A. Introduction of WETLAND

In 2009, Fuhua Primary School had constructed a Constructed Wetland that helps to educate pupils about recycling of rain water to potable water. It is based on the technology on phytoremediation. It uses plants and sunlight to reduce acidity found in rain water.

Rain falling from the sky is captured by the raincatcher. The rainwater flows through the distributor pipe into Stage 1, which is a free water surface system. Here, the water passes through a bed of elephant ear (Alocasia macrorrhiza), taro yam (Colocasia esculenta), water primrose (Ludwigia adscendens), arrowhead (Sagittaria sagittifolia) and pennywort (Hydrocotyle spp.)
 
The high protein content of the elephant ear and taro yam tubers mean that these plants consume dissolve nitrates heavily, greatly reducing the dissolved nitrate content of the water. The water primrose possesses a unique ability: when in contact with acidic water, the plant will secrete ammonia (NH3). This will result in the formation of ammonium nitrate (NH4NO3) and ammonium sulphate ((NH4)2SO4), which are both very good plant nutrients. As both arrowhead and pennywort have phenomenal growth rates, they will consume the dissolved anions at a very rapid rate, greatly reducing their concentration in the process.
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