Research on microbial lipid production from potato starch wastewater as culture medium by Lipomyces starkeyi.

In this paper, potato starch wastewater as culture medium was treated by the oleaginous yeast Lipomyces starkeyi to biosynthesize microbial lipid. The result indicated that carbon source types, carbon source concentration, nitrogen source types, nitrogen source concentration, inoculum size, and cultivation time all had a significant effect on cell growth and microbial lipid accumulation in batch cultures. A measure of 120 g/L of glucose concentration, 3.0 g/L of (NH4)2SO4 concentration, 10% inoculum size, and incubation time 96 h cultivated in a shaking flask at 30 °C were found to be the optimal conditions not only for cell growth but also for lipid synthesis. Under this condition, the cellular biomass and lipid content could reach 2.59 g/L and 8.88%, respectively. This work provides a new method for effective utilization of potato starch wastewater, which has particular social and economic benefits for yeast treatment technology.

Effect of preparation conditions and washing of activated carbon from paper mill sewage sludge on its adsorptive properties.

Sludge-based activated carbon (SAC) was prepared from paper mill sewage sludge by physical activation with steam for wastewater treatment in this study. The effects of preparation variables, including carbonization temperature, carbonization time, activation temperature and activation time, on iodine number and yield were investigated through orthogonal experiments. The influences of washing by deionized water and acid on the characteristics and adsorption capacities of SAC for phosphate, methylene blue and reactive red 24 were also studied. The results indicated that the optimal preparation conditions were: carbonization temperature of 350 °C, carbonization time of 40 min, activation temperature of 800 °C and activation time of 20 min. The characteristics and adsorption capacities of SAC were obviously different before and after washing, especially by acid. The surface area was improved and adsorption capacities for dyes increased after washing, while adsorption capacity for phosphate decreased. The maximum adsorption capacities provided strong evidence of the potential of SAC as an alternative adsorbent for wastewater treatment.

[Effect of Different Cationic Polyacrylamide Organic Dehydrating Agents on Sludge Dewatering Performance].

To study the effect of different cationic polyacrylamide organic dehydrating agents on sludge dewatering performance, eight commercially available cationic polyacrylamides of the same series with different properties were used. Based on the different cationic degree, they were named 9101, 9102, 9103, 9104, 9106, 9108, 9110, and 9112, respectively. Their properties were characterized by instruments and chemical analysis, and the indexes of sludge after treatment were also measured. The results showed that the properties of the eight organic dehydrants were different, among which the charge density, cationicity, viscosity, and Zeta potential had homologous trends, which all increased gradually from 9101 to 9112. The four indexes of 9112 were as high as 2.98 meq·L-1, 17.42%, 85.07 mPa·s, and 67.10 mV, respectively. The dewatering performance of sludge was improved by improving the specific resistance of filtration (SRF), floc properties, viscosity, Zeta potential, the bound water content, and the distribution of extracellular polymeric substances (EPS) after dosing organic dewatering agents. The results showed that the viscosity, charge density, cationic degree, and Zeta potential of the dewatering agents had a great influence on the sludge dewatering performance. The SRF of sludge was negatively correlated with the viscosity of the organic dewatering agent, and the correlation coefficient was as high as 0.92025, indicating that the sludge dewatering performance was improved mainly through the adsorption bridging effect of the organic dewatering agent in sludge dewatering.

Preferential capture of phosphate by an Enteromorpha prolifera-based biopolymer encapsulating hydrous zirconium oxide nanoparticles.

Preferential removal of phosphate from aqueous was conducted by a novel biomass-based nanocomposite (EP-N+-Zr) with encapsulated hydrous zirconium oxide, and the biopolymer EP-N+-Zr features were described. EP-N+-Zr exhibited high selective sequestration toward phosphate when humic acid or other competing anions (Cl-, SO42-, NO3-, ClO4-) coexisted at relatively high levels. Such excellent performance of EP-N+-Zr was attributed to its specific two site structures; the embedded HZO nanoparticles and quaternary ammonia groups [N+(CH2CH3)3Cl-] bonded inside the biomass-Enteromorpha prolifera, which facilitated preferable capture towards phosphate through specific affinity and nonspecific preconcentration of phosphate ions on the basis of the ion exchange, respectively. The maximum adsorption capacity of phosphate (20 °C) as calculated by Langmuir model was 88.5 mg(P)/g. Regeneration tests showed that EP-N+-Zr could be recycled at least five times without noticeable capacity losses using binary NaOH-NaCl as eluent.

Phosphate removal from aqueous solution by adsorption on modified giant reed.

