Treatment of wastewater containing aromatic nitro compounds using the A2O-Mbbr method

Abstract

2,4,6-Trinitrotoluene (TNT) is widely used in explosives production. Since it is toxic and mutagenic to humans and animals, decontamination of TNT wastewater is necessary. Wastewater, containing TNT, from four factories in Vietnam producing industrial explosives were collected. The samples had different characteristics and varied widely, especially in terms of TNT concentration, depending on the technology and production management method at each plant. The TNT concentration ranged from 25 to 128 mg/l, chemical oxygen demand (COD) ranged from 128 to 650 mg/l, BOD5 ranged from 28 to 67 mg/l, NH4+ ranged from 23 to 325 mg/l, T-P ranged from 0.13 to 0.38, and pH ranged from 6.5 to 8.2. In Vietnam, removal of TNT is carried out using granular activated carbon adsorption and an incineration method. This method is expensive and generates secondary pollution. To overcome these drawbacks, the combination of an anaerobic-anoxic-oxic and moving bed biofilm reactor (A2O-MBBR) for treating TNT wastewater was investigated in this study. Reaction tanks of the A2O-MBBR sys-tem were supplemented with activated sludges, from a wastewater treatment station in Chemical and Electrical Engineering Company 15, containing biological preparations of nitrifying and denitrifying bacteria. The results showed that after 30 days under operating conditions of COD of 200-250 mg/l, MSLL of 1800-3000 mg/l, and DO of 5 mg/l, COD removal efficiency reached approximately 70-83%, the TNT concentration decreased by 91-99.7% (to approximately 0.5- 2 mg/l), and the ammonium concentration fell to 15-17 mg/l (reaching 42.8-66% removal effi-ciency after 24 h of treatment).