In this paper we describe the route of the nanoparticles in the WWTP and demonstrate how to use the simulation flow sensitivity analysis within STOATTM program to evaluate the effect of variation of the constant, “k” in the equation v= kCh settling on fixed concentration of nanoparticles in sewage water from a primary tank of physical-biological stage. Wastewater treatment facilities are designed to remove conventional pollutants from sanitary waste. Major processes of treatment includes: a) physical treatment-remove suspended large solids by settling or sedimentation and eliminate floating greases; b) biological treatment-degradation or consumption of the dissolved organic matter using the means of cultivated in activated sludge or the trickling filters; c) chemical treatment-remove other matters by the means of chemical addition or destroying pathogenic organisms through disinfection; d) advanced treatment- removing specific constituents using processes such as activated carbon, membrane separation, or ion exchange. Particular treatment processes are: a) sedimentation; b) coagulation and flocculation; c) activated sludge; d) sand filters; e) membrane separation; f) disinfection. Methods are: 1) using the STOATTM program with input and output data for primary tank and parameters of wastewater. 2) generating a data file for influent using a sinusoidal model and we accepted defaults STOATTM data. 3) After this, getting spreadsheet data for various characteristics of wastewater for 48 hours:flow, temperature, pH, volatile fatty acids, soluble BOD, COD inert soluble particulate BOD, COD inert particles, volatile solids, volatile solids, ammonia, nitrate and soluble organic nitrogen. Findings and Results:1.Graphics after 48 hour;. 2.Graphics for parameters - flow,temperature, pH/units hours; 3.Graphics of nanoparticles; 4. Graphics of others volatile and non-volatile solids; 5. Timeseries data and summary statistics. Biodegradation of nanoparticles is the breakdown of organic molecules that may cause changes in the physical structure or the surface characteristic of the material.