Application of a novel backwashing process in upflow biological aerated filter

To improve the efficiency of backwashing in upflow biological aerated filter （BAF）, a novel backwashing process named air-water siphon backwashing （AWSB） was proposed and applied on laboratory scale. The effects of backwashing on turbidity and suspended solid （SS） in backwashing efluent using this new backwashing process were compared with those of traditional backwashing process, namely air-water backwashing （AWB）. In AWB, the turbidity of backwashing efluent maintained 100 NUT when consumed 60 min and 10.5 L water. However, in AWSB, it declined to 44 NUT, consumed 40 min, and 7 L water. The COD removal of BAF after backwashing was also analyzed. The average removal rate of COD in the reactor backwashed by AWB and AWSB was 89.34% and 90.91%, respectively. Compared with AWB, the backwashing interval had been prolonged 35%. The volume of backwashing water in that AWSB was only 66.7% of that in AWB. The results demonstrated that AWSB required less water and took shorter backwashing timerelative to AWB to achieve the same turbidity of backwashing efluent, and AWSB was more effective in removing fouling than that of AWB. More significant advantage of AWSB was that the backwashing interval was effectively prolonged

Effect of media heights on the performance of biological aerated filter

The optimum media height of carbon oxidation and nitrification in a down-flow biological aerated filter was determined, and the distribution of the heterotrophic and nitrifying populations through studying the changes of organic carbon contents and ammonia concentration at different media height was got. The results showed that as a down flow BAF with granular media, the active layer of nitrifiers was deeper than heterotrophs in BAF. And the optimum media height for the removal of SS, COD Cr and NH + 4-N was 40 cm,60 cm and 80 cm respectively. The removal efficiency of SS, COD Cr and NH + 4-N was 79.1%, 63.9% and 96.4% respectively under the influent COD Cr and NH + 4-N of 122.1 mgCOD Cr /L and 14.84 mgNH + 4-N/L, the influent flux of 15.8 L/h, air to liquid ratio of 3∶1.

Treatment of Slightly Polluted Wastewater in an Oil Refinery Using a Biological Aerated Filter Process

The slightly polluted wastewater from oil refinery contains some COD, oil pollutants and suspended solids （SS）. A small-scale fixed film biological aerated filter （BAF） process was used to treat the wastewater. The influences of hydraulic retention time （HRT）, air/water volume flow ratio and backwashing cycle on treatment efficiencies were investigated. The wastewater was treated by the BAF process under optimal conditions： the HRT of 1.0 h, the air/water volume flow ratio of about 5 ： 1 and the backwashing cycle of every 4-7 days. The results showed that the average removal efficiency of COD, oil pollutants and SS was 84.5%, 94.0% and 83.4%, respectively. And the average effluent concentration of COD, oil pollutants and SS was 12.5, 0.27, 14.5 mg·L^-1, respectively. The experimental results demonstrated that the BAF process is a suitable and highly efficient method to treat the wastewater.

Using a biological aerated filter to treat mixed water-borne volatile organic compounds and assessing its emissions

A biological aerated filter （BAF） was evaluated as a fixed-biofilm process to remove water-borne volatile organic compounds （VOCs） from a multiple layer ceramic capacitor （MLCC） manufacturing plant in southern Taiwan. The components of VOC were identified to be toluene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, bromodichloromethane and isopropanol （IPA）. The full-scale BAF was constructed of two separate reactors in series, respectively, using 10- and 15-cm diameter polypropylene balls as the packing materials and a successful preliminary bench-scale experiment was performed to feasibility. Experimental results show that the BAF removed over 90% chemical oxygen demand （COD） from the influent with （1188 ± 605） mg/L of COD. A total organic loading of 2.76 kg biochemical oxygen demand （BOD）/（m3 packing·d） was determined for the packed bed, in which the flow pattern approached that of a mixed flow. A limited VOC concentration of （0.97 ± 0.29） ppmv （as methane） was emitted from the BAF system. Moreover, the emission rate of VOC was calculated using the proposed formula, based on an air-water mass equilibrium relationship, and compared to the simulated results obtained using the Water 9 model. Both estimation approaches of calculation and model simulation revealed that 0.1% IPA （0.0031-0.0037 kg/d） were aerated into a gaseous phase, and 30% to 40% （0.006-0.008 kg/d） of the toluene were aerated.

