Although the CW is widely applied to wastewater treatment, it has a limited capacity to remove organic matter completely. A CW is generally able to remove as high as 90% of the COD, BOD, SS and bacteriological pollutants from the wastewater, but the removal rates of N and P are only around 50% in most cases(Verhoeven and Meuleman, 1999). Our study also found that the water still contained high levels of N and P after treatment.