H2S GAS ELIMINATION
Hydrogen Sulfide (H2S) Gas Elimination for Sewers, Lift Stations, Force Mains and Lagoons
Hydrogen sulfide (H2S) is the corrosive, toxic gas responsible for the rotten egg smell at sewers, lift stations, force mains and lagoons, and it forms in the wastewater itself before it ever reaches the air above it. Waste Water Innovations (WWI) does not scrub the gas out of headspace air after it has already formed. DRP Accelerator carries usable oxygen to the bacteria already living in your collection system, so those bacteria never need to strip oxygen from sulfate, and the sulfide that becomes hydrogen sulfide gas is not made in the first place. We add no bacteria and no enzymes. The same oxygen lets aerobic bacteria dig into fats, oils and grease (FOG) and organic sludge along the way. We dose it as far upstream as water and power allow, run it as a monthly service, and measure the result in your own numbers.
We do not scrub H2S out of the air. We stop the bacteria from making it.
- Hydrogen sulfide gas forms in wastewater when dissolved oxygen runs out and bacteria strip oxygen from sulfate instead.
- Hydrogen sulfide is heavier than air and collects in confined spaces such as wet wells, sewers and lift stations.
- Hydrogen sulfide gas reacts with moisture on pipe crowns and wet well walls to form sulfuric acid, which corrodes concrete and steel.
- Iron salts, nitrate products, chemical scrubbers and masking agents address hydrogen sulfide after it has already formed rather than preventing its formation.
- DRP Accelerator is an inorganic compound that supplies usable oxygen to bacteria already living in wastewater.
- Force mains, gravity mains that sit and lagoon bottoms are common locations for hydrogen sulfide formation because wastewater there loses dissolved oxygen and is held long enough for sulfate reduction.
- AerobicShift is Waste Water Innovations' term for dosing as far upstream in a collection system as water and power allow.
Why hydrogen sulfide forms in a sewer
Wastewater carries a resident population of bacteria, and those bacteria need oxygen to live, whether they get it from oxygen dissolved in the water or from another source. In a sewer line, a wet well or a lagoon, dissolved oxygen runs out first, often within minutes of leaving a treatment plant or a house. Once dissolved oxygen is gone, the bacteria turn to nitrate, if any is present, then move on to sulfate, which is present in nearly every wastewater stream. Stripping oxygen from sulfate leaves behind dissolved sulfide, which sits in equilibrium with hydrogen sulfide gas at typical wastewater pH. Disturb that water, a drop into a wet well, a pump cycling on, a discharge into open air, and the dissolved gas comes out of solution. Above the waterline it meets a wet surface and reacts to sulfuric acid, the source of the corrosion that follows.
Where hydrogen sulfide forms
Any point in a collection system where wastewater sits long enough to use up its dissolved oxygen is a candidate. Wet wells hold water between pump cycles, so a lift station is one of the more common places to smell it and one of the more dangerous places to work. Force mains push wastewater under pressure to the next lift station or the plant, sometimes for hours, with no exposure to air along the way, so a force main can arrive loaded with hydrogen sulfide before anyone at the discharge end knows there is a problem. A gravity main that sits, a low spot with little flow, a line running well under capacity, behaves the same way. Lagoon bottoms, manure lagoons and digesters share the same underlying condition on a larger scale: a body of water or slurry deep enough, and still enough, that oxygen never reaches its lower layers, so the bacteria there run out and turn to sulfate.
Why it matters beyond the smell
The smell is what a neighbor calls about, but hydrogen sulfide is a safety and asset problem first. The gas is heavier than air, so it collects low in a wet well, a manhole or any confined space, and it can reach a dangerous concentration before a worker's nose would give any warning, since the sense of smell dulls quickly at high concentrations. OSHA sets an eight-hour ceiling of 20 parts per million (ppm) for hydrogen sulfide exposure, a limit a wet well can exceed by a wide margin without treatment. Above the waterline, the same gas turns into sulfuric acid on concrete and steel, so pipe crowns, wet well walls and metal fittings corrode from the inside for as long as the gas keeps forming. None of that shows up as a line item until a manhole needs relining or a motor fails early, and by then a community has usually filed more than one complaint about the smell along the way.
