Research On Odor And Foam Control Technology In The Secondary Pollution Of Wastewater Treatment

The wastewater treatment facilities played an important role in reducing wastewater pollution. However, just because of its complicated particularity, most of wastewater treatment facilities have already become a new pollution source while they improve the environment. Such pollution can be seen as following four aspects: emission of odorous compounds, noise and foam pollution, inproper disposition of sludge. Aimed at the secondary pollution of wastewater treatment facilities, the controlling measure of odour and foam were studied.The application of pure oxygen in decrease of odour output was studied. Under normal pressure, compared with air aeration, pure oxygen aeration has the average removal rate of COD and NH3-N increased by 3% and 11.67%; the output of NH3 was 1/3.6 of air aeration, the output of H2S was 1/7 of air aeration.Compared with the atmospheric pure oxygen aeration, pressurized pure oxygen aeration has the higher removal rate of COD, NH3-N and less output of NH3,H2S. In the pressurized pure oxygen aeration, when the pressure increased from 0.06 MPa to 0.15MPa, the average removal rate of COD and NH3-N increased by 3.76% and 9.67%; the average concentration of NH3 reduced from 0.144mg to 0.061mg, and the average concentration of H2S reduced from 2.087ug to 0.659ug.For the odor has generated, deodorization effect and influence factors of chemical washing packed tower were studied. Under the conditions of this experiment, when the spray volume of Lye and acid wash was 1472L/h?m2 and 1811L/h?m2, the removal efficiency of H2S and NH3 was 97.04% and 79.08%. When the pH value of lye was controlled around 10.6, the removal efficiency of H2S was 92.72%. When the pH value of acid wash was controlled under 2, the removal efficiency of NH3 was 84.53%. When the packing layer height was 750mm, the removal efficiency of H2S and NH3 was 98.18% and 88.03%, and the removal efficiency had no significant increase when the height is higher than 600mm. When gas flow rate is 300L/h, the removal efficiency of H2S and NH3 is 99.38% and 93.06%. With the decrease of the gas flow rate, the removal efficiency would be increased. The results of orthogonal test indicated that, impact of factors was as follows: pH> gas flow rate> spray volume> packing layer height. The average outlet concentration of H₂S and NH₃ attained the first standard of Emission standards for odor pollutants.On the foam pollution, experiment studied on the use of foam separation technologies to control foam.Under normal circumstances, the results show that there are a lot of foam on aerobic pond surface, because the coking wastewater contains a large number of chemicals compounds which are easy to bubble. The use of this method can effectively control the foam around the experimental device.Liquid of the wastewater treatment plant foam was re-separated and enriched by foam fractionation. Removal rate and enrichment ratio of foam fractionation had some relativities with wastewater quality, but did not have regularity relativity with COD. When the height of wastewater was 9cm, enrichment ratio and removal rate reached the maximum 3.24 and 31.33%. When gas velocity was increased from 0.18cm/s to 1.06cm/s, enrichment ratio decreased 2.28, and removal rate increased by 27.37%. When the separation time was increased from 5min to 35min, enrichment ratio decreased 0.78, and removal rate increased by 11.30%. When the temperature was increased from 25℃to 75℃, enrichment ratio increased by 0.69, and removal rate increased by 25.50%. When the height of separation tower was increased from 38.5cm to 70.5cm, enrichment ratio increased by 1.30, and removal rate decreased 13.43%.The results of orthogonal test indicated that, factors that affect enrichment ratio were as follows: the height of separation tower> gas velocity> temperature> the height of wastewater; and factors that affect removal rate were as follows: the height of separation tower> temperature> gas velocity> the height of wastewater.Triangle odor bag method was simplified by introducing a concept which is correction factor. Laboratory assistant could use correction coefficient to correct the measured data when tested sample, to get the odor detection concentration of the sample, which is similar to the results comes from Triangle odor bag method. In the conditions of this experiment, the relative error of the simplified method was 9%¹4% in relation to Triangle odor bag method. In laboratory study, the simplified method was practical, and can be more rapid and simple determine odor concentration.