Characterization of the bacterial communities associated with biofilters in two full-scale recirculating aquaculture systems

Bacteria play a major role in metabolizing ammonia and other metabolites in recirculating aquaculture systems(RASs).To characterize and compare the bacterial communities in the biofilters of two full-scale RASs for the culture of puffer fish,Takifugu rubripes,at different ages and densities were studied.In overall,47807 optimized reads of the 16 S rRNA gene with V4-V5 region were obtained from four biofilm samples collected after biofilm maturation.At 97%cut-off level,these sequences were clustered into 500 operational taxonomic units,and were classified into 19 bacterial phyla and 138 genera.At the phylum level,Proteobacteria and Bacteroidetes were the most abundant,followed by Nitrospirae and Planctomycetes.At the genus level,Colwellia,Marinifilum,Oceanospirillum,Lutibacter,Winogradskyella,Pseudoalteromonas,Arcobacter,and Phaeobacter were the top members.Nitrosomonas and Nitrospira were main ammonia-and nitrite-oxidizing bacteria.Differences in bacterial communities at different sampling dates and similarities of both biofilters were revealed in the Venn diagram and cluster analysis.Maintaining a good water quality and health offarmed fish in RASs depended on the correct management of the bacterial communities.This study provides more accurate information on the bacterial communities associated with the bifilters of both RASs.

Autotrophic Biofilters for Oxidation of Nitric Oxide

Carbon foam—a kind of new engineering material as packing material was adopted in three biofilters with different pore dimensions and adapted autotrophic nitrite nitrobacteria to investigate the purification of nitric oxide (NO) in a gas stream. The biofilm was developed on the surface of carbon foams using nitrite as its only nitric source. The moisture in the filter was maintained by ultrasonic aerosol equipment which can minimize the thickness of the liquid film. The liquid phase nitrification test was conducted to determine the variability and the potential of performance among the three carbon foam biofilters. The investigation showed that during the NO2^-—N inlet concentration of 200 g·L^-1·min^-1 to 800 g·L^-1·min^-1, the 24PPC (pores per centimeter) carbon foam biofilter had the greatest potential, achieving the NO2^-—N removal efficiency of 94% to 98%. The 8PPC and 18PPC carbon foam biofilters achieved the NO2^-—N removal efficiency of 15% to 21% and of 30% to 40%, respectively. The potential for this system to remove NO from a gas stream was shown on the basis of a steady removal efficiency of 41% to 50% which was attained for the 24PPC carbon foam biofilter at specified NO inlet concentration of 66.97 mg·m^-3 to 267.86mg·m^-3 and an empty-bed residence time of 3.5 min.

A New Approach for Removal of Nitrogen Oxides from Synthetic Gas-streams under High Concentration of Oxygen in Biofilters

The potential of using denitrifying and nitrifying concurrent biofilters for the removal of nitrogen oxides from synthetic gas streams was studied under the condition of high oxygen concentration. It was found that more than 85% of nitric oxide was removed from synthetic combustion gas-streams which contained 20% oxygen and 350 μL/L NO, with a residence time of 60 seconds. In the process, it was found that the existing of oxygen showed no evident negative effect on the efficiency of nitrogen removal.

Evaluation of Inocula and Packing Material for Acceleration of Start-Up in Biofilters

Several strategies with different combination of inocula and packing material were investigated to obtain the optimal start-up time and elimination capacity (EC) in toluene biofiltration. The inocula contained the activated sludge and toluene degrading bacteria, and the packing material consisted of different mixing ratios of peat and wood chips. A final toluene load of 21.2 g/(m3·h) was attained step by step in four parallel biofilters. A shortest start-up time of 15 days and a highest EC of 17.0 g/(m3·h) were observed in the biofilter B-4, which was inoculated with a special microbial consortium consisting of three strains of toluene degrading bacteria and was packed with the mixture of peat and wood chips at a ratio of 80:20 (w/w). These results indicated that inoculating pre-acclimatized microbes dramatically shortened the start-up time, and such a composition of packing material could maintain an appropriate environment (with the bed porosity and water content equating to 0.45 and 1.96, respectively) for the growth of dominant toluene degrading bacteria in the biofilter.

