BAF urban sewage secondary processing biological Aerated Filter

2.1 BAF Working Principle      

BAF process types and operating mode has a variety of, with different characteristics, but the basic principle is the same. Biological aerated filters of sewage treatment principle is within reactor on the packing attached microbes in biological membrane oxidative decomposition role, packing and biological film adsorption resistance leave function and along the flow direction of the formation of the predator food chain effect classification, and biological membrane internal microenvironment and anaerobic segment of the denitrifying role.

 2.2 BAF Craft Features
 Biological aerated filters and activated sludge method, it is characterized by the following features:

(1) has a higher concentration of biological and higher organic load. BAF adopted in the rough porous microbial provides for granular packing more better growth environment, easy to hang film and stable operation, can be in packing surface keep more biomass, microorganism quantity per unit volume is far greater than active sludge the microorganism quantity, high levels of microbe quantity of the volume increased load makes BAF, and reduce the pool volume and cover an area of an area, make the construction cost is reduced greatly.

(2) cover an area of an area small. Because of the reactor in BAF, the treatment effect and packing are positive correlated height, so by adding more packing height to reduce cover an area of an area. Biological aerated filters the volume of a high load, BOD5 volume to load 5 ~ 6 kgBOD5 / (m3 / d), is the conventional activated sludge method or contact oxidation of 6 ~ 12 times.

(3) simple process, the construction cost is low. Because of the packing machinery and filter material surface interception effect of microorganism and metabolism of the formation of the viscous material from the adsorption role bridge, therefore, can save the second pond, thereby reducing the infrastructure costs.

(4) affected by temperature effect is small. Due to close partly or fully enclosed BAF structures, the biochemical reactions by external temperature effect is small, so suitable for cold areas for sewage treatment.

(5) bacteria group of reasonable structure. The traditional activated sludge method, the distribution of microorganism is relatively uniform, and in the BAF from top to bottom to form the different advantages of biological strains, hence make except C, nitrification/denitrification occurred in the same pool in and simplify the process flow.

(6) impact resistance ability. BAF ponds to the organic load, hydraulic load, the change of the temperature not as active sludge method that sensitive.

(7) is easy to operation and management. Biological aerated filters impact resistant load ability, good low temperature resistance, no sludge bulking badly and can avoid loss of microorganisms, and keep high microbial biomass, therefore, the daily operation management simple, the treatment effect is stable.

(8) high quality of effluent water.      

BAF Application  

3.1 BAF Biological aerated filters application in slightly polluted water

Biological aerated filters of the application of the slightly polluted water in tsinghua university research shows that the process of the pollution sources BAF water biological pretreatment can obtain good except pollution effect. BAF on organic remove influenced by the source water quality, on the CODMn the removal rate of 5% ~ 45%, the COD removal rate between 20% ~ 60%; BAF ammonia nitrogen removal of water by source water smaller on water quality, in addition to the individual cases as its removal rate generally of more than 80%. In addition, BAF process on turbidity, chroma, iron, manganese and so on also have better remove effect.

3.2 BAF Biological aerated filters application in treatmenting sewage
   In mainland China, biological aerated filters are in promotion stage, dalian horse column river sewage treatment plant is China's first using biological aerated filters technology city sewage treatment plant, is now in the trial run. Dalian horse column river sewage treatment plant engineering through the international bidding determined the SEDIPAC 3 D + BIOFOR process, design processing power for 12 x 104 m3 / D, 4 x 104 m3 / D reuse, service area of 32 km2, service population of 350000, covers an area of 4.3 hm2, engineering direct investment about 160 million yuan. In November 1998, engineering construction, September 2000 enter debug operation, July 2001 through the performance test and formally put into production run.

In southern special low concentration sewage, on the low aeration conditions, gas, hydraulic loading than water, water organic load, carbon and nitrogen, packing layer height than other factors on biological aerated filters the effect of load capacity. The results show that, in gas 3:1 ratio of water, carbon and nitrogen than for 3 ~ 4, 1.1 m3 / hydraulic loading (m2 / h) conditions, CODCr and ammonia nitrogen removal rate of 97.37% and 82.28% respectively, and the effluent organic matter and ammonia nitrogen mass concentration are 3.4 mg/L and 6.94 mg/L. Carbon and nitrogen CODCr volume than the influence of the reactor load of ammonia nitrogen volume is the effect of load more obvious; Ammonia nitrogen removal rate of change by hydraulic loading less effect.