Using desulfurization slag as the aquacultural amendment for fish pond water quality improvement: Mechanisms and effectiveness studies

Abstract The objective of this study was to evaluate the potential of applying desulfurization slag (DS) as pavement materials and amendments in the aquacultural industry for water quality improvement. The results of characteristic analyses and a mobile factor calculation show that the bonding patterns of heavy metals in DS were stable and had low bioavailability and mobility. DS can effectively adsorb ammonia and phosphate according to the pseudo second-order kinetics model. The adsorption isotherm for ammonia can be described by the Langmuir model. Both the Langmuir and Freundlich models can be used for phosphate adsorption isotherm evaluation. Ammonia adsorption involved physical adsorption, and the mechanisms for phosphate removal included adsorption and chemical precipitation. The adsorption of ammonia by DS was a non-spontaneous endothermic process, and the adsorption of phosphate was a spontaneous exothermic process. The results from excitation emission fluorescence matrix analysis show that the organic substances in the fish pond with DS addition included a soluble microbial product, protein-like substance, and humic acid-like substance. This indicates that algal growth and biomass accumulation could be enhanced by DS addition because the released trace elements and hydroxide ions from DS are beneficial to algal growth. Using DS as an amendment and construction material for the fish pond would increase the water alkalinity and prevent acidification of pond water. The results indicate that DS can be used in the aquacultural industry as construction material as well as for pH control and algal growth enhancement.