Effects of exogenous acylated homoserine lactones on biofilms in biofilters for gaseous toluene treatment

Biofilters are typical biofilm reactors, and they usually have poor biofilm formation resulting in limited reactor performance. Exogenous acylated homoserine lactones (AHLs) can enhance biofilm formation in many bioreactors based on quorum sensing regulation. However, their effect on biofilm in biofilters utilized for volatile organic compound (VOC) removal is unknown and needs to be investigated. In this study, the effects of the exogenous AHLs on biofilters for gaseous toluene removal were investigated. Analysis of biofilms in biofilters showed that the addition of exogenous AHLs considerably enhanced biofilm growth;the average biofilm concentration increased by 18%. Furthermore, the average biofilm coverage proportions in biofilters with and without exogenous AHLs were 17 % and 13 %, respectively, demonstrating the positive effect of exogenous AHLs on biofilm coverage. In particular, exogenous AHLs promoted the production of extracellular polymeric substances and the microbial adhesive strength of the biofilm. In addition, the exogenous AHLs showed no significant effect on the gaseous toluene removal efficiency of the biofilter. These results show that exogenous AHLs can enhance biofilm formation and can guide the application of exogenous AHLs in VOC biofilters.

Analytical Expressions of Concentration of VOC and Oxygen in Steady-State in Biofilteration Model

Mathematical models of steady-state biofilteration are discussed. The theoretical results are much useful for the design of biofilters. This model is based on the system of non-linear reaction/diffusion equations contains a non-linear term related to Monod kinetics, Andrews kinetics, interactive model from Monod kinetics and Andrews kinetics. Analytical expression of concentration of VOC (Volatile organic compounds) and oxygen are derived by solving the system of non-linear equations using Adomian decomposition method (ADM) method. Our analytical results are also compared with the simulation results. Satisfactory agreement is noted.

Analytical Solution of the Non-Linear Equation in Biodegradation of N-Butanol in a Biofilter

In this paper, mathematical models of biofilm mixtures of n-butanol biofilters were discussed. The model is based on the mass transfer in the biofilm interface and chemical oxidation in the biofilm phase and gas phase. An approximate analytical expression of concentration profiles of n-butanol in the biofilm phase and gas phase has been derived using the homotopy perturbation method and hyperbolic function method for all possible values of parameters. Furthermore, in this work, the numerical simulation of the problem is also reported using the Matlab program. Good agreement between the analytical and numerical results is noted. Graphical results are presented and discussed quantitatively to illustrate the solution. The analytical results will be useful in finding the yields of biomass and oxygen consumption, the specific biomass surface area, activation energy and saturation constant for the Michaelis-Menten kinetics.

Ambient Air Non-Methane Volatile Organic Compound (NMVOC) Study Initiatives in India–A Review

Different aspects of Volatile Organic Compounds (VOCs) are being investigated in details by different research groups in Indian institutes. The spectrum covers measuring technologies, source apportionment and variability studies, all these are in due process of preparing a guideline for the sustainable development in terms of industrial, infrastructural as well as overall growth of the country. Both the outdoor and indoor air quality has significant impact on human health. With special concentration on BTEX and HAPs, the health related investigations are conducted as part of interdisciplinary studies of environmental science. Newer technologies to remove VOCs under specific industrial and practical conditions are getting emerged as a comparatively new era. It addresses fields like adsorption, condensation, pervaporation, biodegradation and catalytic combustion. Besides, different kinds of biofilters have drawn significant attention nowadays. The final selection of appropriate technology depends on type and concentrations of VOCs, extent of separation required and cost involved. All these technologies are although well studied, but could not be adopted for regular commercial usage till date. There is scope to explore new horizons as well as regular monitoring on the introduced pathways to limit VOC emission in the ambient air. This review aims at a concise discussion on all the areas that come under the umbrella of non-methane VOC technologies.

