In recent years, biochar has been regarded as an efficient adsorbent in potable water treatment owing to its low-cost, larger surface area, functional groups, and carbon-negative texture. However, biochar might not have higher pollutant adsorption capacity owing to its heterogeneous texture and some surface characteristics. Furthermore, biochar can include both positive and negative charges depending on the pyrolysis temperature, which might decrease the adsorption capacity of biochar in order to remove anionic pollutant substances such as fluoride. In this study, the modification of biochar (B) by bentonite, which is a type of nanoclay (NC) for the treatment of fluoride polluted groundwater, was achieved. The nanoclay-assisted biochar (NAB) process for groundwater treatment was also investigated. This research developed a novel modified malt-dust-derived biochar by bentonite for efficient potable water treatment, obtaining new insights into NAB adsorption performance. The water samples were provided from Sarım and Karataş villages located in an arid/semi-arid region in Türkiye. The mixing ratios (NC:B) were 1:1, 1:2 and 1:4, respectively. The results demonstrated that the highest fluoride removal efficiency was achieved by using 15 g/L-groundwater of bentonite and biochar (1:1). Bentonite addition promoted the fluoride removal from groundwater by 18.1% on average. A groundwater remediation index (GRI) was developed and validated by a sensitivity analysis as a result of the Monte Carlo simulation following the NAB process based on treatment efficiencies and water quality parameters. The highest GRI was reported in the range of 0.983-0.99 as a result of the NAB process.