Enhancing Percolation in Phosphatic Clay Using Diatoms under Laboratory Conditions

Abstract

Clay settling areas are large impoundments brought about by phosphate mining with water-holding capacity that renders it very poor for agriculture and crop production. This study aims to enhance water percolation in phosphatic clay using porous diatom frustules under laboratory conditions. Phosphatic clay collected from settling areas was brought to the laboratory for the experiment. Diatom frustules were purchased commercially and dry samples of the diatom, Didymosphenia were provided by the University of Colorado-Boulder. Oven-dried clay was mixed with diatom frustules into 125 mL centrifuge tubes following a 1:1 volume ratio as experimental set-ups while pure phosphatic clay was used as control. Deionized water was poured into each set-up and the percentage of unpercolated water overlying the sediment, water retained in the sediment particles, water that percolated and passed through the hole of the centrifuge tube were monitored for 48 hours. Results showed that the addition of diatom frustules enhances the percolation of water in the sediment mixture especially those with Didymosphenia frustules. However, this mixture also showed higher percentage of water retained in the sediment particles which could be attributed to the high carbon and organic content brought about by the presence of stalks which is a major component of this species morphology. Considering how Didymosphenia disturbs freshwater habitats, proper management may render it useful for the mitigation of clay settling areas in the land environment. The implication of this on crop production remains to be explored and further in situ experimentations need to be conducted.\n\nIMPORTANCEClay settling areas abound in places where phosphate mining is conducted. The very fine particles and the chemical property of this phosphatic clay allows it to hold water more than normal clay sediments making the area unstable and less suitable for agricultural use. Studies show that mitigative measures to enhance surface drainage is very costly leaving most areas barren and unused. Diatoms are unicellular algae in various size and shapes with silicified cell walls that are porous and are ubiquitous in aquatic environments. The significance of our research is being able to demonstrate the potential use of diatoms, most especially the genus Didymosphenia which is regarded as an environmental threat to some habitats, in mitigating the drainage problem in clay settling areas by mixing phosphatic clay with diatom frustules. This process is cost-effective and more importantly provides utilization of a resource that is regarded as nuisance in freshwater environments.