Removal of organic phosphorus and formaldehyde in glyphosate wastewater by CWO and the lime-catalyzed formose reaction.

Glyphosate (PMG) wastewater with 40-600 mg/L organic phosphorus (OP) and 1-4% CH2O was treated by catalytic wet oxidation (CWO) and the lime-catalyzed formose reaction to remove total phosphorus (TP) and improve biodegradability. Activated carbons (ACs) modified by H2O2 oxidation and thermal treatment with melamine were used as CWO catalysts and characterized by N2 adsorption/desorption and XPS. The CWO experiments were performed in an autoclave reactor at 110-130 °C and 1.0 MPa. The modified AC showed higher catalytic activity than the parent AC due to the introduction of nitrogen-containing functional groups, exhibited over 90% OP removal for various real PMG wastewaters, and had good stability for 20 consecutive CWO runs. The CWO effluents were further treated by lime at 80 °C to remove TP and CH2O. The treated effluents, containing 0.5-12 mg/L TP and 20-60 mg/L CH2O, showed good biodegradability with a BOD5/COD ratio of 0.31-0.41. The combination of CWO and lime is an effective treatment method prior to biological treatment for solving the problems of OP and CH2O encountered by the glyphosate industry.