The use of modified giant reed (MGR) as an adsorbent to remove phosphate from an aqueous solution was investigated. The dosage of MGR, pH of the phosphate solution, thermodynamics, and the effects of several factors on kinetics (concentration of phosphate solution, solution temperature, and shaking speed) were studied in batch experiments. The results showed that MGR was particularly effective to remove phosphate and that the effective pH range for the phosphate removal was between 4 and 9. The adsorption process could reach equilibrium in 25 minutes. Three kinetic models have been evaluated to fit the experimental data. It was shown that the pseudo-second-order model best described the adsorption kinetics of phosphate on MGR. The low activation energy of the adsorption suggested a physisorption process for phosphate adsorption. The equilibrium isotherm showed that the adsorption system was consistent with the Langmuir equation. The negative values of standard free energy (AG) and enthalpy (AH) indicated that the adsorption of phosphate onto MGR was a spontaneous and exothermic process.

A comparative study on the properties, mechanisms and process designs for the adsorption of non-ionic or anionic dyes onto cationic-polymer/bentonite.

The adsorption properties and mechanisms of a cationic-polymer/bentonite complex (EPI-DMA/bentonite), prepared from polyepicholorohydrin-dimethylamine and bentonite, for non-ionic dyes (Disperse Blue SBL and Vat Scarlet R) and anionic dyes (Reactive Violet K-3R and Acid Dark Blue 2G) were investigated in this study. The solution pH, presence of salt and surfactant can significantly affect the dye removal efficiency. The equilibrium data were analyzed using the Langmuir and Freundlich models. The Langmuir model is the most suitable to describe non-ionic dye adsorption, but for anionic dyes the Freundlich model is best. The kinetic data for the adsorption of different dyes were analyzed using pseudo first- and second-order equations, and the experimental data conformed to the pseudo second-order kinetic model better. The possibility of intraparticle diffusion was also examined by using the intraparticle diffusion equation. The single-stage batch adsorber design for the adsorption of both types of dyes onto EPI-DMA/bentonite was studied based on the Langmuir isotherm model for non-ionic dyes and the Freundlich isotherm model for anionic dyes. The results showed that the required amount of EPI-DMA/bentonite for 95% dye removal in 5 L dye solution with a concentration of 50 mg/L is 378.0 g for DB SBL, 126.5 g for VS R, 9.7 g for RV K-3R and 15.5 g for ADB 2G.

Bioflocculant production by culture of Serratia ficaria and its application in wastewater treatment.

A bioflocculant-producing bacterium was isolated from soil and identified as Serratia ficaria. Using optimized culture conditions a flocculating activity of 95.4% was obtained. It was found to be effective for flocculation of a kaolin suspension over weakly acidic pH (5-7); divalent cations (Ca2+ and Mg2+) enhanced the flocculating activity, while the co-presence of Al3+ and Fe3+ resulted the negative effect. Measurements of zeta potential revealed that charge neutralization played an important role in the flocculation. It could flocculate a variety of real wastewaters, including river water, brewery wastewater, meat processing wastewater and soy sauce brewing wastewater. The bioflocculant was also used to treat pulp effluent, and the removal rate of color and chemical oxygen demand (COD) were up to 99.9% and 72.1%, respectively, which were better than traditional chemical flocculants.

Cationic polyelectrolyte/bentonite prepared by ultrasonic technique and its use as adsorbent for Reactive Blue K-GL dye.

In this study, the cationic polyelectrolyte polyepicholorohydrin-dimethylamine (EPI-DMA) was intercalated into bentonite using ultrasonic. The structure of EPI-DMA/bentonite and its adsorption of Reactive Blue K-GL (RB K-GL) dye were investigated. Compared with raw bentonite, the EPI-DMA/bentonite had larger interlayer spacing and was more hydrophobic, providing with better surface properties for adsorption. The adsorption of RB K-GL on EPI-DMA/bentonite was described by the adsorption models of Langmuir, Freundlich and Dubinin-Radushkevic. The adsorption kinetics was analyzed using pseudo-first- and second-order kinetic models and intraparticle diffusion model. Results showed that both the intraparticle diffusion and first-order adsorption occur in the initial period of adsorption, and that pseudo-second-order kinetic model was more suitable for describing the whole adsorption process. The reaction rates were also calculated. The changes of free energy, enthalpy and entropy of adsorption were evaluated for the adsorption of RB K-GL onto EPI-DMA/bentonite, suggesting that the adsorption process was spontaneous and exothermic.

