Phosphorous control in a eutrophied reservoir

Abstract

Water in lakes and reservoirs accumulate phosphorous (P) from both internal and external loads. The external P load (EPL) coming from the watershed is considered to be the main cause of eutrophication of water bodies, and control strategies therefore focus on its reduction. However, algae blooms and anoxic conditions often continue even after EPL have been controlled, being the internal P load (IPL) originating from the sediment the main sources of P. To assess the efficiency of the adsorbent Phoslock (a modified bentonite) in controlling P concentrations in water and immobilize releasable P in sediments, mesocosm trials were carried out in a eutrophied reservoir and a model was described and applied that determines the amount of adsorbent and the application frequency necessary to control P concentrations in a eutrophied reservoir. The mesocosm trials confirm that Phoslock reduced P concentrations to or below the limits that define water in mesotrophic state, in approximately 2 weeks. The modeling results suggest that periodic reapplications of the adsorbent are required, unless EPL is reduced by 36 %, which allows the P concentrations in the water column to be constant. Such reduction in EPL would allow future applications of the adsorbent to be required only for control of IPL. The developed model allows planning remediation actions by determining quantities and frequencies for application of adsorbents for P control in eutrophied lakes and reservoirs.

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.…”

Internal phosphorus load in a Mexican reservoir: Forecast and validation

“…Information on the sediment depth from where the release of P occurs (20 ± 5 cm) and the density of the sediment (0.17 ± 0.03 kg dry wt/L) was obtained from Márquez‐Pacheco et al ; the average surface area of the reservoir is 1680 ha. The results of P release per unit area were plotted, and equations were adjusted to describe the P release for sediment areas with specific Eh.…”

“…where M ¼ P released by sediment area (mg/m 2 ); C ¼ P concentration for each increase in Eh (mg/L); x ¼ sediment:water ratio (g/L); r ¼ sediment density (kg/m 3 ); L ¼ sediment depth where P release occurs (m); and 1000 ¼ conversion factor (g/kg). Information on the sediment depth from where the release of P occurs (20 AE 5 cm) and the density of the sediment (0.17 AE 0.03 kg dry wt/L) was obtained from M arquez-Pacheco et al [26]; the average surface area of the reservoir is 1680 ha. The results of P release per unit area were plotted, and equations were adjusted to describe the P release for sediment areas with specific Eh.…”

A theoretical and experimental study on the P-adsorption capacity of Phoslock™

“…Mathematical modeling is generally considered as a powerful tool in order to clearly understand physics and chemistry in phosphates reducing processes along with Phoslock TM use [14]. Furthermore, computational fluid dynamics (CFD) can be used to analyze complex systems involving fluid flow, heat transfer and mass transport processes.…”