Treatment of leachates from the Al Hoceima Landfill using bio-pretreatment and reverse osmosis: Performance, compliance and pollution index (LPI)

Leachate from the controlled landfill at Al Hoceïma (Morocco) has a high pollution load. This study evaluates a process combining biological pre-treatment and reverse osmosis. The raw leachate is characterized by COD ≈ 10,805 mg/L, BOD₅ ≈ 1,530 mg/L, NTK ≈ 5,253 mg/L (NH₄⁺ ≈ 4,827 mg/L), total phosphorus ≈ 58.6 mg/L, TSS ≈ 55.7 mg/L, pH ~ 8.5 and conductivity ~ 29.3 mS/cm. Bio-treatment abates ~66% COD, ~54% BOD₅ and ~93% NH₄⁺; reverse osmosis (RO) brings COD to 74.3 mg/L and BOD₅ to 39.7 mg/L. Total phosphorus falls to 0.426 mg/L. The permeate meets Moroccan standards for COD, BOD₅, TP, SS and pH (minor adjustment), but remains non-compliant for total nitrogen (NTK 257 mg/L). The leachate pollution index (LPI) falls sharply (> 80 to < 10). Management of the RO concentrate remains the main challenge. • Combined bio-pretreatment + reverse osmosis achieved > 97% COD removal. • Treated leachate met Moroccan standards for COD, BOD₅, TSS and phosphorus. • Leachate Pollution Index decreased from > 80 to < 10 after treatment. • Ammoniacal nitrogen reduced by ~93%, though NTK remains non-compliant. • Study proposes sustainable management options for RO concentrate.