An artificial wetland created for purpose of treating anthropogenic discharge like municipal or industrial waste water is known as constructed wetland. Phytoremediation refers to use of plants for removal or degradation of contaminants in soil, sludge, surface water and ground water.

Please check the following links.

http://www.constructedwetlands.net/constructed_wetlands.html

https://agresearchmag.ars.usda.gov/2000/jun/soil

Dear Bama Pakeerathan,

(1) A constructed wetland (CW) is an artificial wetland created for the purpose of treating anthropogenic discharge such as municipal or industrial wastewater, or stormwater runoff. It may also be created for land reclamation after mining, refineries, or other ecological disturbances such as required mitigation for natural areas lost to land development. Constructed wetlands are engineered systems that use natural functions of vegetation, soil, and organisms to treat different water streams.

(2) Phytoremediation is the direct use of living green plants for in situ removal, degradation, or containment of contaminants (hazardous chemicals) in soils, sludges, sediments, surface water and groundwater. It refers to the natural ability of certain plants called hyperaccumulators to bioaccumulate, degrade, or render harmless contaminants in soils, water, or air. Toxic heavy metals and organic pollutants are the major targets for phytoremediation. 

(3) For example, aquatic plant, Water hyacinth (Eicchornia crassipes) is an efficient phytoremediation agent for cleaning/extracting of heavy metals from a constructed wetland.

Hope you find this input interesting and useful.

One other distinction which is important for long term management or function is that if the constructed wetland is developed for the removal or metals (as the previous contributor noted they have been used for mining/industrial waste water treatment), the metal may stay in the wetland - trapped in sediment or detritus if the plants used are not hyperaccumulators (which they often are not). At some point the system can become saturated and loose effectiveness. Phytoremediation of metals generally means they are removed from the soil and the resulting high metal content vegetation is removed and disposed of or processed. Wetlands are not management free when it comes to use for metals polishing and are best suited to removal of degradable organics/nutrients.

phyto remediation is a term used by the soil cleaning comunity while constructed wetlands is a term used by the wastewater community.

Classically the phytoremediation is involving less management than the constructed wetlands, that always crave some pumps, screens structured substrate etc...

Most importantly, CW has substrate which plays key role (compared with plants on CWs) in pollutants removal via physical, chemical and biological processes, while phytoremediation is fully depending on the plants adsorption process, which is relatively weak compared with CWs. However, for heavy metals etc, phytoremediation can play equal role with CWs....