at most 5% (v/v) zero-valent iron particles, approximately 4% (v/v) clay particles, and approximately 91% (v/v) sand particles,

wherein, during flowing an amount of water through a fixed bed filter including the composition, the zero-valent iron particles are configured to oxidize the one or more per- or polyfluoroalkyl substances via a chemical oxidation reaction to generate at least one fluorinated carbon group and an oxidation-reaction-induced byproduct, the oxidation-reaction-induced byproduct including a portion of the one or more per- or polyfluoroalkyl substances, such that the oxidation-reaction-induced byproduct has a length smaller than a length of each of the one or more per- or polyfluoroalkyl substances, thereby promoting adsorption of the oxidation-reaction-induced byproduct by hydrophilic films surrounding the zero-valent iron particles, and thereby removing an amount of the one or more per- or polyfluoroalkyl substances from the water, and

wherein, during flowing the amount of water through the fixed bed filter including the composition, the zero-valent iron particles and the clay particles are configured to promote adsorption of the one or more per- or polyfluoroalkyl substances, thereby removing an amount of the one or more per- or polyfluoroalkyl substances.