[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.

Effects of magnetic nanoparticles on aerobic granulation process.

A novel granulation strategy by introducing magnetic nanoparticles (MNPs) into activated sludge system was investigated in this study. The study of the physicochemical characteristics (appearances, sizes, sludge volume index, and chemical oxygen demand) demonstrated that MNPs could decrease the granulation time and improve the retention of biomass, meanwhile enhanced the compact structure of the granules. The secretion and functional groups especially OH and CO of extracellular polymeric substances (EPS) also had significant changes under the long-term influence of MNPs. The contents of proteins (PN) and polysaccharides (PS) in R2 (with MNPs) were 95.7523mg/gVSS and 43.7129mg/gVSS, while in R1 (without MNPs) they were 85.7523mg/gVSS and 32.8632mg/gVSS, respectively. The contact angles of sludge against water dramatically increased with the increase of MNPs concentration, which means that the addition of MNPs could improve the sludge surface hydrophobicity, playing a positive role in the aggregation process.

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.

The role of sodium alginate in improving floc size and strength and the subsequent effects on ultrafiltration membrane fouling.

BACKGROUND: Dosing environment-friendly polymer as coagulant aids is an encouraging method in water treatment to obtain desirable floc characteristics. Sodium alginate (SA) was used as the coagulant aid for synthetic humic acid (HA) water treatment to investigate the effect on flocs characteristics and ultrafiltration (UF) membrane fouling. RESULTS: When SA content was 0.3 mg L-1, the treatment of HA by polyaluminium chloride (PAC) plus SA (PAC/SA) yielded the maximum removal efficiency of 66.5%, which was higher than the maximum HA removal efficiency of PAC (58%). Moreover, the HA flocs size of PAC would grow from 269 to 367 Iim after SA was added. Strength factor and recovery factor of PAC/SA were larger than those of PAC. These resulted in the improvement in subsequent UF membrane performance. The membrane fouling decreased in the following order: the raw water > PAC coagulated water > PAC/SA coagulated water. CONCLUSION: The study showed that the application of SA as coagulant aids resulted in larger and stronger flocs, which would improve treatment efficiency of the coagulation process. And the flocs formed by PAC/SA contributed to the restriction of the fouling of UF membrane, which would decrease the cost of advanced water treatment.

[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).

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.

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%.

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.

Enhancement of acidic dye biosorption capacity on poly(ethylenimine) grafted anaerobic granular sludge.

Developing a novel biosorbent with high capacity is crucial to remove dyes from waters in an efficient way. This study demonstrated that porous anaerobic granular sludge could be grafted with polyethylenimine (PEI), which definitely improved the sorption capacity towards Acid Red 18 (AR18) removal. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) study revealed that the PEI modification introduced a large number of amino groups on the surface of sludge, and the amino groups played an important role in the adsorption of dye molecule. Analysis of sorption data using a Boyd plot confirms the film diffusion was the rate-limiting step. The equilibrium data were well fitted Langmuir model, with a maximum AR18 uptake of 520.52 mg/g. Removal of AR18 decreased with the increasing pH and the maximum color removal was observed at pH 2.0. The sorption energy calculated from Dubinin-Radushkevich isotherm was found to be less than 8 for the biosorption of AR 18, which suggested that the biosorption processes of dye molecule onto modified anaerobic granules could be taken place by physical adsorption. Various thermodynamic parameters, such as ΔG(0), ΔH(0) and ΔS(0), were also calculated, which indicated that the present system was spontaneous and endothermic process.

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.

Fast start-up, performance and microbial community in a pilot-scale anammox reactor seeded with exotic mature granules.

