ADMI Value Research Articles

Bacteria-mediated bio-degradation of reactive azo dyes coupled with bio-energy generation from model wastewater

The wastewaters produced from dyeing process in textile industries contain xenobiotic mixed reactive dyes that have negative impact on ecosystem when discharged as untreated/partially treated. The present study aims to degrade mixed dyes (reactive red 21 (RR21) and reactive orange 16 (RO16)) present in wastewater by Pseudomonas aeruginosa 23N1. The process optimization and the effect of experimental parameters (like amount of co-substrate, pH and temperature) on process performance are investigated through response surface methodology. To understand the extent of degradation of dye compounds, metabolites extracted from treated water samples were investigated using UV–visible, FTIR and GC-MS analyses. The results reveal that the bacteria could significantly reduce ADMI value of wastewater by ~ 87% against the initial mixed dyes containing aqueous solution (50 mg/L each of RR21 and RO16 dyes). The analysis of extracted metabolites from treated water sample indicates the utilization of dye compounds as nutrient by bacteria. The bacteria might exhibit satisfactory ADMI reduction in the presence of initial ≤ 100 mg/L Cr(VI) concentration. The bio-degradation is performed under microbial fuel cell in the presence of co-substrate yeast extract and found very much promising in terms of faster ADMI reduction and energy production. The maximum output voltage generation of 790 ± 5 mV and power density 940.61 ± 5 mW/m2 are recorded during decolourization of mixed dye-laden real wastewater in a microbial fuel cell. The bacteria studied here confirm the effective bio-decolourization of real textile wastewater.

Tackling colour issue of anaerobically-treated palm oil mill effluent using membrane technology

In this work, the performances of membranes with different properties were evaluated for their capabilities in treating anaerobically-treated palm oil mill effluent (AT-POME). Unlike raw POME, AT-POME is the effluent that has been biologically treated to reduce mainly the organic compounds present in the effluent. The treated effluent however still demonstrates brownish by the time it is discharged to receiving water bodies. The samples treated by membranes were assessed with respect to two colour parameters, i.e. absorbance at 370nm wavelength and ADMI value. Other parameters also considered were total organic carbon (TOC) and total nitrogen (TN). Results showed that nanofiltration membrane (NF270) always demonstrated greater colour removal efficiencies in comparison to ultrafiltration membranes (UF 10kDa and UF 30kDa). The NF270 membrane achieved 97.4–97.9% colour removal compared to 72.4–75.4% and 48.1–50.5% shown by UF 10kDa and UF 30kDa, respectively. Further sample quality analyses revealed that NF membrane could achieve higher TOC and TN removal than those of UF membranes. Although NF membrane demonstrated excellent separation, its performance was compromised by low water flux (6.58L/m2h at 10bar). Since the treated effluent is not targeted for reuse, employing UF 10kDa membrane with reasonably good rejection rate coupled high water flux (9.66L/m2h at 5bar) is considered good enough to meet the discharged requirements. Further investigations have shown that UF 10kDa membrane is less susceptible to fouling when it is operated at low pressure and for the fouled membrane, chemical cleaning could be employed to retrieve water flux.

Decolorization and detoxification of sulfonated toxic diazo dye C.I. Direct Red 81 by Enterococcus faecalis YZ 66.

Isolated Enterococcus faecalis YZ 66 strain shows ability to decolorize various industrial dyes among which, it showed complete decolorization and degradation of toxic, sulfonated recalcitrant diazo dye Direct Red 81 (50 mg/L) within 1.5 h of incubation under static anoxic condition. The optimum pH and temperature for decolorization was 7.0 and 40°C, respectively. Significant induction in the activity of intracellular oxidoreductive enzymes suggested its involvement in the decolorization of Direct Red 81. The biodegradation of Direct Red 81 was monitored by UV-Visible, FT-IR spectroscopy and HPLC. The final products were characterized by GC-MS and possible pathway of the degradation of the dye was proposed. The phytotoxicity assay (with respect to plants Sorghum vulgare and Phaseolus mungo) revealed that the degradation of Direct Red 81 produced nontoxic metabolites. Finally E. faecalis was employed to decolorize actual industrial effluent showing decolorization (in terms of ADMI value) with moderate COD and BOD reduction. Moreover the result increases the applicability of the strain for the treatment of industrial wastewaters containing dye pollutants.Electronic supplementary materialThe online version of this article (doi:10.1186/s40201-014-0151-1) contains supplementary material, which is available to authorized users.

