Got Water?

[edwardofhuncote]

According to the brass dedication plaque, my little Water Plant here in downtown Roanoke is 14 years old today.

I was first assigned here in July of 2010, having been an evening shift Operator at another Water Plant on the other end of the County since 2002. Before that, I had been the Waterworks Operator for a smaller neighboring utility since 1988. (not counting a two-year stint as a bass player between 1996-98… we won’t get into that... )

This place was built as a state-of-the-art ‘membrane’ filtration plant, the biggest of it’s kind at the time of construction. The process of membrane filtration differs somewhat from conventional sand filtration plants, which really hasn't changed much in 100 years, at least not from a technical viewpoint. We're quite blessed by geography here, as the source water comes from a large freshwater spring that runs right out from under a mountain. Flowing consistently close to 5 million gallons per day of very high quality freshwater, (hence the name, “Crystal Spring”) the city quite literally grew up around this little nook beginning with a grist mill, but centuries before that, Indian hunting parties would stop to rest and water here. These days, there’s a regional hospital next door, and a sprawling city of close to 100,000 people, with suburbs of close to another 150,000. The Public Service Authority I work for supplies most of the valley region with water, by way of this, and three other water treatment plants.

So without candles to blow out or cake to divvy up, I thought what might be fun today is to do a Q & A about water treatment… anything you ever wanted to know about your water, but didn’t know who to ask - Go! 

[edwardofhuncote]

Couple pictures... 

[elwoodblue]

Pretty Spiffy Dude !!


 What's with the moptop on the filter canister unit?

[edwardofhuncote]

What's with the moptop on the filter canister unit?

What you're seeing is actually the filter media itself, revealed by the cut-away.

See, these machines are designed in a modular way - each Treatment Unit (there are five - see picture above) employs 102 of these filter cartridges. Inside each filter cartridge are about 25,000 of these polypropylene strands, that when viewed under a microscope are actually a porous straw. The pores of these strands are sized at approximately 0.04 microns, which is giving us between 4 and 5 log removal of anything particulate. (this means something between 99.99% - 99.999%)

As water is pressed into each strand (they're called 'lumens'), it becomes filtered in an osmotic fashion. The filtered water is collected in the filtrate manifolds. (the round hollows you see the cross-section of in the model) The combined filtrate from each unit is then piped to a baffled storage tank (called a Clearwell) before it is pumped into the distribution system. The entire treatment system here is closed - the water is never exposed to atmosphere until it's ready for the customers, it all happens inside the machines.

Each of the treatment units is filtering water at a rate of up to 850 gallons per minute, around-the-clock, 365 days a year. This plant accounts for about 25% of our overall production.

[edwardofhuncote]

Here's a better look at the cartridge as mounted, and another looking at the ends of the lumens media. See how each strand is actually a hollow straw? These things are teeny-tiny. 

[edwardofhuncote]

Here's a magnified view from the O & M manual...

[pauldo]

Gregory, good to know you are "well" versed in water.  Have you heard of 'perch' springs?  We are on top of a hill, recent transplants, and are starting a market farming operation.  We need water for irrigation and have areas on our property where there are wet spots.  We are assessing swales and also means of tapping into these wet spots, which a local referred to as 'perch' springs.

The property is in a township with no zoning, with that said, the well we have is still considered to be 'non-conforming' at least it's location is.  We have no records/ idea how deep the well is.  The water was tested and is safe (and really tastes good!).  So we are not sure how deep the water table is.  Guesstimates by locals is not more then 50 feet.

Any thoughts on how to locate the best area for sourcing additional water for crops?  Or is that more a geological type question?  I do have a set of divining rods and have walked around a bit, but my understand is that their detection can be water, a previously dug trench, underground current (stray or actual voltage) and we have found buried exstension cords!  Previous owners were unique with some of their habits, we got the property cheap, but also got what we paid for . . . .

Thanks
Paul

[David Houck]

… anything you ever wanted to know about your water ...

I need help getting rid of the bacteria in my well water.  Shocking the well is only a temporary solution (and a bit of an inconvenience).

As a side note, in a previous life I used to make deionization water purification systems for laboratory and commercial applications.  I wasn't very good at it.  Left that job to become a full time bass player.

[keith_h]

Dave - What type of bacteria? If it is iron or sulfur reducing bacteria to have any effect you need to treat it at the well which means something like chlorine then filtering it out. You could also use a chlorine treatment tank or water main injection which has the advantage of removing both clear water and killing the bacteria in the water. Again you would need to filter the chlorine and condensed iron out after the chlorine treatment. We have iron reducing bacteria in our well and decided to live with it after shocking the well a couple of times and talking with county health department. We do filter out the clear water iron where the water enters the house. This stops the eventual orange staining and the drain smell due to well bacteria moving in there. We went with a back flushing Pyrolox filter for the iron and it has worked for us. 

