Im-Gyu Byun

Biosorption of a reactive dye (Rhodamine-B) from an aqueous solution using dried biomass of activated sludge

Low cost, locally available biomaterial was tested for its ability to remove reactive dyes from aqueous solution. Granules prepared from dried activated sludge (DAS) were utilized as a sorbent for the uptake of Rhodamine-B (Rh-B) dye. The effects of various experimental parameters (dye concentration, sludge concentrations, swelling, pretreatment and other factors) were investigated and optimal experimental conditions were ascertained. Nearly 15min was required for the equilibrium adsorption, and Rh-B dyes could be removed effectively. Dye removal performance of Rh-B and DAS increased with increasing concentrations. The acid pretreated biomass exhibited a slightly better biosorption capacity than alkali pretreated or non-pretreated biomass. The optimum swelling time for dye adsorption of the DAS within the swelling time range studied was 12h. Both the Freundlich and Langmuir isotherm models could describe the adsorption equilibrium of the reactive dye onto the activated sludge with the Langmuir isotherm showing the better agreement of the two. Second-order kinetic models confirmed the agreement.

Microbial community structure and dynamics in a mixotrophic nitrogen removal process using recycled spent caustic under different loading conditions.

A laboratory-scale Bardenpho process was established to investigate the proper nitrogen loading rate (NLR) when modified spent caustic (MSC) is applied as electron donor and alkalinity source for denitrification. MSC injection induced autotrophic nitrogen removal with sulfur as electron donor and heterotrophic denitrification. The nitrogen removal rate (NRR) did not increase proportionally to NLR. Based on the total nitrogen concentration in the effluent observed in the trials with MSC, the NLR in the influent should not exceed 0.15 kg N/m(3)d in order to satisfy water quality regulations. Microbial communities in the anoxic reactors were characterized by pyrosequencing of 16S rRNA gene sequences amplified by the polymerase chain reaction of DNA extracted from sludge samples. Microbial diversity was lower as MSC dosage was increased, and the injection of MSC caused an increase in SOB belonging to the genus Thiobacillus which is responsible for denitrification using sulfur.

Comparison of nitrogen removal and microbial distribution in wastewater treatment process under different electron donor conditions

The applicability of modified spent caustic (MSC) as an electron donor for denitrification was evaluated in a lab-scale reactor for the Bardenpho process under various electron donor conditions: (A) no electron donor, (B) methanol, (C) thiosulfate and (D) MSC conditions. TN removal efficiency varied in each condition, 23.1%, 87.8%, 83.7% and 71.7%, respectively. The distribution ratio of nitrifying bacteria and DGGE profile including sulfur-reducing or oxidizing bacteria also varied depending on the conditions. These results indicated that the MSC would be used as an efficient electron donor for denitrification by autotrophic denitrifier in wastewater treatment process.

Analysis of nitrifying bacterial communities in aerobic biofilm reactors with different DO conditions using molecular techniques.

In order to assess the relationship between the dissolved oxygen (DO) concentration and the characteristics of nitrifying bacterial communities in an aerobic biofilm reactor, molecular techniques including denaturing gradient gel electrophoresis (DGGE)/cloning based on PCR targeting 16S rRNA and the amoA gene and fluorescence in situ hybridisation (FISH) were conducted. The D-1, D-2, D-3 and D-4 reactors with different DO concentrations (1, 3, 5 and 7 mg/L, respectively) were set up in the thermostat and acclimated. The optimal DO concentration with stable nitrification efficiency was above 5.0 mg/L. As was shown by the results of DGGE and cloning, the community of ammonia-oxidising bacteria (AOB) and the ratio of Nitrosomonas sp. changed only slightly despite their differing nitrification efficiencies. The results of FISH indicated that higher DO concentrations resulted in an increase in AOB and nitrite-oxidising bacteria (NOB), and a reduction in heterotrophic microorganisms. The INT-dehydrogenase activity (DHA) test demonstrated that the activity of AOB decreased with reductions in the DO concentration. This means that the DO concentration does not influence the community of AOB, but rather the activity of AOB. In the relationship between the attached biomass and the nitrification efficiency, only the active biomass affected the nitrification efficiencies.

Monitoring of bioventing process for diesel-contaminated soil by dehydrogenase activity, microbial counts and the ratio ofn-alkane/isoprenoid

Monitoring parameters were evaluated for a bioventing process that was designed to treat soils contaminated with diesel fuel. Statistical analyses were conducted to evaluate correlations between total petroleum hydrocarbon concentrations in the contaminated soil and physico-chemical parameters of soil such as microbial counts, dehydrogenase activity, andn-alkane/isoprenoid ratio. The correlation coefficients (r2) obtained showed that TPH concentrations in the bioventing system were strongly correlated with dehydrogenase activity (DHA), total heterotrophic bacterial count, and hydrocarbon utilizing bacterial count. Thus, it was concluded that these parameters could useful monitoring parameters for soils contaminated with diesel fuel

Evaluation of non-thermal effects by microwave irradiation in hydrolysis of waste-activated sludge

The activation energy (Ea) for waste-activated sludge (WAS) hydrolysis was compared between microwave irradiation (MW) and conventional heating (CH) methods to evaluate the non-thermal effect of MW. The microwave-assisted hydrolysis of WAS was assumed to follow the first-order kinetics on the basis of volatile suspended solids (VSS) conversion to soluble chemical oxygen demand (SCOD) for different initial VSS concentrations. By comparing the VSS decrement and the SCOD increment between MW and CH at different absolute temperatures of 323, 348 and 373 K, the average ratio of VSS conversion to SCOD was determined to range from 1.42 to 1.64 g SCOD/g VSS. These results corresponded to the theoretical value of 1.69 g SCOD/g VSS based on the assumption that the molecular formula of sludge was C10H19O3N. Consequently, the Ea of the MW-assisted WAS hydrolysis was much lower than that of CH for the same temperature conditions. The non-thermal effect of MW in the hydrolysis of WAS could be identified with the lower Ea than that of CH.

