Artificial Constructed Wetland System

Artificial Constructed Wetlands System is usually constructed on a land area with depths measuring less than one meter enough to support growth of aquatic plants such as cattail, water hyacinth and sedges. Construction of these wetlands is very important as they act as an important natural biological filter to remove wastewater contaminants by means of filtration and thus leading to improved water quality by having higher dissolved oxygen level in the treated water. Presence of aquatic vegetation also helps to control and limit the growth of algae and with dense vegetation, this also provides high surface area for formation of bacteria films that can breakdown organic waste.

Lately artificially constructed wetlands is regarded as one of the best method to treat wastewater which has already undergone major COD reduction in main treatment plant and thus, the role of wetlands are more or less regarded as a secondary polishing step. There are generally two types of constructed wetland systems, one is identified and known as Free Water Surface System (FWS) and another is the Subsurface Flow System (SFS). Both systems are relatively the same except that for the free water surface system, the bottom soil layer is made up of impermeable barrier while for the free water surface system, it is usually sands or rocks. As wastewater travels and flows through the heavy plant vegetation, the roots will act to slow down the movement and during this time absorb most of the contaminants. The best system setup should have the channel properly constructed to allow water to be spread out and distributed to achieve maximum efficiency.

One of the key areas to look into when using wetland system is that generally it can only handle small volume of water. As outlined in several reference sources, the annual loading rate can vary and usually the amount can be somewhere between 18 to 60 ft/y. Other important considerations on the idea towards using artificial wetland system is that large open area is definitely required. However, the payoff of using the system is that clean and dependable high quality discharge can be obtained. If there’s a need to discharge the treated wastewater to natural ecosystem, thorough studies and research including doing a cross-checking with local regulatory requirements have to be carried out before this is allowed.

Read also on topic covering Trickling Filter and how the system works.

Recommended Engineering Books