Biosurfactant Mediated Remediation Process Evaluation on a Mixture of Heavy Metal Spiked Topsoil Using Soil Column and Batch Washing Methods

This study investigated the effects of biosurfactant produced by a mangrove isolate on a heavy metal spiked soil remediation using two different methods of biosurfactant addition (pretreatment and direct application) at different concentrations (0.5%–5%) for 10 days employing column and batch method of washings. The FT-IR spectral and biochemical analysis confirmed the chemical nature of biosurfactant as a glycolipid. Pre-addition of biosurfactant at 0.5% concentrations and further incubation for a month resulted in better chromium removal than the direct biosurfactant washing method. A maximum recovery of lead (99.77%), nickel (98.23%), copper (99.62%), and cadmium (99.71%) were achieved with column washing method at 1% biosurfactant concentration. Release of 26% soluble fractions of nickel (pre-addition with biosurfactant) and 40% copper (direct application) were achieved by column washing method at 1.0% concentration of biosurfactant. A total of 0.034 mg/10 g of lead, 0.157 mg/10 g of nickel, 0.022 mg/10 g of copper, 0.025 mg/10 g of cadmium, and 0.538 mg/10 g of chromium were found to remain in the spiked soil after column washing with 1.0% biosurfactant solution. However, pre-addition of 0.5% biosurfactant treatment helps in maximum removal of chromium metal leaving a residual concentration of 0.426 mg/10 g of soil, suggesting effective removal at very low concentration. The average extraction concentration of metals in batch washings was between 93–100%, irrespective of the concentration of biosurfactant studied. In this study, the percentage removal of copper, cadmium, chromium, nickel, and lead from spiked soils by column washing was comparatively lower than batch washing.     

Removal of organic compounds by a biofilm supported on GAC: modelling of batch and column data

The performance of a biofilm of Arthrobacter viscosus supported on granular activated carbon on the retention of organic compounds was evaluated. The presence of functional groups on the cell wall surface of the biomass that may interact with the organic compounds was confirmed by Fourier transform infrared spectroscopy, to assess the applicability of this system to the removal of those compounds. The batch assays showed that the removal percentage decreases with the increasing initial concentration. The removal of phenol ranged from 99.5 to 93.4%, the chlorophenol removal ranged from 99.3 to 61.6% and the o-cresol removal ranged from 98.7 to 73.5%, for initial concentrations between 100 and 1,700 mg/L. The batch data were described by Freundlich, Langmuir, Redlich–Peterson, Dubinin-Radushkevich, Sips and Toth model isotherms and the best fit for the retention of phenol and for the retention of o-cresol was obtained with the Sips model, while for chlorophenol, the best fit was obtained with the Freundlich model. The column tests showed that the retention performance followed the order: phenol > chlorophenol > o-cresol, and increased with the increasing initial organic compound concentration. Data from column runs were described by Adams–Bohart, Wolborska and Yoon and Nelson models with good fitting for all the models.     

Effect of toxic substances in anaerobic treatment of tannery wastewaters

Studies were carried out in the treatment of tannery wastewater using upflow anaerobic contact filter (reactor) and on the role of toxic substances viz tannin, sulphide, chromium (3+) in inhibiting the performance of the reactor. The influent COD concentration was varied in the range of 1500 to 16500?mg/l, at different hydraulic retention times viz 36,48,60 hr. The limiting concentrations of toxicity for the three substances viz tannin, sulphide, chromium (3+) were identified in terms of the performance of the reactor viz COD removal percent, biogas production etc. Toxic limits of the above mentioned substances were further estimated in batch process (in vials) to supplement the evidence. In anaerobic contact filter tannin beyond 914?mg/l inhibited the performance, whereas sulphide concentration even upto 180?mg/l and chromium (3+) concentration even upto 140?mg/l did not affect the reactor performance. In batch process tannin above 77 wt.% affected the anaerobic microbial growth. Hydrolysable tannin was present in these tannery wastewaters.     

