What is Hydrogen Sulfide (H2S)?
- Hydrogen Sulfide (H2S) is a dissolved gas that gives water a characteristic "rotten egg" odor and taste. It corrodes piping, creates odors in the house, and turns water and your fixtures black. Homemakers will notice that it can change sterling silver to a black color almost instantly. H2S can cause odor problems at a concentration level as low as 0.05 mg/l (ppm).
H2S in well water
- H2S often occurs naturally in well water, or can be caused by the presence of sulfate reducing bacteria in a well or water system. Since bacteria are the most common cause, treatment to control them should be tried first. Shock chlorination is the standard treatment for control of sulfate reducing and iron bacteria in a well.
H2S in Water Heaters / Disinfecting Water Heaters
- Problem: Sometimes H2S may only be present in the household hot water. This condition is caused by a biochemical reaction between sulfates in the water, sulfate reducing bacteria, a magnesium rod in the hot water heater or organic matter in the water. If the odor problem in the water heater is caused by heat loving sulfate reducing bacteria, disinfect the water heater with chlorine bleach or hydrogen peroxide. Make sure that the smell is not emitting from the drain. Sometimes the reaction with the magnesium rod is the cause of odor problem. The purpose of the magnesium rod is to prevent corrosion of the water heater. Removing the magnesium rod or replacing it with an aluminum one will only temporarily solve the odor problem. Removing the magnesium rod will void the water heater warranty and will lead to the earlier deterioration of the tank walls. Disinfecting the water heater tank with hydrogen peroxide is the best solution.
- Solution = Disinfection: First and foremost, the water heater must be flushed thoroughly of all sediments. This is done by taking a large diameter garden hose and connecting it to the flush valve at the bottom of the water heater. Flush the water heater under pressure for 15 to 30 minutes or until all sediments have discontinued to flow out of the hose (you can flush water into a white bucket from time to time to see the sediments accumulate in the bucket). Then close the inlet shut off valve to the water heater. The water pressure needs to be drained from the hot water side of the plumbing system. You also then need to close the main house shut off valve in case the valve on the water heater does not shut off all the way. It may also prevent cold water pressure to come backwards through a mixer faucet (hot and cold with one handle). Disconnect the outlet side of the water heater piping (hopefully there is a union there so you do not have to cut and re-plumb the line). Then add 3 or 4 large bottles of hydrogen peroxide. When you have let a little bit of water out of the flush valve to bring the water level down, make sure you do not drain it down past the top element of an electric water heater, or you will burn out the element. You will need a small funnel (available where you buy lawn and garden equipment) to pour the liquid into the water heater. Reconnect the plumbing and then turn the water back on, checking for leaks. Leave the disinfecting agent in the water heater overnight. Then flush the water heater out thoroughly the next day. If you have an older water heater, the hydrogen sulfide may come back. It may take you doing this procedure 2 or 3 times to accomplish your goal. If you have not solved the problem after three attempts at disinfection as described above, then you may be faced with replacing your water heater. Wear rubber gloves and use eye protection.
Water Treatment Options For Removing Hydrogen Sulfide / H2S
- Greensand Plus: The non-chemical way for H2S up to 3 ppm.
- Pyrolox: The non-chemical way for H2S up to 7 ppm.
In order to oxidize sulfur, iron and manganese, you need to have an oxidation value in the water or on the media. We supply both Greensand Plus and Pyrolox systems with a built in air injection system that draws air into the media during the backwash / cleaning cycle. Most other companies on the web fail to provide this important step, so when their system quits working after a short period of time, they try to sell you additional equipment (usually a chlorination system).
OTHER TRADITIONAL METHODS BELOW.
Chlorination and Activated Carbon Filter
- This method requires the installation of a chlorine feeder followed by a retention tank and then an activated carbon filter. The H2S is oxidized by the chlorine and the insoluble sulfide particles are removed by the activated carbon filter. This filter also removes any residual chlorine that is left after oxidization of the hydrogen sulfide. This system is most appropriate in situations where there the H2S present is at a higher level than 5 mg/l (ppm) and no significant amount of iron. The chlorinator is wired to the pressure switch and is activated when the water pump switches on. The retention tank is installed to ensure sufficient mixing and contact time to complete the oxidation process. It should be large enough to retain water for at least 5 minutes at peak filter capacity (as a minimum, a 42 gallon retention tank is recommended). A valve should be provided at the bottom of the retention tank to drain any sediment. Chlorine test valves should be installed just after the pressure tank and just before the activated carbon filter. These are needed to help check the chlorine level in the treatment system.
- Aeration is accomplished by spraying water into a ventilated storage tank. The H2S is gas separated from the water as it is sprayed and drawn off as a gas by the ventilation system. Aeration will remove most of the H2S but chlorination may still be necessary. Some sulfide odors will remain due to the high pH. The lower the pH the better this system will work. A second pressure system is required to pump the water from the storage tank into the distribution system. The problem with this system is that it put the H2S gas into the air, so you can only install it either outside (warmer climates only) or install an elaborate venting system from the aeration storage tank.
Manganese Greensand Iron Filter (has been around for decades)
- A properly maintained manganese greensand filter will effectively remove low levels of H2S, typically less than 5 mg/l (ppm). This type of filter oxidizes the H2S and filters out the resulting sulfide particles. It is very important that these filters have an adequate supply of water for backwash and are adequately regenerated with potassium permanganate. H2S requires 3 times the oxidizing power that iron does so the greensand filter must be regenerated more often than it would for an equal amount of iron. Manganese stripping, from the manganese greensand, can also occur. This stripped manganese can cause black staining. The injector must be cleaned at least once per year, and the chemical tank float valve assembly removed and soaked in a water solution to dissolve the potassium permanganate that has crystallized onto the float valve assembly. The filter pad above the grid inside the tank should be replaced every 2 to 3 years. Potassium permanganate will accumulate insolubles in the tank and on the grid pad, requiring occasional cleaning. Potassium Permanganate is a hazardous material and must be shipped accordingly. It can also stain your hands so wear rubber gloves, eye wear and a dust mask when handling this material.
- Other oxidizing agents besides chlorine can be added to the water to oxidize H2S. These include hydrogen peroxide, potassium permanganate, and ozone. Filtration will still be required after any of these have been added.
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