Sequencing batch biofilter granular reactor for textile wastewater treatment

Textile wastewater is difficult to treat as it usually contains considerable amounts of different pollutants, which are often recalcitrant, toxic and inhibitory. Therefore, complex treatment schemes based on the sequence of various steps are usually required for an effective treatment. This explains why textile effluents are often treated in centralized plants and sometimes mixed with municipal wastewater. The adoption of new technologies for on-site treatment, instead, would be optimal, deeply reducing treatment costs. An innovative technology exhibiting several characteristics appropriate for the attainment of such a goal is sequencing batch biofilter granular reactor (SBBGR). To assess the suitability of this technology, two lab-scale reactors were operated, treating mixed municipal-textile wastewater and a pure textile effluent, respectively. Results have demonstrated that mixed wastewater can be successfully treated with very low hydraulic retention times (less than 10 hours). Furthermore, SBBGR shows to be an effective pre-treatment for textile wastewater for discharge into sewer systems. The economic evaluation of the process showed operative costs of 0.10 and 0.19 € per m(3) of mixed wastewater and textile wastewater, respectively.     

Use of aged refuse-based bioreactor/biofilter for landfill leachate treatment

Sanitary landfilling is a proven way for disposal of municipal solid waste (MSW) in developed countries in general and in developing countries in particular, owing to its low immediate costs. On the other hand, landfilling is a matter of concern due to its generation of heavily polluted leachate. Landfill leachate becomes more refractory with time and is very difficult to treat using conventional biological processes. The aged refuse-based bioreactor/biofilter (ARB) has been shown to be a promising technology for the removal of various pollutants from landfill leachate and validates the principle of waste control by waste. Based on different environmental and operational factors, many researchers have reported remarkable pollutant removal efficiencies using ARB. This paper gives an overview of various types of ARBs used; their efficiencies; and certain factors like temperatures, loading rates, and aerobic/anaerobic conditions which affect the performance of ARBs in eliminating pollutants from leachate. Treating leachate by ARBs has been proved to be more cost-efficient, environment friendly, and simple to operate than other traditional biological techniques. Finally, future research and developments are also discussed.     

Addressing biofilter limitations: A two-phase partitioning bioreactor process for the treatment of benzene and toluene contaminated gas streams

A two-phase partitioning bioreactor (TPPB) achievedsimultaneous and continuous removal and degradation of benzene and toluene froman air stream. The aqueous-organic system utilized n-hexadecane as the organicphase, and the organism Alcaligenes xylosoxidans Y234 in the aqueous phaseto achieve the degradation of benzene and toluene. The system, which operates asa well-mixed dispersion and is therefore resistant to substrate surges, was firstshown to be capable of utilizing toluene while operating at a loading capacity of 235 g m^-3 h^-1with an elimination capacity of 233 g m^-3 h^-1. It was also determined that to characterize TPPB performance in terms of elimination capacity thedefinition of elimination capacity must be extended to include the cell mass present, a readilycontrollable variable given the nature of the system. Based on this criterion, it wasestimated that for a cell concentration of 1 g l^-1 present in the TPPB, thepotential maximum toluene elimination capacity is 1290 g m^-3 h^-1 whichis substantially higher than any toluene elimination capacity achieved by biofiltersat a high removal efficiency. If no other factor were to limit the system, eliminationcapacities could be many times higher still, and are dependent on maintaining desiredcell concentrations above 1 g l^-1. The TPPB was then operated at nominalloading capacities of 63 g m^-3h^-1 (benzene) and 51 g m^-3 h^-1 (toluene) at a removal efficiency greater than 99% to demonstratedthe applicability of this system in dealing with two chemical species simultaneously. TPPBsystems therefore have been shown to be effective at removing gaseous organiccontaminants at high removal efficiencies while also possessing desirable operatingfeatures, such as providing and maintaining high cell concentrations throughout thereactor, and a capacity to effectively deal with high contaminant loadings.     

