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Fighting Odour and Corrosion Problems in Sewers

Big data opens a world of possibilities for operators of sewer networks, enabling them to respond to the still increasing demands of cost effective and odour free processes.

H2S-Sewer is a robust, industrial-grade H2S sensor for liquid phase measurements of dissolved H2S, and it is as such a key enabling sensor system to engage those vast potentials. The sensor measures online and provides realtime data of the dissolved H2S in raw sewage in the network.

Hydrogen sulphide (H2S) is one of the primary corrosion and odour producing molecules in wastewater collection. H2S is formed under anaerobic conditions – typically inpressurized sewer pipes – and it is released at manholes, collection tanks or other places with access to the atmosphere. It is converted into sulphuric acid on various surfaces, which leads to corrossion and collapse of sewer systems, pumps and other equipment, as well as the substantial odour nuisances. H2S can be prevented or converted to other unharmful substances by dosing chemicals in the wastewater, typically nitrate, iron salts or other oxidants.

To determine the concentration of H2S in the sewer system, several gas phase sensors are available on the market. Gas sensors are developed for workplace safety (personal safety equipment) or for monitoring and documenting odour nuisances after customer complaints, but unfortunately, when they are applied for the control of the mitigations based on chemical dosing, they fail on a number of key parameters such as: reaction time, compatibility with water, longterm operation under anaerobic conditions.

The Unisense Industrial-grade H2S-Sewer sensor can measure H2S directly in the liquid as dissolved concentrations and in the gas phase as well. Together with a pH measurement, the total sulphide concentration can therefore be quantified in realtime, and the most optimal dosage control can be applied with 20-80% chemical savings as a result. The microelectrochemical principle of the Unisense H2S-Sewer sensor enables continuous measurement even in oxygen-free environments with a reaction time of a few seconds whereby even short peaks of changes in the wastewater composition can be tracked and handled accordingly by automatic adjustments of the chemical dosing.

Furthermore, reliable H2S measurements based on the Unisense H2S-Sewer sensor can be combined with other sensor inputs from the sewerage network (e.g. from SCADA systems) such as flow, level and temperature measurements, thereby providing a detailed mapping of the H2S distribution in the network enabling location-specific preventive maintenance to avoid sewer line break down.

For further information or discussions on the usage of our Industrial-grade H2S-Sewer sensor, please contact us.