Simple and reliable

Simplicity

The Nègrepelisse wastewater plant is maintained by a CCTVA employee in charge of a total of five plants, with some help for the annual cutting of the reeds. The reed must be cut above the soil every year in the autumn and the stems and leaves disposed off as green waste.

Maintenance requires a basic knowledge in electromechanical engineering (for the running of the pumps, the robot, the flow meters, the samplers…) and a habit of wastewater handling, but the main maintenance tasks are similar to gardening, tasks, not very different from those of a nowadays farmer.

Reed cutting

Reliability

A wastewater plant uses a limited number of very simple, reliable equipment (pumping units, drainpipes, pressure pipes…) and mobilizes natural processes (percolation through gravel layers, contact between wastewater and the bacteria fixed on these gravels…). Dysfunctions are therefore exceptional.

For example, wastewater filters will work normally and meet the outlet quality requirement with a hydraulic load five times higher than the design value during several consecutive weeks.

By comparison, an Activated Sludge plant sends raw wastewater and sludge to the receiving stream as soon as the hydraulic load exceeds the design value. Other example: the maintenance of a pump, a valve or a gate, the only electromechanical devices of a CW plant, is very simple in comparison with the maintenance of the sophisticated equipment of an intensive plant.