Effect of trace amounts of polyacrylamide (PAM) on long-term performance of activated sludge

This study aims at evaluating the impacts of PAM addition on activated sludge performance. Four lab-scale sequencing batch reactors (SBRs), each with a working volume of 3L, were investigated with different PAM concentrations. Experiments were conducted with varying organic loading rate and the sludge volume index (SVI), particle size, zeta potential, specific oxygen uptake rate (SOUR), mixed liquor suspended solids (MLSS), COD and ammonium removal efficiency were monitored over a 105-day period. The results showed that all of the PAM addition not only improved the removal efficiencies of COD and ammonium, but also exhibited some advantages on sludge performance. It was found that the sludge performance of settling property, flocculation and microbial activity increased with increasing concentration of PAM. However, high level of PAM (1mg/L) led to the formation of large amounts of loose-structure flocs, which eliminated dissolved oxygen transfer and caused the sludge disintegration, resulting in bad settleability and lower microbial activity. In this way, when the dosage of PAM was 0.1mg/L, the sludge had the best settling property and activity.     

Effect of C/N ratio on extracellular polymeric substances (EPS) and physicochemical properties of activated sludge flocs

The influences of C/N ratio on the extracellular polymeric substances (EPS) and physicochemical properties of the activated sludge flocs were investigated using laboratory-scale sequencing batch reactors (SBRs). Flocs sizes decreased when C/N ratio increased from 20 to 100 and decreased from 20 to 4. The amount of total EPS, TB-EPS, and the carbohydrate and protein contents in TB-EPS were independent of the C/N ratio. In LB-EPS, the protein content increased and the carbohydrate content decreased at decreased C/N ratio, whereas the protein content decreased and the carbohydrate content increased at increased C/N ratio. Effluent suspended solids (ESS) content, turbidity, sludge volume index (SVI), capillary suction time (CST), and specific resistance to filtration (SRF) increased when the C/N ratio decreased, indicating poor flocculation, settleability and dewaterability of the flocs. However, when the C/N ratio increased, only ESS content, SVI and CST value increased. These properties of the flocs were deteriorated greatly under decreased C/N ratio as compared to increased C/N ratio. The characteristics of the flocs could be recovered when C/N ratio returned to the original value. Only the content of protein in LB-EPS was positively correlated with the flocculation, settleability and dewaterability of the flocs.     

Preparation of sludge-based activated carbon and its application in dye wastewater treatment

A novel activation process was adopted to produce highly porous activated carbon from cyclic activated sludge in secondary precipitator in municipal wastewater treatment plant for dye removal from colored wastewater. The physical properties of activated carbon produced with the activation of 3M KOH solution in the atmosphere of steam were investigated. Adsorption removal of a dye, Acid Brilliant Scarlet GR, from aqueous solution onto the sludge-based activated carbon was studied under varying conditions of adsorption time, initial concentration, carbon dosage and pH. Adsorption equilibrium was obtained in 15 min for the dye initial concentration of 300 mg/L. Initial pH of solution had an insignificant impact on the dye removal. Results indicated that 99.7% coloration and 99.6% total organic carbon (TOC) were removed after 15 min adsorption in the synthetic solution of Acid Brilliant Scarlet GR with initial concentration of 300 mg/L of the dye and 20 g/L activated carbon. The Langmuir and Freundlich equilibrium isotherm models fitted the adsorption data well with R(2)=0.996 and 0.912, respectively. Accordingly, it is concluded that the procedure of developing activated carbon used in this study could be effective and practical for utilizing in dye wastewater treatment.     

