Ying-Chien Chung

Adsorption of Cu(II) and Ni(II) by pelletized biopolymer

Chitosan and Ca-alginate, derivatives of biopolymer, were separately prepared from crab chitin and algin in pellet form for adsorption of Cu(II) and Ni(II) from aqueous solutions. The capability of these biopolymers was also investigated to remove copper and nickel from aqueous solutions in an immobilization system, along with a comparison made of these biopolymers with other adsorbents. Additionally, the feasibility of alginate/chitosan in pellets to remove nickel ion and nickel cyanide complex from polluted water was investigated. Stabilizing chitosan physically in an alginate support medium was deemed possible, by means of which both free metal and metal cyanide ions could be removed from aqueous solutions in an engineering system. However, the crosslinking reaction during immobilization would result in blocking of some adsorption sites.

Operation optimization of Thiobacillus thioparus CH11 biofilter for hydrogen sulfide removal

Abstract Members of the autotrophic species, Thiobacillus thioparus CH11, were isolated from swine wastewater and immobilized with Ca-alginate to produce pellet packing materials for a novel biofilter system that controls hydrogen sulfide emission. The effect of operating parameters, including retention time, temperature, and inlet gas concentration, on the removal efficiency and capacity was evaluated. Criteria necessary for a scale-up design of the biofilter were established and the sulfur balances at various loadings were tabulated. High and satisfactory H2S removal efficiency levels were maintained during operation and the optimal retention time was found to be 28 s corresponding to a H2S removal efficiency greater than 98%. The pH drop was insignificant in this biofilter. The optimal inlet S-loading can be noted as 25 g m−3 h−1 that is at the upper end of linear correlation between inlet loading and removal capacity. We suggest that the Thiobacillus thioparus CH11 immobilized with Ca-alginate is a potent method to control hydrogen sulfide emissions.

Biological elimination of H2S and NH3 from wastegases by biofilter packed with immobilized heterotrophic bacteria

Biotreatment of various ratios of H2S and NH3 gas mixtures was studied using the biofilters, packed with co-immobilized cells (Arthrobacter oxydans CH8 for NH3 and Pseudomonas putida CH11 for H2S). Extensive tests to determine removal characteristics, removal efficiency, removal kinetics, and pressure drops of the biofilters were performed. To estimate the largest allowable inlet concentration, a prediction model was also employed. Greater than 95%, and 90% removal efficiencies were observed for NH3 and H2S, respectively, irrespective of the ratios of H2S and NH3 gas mixtures. The results showed that H2S removal of the biofilter was significantly affected by high inlet concentrations of H2S and NH3. As high H2S concentration was an inhibitory substrate for the growth of heterotrophic sulfur-oxidizing bacteria, the activity of H2S oxidation was thus inhibited. In the case of high NH3 concentration, the poor H2S removal efficiency might be attributed to the acidification of the biofilter. The phenomenon was caused by acidic metabolite accumulation of NH3. Through kinetic analysis, the presence of NH3 did not hinder the NH3 removal, but a high H2S concentration would result in low removal efficiency. Conversely, H2S of adequate concentrations would favor the removal of incoming NH3. The results also indicated that maximum inlet concentrations (model-estimated) agreed well with the experimental values for space velocities of 50-150 h(-1). Hence, the results would be used as the guideline for the design and operation of biofilters.

Biotreatment of H2S- and NH3-containing waste gases by co-immobilized cells biofilter

Gas mixture of H2S and NH3 in this study has been the focus in the research area concerning gases generated from the animal husbandry and the anaerobic wastewater lagoons used for their treatment. A specific microflora (mixture of Thiobacillus thioparus CH11 for H2S and Nitrosomonas europaea for NH3) was immobilized with Ca-alginate and packed inside a glass column to decompose H2S and NH3. The biofilter packed with co-immobilized cells was continuously supplied with H2S and NH3 gas mixtures of various ratios, and the removal efficiency, removal kinetics, and pressure drop in the biofilter was monitored. The results showed that the efficiency remained above 95% regardless of the ratios of H2S and NH3 used. The NH3 concentration has little effect on H2S removal efficiency, however, both high NH3 and H2S concentrations significantly suppress the NH3 removal. Through product analysis, we found that controlling the inlet ratio of the H2S/NH3 could prevent the biofilter from acidification, and, therefore, enhance the operational stability. Conclusions from bioaerosol analysis and pressure drop in the biofilter suggest that the immobilized cell technique creates less environmental impact and improves pure culture operational stability. The criteria for the biofilter operation to meet the current H2S and NH3 emission standards were also established. To reach Taiwans current ambient air standards of H2S and NH3 (0.1 and 1 ppm, respectively), the maximum inlet concentrations should not exceed 58 ppm for H2S and 164 ppm for NH3, and the residence time be kept at 72 s.

