Eutrophication control using a novel bentonite humic-acid composite material Bephos™

The main objective of the present study was to estimate the efficiency of Bephos™ as an active capping agent preventing the phosphate release from eutrophic lake sediments. Bephos™ was compared with unmodified bentonite (N-bentonite) and natural zeolite (N-zeolite), in a ratio 1/10/10 respectively. Bephos™ as a P-inactivation agent resulted in about ∼96.6% reduction of the phosphate flux and ∼75.2% reduction of the ammonium flux from the sediments respectively. N-Zeolite and N-bentonite as capping materials resulted in about 64% and 91.8% reduction of the phosphorus flux and in about 70% and 35.6% reduction of the ammonium flux from the sediments respectively. Moreover, an additional purpose of this study was to investigate the different P-forms present in sediments, their contributions to the P-loadings of the ecosystem and also the effect of Bephos™ amendment on P-binding properties of sediments. The results show that Bephos™ restrained P release from the sediments, reducing the proportion of P-mobile in sediments, which was transformed into non-reactive species. The application of Bephos™ caused an increase in the mass of P present in the more refractory 'apatite bound P' fraction compared to P-mobile, and also more P was stored in the residual P fraction of sediment post-application.