Effects of Phosphorus Concentration on the Treatment of Domestic Wastewater by a Combination of Hydrolytic Acidification and Biological Aerated Filter Filled with Mussel Shells

The combination of hydrolytic acidification and biological aerated filter （BAF） filled with mussel shells was used to treat domestic wastewater, and the removal rates of chemical oxygen demand （COD）, ammonia nitrogen （NH3-N） and total phosphorus （TP） by the system were analyzed under different TP concentrations. When TP concentration ranged from 12.39 to 14.69 mg/L, the removal rate of COD was the best, over 90.92% ; as TP concentration varied from 2.26 to 2.61 mg/L, the removal rates of NH3-N and TP were the best, up to 100.00% and 76.38% respectively. The results show that it is feasible to use mussel shells as the media of BAF, and TP concentration has certain influence on the performance of the system dealing with domestic wastewater.

Enhanced Nutrient Removal with Upflow Biological Aerated Filter for Reclaimed Water

A two-stage upflow biological aerated filter was designed as an advanced treatment process to optimize the operating parameters and study the correlative factors influencing the efficiency of nitrification, denitrification and phosphorus removal. The experimental results showed that the final effluent of the two-stage upflow biofilter process operated in series could meet the stringent limits of the reclaimed water for the total nitrogen of 2 mg/L, and total phosphorus of 0.3 mg/L. The high treatment efficiency allowed the reactor operating at very high hydraulic loadings and reaching nearly complete nitrification and denitrifieation.

Preparation of biological aerated filter media with coal fly ash and coal gangues

A novel kind of filter media has been studied using in biological aerated filter process which is produced by waste coal fly ash and coal gangues.The specific surface area and sum of braking and ware rate are viewed as the main factor for determining preparation conditions,including calcination temperature (in the range of 900 ℃ to 1250 ℃),proportion of coal gangue (in the range of 0 to 25%) and soaking time (in the range of 0 to 40 min).The effects of sintering conditions on the main property parameters are researched and the reasons have been analyzed.Considered with all factors,the optimum technological conditions are chosen as follows:the calcination temperature is 1050 ℃ ;the soaking time is 10 min and the proportion of coal gangue is 5%.When at these condition,the main property parameters of the filter media in the technological conditions are 1.6 m 2 /g for the specific surface area and 2.96 % for sum of braking and are rate respectively.Finally,a scanning electron microscope is used for analyzing the microstructure of the filter media.

Using a zeolite medium biofilter to remove organic pollutant and ammonia simultaneously

A pilot scale zeolite medium biological aerated filter(ZBAF) was designed and used to treat municipal wastewater. It showed that ZBAF could simultaneously remove chemical oxygen demand(COD), ammonia-N and turbidity to satisfied degree at a hydraulic retention time(HRT) of 0.95 h. Their average removal efficiencies were 73.9%, 88.4% and 96.2% with the corresponding average effluent concentrations of 43.4 mg/L, 3.5 mg/L and 3.7 NTU, respectively. These effluent items met with the water quality standard of the treated water reused for cooling water. The COD removal volumetric loading rate increased proportionally with its applied volumetric loading rate with its maximum of 7.1 kg/(m 3·d). Ammonia-N removal loading rate also increased proportionally with its applied loading rate at HRT of longer than 0.95 h and the feasible maximum removal loading rate was 0.9 kg/(m 3·d). The COD loading rate did not affect the ammonia-N removal efficiency significantly when it was lower than 5.5 kg/(m 3·d). ZBAF has good application prospect for its low cost and high removal efficiency in the future.