Characterization of the denitrifying bacterial community in a full-scale rockwool biofilter for compost waste-gas treatment

The potential denitrification activity and the composition of the denitrifying bacterial community in a full-scale rockwool biofilter used for treating livestock manure composting emissions were analyzed. Packing material sampled from the rockwool biofilter was anoxically batch-incubated with 15N-labeled nitrate in the presence of different electron donors (compost extract, ammonium, hydrogen sulfide, propionate, and acetate), and responses were compared with those of activated sludge from a livestock wastewater treatment facility. Overnight batch-incubation showed that potential denitrification activity for the rockwool samples was higher with added compost extract than with other potential electron donors. The number of 16S rRNA and nosZ genes in the rockwool samples were in the range of 1.64–3.27 × 109 and 0.28–2.27 × 108 copies/g dry, respectively. Denaturing gradient gel electrophoresis analysis targeting nirK, nirS, and nosZ genes indicated that the distribution of nir genes was spread in a vertical direction and the distribution of nosZ genes was spread horizontally within the biofilter. The corresponding denitrifying enzymes were mainly related to those from Phyllobacteriaceae, Bradyrhizobiaceae, and Alcaligenaceae bacteria and to environmental clones retrieved from agricultural soil, activated sludge, freshwater environments, and guts of earthworms or other invertebrates. A nosZ gene fragment having 99% nucleotide sequence identity with that of Oligotropha carboxidovorans was also detected. Some nirK fragments were related to NirK from micro-aerobic environments. Thus, denitrification in this full-scale rockwool biofilter might be achieved by a consortium of denitrifying bacteria adapted to the intensely aerated ecosystem and utilizing mainly organic matter supplied by the livestock manure composting waste-gas stream.     

Ion exchange resins as catalyst for the isomerization of alpha-pinene to camphene

Camphene is an industrial intermediate compound for commercial chemicals such as isoborneol, isobornyl acetate and camphor. Industrially, the conventional process for camphene production consists of the isomerization of alpha-pinene using acidic TiO2 as catalyst. The use of this catalyst presents problems such as considerable time for preparation, reproducibility and recovery of catalyst from products after the alpha-pinene isomerization. For the first time, a commercial exchange resin was used as catalyst for this reaction. Based on the concentration of product as a function of the reaction time, the path of the alpha-pinene transformation to camphene and byproducts is proposed. Temperature and alpha-pinene/catalyst ratio were studied in order to optimize the yield to camphene production. The obtained results were comparable with those reported for acidic TiO2.     

Performance and efficiency of a yeast biofilter for the treatment of a Nigerian fertilizer plant effluent

A biofilter composed of yeasts and cassava peel was used to detoxify fertilizer plant effluent. The biological oxygen demand was reduced on treatment from a range of 1200–1400 mg/l to a range 135–404 mg/l. The ammonia-nitrogen (NH₃–N) and nitrate-nitrogen (NO₃–N) were reduced after treatment from 1000 to 10 mg/l and from 100 to 17.6 mg/l, respectively. The biofilter is simple and easy to handle with high efficiency of 98%.     

Development and operation of a trickling biofilter system for continuous treatment of gas-phase trichloroethylene

A parallel trickling biofilter (TBF) system that consists of two TBFs units in parallel, one for biodegradation of trichloroethylene (TCE) and the other for reactivation of an inactivated biofilm, was developed and operated for continuous treatment of gas-phase TCE by Burkholderia cepacia G4. For inlet loadings below 8.6 mg TCE l^–1 d^–1, complete removal of TCE was achieved. The maximal TCE elimination capacity was 17 mg l^–1 d^–1.     

