This work was developed to adjust the equation of head-loss, describing the head-loss process with the depth and operation time of organic filter utilized in treatment of swine wastewater. Sugarcane bagasse, sawdust and coffee husk, by-products of agricultural and agro-industrial activities, were used to fill the filter columns. Data on head-loss in different depths with the time of organic filters operation were collected to analyze the head-loss evolution. In head-loss equations as function of depth and filter operation time high values were obtained for the coefficients of determination and the regression coefficients presented, in almost, significant at 1% probability, predicting the behavior of the filters, constituted of sawdust, sugarcane bagasse and coffee husk. The variables, operation time and the filter columns depth, of the three filtering materials, presented quadratic behavior in the estimate of the total head-loss. The ideal time of the filters uninterrupted operation, without exchange of filtering materials, was approximately 1,5 h and, after this time, the filter material should be replaced.
filtering; wastewater treatment; pressure drop