Advanced sludge treatment affects extracellular polymeric substances to improve activated sludge dewatering

The management of wastewater sludge, now often referred to as biosolids, accounts for a major portion of the cost of the wastewater treatment process and represents significant technical challenges. In many wastewater treatment facilities, the bottleneck of the sludge handling system is the dewatering operation. Advanced sludge treatment (AST) processes have been developed in order to improve sludge dewatering and to facilitate handling and ultimate disposal. The authors have extensively reported lab-scale, semi-pilot and pilot investigations on either thermal and thermochemical processes, or chemical oxidation using hydrogen peroxide. To understand the action of these advanced sludge technologies, the essential role played by extracellular polymeric substances (EPS) needs to be understood. EPS form a highly hydrated biofilm matrix, in which the micro-organisms are embedded. Hence they are of considerable importance in the removal of pollutants from wastewater, in bioflocculation, in settling and in dewatering of activated sludge. The present paper reviews the characteristics of EPS and the influence of thermochemical and oxidation mechanisms on degradation and flocculation of EPS. Experimental investigations on waste activated sludge are conducted by the authors to evaluate the various literature findings. From the experiments, it is concluded that AST methods enhance cake dewaterability in two ways: (i) they degrade EPS proteins and polysaccharides reducing the EPS water retention properties; and (ii) they promote flocculation which reduces the amount of fine flocs.     

Feasibility investigation of oily wastewater treatment by combination of zinc and PAM in coagulation/flocculation

Poly-zinc silicate (PZSS) is a new type of coagulant with cationic polymer synthesized by polysilicic acid and zinc sulfate. It has been used in several sorts of wastewaters treatment, but not used in oily wastewater treatment. In this study, we investigated the coagulation/flocculation of oil and suspended solids in heavy oil wastewater (HOW) by PZSS and anion polyacrylamide (A-PAM). The properties of PZSS cooperated with A-PAM were compared with PAC and PFS in dosages, PAMs amount, settling time, pH value and flocs morphology. The results showed that PZSS was more efficient than PAC and PFS. Under the optimum experimental conditions of coagulation/flocculation (dosage: 100mg/L, A-PAM dosage: 1.0mg/L, settling time time: 40min and pH 6.5-9.5), more than 99% of oil was removed and suspended solid value less than 5mg/L by using PZSS cooperated with A-PAM, which could satisfy the demands of the pre-treatment process for HOW to be reused in the steam boiler or recycled into the injecting well.     

Flocculated amorphous itraconazole nanoparticles for enhanced in vitro supersaturation and in vivo bioavailability

Rapid flocculation of nanoparticle dispersions of a poorly water soluble drug, itraconazole (Itz), was utilized to produce amorphous powders with desirable dissolution properties for high bioavailability in rats. Antisolvent precipitation (AP) was utilized to form Itz nanodispersions with high drug loadings stabilized with hydroxypropylmethylcellulose (HPMC) or the pH-sensitive Eudragit(?) L100-55 (EL10055). The HPMC dispersions were flocculated by desolvating the polymer through the addition of a divalent salt, and the enteric EL10055 by reducing the pH. The formation of open flocs by diffusion limited aggregation facilitated redispersion of the flocs at pH 6.8. Upon redispersion of the flocculated nanoparticles at pH 6.8, the particle size was modestly larger than the original size, on the order of 1 μm. High in vitro supersaturation (AUC) of the flocculated nanoparticle dispersions was observed in micellar media at pH 6.8, after 2 hours initial exposure at pH 1.2 to simulate the stomach, relative to the AUC for a commercially available Itz formulation, Sporanox. Greater in vivo bioavailability in rats was correlated directly to the higher in vitro AUC at pH 6.8 with micelles during the pH shift experiment for the flocculated nanoparticle dispersions relative to Sporanox. The ability to generate and sustain high supersaturation in micellar media at pH 6.8, as shown with the in vitro pH shift dissolution test, is beneficial for increasing bioavailability of Itz by oral delivery.     

A review of thermal sludge pre-treatment processes to improve dewaterability

As a result of the wide application and utilization of the waste activated sludge process, excess sludge presents a serious disposal problem. Many efforts have been devoted to reduce the excess sludge by treatments such as digestion and dewatering. It has been known for many years that a thermal pre-treatment gives an improvement in the dewaterability of sludges. This paper provides a literature review concerning the optimum treatment conditions to obtain enhanced dewaterability and digestibility of sludge. The main commercial hydrolysis processes (Cambi, Porteous and Zimpro) are discussed. The literature findings concerning the optimum treatment conditions of thermal or thermochemical pre-treatments are reviewed. The second part of this paper deals with the fundamentals of improving sludge dewatering. The influence of extracellular polymer (ECP) on settling and dewatering characteristics is discussed, together with the importance of cations and ECP-hydrophobicity in the flocculation and dewatering process. Finally, the effect on exocellular polymer, dewaterability, settleability and colloidal stability of activated sludge by treatment with sulfuric acid was studied.     