废气处理生物滤器微生物生态学研究进展

废气生物处理是一项新兴的气体污染控制技术,已成为当前环境领域的研究热点.本文概述了生物滤器系统(包括生物过滤器系统和生物滴滤器系统)结构及其去除气体污染物的原理,重点阐述了生物滤器微生物的分离、鉴定及其降解特性,微生物丰度、活性与微生物群落结构多样性之间的相关性,运行条件对微生物群落的影响,微生物群落结构时空变化规律,生物膜形成机理和模型等方面的研究进展,并对今后废气处理生物滤器微生物生态学研究方向进行了展望.     

Microbial oxidation of alpha-pinene by Serratia marcescens

Summary A strain of the bacterium Serratia marcescens, isolated from sewage sludge, can oxidise the terpene hydrocarbon -pinene to produce rans-verbenol as the major product, with verbeone and trans-sobrerol as minor products. A change in nitrogen source and inclusion of glucose as a second carbon source caused the bacterium to produce -terpineol as the major oxidation product. Products were identified by gas liquid chromatography and mass spectrometry.     

Application of biological activated carbon as a low pH biofilter medium for gas mixture treatment

Packing material is a crucial component of a bioreactor as it is the microbial population's habitat. This study assessed potential improvements to current biofiltration processes by investigating use of a novel support medium. Biological activated carbon (BAC) with microorganisms growing on granular activated carbon can produce a novel medium in which both adsorption and biodegradation contribute to pollutants removal. Investigation of carbon characteristics demonstrated that BAC was an ideal packing medium for biofiltration. The application of the novel packing medium for gas mixture treatment was evaluated in a low pH biofilter. Results demonstrated that BAC biofilter obtained high removal efficiency for both H(2)S and toluene. The removal mechanisms of BAC were investigated after the biofilter operation and it demonstrated that the performance of the BAC system was mainly controlled by the additive contributions of two removal mechanisms - adsorption and biodegradation. This study also indicated the potential for simultaneous treatment of hydrogen sulfide and toluene at low pH condition.     

Bacterial metabolism of alpha-pinene: pathway from alpha-pinene oxide to acyclic metabolites in Nocardia sp. strain P18.3.

Over 20 gram-positive bacteria were isolated by elective culture with (+/-)-alpha-pinene as the sole carbon source. One of these strains, Nocardia sp. strain P18.3, was selected for detailed study. alpha-Pinene-grown cells oxidized, without lag, alpha-pinene, alpha-pinene oxide (epoxide), and the cis and trans isomers of 2-methyl-5-isopropylhexa-2,5-dienal. No other tested terpene was oxidized at a significant rate. alpha-Pinene was not metabolized by cell extracts in the presence or absence of NADH or NADPH. Cell extracts catalyzed a rapid decyclization of alpha-pinene oxide, in the absence of added cofactors, with the formation of cis-2-methyl-5-isopropylhexa-2,5-dienal. Further oxidation of the aldehyde to the corresponding acid occurred in the presence of NAD. Both activities were induced by growth with alpha-pinene. A rapid, nonenzymic transformation of the cis aldehyde into the trans isomer occurred in glycine buffer. The trans isomer was also a substrate for the NAD-linked aldehyde dehydrogenase. The distribution of the alpha-pinene oxide lyase in alpha-pinene-utilizing Pseudomonas spp. was also investigated and was compatible with the two alternative ring-cleavage sequences that have been proposed on the basis of accumulated metabolites.     

Modeling nitrogen removal for a denitrification biofilter

Nitrous oxide (N₂O) is a major greenhouse gas, heavily contributing to global warming. N₂O is emitted from various sources such as wastewater treatment plants, during the nitrification and denitrification steps. ASM models, which are commonly used in wastewater treatment, usually consider denitrification as a one-step process (NO₃ ⁻ directly reduced to N₂) and are as such unable to provide values for intermediate products of the reaction like N₂O. In this study, a slightly modified ASM1 model was implemented in the GPS-X™ software to simulate the concentration of such intermediate products (NO₂ ⁻, NO and N₂O) and to estimate the amounts of gaseous N₂O emitted by the denitrification stage (12 biofilters) of the Seine-Centre WWTP (SIAAP, Paris). Simulations running on a 1-year period have shown good agreements with measured effluent data for nitrate and nitrite. The calculated mean value for emitted N₂O is 4.95 kgN–N₂O/day, which stands in the typical range of estimated experimental values of 4–31 kgN–N₂O/day. Nitrous oxide emissions are usually not measured on WWTPs and so, as obtained results show, there is a certain potential for using models that quantify those emissions using traditionally measured influent data.     