Removal of nitrogen and phosphorus in a combined A^2/O-BAF system with a short aerobic SRT

A bench-scale anaerobic/anoxic/aerobic process-biological aerated filter （A^2/O-BAF） combined system was carded out to treat wastewater with lower C/N and C/P ratios. The A^2/O process was operated in a short aerobic sludge retention time （SRT） for organic pollutants and phosphorus removal, and denitrification. The subsequent BAF process was mainly used for nitrification. The BAF effluent was partially returned to anoxic zone of the A^2/O process to provide electron acceptors for denitrification and anoxic P uptake. This unique system formed an environment for reproducing the denitdfying phosphate-accumulating organisms （DPAOs）. The ratio of DPAOs to phosphorus accumulating organisms （PAOs） could be maintained at 28% by optimizing the organic loads in the anaerobic zone and the nitrate loads into the anoxic zone in the A^2/O process. The aerobic phosphorus over-uptake and discharge of excess activated sludge was the main mechanism of phosphorus removal in the combined system. The aerobic SRT of the A^2/O process should meet the demands for the development of aerobic PAOs and the restraint on the nitrifiers growth, and the contact time in the aerobic zone of the A^2/O process should be longer than 30 min, which ensured efficient phosphorus removal in the combined system. The adequate BAF effluent return rates should be controlled with 1--4 mg/L nitrate nitrogen in the anoxic zone effluent of A^2/O process to achieve the optimal nitrogen and phosphorus removal efficiencies.

Combined biologic aerated filter and sulfur/ceramisite autotrophic denitrification for advanced wastewater nitrogen removal at low temperatures

An innovative advanced wastewater treatment process combining biologic aerated filter （BAF） and sulfur/ ceramisite-based autotrophic denitrification （SCAD） for reliable removal of nitrogen was proposed in this paper. In SCAD reactor, ceramisite was used as filter and Ca （HCO3）2 was used for supplying alkalinity and carbon source. The BAF-SCAD was used to treat the secondary treatment effluent. The performance of this process was investigated, and the impact of temperature on nitrogen removal was studied. Results showed that the combined system was effective in nitrogen removal even at low temperatures （8℃）. Removal of total nitrogen （TN）, NH4＋ -N, NO3-N reached above 90% at room temperature. Nitrification was affected by the temperature and nitrification at low temperature （8℃） was a limiting factor for TN removal. However, denitrification was not impacted by the temperature and the removal of NO3 -N maintained 98% during the experimental period. The reason of effective denitrification at low temperature might be the use of easily dissolved Ca（HCO3）2 and high-flux ceramisite, which solved the problem of low mass transfer efficiency at low temperatures. Besides, vast surface area of sulfur with diameter of 2-6 mm enhanced the rate of microbial utilization. The removal of nitrate companied with the production of SO42-, and the average concentration of SO27 was about 240mg.L^-1. These findings would be beneficial for the application of this process to nitrogen removal especially in the winter and cold regions.

Performance of a double-layer BAF using zeolite and ceramic as media under ammonium shock load condition

An experiment was carried out to investigate the anti-ammonium shock load capacity of a biological aerated filter （BAF） composed of a double-layer bed. This bed was made up of a top layer of ceramic and a bottom layer of zeolite. The experiment shows that the anti-ammonium shock load process can be divided into two processes： adsorption and release. In the adsorption process, the total removal efficiency of ammonia nitrogen by zeolite and ceramic was 94%. In the release process, the ammonia nitrogen concentration increased significantly and then gradually returned to the normal level four hours after the shock load. The results indicated that the double-layer BAF had a high level of adaptability to the short-term ammonium shock load and long-term operation. The main factors influencing the dynamic process of ammonia nitrogen adsorption were the filter bed height, ammonia nitrogen concentration of influent, and flow rate. The bed depth service time （BDST） model was used to predict the relationship between the filter bed height and breakthrough time at different flow rates, and the results are reliable.

Isolation andapplicationofanibuprofen-degrading bacterium toabiologicalaerated filter forthetreatmentof micro-polluted water

Ibuprofen(IBU)is widely used in the world as anti-inflammatory drug,which posed health risk to the environment.A bacterium capable of degrading IBU was isolated from activated sludge in a sewage treatment plant.According to its morphological,physiologic,and biochemical characteristics,as well as 16S rRNA sequence analysis,the strain was identified as Serratia marcescens BL1(BL1).Degradation of IBU required the presence of primary substrate.After a five-day cultivation with yeast powder at 30℃ and pH 7,the highest degradation(93.47%2.37%)was achieved.The process of BL1 degrading IBU followed first-order reaction kinetics.The BL1 strain was applied to a small biological aerated filter(BAF)device to form a biofilm with activated sludge.IBU removal by the BAF was consistent with the results of static tests.The removal of IBU was 32.01% to 44.04% higher than for a BAF without BL1.The indigenous bacterial community was able to effectively remove CODMn(permanganate index)and ammonia nitrogen in the presence of BL1.