Use of Optical Monitoring to Assess the Breakage of Activated Sludge Flocs

Optical monitoring with a charge-coupled device camera was used to assess the breakage of activated sludge flocs obtained from three different activated sludge plants: two municipal and one industrial. In this method, the samples were processed through the imaging unit and recycled back to a beaker using a centrifugal pump which causes the breakage of flocs together with hydrodynamics forces. Based on the image analysis results, the breakage models of the activated sludge flocs vary between the plants. The major breakage model in the two municipal plants was surface erosion whereas it was large-scale fragmentation in the industrial plant. A larger amount of filaments in the industrial plant most likely caused the large-scale fragmentation. Furthermore, the effect of the addition of a cationic polymer on the strength of activated sludge floc was studied in one sample. When the cationic polymer was used, the flocs started to grow at the start of the breakage process. However, they broke up at the end of the process and remained small, as found in flocs not exposed to any chemical treatment. Based on the results, the optical monitoring seems to be suitable for analyzing the breakage of flocs.     

Optimization of coag-flocculation processes of a newly synthesized quaternized oil palm empty fruit bunch cellulose by response surface methodology toward drinking water treatment process application

An optimization of coagulation and flocculation of kaolin suspension by a newly synthesized quaternized oil palm empty fruit bunch cellulose denoted as a 9QC was investigated using the central composite design of the response surface methodology. The influences of coag-flocculant dosage, pH, and kaolin suspension on turbidity removal efficiency and sludge volume index responses were studied and assessed according to a 2³ full factorial design. The developed quadratic models revealed that the overall optimum values to obtain the highest performance of the responses were 62.5 mg/L of coag-flocculant dosage, pH 7, and 1400 mg/L of kaolin concentration. The predicted optimum responses were found to be in close proximity to the observed responses. The coag-flocculating of river water using 9QC carried out at the optimum values showed encouraging results as compared to alum which is commonly used in drinking water treatment process.     

海藻酸钙凝胶对牙本质小管封闭作用的实验研究

为治疗牙本质过敏症,研究了海藻酸钙对牙本质小管的封闭作用及矿化效果。以海藻酸钠(SA),碳酸钙,葡萄糖酸内酯(GDL)为原料,在牙本质上通过原位相转变制备海藻酸钙(CA)凝胶。测定了单一变量条件下不同海藻酸钠浓度、f值(钙离子与羧基的摩尔比)及n值(葡萄糖酸内酯与钙离子的摩尔比)对海藻酸钙凝胶的凝胶化时间和浸提液pH值的影响。扫描电镜观察海藻酸钠混合液处理前后牙本质微观形貌改变,并对封闭后牙本质小管进行了矿化研究。结果表明海藻酸钠浓度为2.5%、f=0.5及n=0.6为最佳配比。海藻酸钠处理后,开放的牙本质小管明显变小或封闭,显示海藻酸钠溶液可进入牙本质小管形成凝胶,并封闭牙本质小管。矿化后凝胶表面呈致密的矿化层,XRD分析为单一的高结晶羟基磷灰石,CA凝胶有利于诱导高结晶度HA的生成,为继续探索牙本质的仿生矿化提供新思路。     

Flocculated amorphous itraconazole nanoparticles for enhanced in vitro supersaturation and in vivo bioavailability