Bioremediation of toxic chromium from electroplating effluent by chromate-reducing Pseudomonas aeruginosa A2Chr in two bioreactors

The chromate-reducing ability of Pseudomonas aeruginosa A2Chr was compared in batch culture, with cells entrapped in a dialysis sac, and with cells immobilized in an agarose-alginate film in conjunction with a rotating biological contactor. In all three systems, the maximum Cr(VI) reduction occurred at 10 mg Cr(VI)/l. Whereas at 50 mg Cr(VI)/l concentration, only 16% of the total Cr(VI) was reduced, five spikings with 10 mg chromate/l at 2-h intervals led to 96% reduction of the total input of 50 mg Cr(VI)/l. Thus maximum Cr(VI) reduction was achieved by avoiding Cr(VI) toxicity to the cells by respiking with lower Cr(VI) concentrations. At 10 mg Cr(VI)/l, the pattern of chromate reduction in dialysis-entrapped cells was almost similar to that of batch culture and 86% of the bacterially reduced chromium was retained inside the dialysis sac. In electroplating effluent containing 100 mg Cr(VI)/l, however, the amount of Cr(VI) reduced by the cells immobilized in agarose-alginate biofilm was twice and thrice the amount reduced by batch culture and cells entrapped in a dialysis sac, respectively.     

Short-term batch studies on biological removal of chromium from synthetic wastewater using activated sludge biomass

Biological treatment of Cr(VI)-containing wastewater has drawn much attention recently as a method to treat environmental Cr(VI) contamination. The activated sludge method, due to its convenient operation and easy-to-scale-up, has been widely applied to treat municipal wastewater and some industrial wastewaters. In order to develop a suitable technique using activated sludge as the biomass to continuously remove Cr(VI) from wastewater, this paper investigated in short-term batch experiments the environmental elements affecting chromium biological removal from synthetic wastewater. The dissolved oxygen (DO), Cr(VI) initial concentration, biomass density, temperature, glucose content in the influent and contact time were observed to strongly influence chromium removal. It was found that the chromium removal efficiency decreased with the increase of DO and Cr(VI) initial concentration as well as glucose content in the feed, but increases in temperature and contact time improved the chromium removal efficiency. Although raising biomass concentration resulted in an increased chromium removal efficiency under both anaerobic and aerobic conditions, its influence on specific chromium removal was not significant.     

Preliminary studies on continuous chromium(VI) biological removal from wastewater by anaerobic-aerobic activated sludge process

The long-term continuous chromium(VI) removal from synthetic wastewater affected by influent hexavalent chromium (Cr(VI)) and glucose concentrations were studied with an anaerobic-aerobic activated sludge process. It was observed that before activated sludge was acclimated, the chromium in the effluent increased immediately as the influent chromium increased. However, both Cr(VI) and total chromium (TCr) in the effluent significantly decreased after acclimation. In the acclimated activated sludge, the chromium removal efficiency was 100% Cr(VI) and 98.56% TCr at influent Cr(VI) levels of 20 mg/day, 100% Cr(VI) and 98.92% TCr at influent Cr(VI) levels of 40 mg/day, and 98.64% Cr(VI) and 97.16% TCr at influent Cr(VI) levels of 60 mg/day. The corresponding effluent Cr(VI) and TCr concentrations were 0 and 0.012 mg/l, 0 and 0.018 mg/l, and 0.034 mg/l and 0.071 mg/l, respectively. When the influent glucose increased from 1125 to 1500 mg/l at influent Cr(VI) dosage of 60 mg/day, the Cr(VI) and TCr removal efficiency with the acclimated activated sludge improved from 98.64% and 97.16% to 100% and 98.48%, respectively, and the chromium concentration in the effluent decreased from 0.034 mg/l of Cr(VI) and 0.071 mg/l of TCr to 0 (Cr(VI)) and 0.038 mg/l (TCr). The effluent COD and turbidity was around 40 mg/l and 0, respectively, after the activated sludge was acclimated. Further studies showed that after the activated sludge was acclimated, its specific dehydrogenases activity (SDA) and protein contents increased. The SDA and protein increased respectively 15% and 10% when influent Cr(VI) increased from 20 to 60 mg/day.     