Preparation and utilization of wheat straw anionic sorbent for the removal of nitrate from aqueous solution.

In order to reduce the impact of eutrophication caused by agricultural residues (i.e., excess nitrate) in aqueous solution, economic and effective anionic sorbents are required. In this article, we prepared anionic sorbent using wheat straw. Its structural characteristics and adsorption properties for nitrate removal from aqueous solution were investigated. The results indicate that the yield of the prepared anionic sorbent, the total exchange capacity, and the maximum adsorption capacity were 350%, 2.57 mEq/g, and 2.08 mmol/g, respectively. The Freundlich isotherm mode is more suitable than the Langmuir mode and the adsorption process accords with the first order reaction kinetic rate equation. When multiple anions (SO4(2-), H2PO4(-), NO3(-), and NO2(-)) were present, the isotherm mode of prepared anionic sorbent for nitrate was consistent with Freundlich mode; however, the capacity of nitrate adsorption was reduced by 50%. In alkaline solutions, about 90% of adsorbed nitrate ions could be desorbed from prepared anionic sorbent. The results of this study confirmed that the wheat straw anionic sorbent can be used as an excellent nitrate sorbent that removes nitrate from aqueous solutions.

Natural organic matter (NOM) removal from surface water by coagulation.

Poly-aluminum-chloride-sulfate(PACS) with different SO4(2-)/Al3+ mole ratios and bacicity(y) of 2.0 was synthesized using AlCl3 x 6H2O, Al2 (SO4 )3 x 18H2O and Na2CO3 as raw materials. The effect of SO4(2-)/Al3+ ratio on the performance of PACS for removal of natural organic matter(NOM) with humic-rich actual water was examined. It was found that PACS with SO4(2-)/Al3+ mole ratio of 0.0664 achieved the best NOM removal results and was selected to investigate its performance in comparison with PAC, FeCl3 and alum (Al2 (SO4)3 x 18H2O). The experimental results showed that the optimum NOM removals were achieved at pH 5.0-8.2 and the dose of about 5.0 mg/L as Al both for the selected PACS and PAC, at pH 5.0-6.0 and the dose of about 7.0 mg/L as Fe for FeCl3, and at pH 5.0-7.0 and the dose of about 7.0 mg/L as Al for alum, respectively. At the optimum conditions, the selected PACS achieved the best NOM removal result, followed by PAC, FeCl3, and then alum. The concentration of residual aluminum in treated water by the selected PACS and PAC under the optimum coagulant conditions was approximately 115 microg/L, which can completely comply with the regulated limits.

Electrokinetic characteristic and coagulation behavior flocculant polyaluminum silicate chloride (PASiC).

The electrokinetic characteristics and coagulation behaviors of polyaluminum silicate chloride (PASiC) and polyaluminum chloride (PAC) were studied and compared by streaming current (SC) measurement and jar test method. The experimental results showed that the interaction between polysilicic acid characterized negative charge and hydrolyzed aluminum species result in a decrease of the charge-neutralizing ability of PASiC, compared to PAC. The decrease has a close relationship with the basicity (B) and Al/Si molar ratio in PASiC. The less the B value and the Al/Si molar ratio, the lower the charge-neutralizing ability of PASiC is. In contrast, the preparation technique for PASiC affects the charge - neutralization of PASiC to a smaller extent. In addition, compared with PAC, PASiC may enhance aggregating efficiency and give better coagulating effects.

Removal of Cu(II) and Cr(VI) from wastewater by an amphoteric sorbent based on cellulose-rich biomass.

A cellulose-rich biomass was modified as a new amphoteric sorbent to eliminate toxic Cu(II) and Cr(VI) from wastewater. The product (WSCA, which stands for modified wheat straw containing both cationic and anionic characters) presents high sorption capacities for the two ions which was evidenced by the comparison with unmodified wheat and other similar samples. Kinetic data and sorption equilibrium isotherms were conducted in batch process. The sorption kinetic analysis revealed that sorption of Cu(II) and Cr(VI) followed the pseudo second-order model well during the whole sorption process. The linear Langmuir isotherm model could perfectly describe the equilibrium data for Cu(II), while the sorption data of Cr(VI) were well fitted by the Freundlich. Results of the static test illustrated the complicated interactions between Cr(VI)/Cu(II) and WSCA including complexation and/or electrostatic attraction mechanisms.

[Coagulation characteristics of polyferric chloride-poly (epichlorohydrin-dimethylamine) composite flocculant for simulated water treatment].

