Filtration is one of the oldest techniques and by far the most widely applied in water treatment operations. It is considered one of the most effective methods for purifying waste water. Sand filtration consists of passing water loaded with suspended and colloidal matter through a filtering material in order to clarify it. In Ouargla region, wastewater is evacuated in a closed system without any treatment, which presents a natural risk to public health and endangers the sustainability of agriculture and the environment. In this modest study, two sand samples of different grain size and shape were used as the filter bed. Several filters were constructed using two types of sand with the same dimensions and different characteristics. The filter was exposed to clogging during the operation, which is prejudicial to the filtration process. For this reason, our study aims to see the influence of the type of sand on this process and analyze the phenomenon of filter clogging: the causes of its appearance, its types and their location as well as the parameters governing it. The most important thing is to evaluate the quantity of organic matter deposited in the different layers of the filter, and see its distribution as a function of time over the whole the depth of the filters. This study shows that the sand filter is subjected to progressive clogging. This clogging is classified into three fragments: mechanical, physical and organic. The study showed that the finer the granulometry, the greater the accumulation of Organic Matter. From the third week onwards, the formation of a biological film has been observed, which allows for very thorough purification. In other words, a quantity of suspended matter settles as the biomass degrades the organic matter.