Decolorization and detoxification of sulfonated azo dye C.I. Remazol Red and textile effluent by isolated Lysinibacillus sp. RGS

A novel bacterium was isolated from the soil of Ichalkaranji textile industrial area. Through 16S rRNA sequence matching and morphological observation it was identified as Lysinibacillus sp. RGS. This strain has ability to decolorize various industrial dyes among which, it showed complete decolorization and degradation of toxic sulfonated azo dye C.I. Remazol Red (at 30°C, pH 7.0, under static condition) with higher chemical oxygen demand (COD) reduction (92%) within 6h of incubation. Various parameters like agitation, pH, temperature and initial dye concentrations were optimized to develop faster decolorization process. The supplementation of cheap co-substrates (e.g., extracts of agricultural wastes) could enhance the decolorization performance of Lysinibacillus sp. RGS. Induction in oxidoreductive enzymes presumably indicates involvement of these enzymes in the decolorization/degradation process. Analytical studies of the extracted metabolites confirmed the significant degradation of Remazol Red into various metabolites. The phytotoxicity assay (with respect to plants Phaseolus mungo and Sorghum vulgare) revealed that the degradation of Remazol Red produced nontoxic metabolites. Finally Lysinibacillus sp. RGS was applied to decolorize mixture of dyes and actual industrial effluent showing 87% and 72% decolorization (in terms of decrease in ADMI value) with 69% and 62% COD reduction within 48h and 96h, respectively. The foregoing result increases the applicability of the strain for the treatment of industrial wastewaters containing dye pollutants.

Decolorization and degradation of reactive azo dyes by fixed bed bioreactors containing immobilized cells of Proteus vulgaris NCIM-2027

Immobilized cells of Proteus vulgaris NCIM 2027 completely decolorized C.I. Reactive Blue 172 (50 mg/L) within 8 h along with a nearly 80% reduction in TOC and COD. The dye degradation efficiency of the immobilized cells was further improved by optimizing the physicochemical conditions, including agitation, temperature, pH, dye concentration, and biomass loading. Microbial toxicity study revealed the non-toxic nature of the degraded products. Repeated-batch decolorization was conducted to evaluate the reusability of the immobilized cells. The immobilized cells were used for continuous dye decolorization in a fixed bed bioreactor under different volumetric flow rates and dye feeding concentrations. In addition, the immobilized cells were applied to decolorize a mixture of seven reactive dyes in batch and continuous modes, resulting in efficient decolorization (in terms of ADMI value) and significant reduction in TOC and COD. This suggests the potential of using immobilized cells to treat dye-containing wastewater.

Fixed-bed decolorization of Reactive Blue 172 by Proteus vulgaris NCIM-2027 immobilized on Luffa cylindrica sponge

Proteus vulgaris NCIM-2027 cells immobilized on Luffa cylindrica (Loofa) completely decolorized C.I. Reactive Blue 172 at 37 °C and pH 8.0 under 5-h static incubation with high total organic carbon (TOC) and chemical oxygen demand (COD) reduction. The repeated-batch decolorization experiments also indicate good reusability of the immobilized biocatalyst. Some oxidoreductive enzymes were shown to be involved in the decolorization and degradation process. Loofa immobilized cells were also able to decolorize a mixture of reactive dyes in batch mode (in terms of ADMI value) with significant reduction in TOC and COD. Loofa immobilized cells were also used for continuous decolorization of individual and mixture of reactive dyes in a fixed bed bioreactor.

Ecofriendly degradation of sulfonated diazo dye C.I. Reactive Green 19A using Micrococcus glutamicus NCIM-2168

Micrococcus glutamicus NCIM-2168 exhibited complete decolorization and degradation of C.I. Reactive Green 19A (an initial concentration of 50 mg l −1) within 42 h at temperature 37 °C and pH 8, under static condition. Extent of mineralization was determined with total organic carbon (TOC) and chemical oxygen demand (COD) measurement, showing a satisfactory reduction of TOC (72%) and COD (66%) within 42 h. Enzyme studies shows involvement of oxidoreductive enzymes in decolorization/degradation process. Analytical studies of the extracted metabolites confirmed the significant degradation of Reactive Green 19A into various metabolites. The microbial toxicity and phytotoxicity assay revealed that the degradation of Reactive Green 19A produced nontoxic metabolites. In addition, the M. glutamicus strain was applied to decolorize a mixture of ten reactive dyes showing a 63% decolorization (in terms of decrease in ADMI value) within 72 h, along with 48% and 42% reduction in TOC and COD under static condition.

Calcium enhanced COD removal for the ozonation of phenol solution

In order to improve the chemical oxygen demand (COD) removal rate for the ozonation of phenol solution, ozonation combined with calcium binding was investigated. The results show that the addition of Ca 2+ can effectively enhance the COD removal rate. During the ozonation, calcium ion can bind with some of the intermediate products of phenol, including high molecular weight products, maleic acid and oxalic acid, to form insoluble precipitates. These calcium binding effects are responsible for the enhancement of COD removal. The variations of ADMI value during ozonation are similar for solutions with and without Ca 2+. However, the peak ADMI value in calcium-contained solution is lower than that without Ca 2+. As the phenol was completely decomposed, the ozone gas outlet concentration rapidly increases. The increasing rate of the ozone gas outlet concentration for ozonation with the presence of Ca 2+ is faster than that without Ca 2+. The optimal initial calcium dosage shows linear relationship with the initial phenol concentration, which is useful for practical application.

