Activated carbon and hydrogen sulfide
Q:I recently had my water softener rebedded with gravel, resin and carbon. After a three-week vacation we came home to very bad smelling water. It seems to be mostly the cold water for the first minute or so. The odor is very rotten egg smelling, like sulfur well water. We live in the Orlando, Florida, area and have city water. One water treatment system guy told me he thinks it is hydrogen sulfide being exposed from the new bedding doing so good a job removing all the chlorine. What do you think? He told me that he could put a post tank on with carbon and a couple other things to remove the hydrogen sulfide.

A:The “water treatment system guy” could be partially right. If your city source has hydrogen sulfide (rotten egg smell), the city chlorination would probably be destroying it. Activated carbon is a very efficient remover of chlorine but not very good at removing hydrogen sulfide.

But, I strongly dislike the placement of a few inches of carbon on top of water softener resin. There is almost always too little carbon for it to last very long before it becomes exhausted. Also, when the softener backwashes the carbon becomes mixed with the softening resin and cannot be separated for replacement purposes.

If there is hydrogen sulfide in the city water, the chlorine should have destroyed it before it reached your house. If the purpose of the carbon was to rid your water of chlorine taste, I’d recommend that you install a full size catalytic activated carbon tank before the softener (chlorine is harmful to the softening resin) or use activated carbon cartridges wherever you draw drinking water.

I’m also thinking that the three-week sitting period was part of the problem, but I can’t be sure without more information.

High hardness
Q:I have a customer with water that is 100 gpg total hardness, 2.5 ppm iron and 1270 ppm TDS. There are sulfates along with hydrogen sulfide.

I am treating it presently with a hydrogen peroxide filter with activated carbon followed by two water softeners. The second one is set on a low salt dose. I am not happy with the results, but the customer is not complaining at this time.

I am interested in a comment on this to see if you have any suggestions for treatment or if we should run a line from a bottled water company 100 miles away. It might be cheaper.

A:I don’t see why this water couldn’t be treated satisfactorily. My calculations show that this hardness, with a factor included for ferrous iron (Fe2) and at a salt dose of 15 lbs. per cubic foot of resin, should yield softened water containing about 3-4 gpg of hardness and no iron. This should be a very acceptable amount of hardness under the circumstances and the 15 lb. salt dose should give you a capacity of about 20,000 grains per cubic foot. Remember that ferrous iron is more strongly attracted to softening resin than is hardness. The important thing is to get the iron off the resin during regeneration.

In addition to the hydrogen peroxide and carbon filter, the hydrogen sulfide (H2S) can be removed by preceding the softener with a tank of catalytic activated carbon or a system that includes an empty tank with compressed air introduction and air relief, followed by a catalytic activated carbon filter.

You didn’t specify the level of sulfate but the US EPA Secondary Drinking Water Standards recommends (not mandates) a maximum level of 250 ppm. You might want to check the sulfate concentration.

Whole-house RO
Q:I consume an average of 200 gallons of water a month, all of which I collect from rain, channeling roof (1,800 sq. ft.) runoff into a 2,000 gallon, above-ground, swimming pool from two gutters. The initial runoff (wash) from each gutter is diverted into two 50-gallon drums; when the drums are filled, the water diverts to the pool. The pool is covered and I maintain the pool water between 1-4 ppm chlorine and initially filter it with the pool filter to remove the bulk of any sediment. I then pump the pool water into a 550-gallon poly storage tank, which I also maintain at 1-4 ppm chlorine. I then pump the water through a 5-micron carbon filter into a pressure tank for household distribution. For drinking and cooking, I run the water through an RO unit, recycling the RO wastewater.

My goal is to eliminate the RO unit because of the waste produced — about five to seven gallons for each RO gallon. I also wish to replace the chlorine disinfection with UV. My tentative solution is to pump the filtered, unchlorinated water from the pool to the poly tank for storage; then pump the tank water through the 5-micron (or other) filter; then through the UV unit. At this point, the water would be restricted to general household use (cleaning, bathing and toilet). For drinking and cooking (maximum of three gallons a day), I am considering a ceramic or other filtration regime.

So my search is to define the most efficient way for me to filter the rain water to eliminate shadowing vis-à-vis UV disinfection, and then re-filter the water for drinking and cooking to enhance the taste and remove whatever potentially harmful stuff there might be lingering that was washed off the roof and bypassed the carbon filter.

A:By necessity, you have a rather complicated system and I’m not sure my response will cover everything sufficiently. So consider this food for thought as opposed to a guaranteed solution.

Every tank where you presently have chlorine you have constant disinfection. If you use UV, which carries no residual disinfection, you will have to recirculate the water in these tanks. This can be done by having a small UV on each tank with a recirculating pump or having a larger UV to recirculate through a greater segment of your system. Discuss “turnover” time with a UV manufacturer.

Then consider replacing the RO with a whole-house UF (ultrafiltration) membrane system. This can be installed after your pressure tank. These are available, with certification-testing, to remove bacteria and cysts, with a nominal micron rating of about 0.02. Keep your 5-micron filter ahead of this. A whole-house UF requires only brief backwashing upon excessive pressure loss. A UF membrane is coarser than a RO membrane and as such does not remove dissolved minerals like RO. You should not need mineral reduction because your source is rainwater.

As a safety measure, you could consider another UV after the UF for added protection.