Low Temperature Effects on the Nitrification in a Nitrogen Removal Fixed Biofilm Process Packed with SAC Media

A fixed biofilm reactor system composed of anaerobic, anoxic(1), anoxic(2), aerobic(1) and aerobic(2) reactor was packed with synthetic activated ceramic (SAC) media and adopted to reduce the inhibition effect of low temperature on nitrification activities. The changes of nitrification activity at different wastewater temperature were investigated through the evaluation of temperature coefficient, volatile attached solid (VAS), specific nitrification rate and alkalinity consumption. Operating temperature was varied from 20 to . In this biofilm system, the specific nitrification rates of , and were 0.972, 0.859 and 0.613 when the specific nitrification rate of was assumed to 1.00. Moreover the nitrification activity was also observed at which is lower temperature than the critical temperature condition for the microorganism of activated sludge system. The specific amount of volatile attached solid (VAS) on media was maintained the range of 13.6-12.5 mg VAS/g media at . As the temperature was downed to , VAS was rapidly decreased to 10.9 mg VAS/g media and effluent suspended solids was increased from 3.2 mg/L to 12.0 mg/L due to the detachment of microorganism from SAC media. And alkalinity consumption was lower than theoretical value with 5.23 mg as /mg -N removal at . Temperature coefficient () of nitrification rate () was 1.033. Therefore, this fixed film nitrogen removal process showed superior stability for low temperature condition than conventional suspended growth process.

The feasibility of using spent sulfidic caustic as alternative sulfur and alkalinity sources in autotrophic denitrification

Batch experiments using acclimated sludge to sulfur utilizing autotrophic denitrification were performed to determine the applicability of spent sulfidic caustic in autotrophic denitrification as alternative sulfur and alkalinity sources. Fluorescence insitu hybridization (FISH) analysis showed that the microbial community of β-proteobacteria/ Eubacteria increased from 45% to 69% during enrichment period and nitrate removal reached up to 84% under this enriched sludge condition. In thiosulfate utilizing autotrophic denitrification, the initial condition at a sulfur/nitrate (S/N) ratio of 1.5 showed higher nitrate removal with 95.9%, and nitrate removal could be expressed by a first-order function of biomass concentration if all parameters such as pH, alkalinity and S/N ratio were in the optimum range. In spent sulfidic caustic utilizing autotrophic denitrification, the sulfate formation ratios to nitrate reduction were lower than those in thiosulfate utilizing autotrophic denitrification with a range of 2.65 to 2.78, and nitrate removal was over 95% at 1.0 and 1.5 S/N ratios. For S/N ratios of 1.0 and 1.5, initial alkalinities were sufficient to maintain optimum pH range of autotrophic denitrification. Furthermore, well enriched seeding sludge showed good activity of autotrophic denitrification at pH over 10. Therefore, spent sulfidic caustic could be effectively applied to autotrophic denitrification as an alternative sulfur source and an alkalinity source

Characteristics of nitrogen removal and microbial distribution by application of spent sulfidic caustic in pilot scale wastewater treatment plant

Since spent sulfidic caustic (SSC) produced from petrochemical industry contains a high concentration of alkalinity and sulfide, it was expected that SSC could be used as an electron donor for autotrophic denitrification. To investigate the nitrogen removal performance, a pilot scale Bardenpho process was operated. The total nitrogen removal efficiency increased as SSC dosage increased, and the highest efficiency was observed as 77.5% when SSC was injected into both anoxic tank (1) and (2). FISH analysis was also performed to shed light on the effect of SSC dosage on the distribution ratio of nitrifying bacteria and Thiobacillus denitrificans. FISH results indicated that the relative distribution ratio of ammonia-oxidizing bacteria, Nitrobacter spp., Nitrospira genus and Thiobacillus denitrificans to eubacteria varied little with the pH of the tanks, and SSC injection did not give harmful effect on nitrification efficiency. These results show that SSC can be applied as an electron donor of autotrophic denitrification to biological nitrogen removal process effectively, without any inhibitory effects to nitrifying bacteria and sulfur-utilizing denitrifying bacteria.

The Effect of Strong Acid and Ionic Material Addition in the Microwave-assisted Solubilization of Waste Activated Sludge

The study of waste activated sludge (WAS) solubilization has been increased for sludge volume reduction and enhancing the efficiency of anaerobic digestion. Microwave (MW)-assisted solubilization is an effective method for the solubilization of WAS because this method can lead to thermal, nonthermal effect and ionic conduction by dielectric heating. In this study, the solubilization of WAS by MW heating and conductive heating (CH) was compared and to enhance the MW-assisted solubilization of WAS at low MW output power, chemical agents were applied such as H2SO4 as the strong acid and CaCl2, NaCl as the ionic materials. Compared to the COD solubilization of WAS by CH, that by MW heating was approximately 1.4, 6.2 times higher at 50°C, 100 °C, respectively and the highest COD solubilization of WAS was 10.0% in this study of low MW output power condition. At the same MW output power and reaction time in chemically agents assisted experiments, the COD solubilization of WAS were increased up to 18.1% and 12.7% with the addition of H2SO4 and NaCl, however, that with the addition of CaCl2 was 10.7%. This result might be due to the fact that the precipitation reaction occurred by calcium ion (Ca) and phosphate ion (PO4) produced in WAS after MW-assisted solubilization. In this study, H2SO4 turned out to be the optimal agent for the enhancement of MW efficiency, the addition of 0.2 M H2SO4 was the most effective condition for MW-assisted WAS solubilization.