Landfill leachate treatment by an anaerobic process enhanced with recyclable uniform beads (RUB) of seaweed species of Gracilaria

Landfill leachate containing heavy metals was subjected to anaerobic treatment by using an upflow anaerobic sludge blanket (UASB) reactor combined with recyclable uniform beads (RUB) of seaweed species of Gracilaria. During the treatment of leachate without the RUB, the organic loading rate (OLR) was increased in stages from 0.125 to 0.833 kg chemical oxygen demand (COD) m(-3)d(-1) and further increased to 2.50 kg COD m(-3)d(-1) by reducing the hydraulic retention time from 4 to 1 d. Results showed that the COD removal efficiency declined from 65.70% to 9.33% when the OLR was increased from 0.125 to 2.50 kg COD m(-3)d(-1). The removal of cadmium (Cd), nickel (Ni), and iron (Fe) was almost constant, regardless of the OLR (around Cd [36%], Ni [32%], and Fe [29%]). However, when the leachate was treated with UASB + RUB, a complete removal (100%) of Cd, Ni, and Fe was witnessed. Fourier-transform infrared spectrometer spectra of RUB pre and post leachate treatment indicated clearly that RUB was the major component that worked to remove the heavy metals. The functional groups that were responsible for the removal of heavy metals were hydroxide (O-H), amine (N-H), carboxylic (C=O), amide (N=O), sulfinyl (S=O), and sulfides (C=S).