2.6 What are the O&M Requirements?

Constructed wetlands are natural systems that require minimal operator intervention, and monitoring is the only routine operation. Appropriate action is taken when problems arise.

The critical items requiring operator intervention are:

Water Level and Flow Control

Water level and flow control are usually the only operational variables that have a significant impact on constructed wetland performance. Water level changes affect residence time, oxygen diffusion, and plant cover. Investigate big water level changes right away, as they may indicate leaks, blockages, breaches, stormwater, or other problems.

Maintenance of Uniform Flow

Maintenance of uniform flow across the wetland is crucial for treatment performance. The inlet and outlet manifolds need regular inspection, adjustment, and cleaning to prevent clogging. Debris and bacterial slimes should be removed from the screen surfaces. Submerged manifolds should be flushed occasionally. High-pressure water spray or mechanical cleaning may also be needed. Influent suspended solids will build up near the inlets and reduce detention times. These solids will have to be removed over time.

Vegetation Management

Wetland plants are self-sustaining and cycle annually. The main goal of vegetation management is to keep the desired plants in the wetland. This can be done by changing water levels and removing unwanted plants. If plant cover is low, management actions may involve water level changes, lower loadings, pesticides, and replanting. Harvesting and litter removal may depend on the wetland design. A good subsurface flow wetland should not need regular harvesting.

Odour Management

Odours are rare in well-loaded wetlands. They are caused by anaerobic conditions from high BOD and ammonia loadings. Odour can be avoided by distributing water evenly in the bed and avoiding surface flooding. If the primary treatment is too large, wastewater may become anaerobic and odorous, but this is minor as it drains fast in the bed unless there is clogging.

For further information, please click on the Materials tab at the top of the page.