Phosphorus retention capacity of iron-ore and blast furnace slag in subsurface flow constructed wetlands

Abstract

The suitability of iron-ore and blast furnace slag for subsurface flow (SSF) constructed wetlands was studied over a period of four months. Dairy farm wastewater (TP 45 mg l-1) was percolated through buckets planted with reed (volume 9.1 l; hydraulic load 15 l m-2d-1). One group of buckets was kept under aerobic conditions and the other group under anaerobic conditions, monitored by continuous redox potential measurements. Even at high mass loading rates of 0.65 g P m-1d-1 the slag provided 98% removal efficiency and showed no decrease in performance with time. However, phosphorus fractionation data indicate that the high phosphorus retention capacity under aerobic conditions is to a great extent attributable to unstable sorption onto calcium compounds (NH4Cl-P). Phosphorus sorption of both the slag (200 μg P g-1) and the iron-ore (140 μg P g-1) was promoted by predominantly anaerobic conditions due to continuous formation of amorphous ferrous hydroxides. None of the substrates had adverse affects on reed growth.

Organic xenobiotics removal in constructed wetlands, with emphasis on the importance of the support matrix

“…Some industrial waste materials, including fly ash, have already been tested as support matrix components of CWS [242,[274][275][276][277][278][279][280], although the target of the treatment systems have been mostly nutrients and other inorganic pollutants such as metals. Still, some of these support materials seemed adequate for the development of the biotic CWS components.…”

The Use of Blast Furnace Slag for Removal of Phosphorus from Wastewater in Sweden—A Review

“…These researchers investigated a number of different filter materials (both natural and man-made materials) available in Sweden, with regard to their capacities to remove P from a variety of wastewaters. Among these materials, blast furnace slag (BFS) has attracted attention by several researchers, not only in Sweden but also elsewhere in the world [11][12][13][14][15][16][17].…”

“…Brogowski and Renman [37] suggested opoka, siliceous bedrock, heated in a way that transformed CaCO 3 into CaO, which is a more advantageous form of calcium to which P can be attached. Compared to BFS materials that have been produced in other parts of the world and investigated by researchers outside Sweden, e.g., in Japan [38,39], Australia [11] and Germany [13] the Swedish slag is rich in MgO and Al 2 O 3 , but have much lower CaO content [5]. If the CaO content in the Swedish produced BFS could be higher through some kind of treatment, larger amounts of P might be removed by the BFS.…”

Use of Two Industrial Wastes as Soil Amendments: Effect on Dissolved Reactive Phosphorus in Runoff

“…Blast furnace slag and electric arc furnace slag have been extensively explored as substrates for P removal from constructed wetland systems, both in laboratory and field experiments (Westholm, 2006). Many research reports have proven the ability of BFS to effectively remove P from constructed wetlands (Camargo Valero et al, 2009;Grüneberg and Kern, 2001;Sakadevan and Bavor, 1998;Mann, 1997). Blast furnace slag has also been reported to remove 99 to 100% of P in aquatic systems (Sheng-Gao et al, 2008;Oguz, 2004).…”