Study Of Oily Wastewater Treatment By Agricultural Fibers Filtration

The filtration technique utilizing agricultural fibers to purify the oilfield sewage is a novel method which breaks through the concepts of traditional filtrating and backwashing, for the filter medium derives from farming and forestry residues which can be treated simply as high energy fuel without backwashing after use. In this way, this technique can make waste profitable with effective filtering. Based on the domestic and overseas literatures, the thesis elaborates on the invention of a simple and effective preparation method of filter medium, and the oil-absorbing abilities of several agricultural fibers which are measured by static experiment. Then select A as filter medium to perform the filtration experiment. At last, further screen the filter medium types to optimize, and treat them simply after use.According to the static experiment, it is found that the agricultural fibers can absorb oil fast, and their oil absorptions all reach the maximum after 25s. By comparing, it is revealed that agricultural fibers of Gramineae absorb most oil rapidly, while those of bast agricultural fibers perform worst. The A performs the best oil absorption ratio of 8.6 g·g-1, which is close to that of synthetic polypropylene fiber (10g·g-1). The oil-absorbing ability of medium is related to the surface property and internal structure which can impact on the filtration performance directly. Thus using the A as filter medium to research the parameters such as the medium particle size, bulk density, hydraulic loading, original oil concentration, PH and bed depth. Series of experiments show that smaller particle size can improve the filtration; bulk density can impact on the head loss greatly, and exist optimal value; decreasing the hydraulic loading can prolong the penetration time a lot, and 6m·h-1 can be considered in practice for at 6m·h-1 the filtration performs best; decreasing the original oil concentration can prolong the penetration time a lot, while the filtering effect decreases; PH can change the properties of sewage and filter medium, the filtering effect is best in weak acidity condition, while worst in alkalescency condition; the penetration time lengthens with the increase of the depth of filter bed, while the cumulative pollutant of a unit mass media decreases.From the type-screening experiments and optimization experiments, it is obtained that the B and C can perform great filtering effect, which is related to their structure and composition, i.e. suitable surface oil-absorption and large oil-storage cavity. The optimization experiments choose B and C as filter medium of double-deck experiment, for they have better filtering effect. It is found that the filtering effect improves significantly, and the penetration time increases by 56% over that of single-deck experiment using reed fibers, while the unit mass filter medium cumulative pollutant carrying quantity increases by 75%. Hence, double-deck filter medium in reasonable collocation can help the filter bed perform at full steam, and improve the filtering effect. The filter medium can be treated expediently by simple extrusion after use.