Odour & Hydrogen Sulphide

Prevention's and Cures

Hydrogen sulphide (H₂S) is the most common cause for odour in wastewater. H₂S can also result in the corrosion of concrete and steel in sewerage networks.

Do you smell a rotten egg protruding from a manhole or sewer line? In most cases, that odour is hydrogen sulphide, a toxic gas formed from septic conditions. We treat everything from small grease traps to some of the world’s largest industries with tanks that emit toxic levels of sulphide.

What is Hydrogen Sulphide?

Hydrogen Sulphide (H2S) often is a colourless gas with a rotten egg odour. H2S gas is highly poisonous and highly corrosive in wastewater applications. There are various problems associated with hydrogen sulphide generation, such as toxicity, noxious odours, and the generation of corrosive sulphuric acid.

Sulphide-containing contaminants will either be oxidized (react with metals to form insoluble metal sulphides) or be released to the sewer. When sewage becomes stagnant, H2S gas is generated in anaerobic conditions. H2S can start to form sulphuric acid in lift stations and wastewater treatment plants, which will rapidly corrode cement and steel structures.

Sulphide Corrosion

Corrosion of metal and concrete is a major issue associated with the generation of sulphuric acid caused by hydrogen sulphide. The rate of corrosion depends on the permeability of concrete and the amount of hydrogen sulphide gas that is adsorbed to the moist sewer walls. Signs of prolonged exposure to mild acid attack include rust bleeding, cracking and spalling of the concrete.

H2S Gas Toxicity Concerns

Hydrogen sulphide is a toxic concern for wastewater operators, especially if odour-masking agents are used, since it can affect the nervous system causing headaches, nausea, irritation of the skin, eyes, and respiratory tract, and at high doses it can cause death.

Hydrogen Sulphide Treatment:

Many wastewater facilities that experience sulphide problems generally use aeration, chemical oxidizers, such as hydrogen peroxide, and/or odour-masking agents (essential oils). These only mask the underlying problem and do not actually remove the sulphur/sulphide molecules from the system.

Preventing H2S from being produced removes the problems of odour and corrosion from the waste stream. Below you will find our range of non-hazardous and proven hydrogen sulphide treatment options.

Products

Industry leading solutions
odour and H₂S control

ACTI-Mag

Magnesium Hydroxide Liquid, a preferred solution for odour control

ACTI-Mag is one of the safest, most cost-effective and earth-friendly ways to manage many aspects of wastewater treatment:

Odour and H₂S control

Hydrogen sulphide is present due to anaerobic activity, which favours sulfate reducing bacteria (SRB) and results in the generation of a poisonous rotten egg gas called H2S. Unlike other agents, which can be costly, potentially hazardous, and targeted at a single issue, ACTI-Mag offers a safe and cost-effective strategy for managing odour.

Caustic soda (sodium hydroxide) replacement

While ACTI-Mag is typically more expensive than 50% NaOH on a “price per unit” basis, it is significantly less expensive in use – because every 1.0 kg of 50% NaOH can be replaced by 0.6 kgs of 60% Mg(OH)2 to provide the same number of moles of hydroxide (OH-) for pH neutralization.

The Science Behind It

Odour Control Cleansing The Sewer

Unlike other odour control agents, which can be costly, potentially hazardous, and narrowly targeted at a single issue, ACTI-Mag magnesium hydroxide slurry offers a safe and cost-effective strategy for managing odour, but also prolonging infrastructure life, reducing fats, oils and greases (FOGs) issues and enhancing wastewater treatment processes downstream.

ACTI-Mag has a higher neutralising value per kilo when compared with caustic whilst being significantly safer to handle than other
traditional alkalis, making it a very safe and cost-competitive option for hydrogen sulphide gas (H2S) control in sewers.

CONTROL H2S FOR A SAFER WORKPLACE AND NO MORE ODOUR COMPLAINTS
Highly toxic, hydrogen sulphide (H2S) gas is produced in sewage with a distinctive and unpleasant rotten egg smell causing frequent odour complaints. Hydrogen sulphide is present due to anaerobic activity, which favours sulfate reducing bacteria (SRB) and results in the generation of a poisonous rotten egg gas called H2S.

ACTI-Mag effectively locks up H2S by increasing pH and transforming into non-strippable HS- to prevent release as a gas that produces odour and facilitates corrosion. ACTI-Mag is safe to handle and cost effective with many knock-on benefits that reduce treatment costs at the Wastewater Treatment Plant (WWTP).