Removal of hydrogen sulphide by immobilized Thiobacillus sp. strain CH11 in a biofilter

An autotropic Thiobacillus sp. CH11 was isolated from piggery wastewater containing hydrogen sulphide. The removal characteristics of hydrogen sulphide by Thiobacillus sp. CH11 were examined in the continuous system. The hydrogen sulphide removal capacity was elevated by the BDST (Bed Depth Service Time) method (physical adsorption) and an immobilized cell biofilter (biological conversion). The optimum pH to remove hydrogen sulphide ranged from 6 to 8. The average specific uptake rate of hydrogen sulphide was as 1.02 x 10 -13 mol-S cell -1 h -1 in continuous systems. The maximum removal rate and saturation constant for hydrogen sulphide were calculated to be V m = 30.1 mmol-S day -1 (kg-dry bead) -1 and K s = 1.28 μmol dm -3 , respectively. A criterion to design a scale-up biofilter was also studied. The maximum inlet loading in the linear region (95% removal) was 47 mmol-S day -l (kg-dry bead) -1 . Additionally, the biofilter exhibited high efficiency (>98.5%) in the removal of hydrogen sulphide at both low (<0.026 mg dm -3 ) and high (0-078 mg dm -3 ) concentrations. The results suggested that the Thiobacillus sp. CH11 immobilized with Ca-alginate is a potential method for the removal of hydrogen sulphide.

BIOTREATMENT OF AMMONIA FROM AIR BY AN IMMOBILIZED ARTHROBACTER OXYDANS CH8 BIOFILTER

A heterotrophic Arthrobacter oxydans CH8 that was capable of removing NH3 from NH3 containing gas was isolated from livestock farming wastewater. The A. oxydans CH8 was immobilized with calcium alginate packed into filter column. Metered NH3‐containing gas was partially humidified and passed through the glass column. Extensive tests including the removal characteristics, the removal efficiencies, and the metabolic products of NH3 by A. oxydans CH8 were conducted. Additionally, the operation criteria for the biofilter was also established. NH3 removal capacities were elevated by the immobilized‐cell (biological conversion) method and the BDST (bed depth service time) method (physical adsorption), respectively. The optimum temperature for removing NH3 was 30 °C, while the nitrification ability remained 80% at 40 °C. The high efficiency (>97%) in the removal of NH3 was attained at 36 L/h with pH control and was not decreased because of high NH3 inlet concentration. In addition, the high maximum removal rate (1.22 g of N/day·(kg of bead) ) enhanced the use of the biofilter in industrial‐scale NH3(g) pollution control. The ability to remove NH3 at high inlet concentration and temperature suggested that the immobilized A. oxydans CH8 biofilter has potential in processing NH3 gas.

Biofiltration of trimethylamine, dimethylamine, and methylamine by immobilized Paracoccus sp. CP2 and Arthrobacter sp. CP1

A biofilter using granular activated carbon with immobilized Paracoccus sp. CP2 was applied to the elimination of 10-250 ppm of trimethylamine (TMA), dimethylamine (DMA), and methylamine (MA). The results indicated that the system effectively treated MA (>93%), DMA (>90%), and TMA (>85%) under high loading conditions, and the maximum degradation rates were 1.4, 1.2, and 0.9g-Nkg(-1) GAC d(-1). Among the three different amines treated, TMA was the most difficult to degrade and resulted in ammonia accumulation. Further study on TMA removal showed that the optimal pH was near neutral (6.0-8.0). The supply of high glucose (>0.1%) inhibited TMA removal, maybe due to substrate competition. However, complete TMA degradation was achieved under the co-immobilization of Paracoccus sp. CP2 and Arthrobacter sp. CP1 ( approximately 96%). Metabolite analysis results demonstrated that the metabolite NH(4)(+) concentrations decreased by a relatively small 27% while the metabolite NO(2)(-) apparently increased by heterotrophic nitrification of Arthrobacter sp. CP1 in the co-immobilization biofilter.

