Performance of batch vacuum distillation process with promoters on coke-plant wastewater treatment

This paper presents a simple study of laboratory-scale vacuum distillation process with promoters (VDP) on coke-plant wastewater, which has the advantage that the chemical reaction and pollutants separation can be concurrent in one pot. The main parameters that evaluate the efficiency of VDP are conductivity, chemical oxygen demand (COD) and ammonia nitrogen compounds (NH3-N). The blank experiment, vacuum distillation (VD) process was also investigated for comparison. The effects of some operating factors, such as, vacuum degree of system, the temperature of wastewater and temperature gradient (ΔT) on the treatment efficiency were investigated in detail. And satisfactory results were obtained in the VDP system with caustic soda and slaked lime as promoters. It was found that high COD removal of 99.7% can be obtained in 180 min for caustic soda promoted system (the detailed condition: NaOH 2.0 g, vacuum degree −85 kPa, ΔT 11 °C). Meanwhile, near 100% NH3-N removal can be obtained simultaneously in this VDP process.