Treatment of Sewage Systems and Odor Nuisances

The formation of hydrogen sulfide (H2S) in sewer pipes and wastewater systems poses a health hazard, causes corrosion in sewer systems, and results in odor problems due to the gas volatilizing into the pipeline spaces and free air with the aroma of rotten eggs.

The main damages resulting from the formation of hydrogen sulfide in sewage:

1. 1. Corrosion – Hydrogen sulfide is corrosive to pipeline systems (iron and concrete), pumps, manholes, pumping stations, and facilities in sewer systems. In the US alone, there were approximately 1,483,000 km (876,000 miles) of sewer pipes and 16,400 municipal sewage treatment facilities in 2002 that suffered annual damage due to corrosion amounting to an estimated $14 billion, of which $2.2 billion are direct corrosion damages and $1.7 billion are annual maintenance costs due to corrosion. The market is significantly increasing, and there are now over 30,000 wastewater treatment facilities, with a significant rise in market needs expected in the coming years up to 2032. These corrosion issues in wastewater facilities exist worldwide wherever there are sewage collection and treatment systems. Without proper treatment of the water-soluble gas that volatilizes into the pipeline, concrete pipes, for example, are expected to last only 20 years instead of the planned 50-100 years.

1. 1. Odor – The unpleasant smell of hydrogen sulfide originating from sewage constitutes a nuisance in many areas where the sewer lines are long or where the sewage residence time is long, and their redox potential is low or negative. Hundreds of thousands of complaints about bad odors from sewage are received worldwide every year, leading to situations where the property value of homes near strong odor sources is significantly affected. Additionally, hydrogen sulfide can react with other sewage components to produce strong-smelling compounds such as mercaptans and organic sulfides. As a result, enormous sums of money are invested in preventing odor nuisances from sewage, often without success. For example, a study examining five methods of neutralizing sewage odors found that only one method – oxidation with a strong oxidizer – was effective.

1. 1. Pipeline Blockages by Biofilm – The organic and mineral matter in sewage serves as a basis for bacterial growth in sewer pipes. This population mainly consists of anaerobic bacteria, including those that produce hydrogen sulfide after using sulfate as the final electron acceptor. The biofilm builds up on the pipe walls, gradually reducing their diameter until there is a significant reduction in the efficiency of sewage transfer. Without therapeutic intervention, biofilm can accumulate carbonate deposits over time and become a difficult-to-remove nuisance that may block the pipes.

1. Health Hazard – Exposure to high concentrations of hydrogen sulfide can cause a variety of human health risks, ranging from a burning sensation in the eyes and respiratory system damage to loss of consciousness and death in extreme cases (mainly among unprotected workers maintaining unventilated sewer pits).

Currently, good methods for root treatment of the problem are lacking. Existing methods mainly address the odor problem by using expensive filters for air filtration (a solution that does not address corrosion or the root cause). Sewage treatment focuses on adding calcium nitrate, which is reduced before the sulfate but requires continuous injection of another pollutant into the sewage (a nitrogen source). In acute cases, disinfectants such as nitric acid or chlorination, which are expensive and create additional problems in the sewage, are used. The volume of sewer pipes is filled with sewage, which quickly becomes anaerobic, producing sulfides that are released with the sewage and emit odors along the entire sewer line through air vents, primarily at the end of the line, causing an environmental nuisance.

Existing solutions are divided into four main families:

1. 1. Planning to Prevent Conditions for Hydrogen Sulfide Formation – Planning wide-diameter and ventilated sewer systems to reduce the production of anaerobic conditions.

1. 1. Solution for Air Polluted with Hydrogen Sulfide – Activated carbon filters (requiring frequent replacement) or a combination of biological filters (where bacteria oxidize the hydrogen sulfide) that occupy a large area and require continuous maintenance to preserve bacterial activity (maintaining appropriate moisture, micronutrients, preventing toxicity, etc.).

1. 1. Solution to Prevent Hydrogen Sulfide Production in the Sewage – Adding nitrate to the sewage as a preferred final electron acceptor over sulfate.

1. Solution for Oxidizing or Adsorbing Hydrogen Sulfide – Adding iron salts that bind to hydrogen sulfide and precipitate as poorly soluble salts in the sewage. Oxidizing hydrogen sulfide in the sewage using oxidizing agents such as hydrogen peroxide, permanganate, or persulfate.

Our Solution

Nanoplus solves all these problems through ozone nano-bubble technology to create an interface between water and gas (air, oxygen, and ozone). The application of ozone nano-bubbles directly in sewage for the oxidation of hydrogen sulfide in the sewage (before it reaches the air) and disrupting the activity of sulfate-reducing bacterial populations (anaerobic bacteria). This is an innovative solution to all the problems associated with hydrogen sulfide production in sewage. The solution is based on the creation of gas nano-bubbles developed by the company, capable of applying all types of gases in the form of nano-bubbles that, unlike regular ozone bubbles, do not leave the sewage but continue to act in the sewage as a colloidal material. This allows, for example, the use of the strong oxidizer ozone without exposure to the problems of excess ozone in the air (a corrosive gas) because the gas bubbles remain in the sewage until they decompose and do not exit the sewage as macro-gas bubbles created by diffusers do. The solution is applied in pumping stations and sewer manholes.