Slow sand filtration is a simple technology that is capable of achieving high standards of treatment without the use of costly chemicals and energy. It can be constructed with the available local materials, labor-intensive operations, and maintenance. Despite being a well-known technique and simple in technology, application in water treatment is not effective in high turbid surface water. Therefore, the study aimed to increase the slow sand filtration efficiency. Experimental study was done by constructing different dimensions of Horizontal roughing filters and tested the filtration capacity under different level of turbidity. Descriptive and ANOVA statistical analysis were employed for data analysis. The results showedthat the turbidity removal efficiency ranges 37-77%. High removal efficiency recorded in low level of turbidity and as the length of filter increase the removel effeicency significantly increased. From ANOVA analysis result, removal effeicency of the treatment unit significantly different between the treatment systems (constructed models). The study recommened that a horizontal roughing filter has an effective water treatment on the removal efficiency is 79% when the turbidity lower than 209 NTU surface water. Keywords: Horizontal Roughing Filter, HRF length, rainy season, Surface water;