Impact of dissolved oxygen on the production of nitrous oxide in biological aerated filters

Polymerase chain reaction-denaturing gradient gel electrophoresis （pCR-DGGE） and microelectrode technology were employed to evaluate the Nitrous oxide （N2O） production in biological aerated filters （BAFs） under varied dissolved oxygen （DO） concentrations during treating wastewater under laboratory scale. The average yield of gasous N2O showed more than 4-fold increase when the DO levels were reduced from 6.0 to 2.0 mg·L^-1, indicating that low DO may drive N2O generation. PCRDGGE results revealed that Nitratifractor salsuginis were dominant and may be responsible for N2O emission from the BAFs system. While at a low DO concentration （2.0 mg·L^-1）, Flavobacterium urocaniciphilum might playa role. When DO concentration was the limiting factor （reduced from 6.0 to 2.0 mg·L^-1） for nitrification, it reduced NO2^--N oxidation as well as the total nitrification. The data from this study contribute to explain how N2O production changes in response to DO concentration, and may be helpful for reduction ofN2O through regulation of DO levels.

Advanced nitrogen and phosphorus removal in A^(2)O-BAF system treating low carbon-to-nitrogen ratio domestic wastewater

A laboratory-scale anaerobic-anoxic-aerobic process(A^(2)O)with a small aerobic zone and a bigger anoxic zone and biologic aerated filter(A^(2)O-BAF)system was operated to treat low carbon-to-nitrogen ratio domestic wastewater.The A^(2)O process was employed mainly for organic matter and phosphorus removal,and for denitrification.The BAF was only used for nitrification which coupled with a settling tank Compared with a conventional A^(2)O process,the suspended activated sludge in this A^(2)OBAF process contained small quantities of nitrifier,but nitrification overwhelmingly conducted in BAF.So the system successfully avoided the contradiction in sludge retention time(SRT)between nitrifying bacteria and phosphorus accumulating organisms(PAOs).Denitrifying phosphorus accumulating organisms(DPAOs)played an important role in removing up to 91%of phosphorus along with nitrogen,which indicated that the suspended activated sludge process presented a good denitrifying phosphorus removal performance.The average removal efficiency of chemical oxygen demand(COD),total nitrogen(TN),total phosphorus(TP),and NH_(4)^(+)-N were 85.56%,92.07%,81.24%and 98.7%respectively.The effluent quality consistently satisfied the national first level A effluent discharge standard of China.The average sludge volume index(SVI)was 85.4 mL·g^(-1)additionally,the volume ratio of anaerobic,anoxic and aerobic zone in A^(2)O process was also investigated,and the results demonstrated that the optimum value was 1:6:2.

Comparison and modeling of two biofilm processes applied to decentralized wastewater treatment

In order to control water pollution in the rapidly urbanizing South China area,biological contact oxidation(BCO)process and biological aerated filter(BAF)process were applied in a pilot-scale experiment for decentralized wastewater treatment.An investigation to find the optimal parameters of the two biofilm systems was conducted on hydraulic loading,organic loading,and aeration rate.The results indicated that the water reuse criteria required a maximum hydraulic and organic loading of 30.0 m^(3)/(m^(2)·d)and 4.0 kg COD/(m^(3)·d),respectively,as well as a minimum effluent DO of 4.0 mg/L.The utilization of a new media allowed BAF to perform better than BCO.The kinetic description of the COD removal process for BAF and BCO are Se=S0e^(-0.639t)/(1+1.035t),and S_(e)=S_(0)/[(1+0.947t)(1+1.242t)],respectively.The correlativity analysis showed that the two models could predict the effluent water quality based on the hydraulic retention time.Thus,the appropriate hydraulic loading for certain effluent water quality demands could be determined.The two models could be applied to wastewater treatment practice.