Two-Stage Biofilter for Effective NH3 Removal from Waste Gases Containing High Concentrations of H2S

Abstract A high H2S concentration inhibits nitrification when H2S and NH3 are simultaneously treated in a single biofilter. To improve NH3 removal from waste gases containing concentrated H2S, a two-stage biofilter was designed to solve the problem. In this study, the first biofilter, inoculated with Thiobacillus thioparus, was intended mainly to remove H2S and to reduce the effect of H2S concentration on nitrification in the second biofilter, and the second biofilter, inoculated with Nitrosomonas europaea, was to remove NH3. Extensive studies, which took into account the characteristics of gas removal, the engineering properties of the two biofilters, and biological parameters, were conducted in a 210-day operation. The results showed that an average 98% removal efficiency for H2S and a 100% removal efficiency for NH3 (empty bed retention time = 23–180 sec) were achieved after 70 days. The maximum degradation rate for NH3 was measured as 2.35 g N day-1 kg of dry granular activated carbon-1. Inhibition of nitrification was not found in the biofilter. This two-stage biofilter also exhibited good adaptability to shock loading and shutdown periods. Analysis of metabolic product and observation of the bacterial community revealed no obvious acidification or alkalinity phenomena. In addition, a lower moisture content (`40%) for microbial survival and low pressure drop (average 24.39 mm H2O m-1) for system operation demonstrated that the two-stage biofilter was energy saving and economic. Thus, the two-stage biofilter is a feasible system to enhance NH3 removal in the concentrated coexistence of H2S.

Operational Characteristics of Effective Removal of H2S and NH3 Waste Gases by Activated Carbon Biofilter

Abstract Simultaneous removal of hydrogen sulfide (H2S) and am- gases. monia (NH3) gases from gaseous streams was studied in a biofilter packed with granule activated carbon. Extensive studies, including the effects of carbon (C) source on the growth of inoculated microorganisms and gas removal efficiency, product analysis, bioaerosol emission, pressure drop, and cost evaluation, were conducted. The results indicated that molasses was a potential C source for inoculated cell growth that resulted in removal efficiencies of 99.5% for H2S and 99.2% for NH3. Microbial community observation by scanning electron microscopy indicated that granule activated carbon was an excellent support for microorganism attachment for long-term waste gas treatment. No disintegration or breakdown of biofilm was found when the system was operated for 140 days. The low bioaerosol concentration emitted from the biofilter showed that the system effectively avoided the environmental risk of bioaerosol emission. Also, the system is suitable to apply in the field because of its low pressure drop and treatment cost. Because NH3 gas was mainly converted to organic nitrogen, and H2S gas was converted to elemental sulfur, no acidification or alkalinity phenomena were found because of the metabolite products. Thus, the results of this study demonstrate that the biofilter is a feasible bioreactor in the removal of waste gases.

Elimination of high concentration hydrogen sulfide and biogas purification by chemical–biological process

A chemical-biological process was performed to remove a high concentration of H2S in biogas. The high iron concentration tolerance (20gL(-1)) of Acidithiobacillus ferrooxidans CP9 provided sufficient ferric iron level for stable and efficient H2S elimination. A laboratory-scale apparatus was setup for a 45 d operation to analyze the optimal conditions. The results reveal that the H2S removal efficiency reached 98% for 1500ppm H2S. The optimal ferric iron concentration was kept between 9 and 11gL(-1) with a cell density of 10(8)CFUg(-1) granular activated carbon and a loading of 15gSm(-3)h(-1). In pilot-scale studies for biogas purification, the average inlet H2S concentration was 1645ppm with a removal efficiency of up to 97% for a 311d operation and an inlet loading 40.8gSm(-3)h(-1). When 0.1% glucose was added, the cell density increased twofold under the loading of 65.1gSm(-3)h(-1) with an H2S removal efficiency still above 96%. The analysis results of the distribution of microorganisms in the biological reactor by DGGE show that microorganism populations of 96.7% and 62.7% were identical to the original strain at day 200 and day 311, respectively. These results clearly demonstrate that ferric iron reduction by H2S and ferrous iron oxidation by A. ferrooxidans CP9 are feasible processes for the removal of H2S from biogas.