International Academy of Ecology and Environmental Sciences Proceedings of the International Academy of Ecology and Environmental Sciences 2220-8860 9 4 2019 12 1 Acidification of recalcitrant effluent: Optimization of time and reagent volume 164-174 EN Maria Luisa P. R. Alves Elisangela Maria R. Rocha Samara Teixeira Pereira Elson Santos da Silva Romildo H. dos Anjos Junior http://www.iaees.org/publications/journals/piaees/articles/2019-9(4)/acidification-of-recalcitrant-effluent.pdf> Hydric bodies suffer from the discharge of recalcitrant effluents, such as landfill leachate, which requires advanced treatment, such as photo-Fenton. Though, it requires a acidification step of effluent to adjust it to pH=3. The objective of this work was to apply sulfuric acid (H2SO4) and hydrochloric acid (HCl) in different concentrations in the gross leached, and decide which of one would be better in relation to time optimization and volume of acid spent. Potentiometric curves and trend lines were formulated by the polynomial regression degree 5 and the hypothesis test was used to determine the volumes to be added, to achieve the desired pH (pH 3). The H2SO4 (6 N) presented better results in the average time control of 6 min 35 s - while spending 27 min 50 s without the potentiometric curves. From hypothesis test, sulfuric acid achieved the best result when compared to the final, theoretical and real volume used in the acidification of the leachate.