It's a light that gets installed in the water line (very easy to do, some companies charge thousands to install this miracle "fix")
It should eliminate all, or at least 99.99% of total-E and C, but I don't think it hurts to shock the well anyway...kinda like a thorough cleansing before a colonoscopy, if you know what I mean.
About 20 years ago, with my first house, I use to test my water every year back then and it showed up with some issues. I also noticed my neighbors septic fields leeching out at the bottom of our common road. I asked him what was up with it and at first he blamed it on high water table, but then reassured me someone was coming "soon" to fix it. I was in the contracting business at the time and told him I would help him get an excavator and work with the town to get it fixed...nope...not good enough. So I press for a date, explain that I think his septic is recharging my well, and this is jepordizing our health, and again...a bunch of lip service.
Now I'm buying bottled water, months go buy, and ready to go off like the space shuttle, this dude does not give a s***. So I sneak over at 2 am and drop some dye into the uncovered tank (it was that way for months because he was going to fix it himself, to save money. Of course it starts to show up like a gulf coast oil slick in the bottom yard. I grab my camera at daylight and start snapping pictures and he opens the door screaming and hollaring for me to stop being such an a****** and a few other things and leave them alone..lol..ok.
Then he sees the green dye pool...
He wants to know how that got there ..yaddy, yaddy, blah blah...I'm gonna arrest you for tresspassing..I'm gonna sue you..needless to say he was very, very upset...

I suggested maybe the contractor he "allegedlly hired" did it...
So I've had it, go buy a light, install it, shock my well once a month, and keep all my reciepts. I explain to dip**** I'm going to the town, then the DEC, then my lawyer..but in the interest of not taking his house for health damages to my family for 9 months, I wanted an exact date when it will be fixed.
His response was "go for it"!....wrong answer Scooter..
So ...
Monday I take off, go to the town, run out to New Paltz office of the DEC, and go see my lawyer. Town inspector comes out Tuesday, DEC officer comes on Wendesday, and by Friday when he comes home from work THE DEC HAS COMDEMNED THE HOUSE AND HE HAS TO MOVE TO A MOTEL....


Needless to say, I made sure he paid double when dealing with a contractor, that an inspector was there for most the job, and by then my lawyer had contacted him about drilling a new well for me, and liable for damages to our health. Ohh..he also had a hire an engineer that certify and approve the finished project. He comes crawling to me by the end of the first week out of his house, saying it was all a big misunderstanding, he lost all his savings...lol...almost had ME in tears...

In the interest of maintaining a neighborly atmosphere...i also recommended a good banker...thinking he may need one once the lawsits start rolling in...lolol.
Anyways, to end this fiasco, he gets his septic fixed, I get all my money back, and this day he still won't look in my direction...hahaha