Biodegradability enhancement by wet oxidation in alkaline media: delignification as a case study.
Nowadays many industries are considering the recycling of process waters as a way of improving environmental safety, preventing pollution, and avoiding the loss of valuable production materials. One industry in the forefront of this trend is the pulp and paper industry. Lignin is a pollutant present in the mill process waters and such macromolecules can cause problems during biological treatment of process waters. Wet oxidation (WO) is a process that can be used as a pre-treatment method for lignin fragmentation and improvement of biodegradability. Wet oxidation (WO) under alkaline conditions permits faster lignin fragmentation than the conventional WO process and, therefore, should favour biodegradability improvement. In this study, the experiments were carried out in a high-pressure batch reactor with an alkali lignin solution at temperatures up to 438 K, an alkali concentration of 1.5-3.5 g l(-1) and an oxygen partial pressure of 0.4 to 1.5 MPa. At an alkali concentration of 3.5 g l(-1)1 and 0.4 MPa of oxygen partial pressure, an increase in BOD/COD ratio was achieved from an initial 11% to 71%. The experiments also showed that the amount of small molecules in the solution measured by Immediately Available BOD (IA BOD) depends on the amount of alkali added and the operating temperature.
Laboratory of Chemical Engineering, Lappeenranta University of Technology, Finland.
S
S
Verenich
J
J
Kallas
D001673:Biodegradation, Environmental; D003247:Conservation of Natural Resources; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste; D008031:Lignin / Q000378:metabolism*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D010209:Paper; D014867:Water
D007220:Industrial Waste; D014867:Water; D008031:Lignin; D010100:Oxygen