The enhancement of the biodegradability of phenolic solution using preozonation based on high ozone utilization

In this research, the effects of preozonation on the biodegradability of 4-cresol, 4-nitrophenol and 2-chlorophenol solutions were investigated using a new gas-inducing reactor with high ozone utilization rate. The extent of preozonation may be monitored by determining the characteristic ozonation behaviors of preozonized phenolic solutions, such as residual phenolic concentration, ADMI value and ozone gas outlet concentration. Experimental results showed that as the initial phenolic compounds decomposed completely, the ozone gas outlet concentration rapidly increases. In addition, at pH 7, a peak ADMI value appears during the preozonation of 4-cresol and 2-chlorophenol, while for 4-nitrophenol the ADMI value decreases monotonically. Based on the characteristic ozonation behaviors and the ozone utilization rate, three characteristic times were chosen in order to have better control on the extent of preozonation. The effect of preozonation on the biodegradability of preozonized phenolic solution was studied based on these characteristic times. The intermediate products during the preozonation were also identified. The variation of BOD 5 is strongly dependent on the accumulation of intermediate products. It is suggested that the best characteristic time is as the rapid increase of ozone gas outlet concentration in this study. The biodegradability (BOD 5/COD) of preozonized 4-cresol, 2-chlorophenol and 4-nitrophenol solutions increase to 0.18, 0.26 and 0.33, respectively, for the best characteristic time.

The Preozonation of Phenolic Aqueous Solution and Its Effect on the Improvement of Coagulation Treatment

Phenolic solutions are difficult to treat with coagulation processes because phenol is well soluble in water. However, with suitable preozonation, the ozonized organic components can be removed more effectively by coagulation processes. In order to avoid excessive preozonation, a good control on the degree of preozonation is crucial for practical applications. The degree of preozonation of phenolic solution was evaluated by measuring the phenol decomposition rate, ADMI value and ozone outlet concentration during the ozonation. Three characteristic times were observed, namely (1) ADMI value reaches the peak value during preozonation, (2) the ozone outlet concentration starts increasing, and (3) the ADMI value reaches the discharge standard (500 value, EPA Taiwan). These characteristic times provide the useful means as real-time control parameters on the extent of preozonation. The results of HPLC and GPC show that phenol is almost completely decomposed after 43 min of preozonation. The major components after preozonation are oxalic acid and coupling compounds. The preozonized solution, containing phenol decomposition products, was then subjected to coagulation treatments. The coagulation behavior of preozonized solution is dependent on the extent of preozonation. Three types of coagulant were investigated, namely alum, ferric chloride (FeCl3) and poly aluminum chloride (PAC). Both PAC and FeCl3 are effective coagulants for COD removal. As an example, phenol solution (initial phenol concentration=300 mg/L, C O 3,i=20 mg/L) was preozonized for 50 minutes, followed by FeCl3 coagulation treatment. After preozonation and coagulation processes, the total COD and ADMI removal rates are as high as 70% and 80%, respectively. Most of the coupling compounds and oxalic acid are removed by the coagulant.

Correlation among indicators in regulating colored industrial wastewaters

Color indicators for industrial effluents, including the transparency (TRA), dilution ratio (DR), ADMI tristimulus filter (ADMI) and Lavibond unit (LU), are adopted in many countries. The aims of this study were to (1) investigate the effects of suspended solids (SS) and color on the TRA values, (2) study the effects of water sample pH and pore size of filter papers on the color values, and (3) evaluate the relationships among these color indicators. Results showed that the TRA measurement is markedly affected by both the hues of color and SS. For an effluent of the same TRA value, the ADMI value ratio varied by a factor of 2 to 50. This implies that TRA is not a suitable indicator in quantifying the effluent color strength. The pore size of filter papers affects the ADMI values more than the water sample pH does. Furthermore, although the TRA does not correlate to any of the other three indicators, i.e., DR, LU or ADMI, the statistical analysis from both synthetic and real colored effluents shows that there exists a high correlation among DR, LU and ADMI values. The information presented in this study enables the conversion of color value from one country (area) to another depending on the color indicator adopted.

ON-LINE MONITORING AND CONTROL OF THE TEXTILE WASTEWATER COLOR REMOVAL PROCESS

On-line monitoring of the wastewater color and ORP values is used to carry out laboratory studies for collecting data to assist in formulating model equations that can be used to achieve better control and automation of the oxidation process for color removal from textile finish wastewaters. Laboratory studies show that the ORP value, the solution pH, the chemical dosage applied and the resulting color of the treated samples are well correlated by linear relationships. Additionally, the ORP value of the solution that is highly related to the color or the ADMI value of the sample being oxidized can be used as a control parameter of the oxidation process. Nernst equation is modified to generalize the findings and the reaction kinetics can be delineated by Ct = In (ADMIo/ADMIt). The term Ct is a function of ORP, pH and reaction time while ADMIt and ADMI, are the color of the raw wastewater and the treated effluent, respectively. Using the model, the dosage requirement, the color removal efficiency, and the time required to complete the oxidation reaction can be calculated. On-line monitoring and automatic control of the de-coloring process to achieve a more efficient and better cost-effective color removal can be made practical.