Carly from New York City Writes:
What is with that rotten egg smell and taste that you find in various water sources?
Hi Carly, thanks for the question.
The rotten egg smell you describe comes from a chemical called hydrogen sulfide. Hydrogen sulfide is produced by sulfur reducing bacteria that sometimes reside in various parts of shallow water aquifers.
The hydrogen sulfide is the bacterial by product of it’s metabolic processes when it reduces sulfur for energy. Basically, hydrogen sulfide is bacterial waste matter.
Only certain shallow wells have this problem. It is more likely to occur if you have a dug well or bored well, but it can occur in any well in a shallow aquifer. Sometimes it’s a seasonal issue, and with other wells it occurs all the time.
Hydrogen sulfide is a very powerful odour causing chemical. The human threshold for detecting hydrogen sulfide is a concentration of only 0.0005 parts per million. At 0.1 ppm, it becomes very displeasing to people.
As bad as it smells, at the low concentrations found in well water it is not toxic. It’s not even an irritant, it’s only an aesthetic problem. The chemical is easily removed from water as well. It’s easily oxidized by chlorine, or another oxidant. I’ve installed treatment equipment in three locations that have hydrogen sulfide in the water. I’ve used hydrogen peroxide to oxidize the sulfide with great success. If the water is a pH of less than 7, the sulfide reduces to colloidal sulphur, which does not smell. At a pH of greater than 7, it forms sulphate, which also does not smell. As a bonus, hydrogen peroxide itself reduces to water and produces no chemical by products like chlorine may.
The chemical can also be removed with an activated carbon filter. You can either purchase an inline whole house filter, small filters that go under the sink and have a separate spigot to treat only the water you drink or cook with, or there are water jugs with built in carbon filters. Because carbon filters are an excellent breeding ground for bacteria, it is of utmost importance to replace the filter at the manufacturer recommended intervals.
Hydrogen sulfide also is a product of microbiological activity in sewers, and it’s a component of sewer gas. Often people who complain of rotten egg smell in their water are actually smelling sewer gas.
Sinks all have what’s called a P-trap in their drains. I’m sure you’ve seen the goose neck plumbing under a sink. The purpose of a P-trap is to trap some water in the drain at all times, as a barrier to sewer gas. With some P-traps of inferior design, as soon as you turn the tap on the flowing water will break the water barrier and allow some sewer gas to come up from the drain. You will then smell some sewer gas and you will associate it with the water, because you did not smell it until you turned the tap on.
While the rotten egg smell in your water is an annoyance, it can be easily remedied with some simple technologies.
I hope this has answered your question Carly. If you have any other questions or require any clarifications, please do not hesitate to contact us again.
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