As one of the UK’s most innovative and proactive water companies, Yorkshire Water has embarked on a ground-breaking project, utilising a first-of-its-kind, combined liquid and gas smart sensor technology solution to monitor, manage and control septicity.  ATi’s Senior Service Engineer, Mark Holmes, discusses how this latest technology is transforming wastewater and sewer network management, offering the ultimate smart septicity solution.

Septic sewage delivered into an activated sludge plant creates considerable process complications, with far-reaching consequences across the whole water distribution system and the environment.  With regulations now more stringent, managing and controlling septicity has become increasingly complex and is one of the most critical challenges in wastewater treatment, with high levels proving costly due to toxicity, corrosion and odour.

Until now, water professionals traditionally used a range of monitoring techniques, including weekly samples, analysing sediments, controlling flow and developing aerobic environments.  Controlling septicity also relied on maintaining the supply of oxygen to oxidise previously formed Sulfide; minimising Hydrogen Sulfide (H₂S) gas emissions into the atmosphere, deodorising vented air and the use of protective coatings on pipes. 

However, as one of the only specialist manufacturers of both water and gas analytical sensors, ATi knew that negative Oxidation-Reduction Potential (ORP) readings in the region of -150mV and below, paired with high H₂S gas values of 5ppm and above, were an indicator of septicity. By applying decades of expertise, ATi developed SeptiNet to provide a unified, smart solution for septicity monitoring and detection, utilising class-leading H₂S gas and ORP water quality sensing.

As one of the UK’s most forward-thinking water companies, Yorkshire Water were keen to embrace these technological advances and became the first water utility to install the only pioneering, all-in-one septicity monitoring solution within a recently refurbished CSO as part of their drive for optimisation, resilience and safeguarding the environment. 

SeptiNet’s scalable, modular nature enables its operators to monitor wastewater quality, offering real-time, continuous data to their preferred platform via wireless or wired communications, delivering critical values to identify pollution issues.

Safeguarding Sewage

Wastewater becomes septic when organic matter decomposes and forms a foul smell, due to the absence of free oxygen. This common problem occurs within sewers when low flows and long retention times combine, resulting in bacteria multiplying in the anaerobic conditions that creates septicity. 

Consequent formation of H₂S gas then causes a nuisance with its characteristic foul smell, leading to customer complaints.  This lethal gas also causes a hazard during entry into chambers and its reaction with moisture results in the formation of Sulphuric Acid, which has a costly, corrosive effect.

SeptiNet’s pioneering, preventative nature sees the ORP sensor submerged within the channel’s flow using ATi’s stainless steel, post-mount bracket system, offering flexibility when either positioning the sensor or when removing it for maintenance and cleaning.  The H₂S gas sensor is then positioned above the channel and away from the sample water, with consideration taken as to where the H₂S gas can be measured. Both sensors are directly hardwired into a GSM, which can be mounted either internally or externally to the CSO.

The unique nature of this combined data offers early indications of septicity, enabling access to data for both online and offline analysis and modelling.  This provides operators with an alert, allowing early decisions whether to dose chemical to counteract the septicity, or divert the flow. 

Early data from this project (see below) confirms the CSO is “healthy”, with ORP and H₂S values within the accepted range.  However, if these levels deviate from the norm, it allows the water company to take preventative measures before septicity compromises the whole sewer network.

Prevention is better than the cure

Designed specifically for WWTW inlets, storm tanks, CSO inlets, outlets & overflows, pumping stations and manholes within the network, SeptiNet provides odour and corrosion management, reduces the formation of hazardous atmospheres and negative environmental impacts, safeguarding plants, whilst reducing overflow and pollution to rivers.

SeptiNet offers an end-to-end approach to managing wastewater assets and through innovative, smart technology, it is creating resilient, cost-effective and environmentally friendly wastewater systems, prolonging the life of assets and reducing pollution for a better, greener world. 

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