A Comparative Study on Nitrogen Removal from Polluted Water by Floating Beds Planted with Phragmites australis and Acorus calamus

Lab-scale experiments were carried out to compare the efficiency of nitrogen(N)removal by floating beds planted with common reed(Phragmites australis)and calamus(Acorus calamus)in eutrophic water man-made from water of Khanka Lake. The rhizome characteristics and the efficiency and rate of nitrogen removal by Phragmites australis and Acorus calamus were examined to study nitrogen removal mechanisms and major influencing factors. Results demonstrated that floating beds planted with Phragmites australis(3 replicas) and A-corus calamus(3 replicas) had water purifying ability. The average TN removal percentage was 91.5% and 84.2% for the reed beds and89.9% and 82.8% for the calamus beds at 9.63 mg·L-1(feed A)and 4.58 mg·L-1(feed B)of TN concentrations in the feed water, respectively. Plant uptake contributed to 36.4%~77.1% of TN removal. The mean TN removal rate by the reed beds at late growth stage was 4.20mg·L-1·d-1and 1.77 mg·L-1·d-1, while that of the calamus beds was 1.75 mg·L-1·d-1and 1.04 mg·L-1·d-1, respectively, for feed A and feed B. Significant correlations(R≥0.826 and P0.01)were found between TN removal rates and total length, surface area and volume of plant roots. The plant roots is found to be the determinant factor of nitrogen removal efficiency in floating beds.