The possibility to introduce the exotic anammox sludge to seed the pilot-scale anammox granular reactor and its fast start-up for treating high nitrogen concentration wastewater were evaluated in this study. The reactor was started up successfully in two weeks; in addition, high nitrogen removal was achieved for a long period. Stoichiometry molar ratios of nitrite conversion and nitrate production to ammonium conversion were calculated to be 1.26±0.02:1 and 0.26±0.01:1, respectively. The Stover-Kincannon model which was first applied in granular anammox process indicated that the granular anammox reactor possessed high nitrogen removal potential of 27.8 kg/m(3)/d. The anammox granules in the reactor were characterized via microscope observation and fluorescence in situ hybridization technique. Moreover, the microbial community of the granules was quantified to be composed of 91.4-92.4% anammox bacteria by real-time polymerase chain reaction. This pilot study can elucidate further information for industrial granular anammox application.

Enhanced Cu(II) and Cr(VI) biosorption capacity on poly(ethylenimine) grafted aerobic granular sludge.

The biosorption characteristics of cations and anions from aqueous solution using polyethylenimine (PEI) modified aerobic granules were investigated. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis exhibit the presence of PEI on the granule surface. Compared with the raw granule, the modified aerobic granules with PEI showed a significant increase in sorption capacity for both metal ions. The monolayer biosorption capacity of granules for Cu(II) and Cr(VI) ions was found to be 71.239 and 348.125mg/g. The optimum solution pH for adsorption of Cu(II) and Cr(VI) from aqueous solutions was found to be 6 and 5.2, respectively. The biosorption data fitted better with the Redlich-Peterson isotherm model. FTIR showed chemical interactions occurred between the metal ions and the amide groups of PEI on the biomass surface. XPS results verified the presence of Cr(III) on the biomass surface, suggesting that some Cr(VI) anions were reduced to Cr(III) during the sorption.

[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.

[Coagulation and adsorption on treating the Yellow River and the impact on chlorine decay during chlorination process].

Two types of inorganic polymer coagulants, polyferric chloride (PFC) and polyaluminum chloride (PAC), were chosen to treat the Yellow River water. Different dosages were investigated in order to investigate the turbidity, UV24, DOC and permanganate index removal efficiency and their coagulation mechanisms based on the Zeta potentials. The natural organic matter removal by the combination of coagulation and adsorption with powder activated carbon were analyzed based on different coagulant and adsorbent dosages and dosing orders. The effects of combination of coagulation and adsorption on the residual chlorine decay were analyzed. The results showed that the two coagulants had high turbidity removal efficiency ( > 90%). The UV254, DOC, permanganate index removal efficiency were 29.2%, 26.1% and 27.9% respectively for PAC coagulation and were 32.3%, 23.3% and 32.9% respectively for PFC. Electric neutralization played an important role in the PAC coagulation process while both adsorption bridging and electric neutralization performed when PFC was used. The removal percentage of organic matter increased with the increase coagulant and adsorbent. The adsorption after coagulation process gave the better UV254 and DOC removal efficiency than the coagulation after adsorption. The UV254 and DOC removal efficiency were 95.2% and 99.9% for PAC coagulation after adsorption and were 90.1% and 99.9% for PFC coagulation first. But adding powder activated carbon can improve floc settlement performance and maintained persistent disinfection effect.

Interaction of anammox bacteria and inactive methanogenic granules under high nitrogen selective pressure.

Granular anammox reactors usually adopted anaerobic/aerobic granules as source sludge, in which the washout of other species and enrichment of anammox biomass were very slow because of the competition of the coexisting bacteria. In this study, inactive methanogenic granules were proved to be suitable for rapid anammox granulation under high nitrogen concentrations by investigating their interaction with anammox bacteria. The start-up nitrite concentration was significantly higher than the published toxic level for anammox bacteria and other lab-scale studies. The nitrogen loading rate increased from 141 to 480 mg/L/d in 120 days operation with a total nitrogen removal efficiency of 96.0+/-0.6%. Anammox granules with a diameter of 1.3+/-0.4mm were observed over the course of three months. Molecular analysis showed that over 67% of the cells in the anammox granules were anammox bacteria after 90 days. The accommodations and proliferations of anammox bacteria in the inactive methanogenic granules might be the main reason for the high anammox purity in a short period. The important role of the extracellular polymer in the granule structure was observed via morphological observation.

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.