Mathematical model to predict the energy potential of UASB-based sewage treatment plants

This work aimed at developing a mathematical model to predict the energy potential of biogas and sludge produced in a UASB reactors (from 1000 up to 1 million inhabitants). The model was developed based on Monte Carlo simulation to estimate the energy potential of these by-products in three scenarios that correspond to different sewage and sludge characteristics. Also, in order to determine the energy potential of the sludge, low and high solid contents of mechanically dehydrated sludges were considered. For a typical scenario the energy production of the by-products at Sewage Treatment Plants (STPs) operated with UASB reactors ranged from 1.55 to 3.50 MJ m^-3 sewage and 1.53 to 3.32 MJ m^-3 sewage for high solid content (HSC) and low solid content (LSC), respectively. The biogas potential corresponds to at least 91.0% and 96.0% of the total by-products energy for HSC and LSC, respectively, being the main by-product in terms of energy in UASB-based STPs. The linear regression between the variables Population-inhab (axis y) and By-products energy potential-MJ d^-1 (axis x) for dehydrated sludge with HSC and LSC were y = 0.4004x (R2 = 0.93) and y = 0.3821x (R2 = 0.92), respectively. Significant linear regression coefficients and fit to monitored data indicate that the model can be used to estimate the energy potential of the by-products (biogas and sludge) generated in UASB reactors. (author)