BIOFILTER生物膜反应器处理生活废水

本试验考察了一种新型生物膜填料—Biofilter对生活废水的处理效果。实验结果表明,在水力停留时间(HRT)很短的情况下(6h),该填料对COD的处理效果可达90%以上,对TN也有一定的处理效果,且出水SS可控制在100mg/L以内,无需二沉池,处理成本低。

Biotreatment of Odor Waste Gases by Immobilized Ceramsite Biofilter

[Objective] To find out the process conditions and influence factors for the biotreatment of odor gases of hydrogen sulfide（H2S） and ammonia（NH3）. [Method]The degradation performances on H2 S and NH3 were investigated during the start-up and stable operation process of biofilter with ceramsites as the packing microorganisms. [Result] The biofilm formation of the biofilter system to purify the waste gas of H2 S was completed within 9 d, and the removal rate of H2 S could reach up to 99% with the initial concentration of 100-1 000 mg/m^3 and empty bed residence time（EBRT） of142-290 s. The biofilm formation of the biofilter system to purify the waste gas of NH3 was completed within 10 d with the removal rate reaching up to 94.61%.[Conclusion] Under suitable conditions, the biofilter showed high removal rates to both H2 S and NH3.

Three-stage aged refuse biofilter for the treatment of landfill leachate

A field-scale aged refuse （AR） biofilter constructed in Shanghai Refuse Landfill, containing about 7000 m^3 aged refuse inside, was evaluated for its performance in the treatment of landfill leachate. This AR biofilter can be divided into three stages and can manage 50 m^3 landfill leachate per day. The physical, chemical, and biological characteristics of AR were analyzed for evaluating the AR biofilter as leachate treatment host. The results revealed that over 87.8%-96.2% of COD and 96.9%-99.4% of ammonia nitrogen were removed by the three-stage AR biofilter when the infiuent leachate COD and ammonia nitrogen concentration were in the range 5478-10842 mg/L and 811-1582 mg/L, respectively. The final effluent was inodorous and pale yellow with COD and ammonia nitrogen below 267-1020 mg/L and 6-45 mg/L, respectively. The three-stage AR biofilter had efficient nitrification but relative poor denitrification capacity with a total nitrogen （TN） removal of 58%-73%. The external temperature of AR biofilter did not influence the total ammonia nitrogen removal significantly. It was concluded that the scale-up AR biofilter can work very well and can be a promising technology for the treatment of landfill leachate.

Temperature effect on aerobic denitrification and nitrification

Nitrogen loss without organic removal in biofilter was observed and its possible reason was explained. A lower hydraulic loading could improve aerobic denitrification rate. Aerobic denitrification was seriously affected by low temperature(below 10℃). However, nitrification rate remained high when the temperature dropped from 15℃ to 5℃. It seemed the autotrophic biofilm in BAF could alleviate the adverse effect of low temperature.

Biodegradation of mixture of VOC's in a biofilter

Volatile organic compounds(VOC's) in air have become major concern in recent years. Biodegradation of a mixture of ethanol and methanol vapor was evaluated in a laboratory biofilter with a bed of compost and polystyrene particles using an acclimated mixed culture. The continuous performance of the biofilter was studied with different proportion of ethanol and methanol at different initial concentration and flow rates. The result showed significant removal for both ethanol and methanol, which were composition dependent. The presence of either compound in the mixture inhibited the biodegradation of the other.

Anaerobic ammonium oxidation for advanced municipal wastewater treatment: is it feasible?

