Investigation of decolorization of textile wastewater in an anaerobic/aerobic biological activated carbon system (A/A BAC).

The aim of this study is to investigate the decolorization in anaerobic/aerobic biological activated carbon (A/A BAC) system. The experiment was divided into 2 stages; stage I is batch test for preliminary study of dye removal equilibrium time. The preliminary experiment (stage I) provided the optimal data for experimental design of A/A BAC system in SBR (stage II). Stage II is A/A BAC system imitated Sequencing Batch Reactor (SBR) which consist of 5 main periods; fill, react, settle, draw and idle. React period include anaerobic phase followed by aerobic phase. The BAC main media; Granular Activated Carbon (GAC), Mixed Cultures (MC) and Biological Activated Carbon (BAC) were used for dye and organic substances removal in three different solutions; Desizing Agent Solution (DAS), dye Solution (DS) and Synthetic Textile Wastewater (STW). Results indicate that GAC adsorption plays role in dye removal followed by BAC and MC activities, respectively. In the presence desizing agent, decolorization by MC was improved because desizing agent acts as co-substrates for microorganisms. It was found that 50% of dye removal efficiency was achieved in Fill period by MC. GC/MS analysis was used to identify dye intermediate from decolorization. Dye intermediate containing amine group was found in the solution and on BAC surfaces. The results demonstrated that combination of MC and BAC in the system promotes decolorization and dye intermediate removal. In order to improve dye removal efficiency in an A/A BAC system, replacement of virgin GAC, sufficient co-substrates supply and the appropriate anaerobic: aerobic period should be considered.

Toxicity of reactive red 141 and basic red 14 to algae and waterfleas.

Textile wastewater normally has a visible color although it has low concentration. This may affect the aquatic ecosystem. Two dyestuffs, Reactive Red 141 (RR141) and Basic Red14 (BR14) were used as compound models. RR 141 is an anionic dye which has a big molecule whereas BR 14 is a cationic dye and has a small molecule. The target organisms for toxicity test were green algae (Chlorella sp.) and waterfleas (Moina macrocopa). The effect of humic acid on the toxicity of dyestuffs to test organisms was also investigated. From the observation of cell counts, Chlorophyll a and dry weight of algae in the dye solutions for 4 days, it was found that all parameters increased as times increased. This revealed that algae could utilize dyestuffs as a carbon source. However, BR14 gave higher absorbance than RR141 at the wavelength of 430 nm which competed to the Chlorophyll a for algal photosynthesis. This resulted in the 96-h EC50 of BR14 and RR141 to Chlorella sp. were 10.88 and 95.55 mg/L, respectively. As for dye toxicity to waterfleas, the 48-h LC50 of BR14 and RR141 to waterfleas were 4.91 and 18.26 mg/L, respectively. The high toxicity of BR14 to waterfleas related to the small molecule of dye could pass into the cell and was absorbed by organelles of waterfleas. Toxicity of BR14 in humic acid solution to Chlorella sp. showed less toxic than RR141 in humic acid solution. This dues to the negative charge of humic acid could bound with a positive charge of BR14, resulted in low amount of BR14 remaining in the bulk solution. The toxicity of BR14 and RR141 in humic acid solution to waterfleas was increased as humic acid increased. Hence, the proper treatment of textile wastewater to yield low concentration of dyes in the effluent before discharging to the natural water is needed.

Modification of granular activated carbon surface by chitosan coating for geosmin removal: sorption performances.

This study presents the results of the sorption performances for geosmin removal by sorption onto granular activated carbons (GAC) manufactured from different raw materials of coconut shell and bituminous coal. The surface of GAC was modified by chitosan coating. The 90% deacetylated chitosan flakes were used for coating on GAC with the GAC: chitosan ratio of 5:1. The surface of GAC was characterised by scanning electron microscope (SEM) analysis, Fourier transform infrared spectroscopy and measurement of the pH solution of GAC samples. The sorption of geosmin onto the chitosan for both uncoated and coated GACs could be described by the Freundlich adsorption model. Data revealed that the sequence of Freundlich constant (K(F)) was chitosan coated bitominous coal (CB) > uncoated bituminous coal (UB) > chitos approximately equal to an coated coconut shell (CC) approximately equal to uncoated coconut shell (UC). The bituminous coal based GAC with chitosan coating had a maximum capacity of 23.57 microg/g which was approximately two-fold of uncoated bituminous coal based GAC. Two simplified kinetic models, pseudo-first order and pseudo-second order, were tested to investigate the sorption mechanisms. It was found that the intraparticle diffusion was a rate controlling step for the sorption and followed the pseudo-second order equation.

Degradation of organic substances and reactive dye in an immobilized-cell sequencing batch reactor operation on simulated textile wastewater.

Textile wastewater generally consists of high organic substances and is strongly colored. Reactive dye has been used extensively in the textile industries. It is water soluble and difficult to remove by chemical coagulation. Removal of organic substances simultaneously with dye can be achieved by a biological process. This study aims to investigate the treatability of the organic substances and reactive dye in immobilized-cell sequencing batch reactors (SBR). Three different supporting medias namely activated carbon, steel slag and plastic were used. The performance of each reactor was compared with a conventional sequencing batch reactor. The simulated textile wastewater containing the reactive azo dye Procion Red H-E7B of a concentration of 40 mg/L and COD 300 mg/L, was fed into the reactors. The supporting media in the SBR system, it will enhance the capability of COD and dye operating of the SBRs consisted of 5 periods; Fill 1.5 h, React (anoxic:oxic) 20 (14:6) h, Settle 1.5 h, Draw 0.5 h and Idle 0.5 h. The results revealed that by adding removal. During a steady state of operation, the COD and dye concentrations of each period were investigated. In addition, the prolonged anoxic period brought about better decolorization efficiency.

