Heavy metals in a constructed wetland treating industrial wastewater: distribution in the sediment and rhizome tissue

Abstract

This study assessed copper and zinc distribution in the surface layer of sediment and rhizome tissue within the saturated surface vertical flow constructed wetland of CSBP Ltd, a fertiliser and chemical manufacturer located in Western Australia. Sediment and Schoenoplectus validus rhizome samples were collected at various distances from the inlet pipe while water samples are routinely collected. Water samples were analysed for nutrients and metals, sediments were analysed for total and bioavailable metals and rhizomes were analysed for total metals only. Mean influent copper and zinc concentrations were 0.19mg/L and 0.24mg/L respectively. The distribution of bioavailable Cu and Zn in the top sediment layer follows a horizontal profile. Analysis of variance (ANOVA) showed that the bioavailable fraction of these metals in sediments near the inlet pipe (30.2mg/kg Cu and 60.4mg/kg Zn) is significantly higher than in sediments at the farthest location (10.3mg/kg Cu and 26.1mg/kg Zn). The average total Cu concentration in the sediment at the 2m location has reached the 65mg/kg trigger value suggested by the Interim Sediment Quality Guidelines (ANZEEC 2000). Cu and Zn concentrations in the rhizome of S. validus do not vary significantly among different locations. Whether Cu and Zn concentrations at the CSBP wetland may reach toxic levels to plants and bacteria is still unknown and further research is required to address this issue. The surface component of the wetland favours sedimentation and binding of metals to the organic matter on the top of the sediment, furthermore, the sediment which tends to be anoxic with reducing conditions acts as a sink for metals. 1Title: Heavy metals in a constructed wetland treating industrial wastewater: distribution in the sediment and rhizome tissue. Water samples were analysed for nutrients and metals, sediments were analysed for total and bioavailable metals and rhizomes were analysed for total metals only. Mean influent copper and zinc concentrations were 0.19mg/L and 0.24mg/L respectively. The distribution of bioavailable Cu and Zn in the top sediment layer follows a horizontal profile. Analysis of variance (ANOVA) showed that the bioavailable fraction of these metals in sediments near the inlet pipe (30.2mg/kg Cu and 60.4mg/kg Zn) is significantly higher than in sediments at the farthest location (10.3mg/kg Cu and 26.1mg/kg Zn). The average total Cu concentration in the sediment at the 2m location has reached the 65mg/kg trigger value suggested by the Interim Sediment Quality Guidelines (ANZEEC 2000). Cu and Zn concentrations in the rhizome of S. validus do not vary significantly among different locations. Whether Cu and Zn concentrations at the CSBP wetland may reach toxic levels to plants and bacteria is still unknown and further research is required to address this issue. The surface component of the wetland favours sedimentation and binding of metals to the organic matter on the top of the sediment, furthermore, the sediment which tends to be anoxic with reducing c...

Nutrient release from integrated constructed wetlands sediment receiving farmyard run‐off and domestic wastewater

“…However, previous research indicated that treatment wetland sediment can be significantly contaminated with metals, such as copper, zinc and cadmium (Domingo et al . ; Lesage et al . ).…”

Accumulation and Distribution of Lead and Chromium in Laboratory-Scale Constructed Wetlands Inoculated with Metal-Tolerant Bacteria

“…The use of CW for the removal of Pb and Cr was under neutral and oxidizing conditions, which is a common finding in studies with similar operating conditions (Domingos et al 2009). Moreover, tolerance developed towards heavy metals occurs under the pH values registered the present study.…”

“…Absence of significant differences between CWP I and CWP, is possibly related to the ability of emergent macrophytes to assimilate and distribute Cr and others heavy metals in their organs, this is independent of the microorganisms associated to their rhizosphere, as suggested by studies on phytoremediation (Eapen and D'Souza 2005;Domingos et al 2009). …”

“…CW are a biological treatment system for wastewaters that are characterized by low operation, construction and maintenance costs, as well as by their tolerance to fluctuations of organic loads. Several studies around the world have demonstrated the effectiveness of CW for heavy metal removal, such as lead and chromium, although they are limited by phytoremediation (Cheng et al 2002;Lee and Scholz 2006;Domingos et al 2009). In addition, recent studies have focused on bacteria tolerant to heavy metals, particularly those that inhabit the rhizosphere of natural wetlands (Amor, Kennes, and Veiga 2001;Sultan and Hasnain 2007;Salgado-Bernal et al 2012).…”

Nitrogen removal and ammonia-oxidising bacteria in a vertical flow constructed wetland treating inorganic wastewater

“…With a total holding volume of 7695m 3 , an average theoretical hydraulic retention time (HRT) of 6.9 days can be assumed. Heavy metal removal performance for this wetland has been described by Domingos et al (2009). …”