Untreated agricultural and municipal waste poses a threat to environmental pollution, however, it can became valuable fertilizer after the appropriate treatment. The fertilizer can be prepared as compost and biochar, in which case it can have a positive influence on hydraulic and chemical soil properties. The use of composted sewage sludge and olive pomace, as well as the use of biochars from these materials, has become increasingly interesting due to their positive impact on soil structure and fertility, nutrient returns to the soil and crop yield. Organic waste is often rich in phosphorus, especially municipal sludge and can have an impact on hydraulic and transport processes in the soil. The influence of the application of bio-waste on soil and on water flow and transport processes can be quantified by numerical simulations, among other techniques. The aim of this thesis was to investigate the effects of biochar and compost produced from sludge from waste waters and olive pomace on hydraulic properties of soil, water flow and transport of phosphorus by numerical modelling using the HYDRUS-1D model. Two amendments were added (biochar and compost), from municipal sludge and olive pomace, which were applied at two application rates calculated on a P content basis (amendment rate containing P concentration according to the Croatian legislation, and at a rate ten times (10×) higher) to two soil types (Terra Rosa and rendzina). The mixed soil was placed in pots (20 treatments). The HYDRUS program was used for modeling of water flow and phosphorus transport (P) in the unsaturated soil zone, in this case on test pots. The numerical model was tested on the basis of data obtained from individual pots (termination of percolate and concentration of PO4-P. Soil hydraulic parameters were analyzed by HYPROP-FIT system, for individual combinations of municipal sludge and olive pomace. The results showed high phosphorus sorption in all treatments (Kd 21.24 to 53.68 cm3 g-1) and high reliability of the van Genuchten model in inverse modelling (R2 0.93 to 0.99). Overall, the addition of compost of sewage sludge or olive pomace as compost or biochar in both cases improved water retention in Terra Rosa and Rendzina, but did not increase phosphorus mobility in that soil, which proved to be a sustainable source of carbon and phosphorus-rich materials.