Quantitative bioregeneration of granular activated carbon loaded with phenol and 2,4-dichlorophenol.

Lignite based granular activated carbon of 20x30 mesh size was used to investigate the extent of bioregeneration of phenol and 2,4-DCP in a batch system. The adsorption isotherm fits very well with the Freundlich isotherm and it is apparent that 2,4-DCP is more adsorbable than phenol. The degree of reversible adsorption for phenol and 2,4-DCP were 32.9 and 10.6 %, respectively. The low percentages of their reversibility meant that the adsorption phenomena of both phenol and 2,4-DCP were not fully physicosorption. The microorganisms can regenerate 31.4% (21.2 mg g(-1)) of GAC loaded with phenol and 14.3% (24.8 mg g(-1)) of GAC loaded with 2,4-DCP over a period of 7-10 days. The bioregeneration of phenols closely followed the first order kinetics with the rate constant of 0.046 day(-1) at initial phenol concentration of 100 mg l(-1) and biomass concentration of 20 mg l(-1) MLVSS. The rate constant was 0.021 day(-1) at initial 2,4-DCP concentration of 200 mg l(-1) and 200 mg l(-1) MLVSS. In addition, the increasing in initial concentration of biomass in the solution shortened the time required to reach the asymptotic limit on the bioregeneration but rendered little impact on the bioregeneration percentage.

A modeling approach to bioregeneration of granular activated carbon loaded with phenol and 2,4-dichlorophenol.

A predictive isotherm model was developed to evaluate the extent of bioregeneration of granular activated carbon loaded with phenol and 2,4-dichlorophenol (2,4-DCP). Two basic substrates (116 mg/L of phenol and 100 g/L 2,4-DCP) as single solute were prepared. The mixture of them was provided to bisolute system for assessing the competitive adsorption. The effect of by-products, which were generated during biodegradation of substrate and measured as COD, on bioregeneration in the bisolute was investigated. Freundlich adsorption parameters (Kads and 1/n) of 2,4-DCP were obviously higher than those of phenol in both single and bisolute. By-products in the bulk solution brought an adverse effect on adsorption capacity of GAC in all cases. By taking into account the by-product effect on adsorption, the Freundlich isotherms were used to formulate a predictive model of bioregeneration. Simulated results showed good consistency of observed results. Practical relevant of the proposed model for assessing of bioregeneration in the wastewater treatment was discussed by applying model to the BAC-SBR in the steady-state operation.

Fish vaccines.

Fish vaccines can be delivered the same way we immunize warm-blooded animals. Fish can be immunized by immersion in vaccine for a short period of time--30 seconds to 2 minutes. They can be immunized by injection, intramuscularly or intraperitoneally, and orally by mixing vaccines with feed either by top dressing or by incorporating into feed as an ingredient. Fish also respond to vaccine the same way as other animals do, but since fish are cold-blooded animals, the response to vaccine depends largely on the water temperature. In general, the higher the water temperature, the faster the immune response of fish to the vaccine. During the past 20 years fish vaccines have become an established, proven, and cost-effective method of controlling certain infectious diseases in aquaculture worldwide. Fish vaccines can significantly reduce specific disease-related losses resulting in a reduction of antibiotics use. The final result is the decrease of overall unit costs and more predictable production. Fish vaccines are advantageous over antibiotics because they are natural biological materials that leave no residue in the product or environment, and therefore will not induce a resistant strain of the disease organism. Fish vaccines are licensed by the federal government and closely regulated in the same manner as all other veterinary vaccines to ensure safety, potency, and efficacy. Even though commercial vaccines for aquaculture work really well in terms of protecting the fish against certain diseases, they should be used only as part of the overall fish health management program, because fish vaccines are not a cure-all. Animal husbandry is still the key to success in aquaculture.

Comparison of whole-cell antigens of pressure- and formalin-killed Flexibacter columnaris from channel catfish (Ictalurus punctatus).

OBJECTIVE: To identify and compare immunodominant antigens in whole-cell lysates of pressure- and formalin-killed Flexibacter columnaris. ANIMALS: Sera from naturally infected and vaccinated channel catfish. PROCEDURES: Whole-cell lysates of pressure- and formalin-killed F columnaris were compared, and antigens were isolated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The antigens were identified by staining, western blotting, and specific monoclonal antibodies to glycoproteins. Western blotting was performed, using sera from channel catfish (Ictalurus punctatus) with naturally acquired F columnaris infection and sera from channel catfish vaccinated with an experimental prototype F columnaris vaccine. RESULTS: Whole-cell lysates of pressure and formalin-killed F columnaris shared 4 proteins: 100, 80, 66, and 60 kd. The 60-kd antigen was a glycoprotein. Western blotting, using sera from naturally infected channel catfish, revealed the same proteins for pressure- and formalin-killed F columnaris. Sera from vaccinated fish reacted only to pressure-killed lysate antigens. CONCLUSIONS: Pressure- and formalin-killed F columnaris whole-cell lysates share 100-, 80-, 66-, and 60-kd proteins and are recognized by antibodies from naturally infected catfish and those vaccinated with formalin-killed F columnaris. Formalin treatment modifies or inactivates the 60-kd protein antigens, rendering them unrecognizable to antibodies from channel catfish naturally infected with F columnaris, suggesting that formalin-killed F columnaris may not be suitable for use as a bacterin against columnaris disease.