Surface water contaminated with arsenic as a result of anthropogenic activities or naturally occurring events is harmful to health and the environment. Thus, the research proposed to use solar energy as a technology for the treatment of arsenic-contaminated water from the Rimac river in Lima, Peru. The treatment consisted of using solar radiation with an average rate of 550.18 W/m2, with the presence of iron wire as an absorbent and lemon juice as a catalyst. The results showed that arsenic was reduced from 1.64 mg/L to 0.128 mg/L (92.2% efficiency), using 4g of iron wire and 6 mL of lemon juice. The resulting treatment data were statistically processed by multiple linear regression, and the linear model was found to be: Y = 0.417 + 0.0930X1 + 0.0234X2 - 0.0014X3; where X1 is the amount of iron wire (g), X2 is the lemon juice (mL) and X3 is the solar radiation (W/m2). Finally, it is concluded that the method is effective in the reduction of arsenic in surface water with the advantage of being easy to use, low cost and environmentally friendly.