River water quality improvement by natural and constructed wetland systems in the tropical semi-arid region of northeastern Brazil.
The efficiencies of a natural Typha spp wetland (Wn) formed on a river bed and its effluent treatment in a constructed wetland (Wc, subsurface horizontal flow) were investigated in northeastern Brazil (Paraiba State). The Wc system (12 tanks with stone gravel, 4.13 m2, 0.22 m3, 20 Typha spp rhizomes, m(-2) each, with 38, 29, and 19 mm x d(-1) hydraulic loadings, and 5, 7, and 10 days HRT) was fed daily with effluent from a Wn. Wn removal presented the highest values after Typha spp were cut during the 5th week. Removal values were (1st and 2nd periods or before and after cutting): 75% and 81% BOD5; 10-53% total phosphorus; 13%-55% ammonia; 89%-91% FC; 90-96% coliphages and bacteriophages. Wc removals increased with time with best results on 10 d HRT. Removals were also higher in the 2nd period: 74%-78% BOD5; 58%-82% ammonia; 90% FC; 94-98% FS; and 92%-96% coliphages and bacteriophages. Despite the high remaining values of FC (1.4 x 10(4) CFU/100 ml) and FX (4 x 10(3) CFU/100 ml), the removals were satisfactory and HRT dependent, suggesting a gradual optimization of the system with time. The Wc exhibited good efficiency for improving water quality from polluted river.
de Ceballos
B S
BS
Department of Civil Engineering-Environmental and Sanitation Area, Federal University of Paraiba, Campina Grande, Brazil.
Oliveira
H
H
Meira
C M
CM
Konig
A
A
Guimarães
A O
AO
de Souza
J T
JT
D001938:Brazil; D003247:Conservation of Natural Resources; D017753:Ecosystem; D005374:Filtration; D010944:Plants; D014329:Tropical Climate; D014871:Water Microbiology; D014872:Water Movements; D014876:Water Pollution / Q000517:prevention & control*