A Novel Microbial Biofilm for Bioremoval of Nickel from Aqueous Media

This study evaluated the efficacy of a microbial biofilm in removing Ni ions in aqueous media. The biofilm was developed incorporating a garden soil fungus with a bacterium isolated from Ni-rich serpentinite soil. The biofilm was characterized using microscopy, scanning electron microscopy, Fourier transform infrared (FTIR) investigations, and Boehm and potentiometric titrations. Ni removal was determined using batch experiments as a function of pH, Ni concentration, and time. The adsorption isotherm assay was conducted with varying Ni concentrations from 25 to 500 mg/L for 4 days. Isotherm and kinetic modeling were applied to the experimental data to understand the mechanisms of Ni removal. The zero point charge at pH 4.5 indicated the pH values greater than 4.5 is favorable for Ni adsorption. Acidic nature of the biofilm was reflected from Boehm titration data showing higher number of acidic groups than basic groups. With the increase in initial Ni concentration, the uptake increased from 3.43 to 38.16 mg/g. Hill, the best-fitted isotherm model, indicated a maximum adsorption capacity of 165.37 mg/g. After 4 days, the adsorption rate reached an equilibrium with a maximum sorption of ～30 mg/g for an initial concentration of 100 mg/L. Kinetic model fitting with Power function further demonstrated the chemisorptive interaction of Ni with the biofilm surface. A clear involvement of functional groups of the biofilm in Ni bonding was observed from the attenuated total reflection (ATR)-FTIR spectrum. The microbial biofilm showed an efficient but slow removal of Ni from aqueous media.     

Chromium and cadmium removal from wastewater using duckweed - Lemna gibba L. and ultrastructural deformation due to metal toxicity

Phytoremediation potential of Lemna gibba was evaluated for chromium (Cr) and cadmium (Cd) under laboratory conditions for variable metal load of 1?mg/l, 3?mg/l, 5mgl, 7?mg/l and 9?mg/l, respectively, for 7 and 15?days of treatment period. Effects of both metals on structural attributes of L. gibba were also analyzed by Scanning Electron Microscopic (SEM) study. The metal removal percentage by L. gibba for Cr metal was found in the range of 37.3% to 98.6% and for cadmium it was found within the range of 81.6% to 94.6%. Bio concentration factor (BCF) of L .gibba was observed within the range of 37 to 295 for Cr metal and for Cd metal it ranged from 237 to 1144, which shows that the plant is a hyper accumulator for Cd metal and moderate accumulator for Cr metal. Statistical analysis (Two-way ANOVA) was performed on experimental results to confirm the individual effect of metal concentration and treatment period as well as cumulative effect of both factors together on percentage metal removal and on BCF. Research studies indicated that with the progress of treatment period metal removal percentage increases but increasing metal load during experiment negatively co-relates the metal removal percentage and BCF.     

Removal of chromium from industrial waste by using eucalyptus bark

Several low cost biomaterials such as baggase, charred rice husk, activated charcoal and eucalyptus bark (EB) were tested for removal of chromium. All the experiments were carried out in batch process with laboratory prepared samples and wastewater obtained from metal finishing section of auto ancillary unit. The adsorbent, which had highest chromium(VI) removal was EB. Influences of chromium concentration, pH, contact time on removal of chromium from effluent was investigated. The adsorption data were fitted well by Freundlich isotherm. The kinetic data were analyzed by using a first order Lagergren kinetic. The Gibbs free energy was obtained for each system and was found to be -1.879 kJ mol(-1) for Cr(VI) and -3.885 kJ mol(-1) for Cr(III) for removal from industrial effluent. The negative value of deltaG0 indicates the feasibility and spontaneous nature of adsorption. The maximum removal of Cr(VI) was observed at pH 2. Adsorption capacity was found to be 45 mg/g of adsorbent, at Cr(VI) concentration in the effluent being 250 mg/l. A waste water sample containing Cr(VI), Cr(III), Mg, and Ca obtained from industrial unit showed satisfactory removal of chromium. The results indicate that eucalyptus bark can be used for the removal of chromium.     

