Sustainability assessment and comparison of efficacy of four P-inactivation agents for managing internal phosphorus loads in lakes: sediment incubations

Abstract

A novel application of a continuous flow incubation system (CFIS) was used to assess four phosphorus (P) inactivation agents-alum, Phoslock TM , a new modified zeolite (Z2G1 or Aqual-P TM ), and allophone-when used as sediment capping agents to manage internal P loads in lakes. The CFIS technique allowed combined efficacy and sustainability assessment, including: (1) flux measurements during simulation of stratified (anoxic) and mixed (aerobic) conditions on the same sediment through multiple cycles to assess the longevity of a range of product doses; (2) simulation of a summer algal bloom collapse and subsequent burial of the products; and (3) investigation of non-target effects on nitrification and denitrification processes at the sediment-water interface. Minimum P-removal dose rates were found to differ substantially at 80 g m -2 for alum, 190 g m -2 for Z2G1, 220 g m -2 for allophane and 280 g m -2 for Phoslock TM , for similar capping layer thickness of about 2 mm, and would be effective for at least 4 years. All products temporarily suppressed nitrification and denitrification under aerobic conditions, and it may be important to minimise product application to any permanently aerobic zones, such as the littoral areas of a lake. While the aluminium (Al)-based products did not enhance Al fluxes in the CFIS, lanthanum (La) was released at a near constant rate of around 2 mg La m -2 day -1 from the Phoslock TM treatments over a period of at least 14 days. Spatial variability of sediment P, bioturbation, and burial are factors that will affect upscaling these results to a whole lake.

Adsorption of phosphate from water on lake sediments amended with zirconium-modified zeolites in batch mode

“…termed P-capping agents; Meis et al, 2012Meis et al, , 2013Spears et al, 2013a;Wang et al, 2013aWang et al, , 2013b, etc. Among these methods, in situ P immobilization technology, which involves adding the Pcapping agents into sediments to increase the P binding capacity of the sediments or placement of a layer of the P-capping agents at the sediment-water interface to create a barrier between the sediment and the overlying water, have gained a great deal of attention by many researchers and is considered as a promising method for controlling the internal loading of P in lakes (Gibbs et al, 2011;Márquez-Pacheco et al, 2013;Meis et al, 2012Meis et al, , 2013Reitzel et al, 2013;Spears et al, 2013aSpears et al, , 2013bvan Oosterhout and Lürling, 2013;Wang and Pei, 2013;Wang et al, 2012;Wang et al, 2013a;Wang et al, 2013b;Wang et al, 2013c;Wang et al, 2013d).…”

“…In recent years, the application of some P-capping agents such as the lanthanum-modified bentonite clay (Phoslock ® ) and the aluminum/ferrum based drinking water treatment residuals (Al/Fe based WTRs) to control the internal loading of P from sediments into the water column have been investigated (Gibbs et al, 2011;Márquez-Pacheco et al, 2013;Meis et al, 2012Meis et al, , 2013Reitzel et al, 2013;Spears et al, 2013aSpears et al, , 2013bvan Oosterhout and Lürling, 2013;Wang and Pei, 2013;Wang et al, 2012;Wang et al, 2013a;Wang et al, 2013b;Wang et al, 2013c;Wang et al, 2013d). However, these P-capping agents are suffered from some drawbacks.…”

Assessing the mode of action of Phoslock® in the control of phosphorus release from the bed sediments in a shallow lake (Loch Flemington, UK)

“…Cycling of P between lake sediments and the water column (internal P-loading) can delay the recovery of shallow lakes following reductions in external P-load (Marsden, 1989;Sas, 1989;Søndergaard et al, 2003;Jeppesen et al, 2005). Various methods have been trialled to 'speed up' the recovery process by reducing internal P-loading (Cooke et al, 2005;Hupfer and Hilt, 2008;Hickey and Gibbs, 2009), including sediment removal (Hupfer and Hilt, 2008), hydraulic flushing (Hosper and Meyer, 1986), sediment capping using modified local soils (Pan et al, 2012) and the application of active P-stripping/ sediment P-capping agents (hereafter termed P-capping agents; Gibbs et al, 2011). P-capping agents are designed to increase the P-binding capacity of sediments in order to increase P-retention in bed sediments.…”

Effects of Dredging and Lanthanum-Modified Clay on Water Quality Variables in an Enclosure Study in a Hypertrophic Pond

“…The subsequent increase in phosphate in the LMB-treated enclosures (Appendix A, [23]) clearly points to inefficient P interception. In fact, when these enclosures developed anoxia both an increase in filterable Fe and phosphate could be observed (Appendix D), while the P efflux from the sediment should have been reduced strongly [68]. A relatively low phosphate reduction of 35-40% has also been observed when lake water with an algal bloom was treated with LMB, where the authors pointed out that humic substance could have played a role [14].…”