Anaerobic ammonium oxidation（ANAMMOX） is a recently developed process to treat ammonia-rich wastewater. There were numerous articles about the new technology with focus on the ammonium-rich wastewater treatment, but few on advanced municipal wastewater treatment. The paper studied the anaerobic ammonium oxidation （ANAMMOX） process with a down flow anoxic biofilter for nitrogen removal from secondary clarifier effluent of municipal wastewater with low COD/N ratio. The results showed that ANAMMOX process is applicable to advanced wastewater treatment with normal temperature as well as ammonia-rich high temperature wastewater treatment. The results indicated that ammonia removal rate was improved by raising the nitrite concentration, and the reaction rate reached a climax at 118.4 mgN/L of the nitrite nitrogen concentration. If the concentration exceeds 118.4 mgN/L, the ANAMMOX process was significantly inhibited although the ANAMMOX bacteria still showed a relatively high reactivity. The data also indicated that the ratio of NO2^- -N：NH4 ＊ -N = 1.3：1 in the influent was appropriate for excellent nitrogen removal. The pH increased gradually along the ANAMMOX biofilter reactor. When the ANAMMOX reaction was ended, the pH was tend to calm. The data suggested that the pH could be used as an indicator to describe the course of ANAMMOX reaction.

Investigation of factors on a fungal biofilter to treat waste gas with ethyl mercaptan

The biofilter is cost-effective for the waste gases treatment. The bacterial is the main microorganism in the conventional biofilters. However, it faces some problems on the elimination of hydrophobic compounds. In order to overcome these problems, the biofilters with fungi were developed. The objective of this study is to investigate the factors affecting ethyl mercaptan(EM)-degradation using a fungal biofilter. A laboratory experiment was set up. The effects of loading rate, empty bed residence times(EBRT) and pH on EM degradation were investigated. Over 95% removals of EM could be achieved, under the condition of the influent loadings below 50 g/(m·h). Removal efficiencies improved to 98% with EM loading decreased to 45 g/(m·h). For long EBRT of 58 s corresponding to a flow rate of 0.3 m3/h, the EM removal efficiencies of over 98% were observed. However, when EBRT was decreased to 14 s, the removal efficiencies fell under 80%. The pH range of 3—5 was feasible to fungi.

Advanced treatment of biologically pretreated coking wastewater by intensified zero-valent iron process(IZVI) combined with anaerobic filter and biological aerated filter(AF/BAF)

Experiments were conducted to investigate the behavior of the sequential system of intensified zero-valent iron process(IZVI) and anaerobic filter and biological aerated filter(AF/BAF) reactors for advanced treatment of biologically pretreated coking wastewater. Particular attention was paid to the performance of the integrated system for the removal of chemical oxygen demand(COD), ammonia nitrogen(NH3-N) and total nitrogen(TN). The average removal efficiencies of COD, NH3-N and TN were 76.28%, 96.76% and 59.97%, with the average effluent mass concentrations of 56, 0.53 and 18.83 mg/L, respectively, reaching the first grade of the national discharge standard. Moreover, the results of gas chromatography/mass spectrum(GC/MS) and gel permeation chromatography(GPC) analysis demonstrated that the refractory organic compounds with high relative molecular mass were partly removed in IZVI process by the function of oxidation-reduction, flocculation and adsorption which could also enhance the biodegradability of the system effluent. The removal efficiencies of NH3-N and TN were achieved mainly in the subsequent AF/BAF reactors by nitrification and denitrification. Overall, the results obtained show that the application of IZVI in combination with AF/BAF is a promising technology for advanced treatment of biologically pretreated coking wastewater.

Performance of rotating drum biofilter for volatile organic compound removal at high organic loading rates

Uneven distribution of volatile organic compounds （VOCs） and biomass, and excess biomass accumulation in some biofilters hinder the application of biofiltration technology. An innovative multilayer rotating drum biofilter （RDB） was developed to correct these problems. The RDB was operated at an empty bed contact time （EBCT） of 30 s and a rotational rate of 1.0 r/min. Diethyl ether was chosen as the model VOC. Performance of the RDB was evaluated at organic loading rates of 32,1, 64.2, 128, and 256 g ether/（m^3·h） （16.06 g ether/（m^3·h） ≈ 1.0 kg chemical oxygen demand （COD）/（m^3·d））. The EBCT and organic loading rates were recorded on the basis of the medium volume. Results show that the ether removal efficiency decreased with an increased VOC loading rate. Ether removal efficiencies exceeding 99% were achieved without biomass control even at a high VOC loading rate of 128 g ether/（m^3·h）. However, when the VOC loading rate was increased to 256 g ether/（m^3·h）, the average removal efficiency dropped to 43%. Nutrient limitation possibly contributed to the drop in ether removal efficiency. High biomass accumulation rate was also observed in the medium at the two higher ether loading rates, and removal of the excess biomass in the media was necessary to maintain stable performance. This work showed that the RDB is effective in the removal of diethyl ether from waste gas streams even at high organic loading rates. The results might help establish criteria for designing and operating RDBs.

