Study On The Treatment Of Oil In Restaurant Wastewater

Restaurant wastewater is a kind of water with high oil content and high COD value. Animal oil and vegetable oil are main contaminators. The reduction of oil content has the direct affect on the drop of COD value. In this paper, aimed at dealing with oil content in restaurant wastewater, the process of oil/water separation by gravity, air-flotation and filter is analyzed in theory. On the basis of quality and quantity of restaurant waste effluent, the gravity and air-flotation separator combined with filtering system process is designed. With the principle of hydraulic shrink and magnify theory, the measurements of the separator models are calculated and designed. The performance of the oil removing system is studied by experiments.It is found that:1. The small aperture device used for air-flotation can strengthen the process of oil/water separation. The diameter of oil drop more than 40μm can be removed by the separator.2. Surface hydraulic load, oil content in influent, stages of ail-flotation, ratio of air against water are four important parameters.3. The experiment was carried on, and the result indicated that: the surface hydraulic load should be controled at 0.4m/h;the separator has good adjustability to the fluctuating oil content in influent, when the oil content in influent varies from 30 to 150mg/L, the oil content fluctuation in effluent is low;the air-flotation is beneficial for oil/water separation, the selectivity of air-flotation stages and ratio of air against water are crucial to oil removal efficiency of the separator, the result is better for air-flotation in first stage than both in the first two stages or in all three stages, the ratio of air against water controled about 43.75ml/(L/cm) can attain sound effect.4. Modified fiber ball filter combined with air-flotation three stage oil/water separator, the results indicate that: the oil content can be reduced further oil removal efficiency can be enhanced, the filtration rate is high and modified fiber ball can be washed easily;in the tentative experiment, the diameter of oil drop is less than 10μm in the effluent;the oil content in influent can affect more than the filtration rate.5. In the oil intercepting experiment, it can be roughly estimated that, the intercepting ability of the modified fiber ball is 1100-2600 grams oil per cubic meter fiber ball.It is effective to remove oil content in restaurant wastewater by using air-flotation three stage oil/water separator combined with modified fiber ball filtration system. And it has promising application foreground.