Rapid flocculation of nanoparticle dispersions of a poorly water soluble drug, itraconazole (Itz), was utilized to produce amorphous powders with desirable dissolution properties for high bioavailability in rats. Antisolvent precipitation (AP) was utilized to form Itz nanodispersions with high drug loadings stabilized with hydroxypropylmethylcellulose (HPMC) or the pH-sensitive Eudragit^® L100-55 (EL10055). The HPMC dispersions were flocculated by desolvating the polymer through the addition of a divalent salt, and the enteric EL10055 by reducing the pH. The formation of open flocs by diffusion limited aggregation facilitated redispersion of the flocs at pH 6.8. Upon redispersion of the flocculated nanoparticles at pH 6.8, the particle size was modestly larger than the original size, on the order of 1 μm. High in vitro supersaturation (AUC) of the flocculated nanoparticle dispersions was observed in micellar media at pH 6.8, after 2 hours initial exposure at pH 1.2 to simulate the stomach, relative to the AUC for a commercially available Itz formulation, Sporanox. Greater in vivo bioavailability in rats was correlated directly to the higher in vitro AUC at pH 6.8 with micelles during the pH shift experiment for the flocculated nanoparticle dispersions relative to Sporanox. The ability to generate and sustain high supersaturation in micellar media at pH 6.8, as shown with the in vitro pH shift dissolution test, is beneficial for increasing bioavailability of Itz by oral delivery.     

Stability of alginate microbead properties in vitro

Alginate microbeads have been investigated clinically for a number of therapeutic interventions, including drug delivery for treatment of ischemic tissues, cell delivery for tissue regeneration, and islet encapsulation as a therapy for type I diabetes. The physical properties of the microbeads play an important role in regulating cell behavior, protein release, and biological response following implantation. In this research alginate microbeads were synthesized, varying composition (mannuronic acid to guluronic acid ratio), concentration of alginate and needle gauge size. Following synthesis, the size, volume fraction, and morphometry of the beads were quantified. In addition, these properties were monitored over time in vitro in the presence of varying calcium levels in the microenvironment. The initial volume available for solute diffusion increased with alginate concentration and mannuronic (M) acid content, and bead diameter decreased with M content but increased with needle diameter. Interestingly, microbeads eroded completely in saline in less than 3 weeks regardless of synthesis conditions much faster than what has been observed in vivo. However, microbead stability was increased by the addition of calcium in the culture medium. Beads synthesized with low alginate concentration and high G content exhibited a more rapid change in physical properties even in the presence of calcium. These data suggest that temporal variations in the physical characteristics of alginate microbeads can occur in vitro depending on synthesis conditions and microbead environment. The results presented here will assist in optimizing the design of the materials for clinical application in drug delivery and cell therapy.     

Effect of phosphorous on the properties of titania produced from Ti-salt flocculated sludge in water treatment

In this study, the removal of phosphorous (P) using Ti-salt flocculation of biologically treated sewage effluent (BTSE) was investigated for a year. The pH, alkalinity and concentration of P, before and after Ti-salt flocculation, were measured and compared. The sludge of Ti-salt flocculation was incinerated at 600 degrees C to produce titania nanoparticles which found to be doped with P Titania nanoparticles were characterised and their photocatalytic activity under UV light irradiation were also tested. Results indicated that the removal of P, which exceeded 97% in average, was not affected by the pH and the alkalinity of BTSE. The concentration of P in titania had no effect on the characteristics of titania nanoparticles in different seasons. Titania nanoparticles exhibited superior properties in terms of BET surface area and photocatalytic activity.     

Mechanism for sludge acidification in aerobic treatment of coking wastewater

This work was undertaken to investigate the cause of sludge acidification that led to disruption of the activated sludge process treating coking wastewater from a steel-making plant in Taiwan. An activated sludge reactor (ASR) with a working volume of 80 L was used as a model system to simulate the behavior of the real wastewater treatment process. Parameters that may cause acidification or inactivation of the sludge (NH(3), SCN(-), S(2)O(3)(2-) and CN(-)) were studied individually to examine for their effects on the performance of the ASR. The results show that high loading of NH(3), SCN(-) and CN(-) did not lead to pH decrease, while the ASR attained 85% COD removal and nearly 100% SCN degradation. In contrast, when the wastewater was supplemented with ca. 1,000 mg/L of S(2)O(3)(2-), the pH dropped to nearly 4.0 in 2 days and the COD and SCN removal yields were significantly lower (at 50 and 0-20%, respectively). Thus, overloading of S(2)O(3)(2-) was apparently a key factor causing sludge acidification. The results suggest that to ensure a normal functioning of the activated sludge, the influent S(2)O(3)(2-) concentration should be closely monitored and that the pH control of the ASR is indispensable when the S(2)O(3)(2-) loading is in excess.     

