Treatment of a sanitary landfill leachate using combined solar photo-Fenton and biological immobilized biomass reactor at a pilot scale

Abstract

A solar photo-Fenton process combined with a biological nitrification and denitrification system is proposed for the decontamination of a landfill leachate in a pilot plant using photocatalytic (4.16 m 2 of Compound Parabolic Collectors – CPCs) and biological systems (immobilized biomass reactor). The optimum iron concentration for the photo-Fenton reaction of the leachate is 60 mg Fe 2+ L −1. The organic carbon degradation follows a first-order reaction kinetics ( k = 0.020 L kJ UV −1, r 0 = 12.5 mg kJ UV −1) with a H 2O 2 consumption rate of 3.0 mmol H 2O 2 kJ UV −1. Complete removal of ammonium, nitrates and nitrites of the photo-pre-treated leachate was achieved by biological denitrification and nitrification, after previous neutralization/sedimentation of iron sludge (40 mL of iron sludge per liter of photo-treated leachate after 3 h of sedimentation). The optimum C/N ratio obtained for the denitrification reaction was 2.8 mg CH 3OH per mg N–NO 3 −, consuming 7.9 g/8.2 mL of commercial methanol per liter of leachate. The maximum nitrification rate obtained was 68 mg N–NH 4 + per day, consuming 33 mmol (1.3 g) of NaOH per liter during nitrification and 27.5 mmol of H 2SO 4 per liter during denitrification. The optimal phototreatment energy estimated to reach a biodegradable effluent, considering Zahn–Wellens, respirometry and biological oxidation tests, at pilot plant scale, is 29.2 kJ UV L −1 (3.3 h of photo-Fenton at a constant solar UV power of 30 W m −2), consuming 90 mM of H 2O 2 when used in excess, which means almost 57% mineralization of the leachate, 57% reduction of polyphenols concentration and 86% reduction of aromatic content.