Biological aerated filter treatment of coking wastewater-BAF, BAF, coking wastewater - water industries

Biological aerated filter treatment of coking wastewater-BAF

, BAF, coking wastewater - water industries

Overview Coking wastewater is a high COD, high phenol value, high ammonia treatment of difficult industrial organic wastewater. Since the 80s of the 20th century, more than the domestic coking wastewater by two biochemical methods, extended aeration method, strong biochemical methods (such as biological iron, biological activated carbon) and other methods, in which A / O method (anaerobic 1 aerobic activated sludge) treatment was best, but the A / O method larger initial investment and operating costs, 1m3 of water costs about 7.4 yuan to deal directly with the general coking enterprises unbearable.

BAF (BiologicalAeratedFilter, referred to as BAF) is the contact with oxygen in biological Chemical industry Art based on the introduction of drinking water treatment filter ideas emerged as an aerobic Membrane Treatment Technology. The basic principle is the primary treatment is based on the primary treatment, with granular Filler The growth of biofilm and its attachment to deal with media, give full play to the role of microbial metabolism, the role of physical filtration, membrane and fill the role of the physical Absorption and bio-reactor, multi-stage predation, in the same unit of pollutant removal reactor . The process has high volumetric loading, hydraulic loading large, hydraulic retention time is short, good effluent quality, small size, less investment in infrastructure, energy consumption and operating costs low. This study will examine the application of coking wastewater treatment refractory feasibility of effective treatment of coking wastewater to seek new ways.

1 test methods and materials Water sources and water quality

1.1 Test wastewater from Ma On Shan Steel Company coking plant, the water quality refers to Table 1

Table 1 Coking Wastewater Quality 1.2 Experimental Materials BAF reactors produce cylindrical plexiglass column, high-1.55m, diameter 0.11m, volume 14.7L, built 8.7L Lytag Filter Media , Filter-storey 1.1m. Way to the stream using water (bottom water), plates, long-handled water filter head cloth, the upper drainage, sintered sand core aeration (YL-888 type gas Pump ), 2 BTOO a SOM-based current pump water.

Lytag filter parameters: diameter of 3 to 5mm, the packing density of 0.89g/cm3, broken rate of 0.07%, specific surface area of 4.8m2 / g, porosity 35%, the wear rate of 5.3% hydrochloric acid soluble rate of 0.5%. BAF structure indicated in Figure 1.

1.3 process and test methods

1.3.1 Process Test process shown in Figure 2. Coking wastewater sedimentation tank by adjusting the pump by the constant injection of BAF bottom of the skillet after the first filter into the filter layer. At the same time from the pump to the filter layer aeration, the water after backwashing pool (storage pool) efflux. Backwash time intervals, combined with air and water backwash. Is: first gas recoil 5min, and then start the water pump, air and water backwash at the same time 5min, the final water rinse 5 - 8min. Backwash water with reactor (ie, Figure 2 backwash pool). Backwash off the biofilm, sludge and other impurities with the backwash water back to the regulator, sedimentation tanks, sedimentation basins, sludge efflux by the set.

1.3.2 operating parameters Air to water ratio of 0.5 to 1; backwash cycle 7 ~ 8d, the joint air and water backwash, air, water backwashing strength was 5 1 8sL / (s * m2), anti-washing time of 15 a 18min; hydraulic load 1.05 ~ 2.5rn3 / (m2? h).

1.3.3 Water Sampling Method

Every 1h, respectively, and in regulating the sedimentation pool backwash twice the sampling, sample water 200mL, and mix the various water samples by mixing the sample population sample (a total of 6 times 1200mL), this can be as much as possible eliminate or avoid a sampling error due to chance, sampling location surface Department under 3cm.

1.4BAF culture biofilm BAF biofilm culture method with continuous feeding. Basic operation is: Maanshan Iron & Steel coke plant will be taken from activated sludge wastewater treatment plant after proper stirring continuously adding Taomi Shui adding aeration reactor and make continuous progress Taomi Shui 3 days after the cessation of sludge increases, water use diluted white inflow of low coking wastewater and adding a small amount of potassium hydrogen phosphate to increase phosphorus levels in wastewater, control the reactor mixture was alkaline, after 20 days on the growth of the thin filter filter a layer of biofilm. Microscopic examination of biofilms under the microscope off the results shown in Figure 3, Figure 4 shows that the biofilm has many ciliates protozoa such as Paramecium, roaming insects, beetles and other beans. The instructions of the growth of mature biofilm protozoa marks. Meanwhile reactor wastewater COD)) removal efficiency of 70%, at this time that the success of biofilm culture, can be test conditions.

1.5 Water Quality Analysis Water quality analysis method based on "Water and Wastewater Monitoring Analysis Method," (4th edition), CODCr was measured with potassium dichromate; ammonia was determined by distillation of a Nessler'Sreagent; pH measured by electrode method; phenol was determined by 4-amino-antipyrine a direct method; cyanide with isonicotinic acid Spectrophotometric a border wow.

2 Results and Analysis 2.1 hydraulic load and the relationship between the removal of COD))

Hydraulic load is directly related to the size of Sewage In the reactor and carrier biofilm contact time. The smaller the value of water and the biofilm reaction time longer, the better. CODCr influent concentration of 820mg / L when, BAF under different hydraulic loading CODcr coking wastewater removal effect shown in Figure 5. BAF can be seen from Figure 5 on the coking wastewater with high organic matter removal, when the hydraulic load is 0.05 of a 0.2m3 / (m2 "h) time, COD. Removal rate reached 90%, and the water concentration of about CODcr to 220mg / L, to GB13456-92 national secondary emission standards.

2.2 phenol, cyanide removal BAF on the coking wastewater phenol, cyanide removal in Table 2. As can be seen from Table 2, when the average hydraulic loading 0.12m3 / (m2 * h) time, BAF phenol wastewater, average removal rates of cyanide up to 980% and 96%, and water to the GB13456-92 countries 1 emission standards.

Figure 6BaF 'on the coking wastewater removal of NH3-N

2.3 Removal of ammonia nitrogen

Influent NH3-N was 160mg / L when, BAF under different hydraulic loading on the coking wastewater removal efficiency of NH3-N shown in Figure 6. Can be seen from Figure 6, BAF coking wastewater removal of NH3-N less effective, when the hydraulic loading of 0.1m3 / (m2 * h) time, BAF on NH3-N removal efficiency is only 45%. Meanwhile, with the hydraulic load growth, the removal rate decreases, when the hydraulic load to 0.25m3 / (m2 * h), the effluent concentrations than influent concentration rather large. Mainly due to

Reactor CODCr, NHS-N concentration was higher, inhibited the metabolism of nitrifying bacteria in wastewater, and with the decomposition of nitrogenous organic matter, resulting in effluent NH3-N concentration.

3 Conclusion

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