Polyferric chloride (PFC) and poly (epichlorohydrin-dimethylamine) [P(EPI-DMA)] were applied as raw materials to prepare a novel inorganic-organic flocculant [PFC-P(EPI-DMA)] with various intrinsic viscosities (eta), basicity (B, OH/Fe molar ratio), and organic component fractions [omega(E)]. The PFC-P(EPI-DMA) prepared was then evaluated for the coagulation treatment of synthetic active dying wastewater and simulated ground water. Effects of B, and omega (E) on the Fe speciation distribution and coagulation performance of PFC-P(EPI-DMA) were comparatively examined as a function of coagulant dosage. The coagulation mechanism of PFC-P(EPI-DMA) was also discussed in this paper. Experimental results indicated the interaction effect of PFC and P (EPI-DMA) component in composite PFC-P (EPI-DMA). The effective Fe speciation content of PFC-EPI-DMA decreased with increasing omega(E), while it was maximized when eta = 850 mPa x As B value increased gradually, the Fe(b) concentration initially increased and then decreased, but the Fe(c) concentration kept continuously increasing. To some extent, higher eta and lower B value was favorable for the improvement of coagulation performance for coagulation treatment of both synthetic dyeing wastewater and simulated ground water. The omega (E) influence on the coagulation performance of PFC-P(EPI-DMA) was related to the treatment target. Both charge neutralization and adsorption bridging effect played roles in the coagulation process of the composite PFC-P(EPI-DMA).

Removal of acid and direct dye by epichlorohydrin-dimethylamine: flocculation performance and floc aggregation properties.

A cationic organic flocculant epichlorohydrin-dimethylamine (EPI-DMA) was employed for the treatment of acid and direct dye. The study aims at investigating the flocculation performance of EPI-DMA for the model dye, and corresponding floc aggregation properties, which were determined by jar test and photometric dispersion analysis, respectively. The interactions between cationic flocculant and anionic dye were investigated through spectra analysis. The results showed that EPI-DMA effectively decolorized the tested acid and direct dye. The viscosity and cationicity of EPI-DMA had different influence on the removal of different dye. Chemical interaction was observed between quaternary ammonium of EPI-DMA and sulfonic group of dye. The flocculation dynamic process showed that flocs with better aggregation and sedimentation properties were produced by EPI-DMA with higher viscosity and cationicity for acid dye. Contrarily, flocs with the best aggregation and sedimentation properties were produced by EPI-DMA with the lowest viscosity and cationicity for direct dye.

Microbial treatment of the monosodium glutamate wastewater by Lipomyces starkeyi to produce microbial lipid.

The monosodium glutamate (MSG) wastewater as a medium was treated by Lipomyces starkeyi to produce microbial lipid in the study. The effect of related factors (initial glucose concentration, inoculation concentration, initial culture pH, and cultivation time) on biomass, lipid production and lipid content was discussed, respectively. According to the experiments, the optimal fermentation conditions were determined: addition of 80g/L glucose, 10% inoculation concentration, initial pH about 5.0, incubation time 96h. Under this condition, the biomass production reached up to 4.61g/L, lipid production and lipid content was 1.14g/L and 24.73%, respectively. Simultaneously, protein and COD removal rate was 78.60% and 74.96%, respectively. The main composition of fatty acid in the resultant lipid was analyzed by gas chromatography-mass spectrometry, which showed: oleic acid (C18:1) 35.85%, palmitic acid (C16:0) 19.91%, palmitoleic acid (C16:1) 17.65%, and myristic acid (C14:0) 16.03%.

Sorption of nitrate onto amine-crosslinked wheat straw: characteristics, column sorption and desorption properties.

The nitrate removal process was evaluated using a fixed-bed column packed with amine-crosslinked wheat straw (AC-WS). Column sorption and desorption characteristics of nitrate were studied extensively. Solid-state (13)C NMR and zeta potential analysis validated the existence of crosslinked amine groups in AC-WS. Raman shift of the nitrate peaks suggested the electrostatic attraction between the adsorbed ions and positively charged amine sites. The column sorption capacity (q(ed)) of the AC-WS for nitrate was 87.27 mg g(-1) in comparison with the raw WS of 0.57 mg g(-1). Nitrate sorption in column was affected by bed height, influent nitrate concentration, flow rate and pH, and of all these, influent pH demonstrated an essential effect on the performance of the column. In addition, desorption and dynamic elution tests were repeated for several cycles, with high desorption rate and slight losses in its initial column sorption capacity.

Characteristics of cellulosic amine-crosslinked copolymer and its sorption properties for Cr(VI) from aqueous solutions.

