Examples of Iron Filtering Technology for Water Well Systems
In my last column, I concentrated on iron filters that worked well when ferric — or visible — iron was present in the groundwater. Old-style pressure tanks — be they the more or less standard or galvanized, or the dreaded buried tanks — produced a lot of this visible iron in the late 1960s or early ’70s. Then our industry moved to captive air tanks, which are sometimes called bladder tanks. These tanks did away with the problem of water logging and also gave the customer far less rusty water. This was because the water in the tank and the air were completely separated. This, however, created a whole new situation regarding iron filtration.
Our industry was now faced with water that contained ferrous iron, the kind in solution that can’t be seen. Make no mistake: The water from the well still contains this iron, just in a different form. In my own experience, as my father and I began to install more and more captive air tanks, we soon realized that cartridge and silica sand filters that had been so effective in series with the older conventional tanks were now virtually useless.
As an example, my father and mother lived on a one-plus acre lot, and in the 1970s, my wife and I moved onto the adjacent one-plus acre lot. As I have written, I had a buried tank at my house and both homes had good capacity 4-inch wells equipped with submersible pumps. When my house was new, I hooked up a silica sand filter and a water softener. The two wells were about 100 yards apart and completed in the same aquifer. My parents’ house was new in 1941, just before the U.S. became involved in World War II. Initially, this house used some cistern water too, but after a number of years, my folks quit using that. My dad maintained that cistern water was not very sanitary and I believe he was right. So they used hard water from their well, which contained iron.
This situation seemed to work well until we built the house next door. One fine Sunday morning, we were all in church and my white shirt was bright white and my father’s white shirt was a kind of dingy, almost white yellow. My mother, who was the child of German immigrants, would have none of this. No way was her daughter-in-law doing a better job of washing than she was. We were instructed that she wanted a water softener — and I mean right now. The water system at my parents’ house had a captive air tank, and so we dutifully installed a silica sand filter and water softener. Of course, this improved the water quality a huge amount and my mother was happy, as her white wash was nearly as white as my wife’s white wash.
Within a few months, however, my dad and I realized that the installation of the silica sand filter after his captive air tank was a waste of money and effort. When backwashed, that filter produced virtually no rust and, as both of the wells in question were sand and sediment free, this filter was not really needed. We put our thinking caps on and quickly realized that the two tanks produced considerably different water. This was because one allowed a lot of air-to-water contact, and the other, no contact at all. This same situation would apply to our customers, too. So we began to search for a different type of filter that could be used with a captive air tank.
On checking with our suppliers and doing some reading (in those days you didn’t have online information — the information was in books), we realized that about the only answer to our problem was a so-called green sand filter. This was not really very much different than the silica sand filter, except the tanks were taller and thinner than the silica sand type. The media inside the tank was vastly different, though. These filters were filled with a sand that had been chemically treated and looked extremely dark green or almost black. When iron-laden water passes over this green sand, the sand changes this iron from invisible to particles. Gosh! We had hit the motherload. Here was a simple, effective way we could reduce the iron load into a water softener or water pipes. However, we quickly learned that the manner was not so simple. These units still had to be regenerated, and that was a major problem.
The regeneration process on these green sand filters was just like the process on a silica sand filter. The normal flow in both of these filters was in at the top and out the bottom. The regeneration began with reversing the flow and flushing the trapped iron out to waste. Then an important next step was required. The green sand had to be replenished, just like a water softener has to be replenished with sodium chloride. And in the green sand case, the replenishing material was potassium permanganate. I kid you not — PP, which we will use to abbreviate its name — is nasty stuff. First of all, it is considered a poison. I guess if you flush a mineral bed with poison and then rinse it out, it is no longer poison. (I never heard of anyone dying from using a green sand filter.) The second problem with PP is that it is sticky and tends to clump up. A third problem is that this material is not easy to buy. One does not go to his local Walmart or Lowes to buy some PP.
Plus, PP is a super oxidizer. Of course, this is its big advantage when it comes to filtering iron. It oxidizes the iron in water so it can be filtered. But, in my opinion, it is a dangerous oxidizer. I once changed out the filter for a customer from a green sand type to another type. He had some PP left over and poured it on the ground next to a tree. It set the tree on fire — it wasn’t a big fire, but he had to put it out with water. Also PP is considered hazardous, so you don’t just put it in the garbage. Of course, in 1970 all these disadvantages of PP were not well known or, if they were, they were not talked about or written about — at least from what I saw and heard. Next time, I will write about the “fun” of regenerating a green sand filter with potassium permanganate.
After a long and nasty winter here in southern Michigan, we are in late March seeing a few signs of spring. First thing in the morning, my famous lawn is all frosty; but later in the morning, it is just brown and dead looking. The unpaved roads are, in spots, nearly impassable and the paved roads here and there have dangerous potholes. Our newly elected governor is proposing to increase our gas tax to over 70 cents per gallon and says this will fix our roads. Of course, that money will be used only for interstates and state-designated highways. Not a single cent will be spent on local roads. ’Til next time, if you live where frozen roads are not a problem, be thankful.
For more John Schmitt columns, visit www.nationaldriller.com/schmitt.