Biosorption of chromium(VI) by spent cyanobacterial biomass from a hydrogen fermentor using Box-Behnken model

The study explores utilization of waste cyanobacterial biomass of Nostoc linckia from a lab-scale hydrogen fermentor for the biosorption of Cr(VI) from aqueous solution. The biomass immobilized in alginate beads was used for removal of the metal in batch mode optimizing the process conditions adopting response surface methodology (RSM). Kinetic studies were done to get useful information on the rate of chromium adsorption onto the cyanobacterial biomass, which was found to follow pseudo second-order model. Four important process parameters including initial metal concentration (10-100 mg/L), pH (2-6), temperature (25-45 °C) and cyanobacterial dose (0.1-2.0 g) were optimized to obtain the best response of Cr(VI) removal using the statistical Box-Behnken design. The response surface data indicated maximum Cr(VI) biosorption at pH 2-4 with different initial concentrations of the metal in the aqueous solution. The biosorbent could remove 80-90% chromium from solutions with initial metal concentration of 10-55 mg/L. Involvement of the surface characteristics of the biomass was studied through its scanning electron micrographs and Fourier transform infrared (FTIR) analysis.     

Effect of initial COD concentration, nutrient addition, temperature and microbial acclimation on anaerobic treatability of broiler and cattle manure

In this study, anaerobic treatability and biogas generation potential of broiler and cattle manure were investigated. For this purpose, seven sets of anaerobic batch reactor experiments were performed using broiler and cattle manure and their mixtures in five different ratios (100% broiler; 75% broiler, 25% cattle; 50% broiler, 50% cattle; 25% broiler, 75% cattle; 100% cattle). These manure mixtures had two different initial chemical oxygen demand (COD) (12,000 and 53,500 mg/l) concentrations. The effects of initial COD concentration, nutrient and trace metal supplementation, microbial acclimation and digestion temperature were investigated. Results revealed that the efficiency of total COD removal was 32.0-43.3% and 37.9-50% for initial COD concentrations of 12,000 and 53,500 mg/l, respectively. The biogas yields observed for initial COD concentrations of 12,000 and 53,500 mg/l were 180-270 and 223-368 ml gas/g COD added, respectively. A decrease in biogas yield was observed as the fraction of broiler manure increased in mixture of broiler and cattle manure at initial COD values of 53,500 mg/l.     

Simultaneous ammonium-nitrogen and copper removal, and copper recovery using nitrifying biofilm from the ultra-compact biofilm reactor

Simultaneous ammonium-nitrogen (NH(4)(+)-N) and copper removal, and copper recovery in synthetic wastewater using nitrifying biofilm from an ultra-compact biofilm reactor (UCBR) was demonstrated in batch studies, which consisted of three phases: Phase 1 for NH(4)(+)-N and copper removals, Phase 2 for copper recovery, and Phase 3 for NH(4)(+)-N removal. The results showed that more than 96.3% of copper was removed within 60min, while 60.1% of the adsorbed copper was recovered through rinsing the biofilms with 0.1mM of ethylenediaminetetraacetic acid (EDTA). The nitrifying biofilm was able to adsorb 0.245mg of copper/g of biofilms. After recovery treatment, 29.4% of copper remained bound within the nitrifying biofilms. No significant inhibitory effects towards NH(4)(+)-N removal in the presence of 0.92mg copper/L was noted in Phase 1 compared with the control test. However, lower initial pH condition in the recovery process and the accumulation of copper on the biofilm led to 50% inhibition on NH(4)(+)-N removal efficiency in the subsequent phase.     

Removal of hexavalent chromium by fungal biomass of <Emphasis Type="Italic">Mucor racemosus</Emphasis>: influencing factors and removal mechanism

This study reported the hexavalent chromium removal by untreated Mucor racemosus biomass and the possible mechanism of Cr (VI) removal to the biomass. The optimum pH, biomass dose, initial Cr (VI) concentration and contact time were investigated thoroughly to optimize the removal condition. The metal removal by the biomass was strongly affected by pH and the optimum pH ranged from 0.5 to 1.0. The residual total Cr was determined. It was found that dichromate reduction occurred at a low very low pH value. At biomass dose 6 g/l, almost all the Cr (VI) ions were removed in the optimum condition. Higher removal percentage was observed at lower initial concentrations of Cr (VI) ions, while the removal capacity of the biomass linearly depended on the initial Cr (VI) concentration. More than half of Cr (VI) ions were diminished within 1 h of contact and removal process reached a relative equilibrium in approximately 8 h. Almost all of the Cr (VI) ions were removed in 24 h when initial concentrations were below 100 mg/l. The equilibrium data were fitted in to the Langmuir and the Freundlich isotherm models and the correlated coefficients were gained from the models. A Fourier transform infrared spectra was employed to elucidate clearly the possible biosorption mechanism as well.     