Performance optimization of coagulation/flocculation in the treatment of wastewater from a polyvinyl chloride plant

This paper presents results of an experimental study of coagulation/flocculation process of wastewater generated from a polyvinyl chloride (PVC) plant. The wastewater contains fine chlorine-based solid materials (i.e. latex). Experiments were carried out using a model wastewater which is chemically identical to the actual plant but is more consistent. Inorganic ions (Al2(SO4)3, FeCl3 and CaCl2) and a water soluble commercial polyelectrolyte (PE) were added to the wastewater sample. Coagulation efficiency was determined by measuring both the turbidity of the supernatants and the relative settlement of the flocs in the jar test. It was found that aluminum and ferric ions were more efficient than calcium ions as coagulants. The addition of polyelectrolyte was found to improve substantially the coagulation/flocculation process. It was found that the (Al2(SO4)3) combined with the polyelectrolyte at certain pH and agitation speed gave the best results compared to calcium chloride or ferric chloride when combined with the same concentration of polyelectrolyte. Only 0.0375g of a solution of (0.5% Al2(SO4)3) was required to coagulate the model wastewater. Ferric chloride (2.5% FeCl3) combined with the polyelectrolyte, on the other hand, required 0.1g while the optimum turbidity is almost the same. As for calcium chloride (2.5% CaCl2) it was found to be the least effective. The coagulation/flocculation process was found to be dependent on both pH and the agitation speed.     

微胶囊化脂肪酶型TTI的制备及其性能研究

针对脂肪酶在时间-温度指示剂的应用中存在热稳定性能差,温度、pH值对其活性影响较大等问题,采用离子凝胶技术制备脂肪酶微胶囊。应用单因素试验和正交试验相结合的方法,以海藻酸钠、壳聚糖、氯化钙浓度为变量,优化脂肪酶微胶囊的制备工艺,对原脂肪酶与脂肪酶微胶囊的热稳定性能、最适温度与pH值进行研究,采用红外光谱(FTIR)、扫描电镜(SEM)对脂肪酶微胶囊结构及形貌进行分析,并对脂肪酶微胶囊在时间-温度指示剂中的应用做出初步研究。得到了脂肪酶微胶囊最佳制备工艺条件为：海藻酸钠质量浓度30 g/L,壳聚糖质量浓度6 g/L,氯化钙浓度0.3 mol/L。脂肪酶微胶囊的热稳定性比原脂肪酶有明显提高。脂肪酶微胶囊制备工艺稳定、可靠,具有应用于时间-温度指示剂中的实用价值。     

Chitosan-Alginate Microparticles as a Protein Carrier

The oral administration of peptidic drugs requires their protection from degradation in the gastric environment and the improvement of their absorption in the intestinal tract. For these requirements, a microsystem based on cross-linked alginate as the carrier of bovine serum albumin (BSA), used as a model protein, was proposed. A spray-drying technique was applied to BSA/sodium alginate solutions to obtain spherical particles having a mean diameter less than 10 μm. The microparticles were hardened using first a solution of calcium chloride and then a solution of chitosan (CS) to obtain stable microsystems. The cross-linking process was carried out at different CS concentrations and pH values of the cross-linking medium. The CS concentration affected the BSA loading in the microparticles prepared at a pH value less than the protein isoelectric point (pI). Moreover, the BSA loading at a pH value less than the pI was higher than that at a pH similar to the pI regardless of the CS concentration. This finding could be attributable to the formation of a BSA/alginate complex. The evaluation of the interaction between BSA and alginate at different pH values by means rheological measurements confirmed this hypothesis. This approach may represent a promising way to devise a microcarrier system with appropriate size for targeting the Peyer's patches, with appropriate immobilization capacity, and suitable for the oral administration of peptidic drugs.     