A model for treating toluene and acetone mixtures by a trickle-bed air biofilter

A mathematical model that incorporates mass transfer process and biofilm reactions is presented to predict the performance of a trickle-bed air biofilter (TBAB) for treating toluene (T) and acetone (ACE) mixtures. The model consists of a set of mass balance equations for T, ACE and oxygen in the bulk gas phase and within the biofilm. The gas phase T and ACE concentrations predicted by the model were in good agreement with the measured data available in a previous study. The important parameters were evaluated in the sensitivity analysis to determine their respective effects on the model performance. Four parameters were identified as strongly influencing the model performance, the surface area of the biofilm per unit volume of packing material (A _S), the empty-bed residence time (EBRT), the maximum specific growth rate of microorganism ( _m), and the microbial yield coefficient (Y). A practical application of the model to derive the performance equation of TBAB is also given.     

A novel three-stage seaweed (Ulva lactuca) biofilter design for integrated mariculture

Seaweed biofilters have proven their usefulness in the treatment of fishpond effluents. However, their performance poses a dilemma: TAN (Total Ammonia N) uptake rate – and with it seaweed yield and protein content – is inversely proportional to TAN uptake efficiency. The ideal for a seaweed biofilter performance would be a high uptake rate together with high uptake efficiency. The novel three-stage seaweed biofilter design described here has solved this dilemma. The design used the finding that the performance of seaweed ponds depended on the flux of TAN through them, and that therefore effluents with reduced TAN concentration could provide the seaweed with a high TAN flux if the water flow increased proportionally. Effluents from a seabream fishpond were passed through a series of three successively smaller (25, 12.5 and 6.25 m², respectively) air-agitated Ulva lactuca ponds. The diminished inflow TAN concentrations to the second and third ponds of the biofilter system were compensated for by the increased water exchange rates, inversely proportional to their sizes. The biofilter performance was evaluated under several TAN loads. TAN was efficiently removed (85–90%), at a high areal rate (up to 2.9 g N m^-2 d^-1) while producing high protein U. lactuca (up to 44% dw) in all three stages, although with mediocre yields (up to 189 g fresh m^-2 d^-1). Performance of each seaweed biofilter pond correlated not with TAN concentration, but with areal TAN loads. The novel three-stage design provides significant functional and economic improvements in seaweed biofiltration of intensive fishpond water.     

A model for treating isopropyl alcohol and acetone mixtures in a trickle-bed air biofilter

A mathematical model that incorporates mass transfer process and biofilm reactions is presented to predict the performance of a trickle-bed air biofilter (TBAB) for treating isopropyl alcohol (IPA) and acetone (ACE) mixtures. The model consists of a set of mass balance equations for IPA, ACE and oxygen in the bulk gas phase and within the biofilm. The effluent gas phase IPA and ACE concentrations predicted by the present model were in good agreement with the measured data available in a previous study. The important parameters were evaluated by sensitivity analysis to determine their respective effects on model performance. Four parameters were identified that strongly influenced model performance: surface area of the biofilm per unit volume of packing material (A_S), empty-bed residence time (EBRT), maximum specific growth rate of microorganism (μ_m), and microbial yield coefficient (Y). Practical applications of the model to derive the performance equation of TBAB for treating different inlet IPA and ACE concentrations were also demonstrated.     

