GE Water undertook an upgrade of a ZeeWeed MBR system for
Northern Ireland Water at the Ballyclare wastewater treatment works. The project objective was to make the MBR system more energy efficient. This involved replacing the existing filter cassettes with a newer more efficient model and redesigning the software to operate the system more efficiently.
The GE engineers replaced the MBR cassettes and Profitec worked closely with process experts at GE to develop the control software to the latest specification.
The existing site ran on a single Siemens S7-414H hot-standby PLC system. As part of the upgrade, this was replaced with the latest Siemens S7-416-5H hot-standby PLC system, to provide a necessary increase in memory to future proof the control system. The PLC system was successfully changed over during a short site shutdown time, as the plant needs to be kept in constant operation.
The new MBR control software has 18 different sequences for each MBR train, from simple permeation and backwashing to the more complex recovery cleaning. The software now controls the operation of the MBR trains in pairs and uses sophisticated resistance calculations to allow the system to run in a low aeration mode for energy saving.
The software was rigorously tested with GE’s process engineers to ensure correct operation in every sequence. Once the software had been demonstrated and proven to be resilient to a variety of fault scenarios, the software was integrated onto the live control system requiring only a five minute shutdown.
The control system ran with no major errors requiring no further site shutdowns. The increased effort spent on bench testing with GE resulted in a greatly reduced commissioning period, with all sequences tested on all six MBR trains within two weeks.