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What’s going on in your tank? Water Detection in an Aeration Grid with Water Sensor and IR Camera

By: Tom Frankel
Post Date: May 1st 2015

Post Tags: disc diffuser, wwtp, wastewater, aeration, fine bubble, telemetry,

Fine bubble aeration systems are designed to be hydrostatically sealed, so that when the operator feeds air to the grid, air is diffused from the membrane diffusers and not through seals or pipe joints. Likewise when the air to the grid is shut off, the grid is supposed to remain dry. Over time, some grids leak. Negative pressure leaks that allow activated sludge into the submerged air piping are a problem because that same sludge gets blown through fine bubble diffusers and clogs slits, pores and orifices, and eventually entire pipes. If a leak is caught early enough, it is usually possible to fix the leak, clean out the pipes and return the aeration system to service. However if a leak is allowed to continue, particularly in an intermittently operated process (like an SBR), the wastewater treatment plant can be in for a major overhaul including replacement of the diffusion media.
Traditionally airlift type moisture purge systems have been used to purge condensate from aeration grids. However, sometimes purge lines don’t work, some plants have continuous purge lines below and don’t have a way to get a visual check, and some plants have purge lines but never use them. An airlift purge line will only work with a full tank, and with a low airflow rate fed to the grid.
SSI has introduced a water sensor to the in-pipe telemetry system, which measures water to different levels in your aeration system. You can see the sensor has been added to the dashboard in the link below. Any measurement of 0.2 or less means the sensor is dry.
We have also added an in-pipe infrared camera. Have a look at the snapshots from the camera on the site below, in the bottom left hand corner. If you watch for a little while, you will see the camera zoom in and out. The color will look grey or white, but if you look closely, you may see a few dirt spots on the pipe wall, but it looks bone dry.