Remoção de fósforo em estação compacta de tratamento de esgotos sanitários através de precipitação química

Abstract

The need to produce high quality treated wastewater to the reuse in urban use and mitigation of the effects of eutrophication in receiving water bodies has become indispensable. The establishment of sewage treatment systems characterized by low cost and reduced environmental impact today is paramount, and if so, required the removal of nutrients. The use of physical-chemical processes for removal of nutrients is widely used technology, getting increasingly promising results. The phosphorus is in these nutrients, is directly responsible for environmental problems such as eutrophication of water bodies receivers. Thus, this work proposes to adapt the technology of UASB reactor followed by aerated submerged biological filter (FBAS) to promote the removal of P adequacy in accordance with relevant legislation. The research was divided m three stages: research and jar-test for selection of dose, type of coagulant aid for coagulation and to remove phosphorus from the effluent produced by WWTP-UFES (Step 1), removal of P scale using association UASB + BF aerated and non aerated (Step 2) and development of mathematical model for removal of phosphorus by the addition of ferric chloride (Step 3). Step 1 showed that the best option for removal of P in the WWTP study was the use of FeCl3 75mg / L as coagulant, which reached the removal efficiency of 77%. The application of coagulant scale (step 2) achieved the removal efficiencies of 66% for Ptot and PO4 3- from 51% in aerobic polishing, and 11% for PO4 3- in polishing anaerobic. The results were quite promising for removal of organic matter, solids and turbidity, achieving removals of respectively 76%, 92% and 77% in the aerobic stage and 47%, 92% and 77% for the anaerobic stage. In Step 3, factors such as pH, initial dose of Fe and PO4 3- were used as initial parameters, and the model was based on 11 equations of equilibrium in the liquid phase and solid phase 4. The system resulting from the mathematical model was solved numerically by iterative process in Mathcad ® software. The effect of pH and residual phosphorus in the liquid phase were evaluated, and removal from the model compared with the observed scale. Removals exceeding 90% were found at different pH values, in condition of excess iron (Fe: P = 3.22). Significant differences between the model results and scale removal of phosphorus was observed, which could be attributed to factors associated with the behavior of biomass in anaerobic granules.