Experimental Study on Wastewater Treatment of Expressway Service Area in BAF
The removal effect of main pollutant which was in the wastewater of expressway service area was investigated in the up-flow biological aerated filter (UBAF) with different hydraulic loadings. The result showed that with the increase of hydraulic loading, the removal rates of the chemical oxygen demand (COD) and turbidity decreased. At hydraulic loading of 0.5 m3/(m2&#x2022;h), removal rates of COD and turbidity were 79.6% and 80.2% respectively, which were better than that of 56.5% and 48.7% at hydraulic loading of 1.25 m3/(m2&#x2022;h).
The effect of bed material heights on the performance of biological aerated filter
when the oxidation of organic content and the nitrification of ammonia are in the same bioreactor, the competition for space, oxygen and organic carbon between the heterotrophic and nitrifying populations in different media heights affect mass transfer reactions and performance of biofilm reactor. The results showed that as a down flow biological aerated filter(BAF) with granular media, the active layer of nitrifiers is deeper than heterotrophs in BAF. And the optimum media height for the removal of SS,COD and NH 3-N is 40 cm,60 cm and 80 cm respectively. The removal efficiency of SS,COD and NH 3-N is 79.1%,63.9% and 96.4% respectively under the influent COD and NH 3-N of 122.1 mgCOD·L -1and 14.84 mgNH 3-N·L -1, influent flowing velocity of 15.8 L·h -1, and air:liquid ratio of 3:1.
Control of activated sludge filamentous bulking—I. Effect of the hydraulic regime or degree of mixing in an aeration tank
Abstract Laboratory experiments were conducted on four activated sludge systems with various flow patterns. The systems were characterized by dispersion numbers which are a numerical expression of the degree of mixing. Perfect mixing has a dispersion number of infinity. The dispersion numbers in the four systems were ∞, 1·06, 0·17 and 0·033. All systems were operated at the same detention period of 8 h and approximately at the same sludge loadings. A mixture of starch and peptone was used as the substrate. The mixed cultures developed in the systems mentioned possessed average SVI values of 517, 300, 91 and 51 ml g −1 respectively. The high SVI values were caused by a high content of the filamentous microorganisms, which consisted mainly of Leucothrix and Sphaerotilus , in the developed mixed cultures. It is concluded that the complete mixing systems tend to lead to excessive growth of the filamentous microorganisms. Aeration systems with a low degree of the axial mixing, i.e. with low dispersion numbers and higher concentration gradients of the substrate along the systems, lead to the growth of non-filamentous and suppress the growth of filamentous microorganisms. It is possible to control the growth of filamentous microorganisms in the mixed cultures by maintaining the concentration gradient of the substrate along the aeration system. The concentration gradient of the substrate depends on the degree of mixing in the aeration system.