Biodegradation of methanol vapor in a biofilter

Volatile organic compounds (VOCs) are a new class of air pollutants posing threat to the environment. Newer technologies are being developed for their control among which biofiltration seem to be most attractive. Biofiltration of methanol vapor from air stream was evaluated in this study. Experimental investigations were conducted on a laboratory scale biofilter, containing mixture of compost and polystyrene inert particles as the filter materials. Mixed consortium of activated sludge was used as an inoculum. The continuous performance of biofilter for methanol removal was monitored for different concentrations and flow rates. The removal efficiencies decreased at higher concentrations and higher gas flow rates. A maximum elimination capacity of 85 g/(m 3·h) was achieved. The response of biofilter to upset loading operation showed that the biofilm in the biofilters was quite stable and quickly adapted to adverse operational conditions.

Improvement of trickling biofilter purification performance on treating chlorobenzene in waste gases using surfactant

A laboratory-scale trickling biofilter column, filled with Raschig rings and inoculated with Pseudomonas putida （ATCC 1785） was used to ＇purify chlorobenzene contained waste gases. Sodium dodecyl sulfonate （SDS） was used to enhance the performance of trickling biofilter. Purification performance of the trickling biofilter was examined for chiorobenzene inlet concentration of 1.20,-5.04 g/m^3 at different EBRTs between 76N153 s. Without SDS addition, with simultaneous increase in chlorobenzene inlet loading rate and gas flow rate, 100% removal efficiency was achieved at EBRT of 109 s and inlet loadings below 5120 mg/m^3. Addition of SDS to nutrient solution led to improvement of trickling biofilter purification performance. By introducing 25 mg/L SDS, the removal efficiency was increased by 21% and elimination capacity up to 234 g/（m^3.h） was achieved at chlorobenzene inlet loading of 241 g/（m^3.h）. Although SDS concentration experienced a low rate reduction after continuous nutrient solution recirculation, this result has period little influence on trickling biofilter＇s removal efficiency in monitoring period.

Biofilter:a promising tool for mitigating methane emission from manure storage

Liquid manure storage may contribute to methane （CH4） emission and this emission can be greatly reduced if appropriate management practices are applied. Biofiltration has been used in other fields for mitigating greenhouse gas （GHG） emission （e.g., landfill） and shown promise for mitigation OH4 emis- sion from liquid manure storage. It has been reported that biofilter was capable of reducing 80% of CH4 emissions from manure storage. The OH4 removal efficiency is influenced by many factors, including OH4 and 02 concentrations, temperature, moisture, composition of the filter bed, nutrient, and empty bed resi- dency time （EBRT）. Biological conversion of methane of a biofilter is a slow process due to the low water solubility of methane. The residence times （EBRT） between 5 min and 5 h have been used, whereas a typical EBRT of 25 s is used for common biofilter applications. Temperature at which methanotrophic bac- teria are active ranges from 10℃ to 45℃. The maximum activity is found at around 30℃. The optimal filter bed water content depends on both the gas flow rate and the type of filter bed （soil, compost, etc.） and ranges from 30%-70% of the water holding capacity. Compost is the best material for filter bed. The optimal pH for methanotrophic bacteria is neutral to slightly acidic. Copper and nitrogen compounds especially nitrate are important nutrients to methanotrophic bacteria but their optimal concentrations have not been founded. Phosphorus and other elements such as potassium and manganese are reported to affect the performance of methanotrophic bacteria but need further confirmation.