Unlike acidic Iron salts ACTI-Mag adds rather than destroys alkalinity & thereby stabilises downstream treatment process pH. Not only that using ACTI-Mag rather than Iron salts removes the need to store dangerous/hazardous goods within the catchment area.

ACTI-Mag lowers chemical consumption and ensures easier use, handling and storage, considerably reducing costs.

Alkalinity & pH adjustment

ACTI-Mag provides more CaCO3 equivalent alkalinity on an equal weight basis when compared to hydrated lime and caustic soda which lowers chemical consumption. Unlike caustic soda, ACTI-Mag is non-hazardous and non-corrosive, and even beneficial to the environment while sodium is a salinity hazard.

Fats oils and greases (FOGs) control

Higher concentration of FOG can lead to the formation of fat bergs, scamming, pump blockages, pipe restriction, pipe blockage plus the formation of odour related issues like hydrogen sulfide gas (H₂S). ACTI-Mag is a safe and environmentally friendly solution for FOGs in wastewater

BOD/COD reduction

Reducing BOD means that the sewage will support the growth of less bacteria and therefore the effluent will be better able to infiltrate tight soils. We can help you reduce the organic component from your wastewater streams.

Caustic soda (sodium hydroxide) replacement

While ACTI-Mag is typically more expensive than 50% NaOH on a “price per unit” basis, it is significantly less expensive in use – because every 1.0 kg of 50% NaOH can be replaced by 0.6 kgs of 60% Mg(OH)₂ to provide the same number of moles of hydroxide (OH-) for pH neutralization.

phosphorus removal

Phosphorus – usually in the form of phosphates – has to be treated and reduced from the wastewater in order to meet environmental standards before it is discharged into a local water body, or land irrigation. With a chemistry similar to the antacids used in our human digestive systems, Calix can safely and cost-effectively remove phosphate from municipal and industrial wastewater.

Why is ACTI-Mag different to generic magnesium hydroxide slurries?

ACTI-Mag is a concentrated and stabilised suspension of magnesium hydroxide (also known as milk of magnesia). An inorganic compound with the chemical formula Mg(OH)2.

Highly fluid, ACTI-Mag has proven to flow easily in most dosing systems. With a higher neutralising value per dry kilo when compared with caustic and lime and being significantly safer than other traditional alkalis, ACTI-Mag is a very cost competitive option for hydrogen sulphide gas (H2S) control in sewers and industrial waste treatment as well as for several other applications including phosphorus and partial nitrogen removal from wastewater.

Calix’s ACTI-Mag has several advantages over other generic MHLs.

Neutralises waste streams up to 30% faster than generic brands.
The pH peaks at 10.3 and buffers in the solution between 8.5 and 9.
The MHL dissolves slowly over time with particles remaining in suspension for as long as needed.

Slurry chemistry podcast ACTI-Mag Magnesium Hydroxide’s reactivity in wastewater treatment

Watch our slurry chemistry podcast to understand ACTI-Mag Magnesium Hydroxide’s reactivity in wastewater treatment:

Case Studies

CASE STUDY SUMMARY

Challenges

Odour in sewage network due to high hydrogen sulphide (H2S) generation.
Heavy build-up of Fats, oils and greases (FOGs) in the network.
Frequent need for vacuum truck cleaning leading to increased maintenance costs.
High treatment costs due to high chemical use (lime and alum) and associated equipment and maintenance.

Objective

Manage H2S and odour levels.
Eliminate or reduce FOGs build-up in the network.
Save on chemical and maintenance at the treatment plant.
Ongoing monitoring and optimisation in remote area.

Solution

Dose the network with Calix’s ACTI-Mag magnesium hydroxide liquid.
Remote monitoring and weekly reporting, to ensure ongoing control of H2S and pH levels, and optimization of ACTI-Mag usage.
Eliminate STP lime dosing & reduce alum dosing.

Videos

Downloads

ACTI-mag Odour and Corrosion Control
Download

De-Sulph-A-Nator

Sulfide Odor Control

De-Sulph-A-Nator is a new reactive sulphide odour control agent that functions by encapsulating odorous sulphides and mercaptans, rapidly trapping them in an irreversible reaction.

De-Sulph-A-Nator is a microencapsulant that contains a molecular structure that reacts with the sulphide molecule. This changes the chemistry of the sulphide and breaks it down.

It works fast and is easy to use when compared to traditional oxidants.