para-Chlorophenol inhibition on COD, nitrogen and phosphate removal from synthetic wastewater in a sequencing batch reactor

COD, nitrogen, phosphate and para-chlorophenol (4-chlorophenol, 4-CP) removal from synthetic wastewater was investigated using a four-step sequencing batch reactor (SBR) at different sludge ages and initial para-chlorophenol (4-CP) concentrations. The nutrient removal process consisted of anaerobic, oxic, anoxic and oxic phases with hydraulic residence times (HRT) of 1/3/1/1 h and a settling phase of 0.75 h. A Box-Wilson statistical experiment design was used considering the sludge age (5-25 days) and 4-CP concentration (0-400 mg l(-1)) as independent variables. Variations of percent COD, NH4-N, PO4-P and 4-CP removals with sludge age and initial 4-CP concentration were investigated. Percent nutrient removals increased with increasing sludge age and decreasing 4-CP concentrations. Low nutrient removals were obtained at high initial 4-CP concentrations especially at low sludge ages. However, high sludge ages partially overcome the adverse effects of 4-CP and resulted in high nutrient removals. COD, NH4-N, PO4-P and 4-CP removals were 76%, 72%, 26% and 34% at a sludge age of 25 days and initial 4-CP concentration of 200 mg l(-1). Sludge volume index (SVI) also decreased with increasing sludge age and decreasing 4-CP concentrations. An SVI value of 104 ml g(-1) was obtained at a sludge age of 25 days and initial 4-CP of 200 mg l(-1).     

Aerobic degradation of the azo dye acid red 151 in a sequencing batch biofilter

The azo dye acid red 151 (AR151) was aerobically biodegraded in a sequencing batch biofilter packed with a porous volcanic rock. AR151 was used as the sole source of carbon and energy for acclimated microorganisms. Acclimation was followed using the degradation time and the oxygen uptake rate. A maximal oxygen uptake rate of 0.5 mg O(2)/(lmin) was obtained. Mineralization studies showed that 73% (as carbon) of the initial azo dye was transformed to CO(2) by the consortia. A maximal substrate degradation rate of 247 mg AR151/(l(reactor)d) was obtained. Color removal was up to 99% using an initial concentration of 50 mg AR151/l. Anaerobic tests suggested that in the interior of the porous material, anaerobic biotransformations can occur, contributing from 14% to 16% of the decoloration of the azo dye.     

Biosorption of Cr (VI) using a bacterial biofilm supported on granular activated carbon and on zeolite

Two mini-columns partially filled with granular activated carbon (GAC) and/or a natural zeolite, covered by a bacterial biofilm of Arthrobacter viscosus, were used in a continuous flow system to remove Cr (VI) from solutions with initial concentration of 70mg/l and a working pH ranging between 4.5 and 5.5. Three different set-up's were used: two columns in series filled GAC covered with a biofilm, two columns in series filled with zeolite covered with a biofilm and a column filled with GAC followed by another column filled with zeolite, both supports covered with biofilm. Comparatively, the biosorption system supported on GAC reaches similar removal values, 19%, as the one supported on the zeolite, 18%, but when these two beds are used in combination better performances are reached, i.e. 42% removal. The maximum uptake values ranged from 0.57mg(Cr)/g(Support) to 3.58mg(Cr)/g(Support). The interactions between metal ions and functional groups on the cell wall surface of the biomass were confirmed by FTIR. GAC was regenerated with steam draughting and reused twice. The first regeneration caused a decrease in the removal capacity of 38% and the second regeneration caused a total decrease in the removal capacity of 76%.     