Microbial treatment of a styrene-contaminated air stream in a biofilter with high elimination capacities

A styrene-utilizing mixed microbial culture was isolated and utilized in a biofilter for the biological treatment of a contaminated air stream. Biofilter media consisted of composted wood bark and yard waste. The biofilters were acclimated at 120 s residence time and further evaluated at 60 and 30 s gas residence times. The biofilters received organic loading rates of up to 350 g/m³ h. The styrene volumetric removal rate was a function of the organic loading rate and increased with increasing loading rates. Average volumetric removal rates of 69–118 g/m³ h observed in our studies were higher than reported values for styrene biofilters. Average styrene removal efficiencies ranged from 65% to 75% (maximum 100%). Axial analysis of styrene concentration along the column indicated that the bulk of the styrene removal occurred in the first section of the biofilter. Analyses of the media indicated that the moisture content of the first section (50–55% w/w) was significantly lower than in the second and third sections (65–70% w/w). The pressure drops across the biofilter were low due to the high concentration of large media particles. The total pressure drops were 1–3, 4–6, and 10–16 mm for the 120-, 60-, and 30-s residence time periods, respectively. Journal of Industrial Microbiology & Biotechnology (2001) 26, 196–202. Received 04 March 2000/ Accepted in revised form 25 January 2001     

Development of a biofilter for the removal of methane from coal mine ventilation atmospheres

Several strains of methane-oxidizing bacteria were isolated and studied to determine their physiological suitability for removal of methane in coal mine atmospheres. One strain, Methylomonas fodinarum ACM 3268, was selected as the most suitable culture for use in the development of a continuous biofilter to be used as a ventilation air scrubber. The experimental biofilter utilising a biofilm of M. fodinarum was shown to reduce methane levels substantially provided the residence times were sufficiently long. In the range 0.25–1.0% methane in air, commonly experienced in coal mine atmospheres, more than 70% of the methane was removed with a residence time of 15 min, with a 90% reduction at 20 min. Even at a residence time of 5 min approximately 20% of the methane in air was removed. Equal quantities of O₂ are consumed during the bacterial oxidation of methane and 1% methane is converted to 0.7% CO₂. Scale-up and alternative biofilter packings are likely to reduce the residence times in the biofilter.     

Mesophilic and thermophilic BTEX substrate interactions for a toluene-acclimatized biofilter

Benzene, toluene, ethylbenzene and xylene (BTEX) substrate interactions for a mesophilic (25°C) and thermophilic (50°C) toluene-acclimatized composted pine bark biofilter were investigated. Toluene, benzene, ethylbenzene, o-xylene, m-xylene and p-xylene removal efficiencies, both individually and in paired mixtures with toluene (1:1 ratio), were determined at a total loading rate of 18.1 g m^–3 h^–1 and retention time ranges of 0.5–3.0 min and 0.6–3.8 min for mesophilic and thermophilic biofilters, respectively. Overall, toluene degradation rates under mesophilic conditions were superior to degradation rates of individual BEX compounds. With the exception of p-xylene, higher removal efficiencies were achieved for individual BEX compounds compared to toluene under thermophilic conditions. Overall BEX compound degradation under mesophilic conditions was ranked as ethylbenzene >benzene >o-xylene >m-xylene >p-xylene. Under thermophilic conditions overall BEX compound degradation was ranked as benzene >o-xylene >ethylbenzene >m-xylene >p-xylene. With the exception of o-xylene, the presence of toluene in paired mixtures with BEX compounds resulted in enhanced removal efficiencies of BEX compounds, under both mesophilic and thermophilic conditions. A substrate interaction index was calculated to compare removal efficiencies at a retention time of 0.8 min (50 s). A reduction in toluene removal efficiencies (negative interaction) in the presence of individual BEX compounds was observed under mesophilic conditions, while enhanced toluene removal efficiency was achieved in the presence of other BEX compounds, with the exception of p-xylene under thermophilic conditions.