One of our neighbors in the old area of the neighborhood had coliform bacteria in their well and went with an ultraviolet treatment system. It works well but they had to put whole house and iron filters before it. I think they went with green sand for the iron filter but might have been a tank. All of it requires periodic maintenance to keep the treatment piping clean and it wasn't cheap (It was well over $5K as I recall).   

[edwardofhuncote]

Paul, I'm not familiar with the term 'perch spring', but it sounds like the water table in that area is shallow. This gets into more of a hydrogeologist's territory than mine, but what you're describing sounds like an unconfined aquifer, meaning there's an impervious layer underneath the water creating a kind of subterranean pool. It's probably going to be fine for the amount of water needed for a household, but could fall short for your irrigation needs. Only way to know is a drawdown test.

Dave, depending on what kind of bacteria you're trying to get rid of... an ultraviolet light fitting might be the ticket for just killing any coliforms. If you're talking about the iron/sulfur reducing type bacteria common in groundwater around our part of the world -they're not harmful but makes the water smell like rotten eggs when aerated-... there are a few commercially available ion exchange media cartridges (not unlike the ones for DI) that can sequester iron and manganese, the chief nutrients for those bacteria colonies. They're tough little bugs to deal with. Believe me, it's awful up here where I live. Fortunately, I've been able to carry my drinking water home from work all these years! (they don't miss a couple gallons out of a few million... )

**Keith beat me to it... well, part of it.

[keith_h]

Paul, One of our houses here in NC had two shallow wells. The first, our household well, was a 32 ft deep bored well that was common here up until the late 80's. It had enough water for household use but would run dry if used for irrigation. In a lower part of the yard we had a 15 ft bored well with about 10 ft of water. Towards the end of summer it could supply water for about 4 hours in the AM and 4 hours late in the day for irrigation at a rate of 5 gpm. I would equate this second well with what you are talking about. Ours basically reflected the ground water table along the back of our property near the creek that made up the property line. The area of your property with the perch springs sounds similar and might be good candidates for a bored well or two for irrigation. 

If you aren't familiar with a bored they well use a huge auger that's about 3 ft in diameter to bore the hole. Then they drive in concrete pipe for the casing. Gravel is poured into the bottom and they will fill up to whatever the ground water table is. They are only used for shallow wells up to 50 ft or so in my area. This is opposed to a drilled well which is either 4 or 6 inches in diameter and goes down to and through the bed rock to find the deeper aquifers. Our current house is on a deep well of about 250 ft with a flow rate of 25 gpm. Enough to handle all of the house and irrigate at the same time. In our area a bored well is about half the cost per foot of a drilled one.

[keith_h]

Paul - One other thing came to mind. Here in the Southeast shallow wells tend to be acidic. This is due to the amount if rain we get that has washed the buffering minerals out of the soil. The effect of this is you need to add some additional lime throughout the growing season to compensate for the well water. I would check with your cooperative extension service to see if this might be an issue for where you are. Soil acidity has a major effect on vegetable yields such as you would grow for market.

[David Houck]

Thanks Greg and Keith;

I am fairly certain it is iron bacteria.  And generally, I put up with it.  I boil water for drinking, but otherwise use it for cooking, washing, etc.

Sometime within the last year, I looked at UV systems, but found that they are expensive, and that for them to be effective, the flow rate has to be reduced significantly.  However, now that I'm looking at this subject again, I may have been confusing myself on the flow rate.

I currently use two standard size 10" whole house filters; a sediment filter followed by a carbon filter.

So an initial search and some reading finds this:

http://www.cleanwaterstore.com/FE011900.html#tab=tab1

Is this, broadly speaking, what you are getting at?

[keith_h]

Unless you have some health issues iron reducing bacteria are innocuous. By boiling the water you are actually concentrating any iron or other metals in the water.

You link is what I have except for the air injection. The air injection lets the unit remove more clear water iron by oxidizing it before the filter. My clear water iron content was about 5 ppm when we moved here 16 years ago. It might be higher now but I don't expect it to be very much. We have no red water iron issues. My iron filter will handle about 4-5 ppm alone. I also have a water softener which can remove up to 4 ppm so according to specs between the two we should be removing all of the iron. It also helps to know the pH of your water. Some methods don't work well with low pH and will require you to go to a chlorine based process or use a calcium based buffer to raise the pH. A basic pH test is good enough. In our old house here in NC we had acidic water so had calcium neutralizing filter in front of the water softener. It required refilling every 2-3 years.

This looks to be more of what we have:
http://www.cleanwaterstore.com/FE011180.html

[pauldo]

Gregory/ Kieth,
Thanks for the replies.  Keith; ". . . .bored well is about half the cost. . . " is a big deal for us right now. I really appreciate the insight.