat of the bulbs was causing a carbonate or possibly some type of metals deposition on the bulb. I designed another UV system for a secondary treatment plant and the client loved it. Said they'd never go back to chlorine. I have not worked with ozone, hydrogen peroxide or other disinfection methods to comment on. However, I'd really like to hear operators comment on this question.