A new cellulosic amine-crosslinked copolymer was prepared after the amination reaction with cotton stalk peel (CSP). The physicochemical characteristics of amine-crosslinked cotton stalk peel (AC-CSP) and raw CSP were determined after the surface analysis (including specific surface area, micropore volume and SEM), zeta potential analysis and spectrum analysis (FTIR and Raman spectrum). The sorption properties of AC-CSP for Cr(VI) were evaluated in the static, column sorption and desorption tests. The surface characteristics indicated the absence of porous adsorption in the potential Cr(VI) sorption mechanism. Zeta potential and spectrum analysis of AC-CSP illustrated the involvement of amine groups in the Cr(VI) sorption process. The sorption capacity of AC-CSP for Cr(VI) was 129.0mg/g as comparison with 14.8 mg/g of raw CSP. Flow rate and influent Cr(VI) concentration were demonstrated as two influencial factors in the column sorption tests. NaCl was used as the eluent, and the desorption efficiencies during three successive cycles were 75.9%, 69.8% and 64.3%, respectively. In addition, the results of the static, column sorption and desorption tests illustrated the complicated interactions between Cr(VI) and AC-CSP including complexation and ion exchange mechanisms.

[Relationship among coagulation effect of Al-based coagulant, content and speciation of residual aluminum].

The application of AlCl3, Al2 (SO4)3 and poly-aluminum chloride (PAC) in humic acid-kaolin simulated water was studied in this article. It is intended to discuss the relationship among coagulation effect of Al-based coagulants in humic acid-kaolin simulated water and content and speciation of residual aluminum. It was found that, the turbidity removal efficiency and UV254 removal efficiency could reach about 90% at the tested dosage. At higher dosage, PAC gave better coagulation effect. The residual total aluminum content and residual aluminum ratio of PAC, which was 0.9 mg/L and - 3.0% or so respectively, were greatly lower than those of AlCl3 and Al2 (SO4)3. The residual total dissolved aluminum was the predominant content in the effluent after coagulation and sedimentation by the three Al-based coagulants. For the total dissolved aluminum, the proportion of dissolved organic aluminum was significantly higher than that of other aluminum speciation. With respect to humic acid-kaolin simulated water, the content of residual total aluminum in the effluent after coagulation and sedimentation by PAC decreased obviously compared to AlCl3 and Al2 (SO4)3. PAC could effectively decrease the content of residual dissolved aluminum speciation which has higher toxicity. The content of residual total dissolved aluminum in the effluent after coagulation and sedimentation by PAC was about 0.6 mg/L.

Preparation of agricultural by-product based anion exchanger and its utilization for nitrate and phosphate removal.

To develop the agricultural by-product adsorbent that possesses anionic exchangeable function, the performance of a new anion exchanger prepared from wheat straw (WS) was evaluated in this study. Wheat straw anion exchanger (WS-AE) was prepared by the grafting of aminated intermediate onto WS. Results indicate that reaction time and temperature in the chemical modification process both affected the preparation of aminated intermediate and WS-AE. FTIR, nitrogen content, solid-state (13)C NMR and zeta potential data validated the existence of grafted amine group in the structure of WS-AE. The maximum sorption capacities of WS-AE for nitrate and phosphate were approximately 52.8 and 45.7mgg(-1), respectively, which shows higher maximum capacity for phosphate and a similar capacity for nitrate in comparison with commercial anion resins. Regeneration studies and column adsorption tests were performed, and the excellent regeneration and column adsorption capacities provided strong evidence of the potential of WS-AE for the technological applications of phosphate and nitrate removal from aqueous solutions.

Preparation and utilization of wheat straw bearing amine groups for the sorption of acid and reactive dyes from aqueous solutions.

Removal of Acid Red 73 (AR 73) and Reactive Red 24 (RR 24) onto modified wheat straw (MWS) from aqueous solutions was investigated. Sorption experiments were carried out as function of MWS dosage, contact time, initial concentration, pH and temperature. Characterizations of MWS were measured and a mass of amine groups were observed in the framework of MWS. The equilibrium sorption data were well represented by the Langmuir isotherm equation, and the calculated thermodynamic parameters indicated a spontaneous and endothermic nature for sorption process. It was shown that pseudo-second-order kinetic equation could best describe the adsorption kinetics. More over, the high maximum sorption capacity (q(e max), 714.3 mg g(-1) for AR 73 and 285.7 mg g(-1) for RR 24) and low cost (1.24 US$ kg(-1)) of MWS provided strong evidence of the potential of MWS for the technological applications of anionic dyes removal from aqueous solutions.