How we remove it
We do not treat hydrogen sulfide after it exists. DRP Accelerator is an inorganic compound that carries usable oxygen to the bacteria already living in your wastewater, in the sewer, the wet well, the force main or the lagoon itself. We add no bacteria and no enzymes; the organisms doing the work are already there, they have simply been starved of oxygen. With that oxygen available, the bacteria take it first and never need to strip it from sulfate, so the sulfide that would become hydrogen sulfide is not made in the first place. That is prevention, not scavenging or masking. The accelerator is consumed as the bacteria use its oxygen, so nothing of it carries downstream to the plant or the lagoon. The same oxygen also lets aerobic bacteria dig into fats, oils, grease and organic sludge along the way, so a program aimed at hydrogen sulfide tends to bring sludge and odor down with it.
How this compares with other approaches
Where a system already has hydrogen sulfide in the water or air and needs a fast, temporary fix, several other approaches can be the better near-term choice. Iron salts bind dissolved sulfide directly and can bring a bad reading down quickly, which suits an emergency or a short-term event better than a program built around prevention. Nitrate products give bacteria an alternate oxygen source to sulfate and can help in specific zones, though they add nitrogen to the water that must be accounted for downstream. Chemical scrubbers and masking agents treat air, not water, so they suit odor at a single point source rather than the gas load across a collection system. Our program is built for the opposite case: a system that wants the gas prevented at the source, continuously, without adding a chemical feed to manage. We keep a fuller comparison on a dedicated page on our site for anyone weighing the options side by side.
The program
The program starts with a review of your flow data, pump cycles and any hydrogen sulfide readings or complaint history you already have, so we can size the dose to the system rather than guess. We identify the point furthest upstream where we can reach water and power, often the lift station wet well or a nearby valve vault, and calculate a dose and frequency from there. The accelerator arrives dry; we mix and activate it in a tank on site, and it drips into the flow continuously rather than in a single batch dose. Tank levels are monitored remotely, and we return to replenish on a schedule set by the tank's size, so your crew is not tracking it. Water quality testing continues alongside the dosing so the change shows up in your own numbers. It is a monthly service with no capital purchase, for as long as you want the result.
COMMON QUESTIONS
Straight answers.
What is hydrogen sulfide and where does it come from in a sewer system?+
Hydrogen sulfide (H2S) is the corrosive, toxic gas responsible for the rotten egg smell at sewers, lift stations and lagoons. It forms when wastewater sitting in a pipe, wet well or lagoon runs out of dissolved oxygen and the bacteria living in it strip oxygen from sulfate instead. The sulfide left behind converts to hydrogen sulfide gas, which comes out of solution wherever the water is disturbed.
Is hydrogen sulfide dangerous, or just a nuisance smell?+
Hydrogen sulfide is dangerous, not only unpleasant. It is heavier than air and collects in confined spaces such as wet wells, where it can overwhelm a worker at a high enough concentration before it is noticed by smell. OSHA sets an eight-hour ceiling of 20 ppm for exposure, and the same gas corrodes concrete and steel above the waterline.
How is your approach to H2S removal different from an iron salt or a scrubber?+
Our approach to H2S removal targets the water, not the air, and it works before the gas forms rather than after. DRP Accelerator supplies usable oxygen to native bacteria upstream so they never strip it from sulfate, which means the sulfide that would become hydrogen sulfide is not made in the first place. Iron salts and nitrate products treat the water after sulfide has formed, and scrubbers and masking agents treat air rather than the cause. We add no bacteria and no enzymes.
Where do you dose to prevent hydrogen sulfide?+
We dose as far upstream as we can reach water and power, which is often a lift station wet well, a valve vault or a headworks channel. Dosing upstream gives the accelerator the most collection system to work through before the wastewater reaches a point where hydrogen sulfide would otherwise form. The same approach applies to force mains, gravity mains that sit, and lagoon bottoms.
Does the accelerator leave anything behind in the water?+
The accelerator does not leave anything behind in the water. It is consumed as the bacteria use the oxygen it carries, so none of it remains downstream once that process runs its course. It is not an oxidizer and it does not attack metals. No chemical additives, no added bacteria and no enzymes go into the process itself.
How does the program run, and is there equipment to buy?+
The program runs as a monthly service, not a capital purchase. We review your flow data, calculate a dose, mix and activate the accelerator in a tank on site, and it drips continuously into the flow we identified. We monitor tank levels remotely and return to replenish on a schedule set by the tank's size, while water quality testing continues alongside so the change shows up in your own numbers.