The concept of utilizing a boron-containing landfill leachate by means of membrane techniques

Landfill leachate characterized by high concentration of boron and heavy metals causes serious environmental problem at Tarnowskie Góry (Poland). Typical elements, their concentration and ionic composition in wastewater are as follows: boron, up to 80 mg/dm³; Fe, 0.022 mg/dm³; Zn, 25 mg/dm³; Cd, 0.16 mg/dm³; Mn, 4.2 mg/dm³; Cu, 0.01 mg/dm³; Pb, 0.75 mg/dm³; Sr, 4.44 mg/dm³; Ni, 0.04 mg/dm³; Zr, 0.008 mg/dm³ and Cr, 0.004 mg/dm ³; Na⁺, 820 mg/dm³; Cl^-, 320 mg/dm³; SO₄^2-, 1130 mg/dm³; Ca ²⁺, 37 mg/dm³; Mg²⁺, 10 mg/dm³ at TDS of approximately 2.5 g/dm³. A rational utilization of such a complex leachate requires many effective steps, including aeration, alkaline precipitation of heavy metals, activated carbon adsorption, softening and finally boron removal. In this work, the strategy of the above-mentioned leachate utilization by means of membrane separation methods was discussed. An effective boron removal and concentrated boron solution preparation are of prime importance in the reduction of the cost of concentrate disposal. Based on our previous results we concluded that boron concentration might be efficiently reduced by means of RO or ED only at a high pH of leachate. Such a high alkalinity constricts a proper leachate pretreatment, i.e. heavy metal removal and chemical or membrane softening of leachate. Based on the aforesaid conclusions the concept of utlization of the Tarnowskie Góry landfill leachate was presented.