Abstract:

A pilot test of low-concentration wastewater in ethylene production treated by coupling isolated-aeration biological filter and ozonization was conducted. The effects of different operation parameters such as the hydraulic retention time (HRT) , the ozonized air flowrate , the dissolved oxygen concentration and the backwashing on the degradation of pollutants including COD _cr,ammonium-nitrogen , volatile phenol , sulfide and oil were investigated.
Moreover , the degradation mechanism of low-concentration ethylene wastewater via the coupling treatment was analyzed.Experimental results show that , with a wastewater feed flowrate of 0. 8 - 1. 5 m³/h ， a low ozone dosage of 0. 5 - 1 mg/L, a HRT of 1. 3 - 2. 5h , and when the contents of inf1uent COD_cr ,ammonium-nitrogen , volatile phenol ,oil and sulfide are respectively not more than 100 , 5. 3 , 3. 0 , 3. 5 and 1. 29 mg/L , the effluent is of an average COD _cr of  29. 1 mg/L , an average oil content of O. 38 mg/L , a maximum ammonium-nitrogen content of less than 0. 4 mg/L ,a maximum volatile phenol content of 0. 12 mg/L and a maximum sulfide content of 0. 135 mg/L , and the average removals of COD_cr, oil , ammonium-nitrogen , volatile phenol and sulfide respectively reach 63. 1 %, 84.2% ,96. 8% , 89. 8% and 88. 6%. It is thus concluded that the effluent after the coupling treatment satisfies the demands of recycled and reused water.

Key words: ozone, oxidation, biological filter, coupling, ethylene wastewater