Distribution of extractable fractions of heavy metals in sludge during the wastewater treatment process

Sludge samples were collected from different treatment steps of Gaobeidian wastewater treatment plant (WWTP) of Beijing City, PR China, to investigate the distributions of total and chemical fractions of Fe, Mn, Ni, Cu, Zn, Cr, Pb, and Mo in different sludges. The highest total concentrations were found for Fe, Mn, Pb, and Mo in digested sludge (DS), Ni and Cr in thickened sludge (TS), Zn in dewatering sludge (DWS), and Cu in active sludge (AS). The lowest concentrations were observed in AS, except for Cu in TS. Significant differences of total metal concentration were observed between AS and TS (or DS), suggesting that sludge thickening and digesting treatments significantly influenced the total metal concentrations. Fe, Cu, Ni, Cr, Mo, and Pb distributed principally in the residual fraction in all sludges, while Zn and Mn presented in a highly available fraction. For same metal in different sludges, the portion of easily mobile fraction decreased significantly along the wastewater treatment process, and metals in AS presented in the highest available fraction. Organic matter contents, TN, and TP of sludges exhibited a significant positive correlation with the concentrations of exchangeable and reducible fraction of Pb, Mo, Cr, Cu, and Fe, while sludge pH demonstrated significant negative correlations with the concentrations of these metals.     

Chitosan-Alginate Microparticles as a Protein Carrier

The oral administration of peptidic drugs requires their protection from degradation in the gastric environment and the improvement of their absorption in the intestinal tract. For these requirements, a microsystem based on cross-linked alginate as the carrier of bovine serum albumin (BSA), used as a model protein, was proposed. A spray-drying technique was applied to BSA/sodium alginate solutions to obtain spherical particles having a mean diameter less than 10 μm. The microparticles were hardened using first a solution of calcium chloride and then a solution of chitosan (CS) to obtain stable microsystems. The cross-linking process was carried out at different CS concentrations and pH values of the cross-linking medium. The CS concentration affected the BSA loading in the microparticles prepared at a pH value less than the protein isoelectric point (pI). Moreover, the BSA loading at a pH value less than the pI was higher than that at a pH similar to the pI regardless of the CS concentration. This finding could be attributable to the formation of a BSA/alginate complex. The evaluation of the interaction between BSA and alginate at different pH values by means rheological measurements confirmed this hypothesis. This approach may represent a promising way to devise a microcarrier system with appropriate size for targeting the Peyer's patches, with appropriate immobilization capacity, and suitable for the oral administration of peptidic drugs.     

Kinetic responses of activated sludge to individual and joint nickel (Ni(II)) and cobalt (Co(II)): An isobolographic approach

The effects of Ni(II) and Co(II) on the activated sludge growth rate have been assessed for a batch growth system, for a range of concentrations between 0 and 320 mg L(-1). The activated sludge was not acclimatized to the above metallic species, while a synthetic rich growth medium was used as substrate throughout out the experimental trials. Ni(II) and Co(II) have been found to stimulate microbial growth at concentrations approximately below 27 and 19 mg L(-1), with maximum stimulation concentrations 10 and 5 mg L(-1), respectively. The lethal concentrations (zero growth) for both species have been found to lie between 160 and 320 mg L(-1), with Co(II) identified as more potent growth inhibitor compared to Ni(II). The behaviour of activated sludge was also tested at the presence of three Ni(II) and Co(II) quotas, at various concentrations (75%Ni-25%Co (w/w), 50%Ni-50%Co (w/w) and 25%Ni-75%Co (w/w)). All the mixtures stimulated more drastically the activated sludge growth at relatively small concentrations, compared with the stimulation of equal concentrations of single species, whilst they also acted as more potent inhibitors at relatively high concentrations. Based on the isobole method, the data indicated that Ni(II) and Co(II) acted synergistically at the increasing stimulation and at the intoxication zones, whilst an antagonistic relation determined at the decreasing stimulation zone. Under the light of the present study, it is obvious that interactions (particularly synergism) between different metallic species should be taken into account in the methodologies used to establish criteria for tolerance levels in the environment.