Influence of the water saturation level on phosphorus retention and treatment performances of vertical flow constructed wetland combined with trickling filter and FeCl3 injection

Abstract

International audienceThe aim of the study was to determine the effects on treatment efficiency of oxidation-reduction (redox) conditions that are caused by different water saturation levels within vertical-flow constructed wetlands (VFCW), with specific attention to phosphorus (P) retention. The study was conducted by monitoring over 18 weeks a pilot-scale system consisting of a biological aerobic trickling filter as a biological pre-treatment step, followed by ferric chloride (FeCl3) addition for phosphate removal and a stage of VFCW. By adjusting the water saturation level, the VFCW was operated successively under fully unsaturated, partly saturated, completely saturated (flooded), and then again unsaturated conditions. Redox potentials (Eh) were measured at three different levels within the VFCW. Results revealed that Eh was logically affected by the water-saturation level and the feeding-resting periods. Treatment efficiency was very good under fully unsaturated and partly saturated conditions. Under flooded conditions, the performance of the filter declined when the flood was maintained for around one week. However, VFCW regained its previous efficiency after the effluent was drained out and aerobic conditions were restored, indicating that the system was resistant and robust enough that periodical flooding did nott affect its performance afterwards

Effect of reductive dissolution of iron (hydr)oxides on arsenic behavior in a water–sediment system: First release, then adsorption

“…The concentration of Fe(II) increased with addition of increasing levels of carbon source. Eh may affect microbial processes and the fate of ferric species (Kim et al, 2014). A negative correlation was observed between the concentrations of S and Fe(II) when the Eh exceeded 80 mV of the system (Fig.…”

“…In aquatic ecosystem restoration, iron chloride (FeCl 3 ) is widely used for improving water clarification or used as a flocculant to remove contaminants such as phosphorus, Cu, Pb, Zn and arsenic (As) from water (Contin et al, 2015;Kim et al, 2014) by co-precipitation of both constituents as contaminant-containing iron (oxyhydr)oxides (Zaaboub et al, 2014), and transfer contaminants from water into sediments. However, some researches showed that iron (hydr)oxides precipitated during sewage sludge flocculation were partially redissolved the acid soil, releasing previously surface adsorbed contaminants (Contin et al, 2015).…”

2D nanoporous membrane for cation removal from water: Effects of ionic valence, membrane hydrophobicity, and pore size

“…In fact, ferric chlorides are effective as primary coagulants due to their associative character in solution. At controlled concentrations, it is excellent for both drinking and wastewater treatment applications, including phosphorus removal, 51 sludge conditioning, and struvite control. 52,53 It also prevents odor and corrosion by controlling hydrogen sulfide formation.…”

Wetland pollutant dynamics and control

“…Similarly, the feedback from 5 years of data obtained from "compact VSSF CWs" showed that this system met the French standards and outperformed the first stage of "classical VSSF CWs". Kim et al (2015) conducted an 18-week study in a pilot-scale wastewater treatment system consisting of a biological aerobic trickling filter as a biological pre-treatment step, followed by the addition of ferric chloride (FeCl 3 ) for phosphate removal and a stage of VSSF CW in France. The aim was to determine the effects on treatment efficiency of oxidation-reduction (redox) conditions caused by different water saturation levels within the VSSF part, with specific attention to P retention.…”