Changes

'''''Subsurface flow constructed wetlands'''''work by delivering pretreated wastewater (either from a septic tank or anaerobic filter) to the wetlands. For the Dumaguete system, wastewater flows from the market through a series of grit and grease traps to an anaerobic baffled reactor and then to the wetlands. As the pretreated effluent flows through the media in the wetlands, the bacteria living on the gravel and plant root surfaces break down the organic matter in the wastewater. The wetlands plants, specifically chosen for this purpose, play an important role by delivering small amounts of oxygen to the root nodules, which provides micro environments where aerobic bacteria can flourish. The plants also add aesthetic value, making this an ideal spot for visitors to stroll and relax in the outdoors.<br/>The drawing on the left illustrates the flow pattern of the wastewater through the wetlands. Note that a coarser grade of gravel is used at the inlet and outlet of the wetlands. This is to provide even distribution throughout the system. Also note that the outlet pipe is at an elevation slightly below the surface of the wetlands cell. This sets the water level so it is always below the top of the gravel, hence the name, subsurface flow wetlands. Keeping the wastewater below the gravel surface eliminates flies and mosquitoes and keeps odors to a minimum.