Figure 2. Laboratory-scale experimental biotrickling filter system. (1) Air compressor; (2) Pressure gauge; (3) Needle Valve; (4) Air filter; (5) Mass flow controller; (6) Check valve; (7) Humidification; (8) Mist removal chamber; (9) H₂S generator; (10) Peristaltic pump; (11) Solutions of Na₂S and HCl; (12) Lead acetate solution; (13) Mass flow controller; (14) Flowmeter; (15) Biotrickling filter; (16) Air outlet; (17) Recycling pump; (18) Solution recycle; (19) Solution make-up.