Biosorption of Cr (VI) from aqueous solution by Rhizopus nigricans

The study was aimed to quantify the Cr sorption ability of powdered biomass of Rhizopus nigricans at the best operating conditions. The influence of solution pH, agitation, Cr (VI) concentration, biomass dosage, contact time, biomass particle size and temperature were studied. The optimum pH for biosorption of Cr (VI) was found to be 2.0. Higher adsorption percentage was noted at lower initial concentrations of Cr ions, while the adsorption capacity of the biomass increased with increasing concentration of ions. Optimum biomass dosage was observed as 0.5% (w/v). More than 75% of the ions were removed within 30 min of contact and maximum removal was obtained after 8 h. Biomass particles of smaller size (90 microm) gave maximum adsorption (99.2%) at 100 mg/l concentration. The adsorption capacity increased with increase in temperature and agitation speed and the optimum were determined as 45 degrees C at 120 rpm. Freundlich and Langmuir isotherms were used to evaluate the data and the regression constants were derived. The adsorption rate constant values (Kad) were calculated for different initial concentration of Cr ions and the sorption was found to be higher at lower concentration (100 mg/l) of metal ion.     

Decolorizing kinetics of a recombinant Escherichia coli SS125 strain harboring azoreductase gene from Bacillus latrosporus RRK1

PCR amplified product containing gene responsible for dye decolorization was cloned and expressed in Escherichia coli. The resulting recombinant strain E. coli SS125 decolorized 200mg/l azo dye (Remazol Red) at 30 degrees C at 255 mg cell/l/h, while the host E. coli (DH5 alpha) had no color removal ability. The dependence of the decolorization rate on initial dye concentration and the maximum rate occurred with the dye at 100 mg l(-1). The decolorization rate of E. coli SS125 was optimal at 37-45 degrees C. Aeration strongly-inhibited the decolorization, but decolorization occurred effectively under static and anaerobic incubation conditions. The E. coli SS125 strain also exhibited excellent stability during reported batch operation.     

Chromium(VI) bioaccumulation capacities of adapted mixed cultures isolated from industrial saline wastewaters

Enrichment mixed cultures tolerating relatively high concentrations of chromium and salt ions were isolated and their bioaccumulation properties improved by adaptation. Mixed cultures were enriched in Nutrient Broth media containing 25-300 mg l(-1) Cr(VI) and 0%, 2%, 4%, 6% (w/v) NaCl. Bioaccumulation of Cr(VI) was studied in a batch system as a function of initial pH (7, 8 and 9), Cr(VI) and NaCl concentrations. Increasing NaCl and Cr(VI) concentrations led to significant decreases in percentage uptake and dried weight of mixed cultures but increased maximum specific chromium uptake. The maximum specific chromium uptake value at pH 8 was 58.9 mg g(-1) for 316.1 mg l(-1) Cr(VI) in the absence of NaCl, while at pH 9 it was 130.1 mg g(-1) in media including 194.5 mg l(-1) Cr(VI) and 2% NaCl concentrations. At 4% NaCl, the maximum Cr(VI) uptake of 127.0 mg g(-1) for 221.1 mg l(-1) Cr(VI) occurred at pH 9, while at 6% NaCl the maximum Cr(VI) uptake of 114.9 mg g(-1) for 278.1 mg l(-1) Cr(VI) was found at pH 7.     

Potential use of green algae as a biosorbent for hexavalent chromium removal from aqueous solutions

The hexavalent chromium Cr(VI) poses a threat as a hazardous metal and its removal from aquatic environments through biosorption has gained attention as a viable technology of bioremediation. We evaluated the potential use of three green algae (Cladophora glomerata, Enteromorpha intestinalis and Microspora amoena) dry biomass as a biosorbent to remove Cr(VI) from aqueous solutions. The adsorption capacity of the biomass was determined using batch experiments. The adsorption capacity appeared to depend on the pH. The optimum pH with the acid-treated biomass for Cr(VI) biosorption was found to be 2.0 at a constant temperature, 45?°C. Among the three genera studied, C. glomerata recorded a maximum of 66.6% removal from the batch process using 1.0?g dried algal cells/100?ml aqueous solution containing an initial concentration of 20?mg/L chromium at 45?°C and pH 2.0 for 60?min of contact time. Langmuir and Freundlich isotherm equations fitted to the equilibrium data, Freundlich was the better model. Our study showed that C. glomerata dry biomass is a suitable candidate to remove Cr(VI) from aqueous solutions.