Performance of pilot-scale constructed wetlands for secondary treatment of chromium-bearing tannery wastewaters

Role of Wetlands

“…Metal (Al, As, Cd, Co, Cu, CN-, Fe, Pb, Mn, Ni, U and Zn) removal in natural wetlands has been widely reported (Hadad et al 2010;Knox et al 2010;Marchand et al 2010;Lesage et al 2007a, b;Groza et al 2010;Dotro et al 2012 (2007b) reported adsorption and precipitation as insoluble salts (mainly sulphides and oxyhydroxides), deposition and rhizosphere activity as the main mechanisms for metal removal. Adsorption is an important mechanism for removal of metals in wetlands.…”

Domestic sewage and secondary effluent treatment using vertical submerged biological filter

“…Biological filters (bio-filters) are invariably cited as a low-cost and low-maintenance technology [1,2] , especially compared with conventional treatment technologies, such as activated sludge [3]. For example, it is practically impossible for activated sludge to treat low-strength wastewater with BOD lower than 20 mg l -1 as the difficulty of maintaining a normal value for MLSS and conventional efficiency.…”

“…Therefore, Bio-filter is needed to filter effluent before discharged into the receiving waters, reused in agriculture, or utilized in body contact recreational reservoirs [14]. Bio-filters could also be applied to perform a post-treatment step for low-strength wastewater purification, e.g., secondary treatment of chromium-bearing tannery wastewaters [3], and secondary or tertiary treatment of municipal wastewater [2,15]. The stability of bio-filter plays an important role in restraining the change of effluent water quality [16].…”

Design parameters affecting metals removal in horizontal constructed wetlands for domestic wastewater treatment

“…Arroyo et al (2010) found differences in metals removal in a Hierarchical Mosaic of Artificial Ecosystems (HMAE 1 ) for municipal wastewater treatment depending on the treatment unit considered. Previous experiences demonstrate the effect of vegetation (Liu et al, 2007;Maine et al, 2009;Marchand et al, 2010), substrate (Arroyo et al, 2013a), shape (Galletti et al, 2010), hydraulic loading rate (HLR) (Dotro et al, 2012;Pimpan and Jinddal, 2009;Ranieri and Young, 2012) or flooding regime (Du Laing et al, 2007) in the performance of wetlands for metals and metalloids. However, there is a lack of studies covering the comparison of a wide variety of CW designs in order to determine the best configuration for trace element removal.…”