effect of waste water treatment on river metal concentrations: removal or enrichment

• Published in: Journal of soils and sediments Vol. 11; no. 2; pp. 364 - 372
• Main Authors: Teuchies, Johannes, Bervoets, Lieven, Cox, Tom J. S, Meire, Patrick, de Deckere, Eric
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Berlin/Heidelberg : Springer-Verlag 01.02.2011; Springer-Verlag; Springer Nature B.V
• Subjects: Acid volatile sulfides (AVS); Aeration; Anoxic conditions; Arsenic; Cadmium; Contaminated sediments; Copper; Earth and Environmental Science; Environment; Environmental Physics; Geochemistry; Household wastes; Industrial wastes; Manganese; Metal availability; Metal concentrations; Metals; oxidation; Oxygen; Redox chemistry; Rivers; Sec 1 • Sediment Quality and Impact Assessment • Research Article; Sediment pollution; Sediments; Simultaneously extracted metals (SEM); Soil Science & Conservation; Sulfides; Surface water; Trace metals; Wastewater treatment plants; Water treatment; Water treatment plants; Europe; Simultaneously extracted metals (SEM); Oxidation; Redox chemistry; Sediments; Acid volatile sulfides (AVS); Metal availability
• ISSN: 1439-0108; 1614-7480
• DOI: 10.1007/s11368-010-0321-4

Purpose Discharge of untreated domestic and industrial waste in many European rivers resulted in low oxygen concentrations and contamination with trace metals, often concentrated in sediments. Under these anoxic conditions, the formation of insoluble metal sulfides is known to reduce metal availability. Nowadays, implementation of waste water treatment plants results in increasing surface water oxygen concentrations. Under these conditions, sediments can be turned from a trace metal sink into a trace metal source. Materials and methods In an ex situ experiment with metal contaminated sediment, we investigated the effect of surface water aeration on sediment metal sulfide (acid volatile sulfides (AVS)) concentrations and sediment metal release to the surface water. These results were compared with long-term field data, where surface water oxygen and metal concentrations, before and after the implementation of a waste water treatment plant, were compared. Results and discussion Aeration of surface water in the experimental setup resulted in a decrease of sediment AVS concentrations due to sulfide oxidation. Metals, known to precipitate with these sulfides, became more mobile and increasing dissolved metal (arsenic (As), cadmium (Cd), copper (Cu)) concentrations in the surface water were observed. Contrary to As, Cd, or Cu, manganese (Mn) surface water concentrations decreased in the aerated treatment. Mn ions will precipitate and accumulate in the sediment as Mn oxides under the oxic conditions. Field data, however, demonstrated a decrease of all total metal surface water concentrations with increasing oxygen concentrations following the implementation of the waste water treatment plant. Conclusions The gradual decrease in surface water metal concentrations in the river before the treatment started and the removal of metals in the waste water treatment process could not be countered by an increase in metal flux from the sediment as observed in the experiment.