Sequential treatment of acid mine drainage using various treatment media in a permeable reactive barrier

• Main Author: Turingan, Casey Oliver A.
• Format: text
• Language: English
• Published: Animo Repository 2023
• Subjects: Acid mine drainage—Purification; Chemical Engineering; Civil and Environmental Engineering
• Online Access: https://animorepository.dlsu.edu.ph/etdm_chemeng/10; https://animorepository.dlsu.edu.ph/context/etdm_chemeng/article/1009/viewcontent/Sequential_treatment_of_acid_mine_drainage_using_various_treatmen_Redacted.pdf
• Institution: De La Salle University

Passive treatment of acid mine drainage (AMD) uses limestone as its most common material due to its abundance and alkaline-generating capacity. However, its treatment capability is severely limited when metal hydroxides precipitate and minimize its dissolution, rendering limestone inert. In this study, laterite mine waste (LMW) and concrete waste were used in sequence with limestone to increase the efficiency and capacity of the treatment system. A full-factorial batch test was done to determine the optimal sequence of these materials based on the pH increase, and metals and sulfates removal of the AMD. A constant ratio of 0.75 mL AMD/ g media was maintained with a 15-minute retention time in each treatment material. The system with limestone, LMW, and concrete waste present in this sequence achieved the highest treatment efficiency. The sequence increased pH to 8.08 and removed 38.90% Fe, 94.30% Ni, 71.76% Al, and 51.69% sulfates. A semi-batch test followed to determine the treatment capacity of the optimal sequence. The results show an initial increase in pH from 2.4 to 10.80 which becomes constant around pH 7 starting from the 10th batch of AMD treatment. Calcium levels were well above the initial concentration and stabilized around 700 ppm. A 32.95% reduction in sulfate was initially observed but returned to near initial concentration by the 8th batch of AMD. Iron, aluminum, and copper were consistently lowered to concentration levels well below the standard set by the DENR Administrative Order (DAO) 2016-08, as amended by DAO 2021-19. Using PHREEQC, it was determined that the most common precipitates present in the effluent were Fe and Al minerals. Additionally, only 69% and 66% of Ca and SO4 were present as ions, respectively. Thus, the use of limestone, LMW, and concrete waste in sequence has the potential to be used as a passive treatment system, or a part thereof, for the removal of Fe, Al, and Cu in AMD.