||Petrochemical industries have great contributions to the economic development of Taiwan. However, some petrochemical processes emit wastewaters with high concentrations of organic nitrogen, ammonia and salinity, which makes the wastewaters difficult to be treated.|
In this study, wastewater samples with ammonia nitrogen in the range of 33.0-94.0 and average 63.5 mg/L and salinity with average chloride of 6,220 and sulfate 6,890 mg/L were tested for nitrification of the ammonia contained therein followed by denitrification in a sequencing batch reactor (SBR) with a total working volume of 4.0 L. The wastewater samples were taken from biological treatment ponds of a complex petrochemical plant located in central Taiwan. In the test, the nitrification reaction time was 24 hours with a daily water replacement rate of 2 liters and a mixed liquor suspended solids content in the range of 1,500-2,000 mg/L was kept during the reaction. The denitrification reaction was operated at a reaction time of 8 hours, a liquid temperature in the range of 25-35oC, and a dissolved oxygen concentration of less than 1.0 mg/L.
Results show that the sludge seeded with nitrifying bacteria taken from a fructose-wastewater treatment plant could promote nitrification of the ammonia nitrogen in the test wastewater to a degree of less than the government regulation of < 20 mg/L with a nitrification time of over 9 hours. Denitrificatin liquor supplemented with a sucrose dose of 125 mg/L could achieve a denitrification efficiency of 60% in the agitation time of 8 hours.
Analysis indicates that the nitrification and denitrification cost a total of NT $ 3.76 for treating a cubic meter of the wastewater.