EVALUATION OF ELECTRODE SURFACE TREATMENTS IN SLUDGE ELECTRO-OSMOSIS DEWATERING”

The drying of sludge produced by Wastewater Treatment Plants (WWTPs) is a very hard process due to the presence of the colloid fraction. Electro-osmosis could be a suitable technique to reduce the water content of the final sludge. Electrical fields of 10 V/cm, 15 V/cm and 20 V/cm have been studied for electro-osmosis tests in a static or dynamic apparatus, obtaining a dry solids content up to 40-45%, with respect to 25-30% obtained by mechanical methods. In order to optimise the apparatus, the corrosion behaviour of the anodic material appears the main critical aspect, due to the high circulating current density. Moreover, wear may be detrimental for the surface of rotating electrodes. We then investigated the behaviour of materials used as electrodes mainly by evaluating the efficiency of the process and their surface aspect after treatment. The full understanding of the electrochemical reactions developed at the anode are a key factor for the material choice. We compared the efficiency and the corrosion resistance of anodes made of titanium MMO with respect to bare stainless steel (AISI 304) and stainless steel coated by PVD technique with TiN, AlTiN and DLC. Characterization of the anodes samples by roughness tests and by AFM show that corrosion resistance of the DSA was the most suitable for our application. However, efficiencies of the electro-osmosis process for all the materials used have been found comparable, in terms of developed current densities and total energy consumptions, for low-test duration

ELECTRO-OSMOTIC DEWATERING OF SEWAGE SLUDGE: PRELIMINARY RESULTS

About half of the organic pollution load treated by the activated sludge process is oxidised and converted into water and carbon dioxide, while the remaining is converted into biomass, called “excess biological sludge” or “waste sludge”. At present, this technique is the cheapest way to remove colloidal and soluble organic pollutants from sewage, but it produces a huge amount of liquid waste sludge, with a dry solid (DS) content of less than 2%, rich in organic substances, mostly biodegradable. Therefore, it needs further processes to reduce its volume, by reducing its water content, and to reduce its polluting potential, due to its high content of biodegradable organic matter. However, sludge produced by Wastewater Treatment Plants (WWTPs) usually has a poor dewaterability. Industrially, mechanical dewatering is the method employed to increase the dry solids (DS) of sewage sludge. The aim of dewatering is the decrease of transport and disposal costs, but the efficiency of the mechanical dehydration methods is low. Electro-osmosis could be a suitable technique to reduce water content of the final sludge by the application of an electric field. Studies about electro-dewatering reported that the DS could increase to values around 40-45%, with respect to 25-30% obtained by mechanical methods, such as centrifuge, filter press and belt press. Aim Here, we investigated the parameters affecting pressure-driven electro-dewatering, with a static and a dynamic device, starting from types of sludge mechanically pre-dehydrated. We focused on the optimization of operating conditions to achieve the best results in terms of solids percentage at the minimum energy consumption. Methods Experiments have been performed by means of a lab-scale device able to produce both a mechanical pressure and an electric field. The use of both these systems could be efficient to increase the amount of dry solids in the final sludge. This device, as illustrated in Figure 1, consists of: • Cylindrical glass vessel (h=176 mm, Ø=80 mm) • Cooling water-jacket • Compressed air system (1-4.5 bar) • Double effect cylinder (200 mm stroke) SMC-CP96 (piston) • DC power supply (30 V-5 A) • Anode: DSA Ti (MMO), fixed to the piston • Cathode: stainless steel mesh (AISI 304) • Cloth: PTT (polytrimethyleneterephthalate) Figure 1-Equipment schematic of electro-dewatering device. Main Results The applied voltage has been set at 10 V, 15 V and 20 V and pressures at 3 bar. The results confirmed values of final DS around 40%. Initial DS and sludge conductivity, together with the applied electric field, are the key factors of electro-osmosis tests. The rotating piston highlighted that a mixing of sludge during the potential application could slightly increase the sludge conductivity, but cakes must be kept under 1.5 cm of thickness in order to achieve a good dewatering. In conclusion, in this paper we assess the feasibility of the electro-osmosis dewatering. It is a promising technique to remove water from sewage sludge, since it is able to increase DS of 15% on average with respect industrial mechanical dewatering. Moreover, this work proved that the treatment of a high DS cake is more difficult than a non-dewatered sludge due to a lower conductivity during the process

Influence of sludge characteristics on pressure-driven electro-dewatering of stabilized sewage sludge

The feasibility of the pressure-driven electro-dewatering (EDW) on aerobically and anaerobically stabilised sludge samples, taken from four different wastewater treatment plants around the metropolitan area of Milan (Italy), has been assessed. First, sewage sludges were characterized by measuring DS content, VS/DS ratio, pH, conductivity, zeta potential and capillary suction time (CST) of the liquid fraction. Then, after a preliminary centrifugation of the sludge samples in the laboratory, pressure-driven EDW tests have been performed in a lab-scale device, under the application of 300 kPa of pressure and an applied voltage of 15 V. The DS content increased up to 18.4-31.1%, (with an increase of 8.6% to 23.0% from the initial DS value) depending on the characteristics of the sludge samples and the polymer dosage. If compared with EDW tests, the increase due to the sole effect of pressure ranged from 3 to 10% and strictly depended on polymer dosage. The characteristics of sludge that affect the increase of the DS content were investigated during both the pressure-driven stage and the EDW stage. Polyelectrolyte addition (4 and 8 g/kgDS) mainly affected the pressure-driven phase of the tests. However, the VS/DS ratio was the main factor affecting the pressure-driven stage on the unconditioned aerobically stabilised samples. CST values could also reliably predict the efficiency of this stage during experiments

Tibial tubercle avulsion fracture during sport activities in adolescent: a case report

BACKGROUND AND AIM OF WORK: Tibial tubercle avulsion fractures (TTAF) are uncommon condition in children and adolescents. These lesions may be misdiagnosed and consequently not properly treated. Reduction and fixation is indicated if displacement is higher than 2mm or if the extensor apparatus is damaged. Authors present a case of a TTAF associated with a complete lateral patellar retinaculum lesion in a 13-year-old male adolescent non-professional basketball player. METHODS: Surgery consisted of reduction and fixation with 2 half threaded cancellous and washers; TTA was then basted and reinforced with a non absorbable suture according to Krachow technique and finally the patellar lateral retinaculum through a direct repair with absorbable material. RESULTS: Clinical evaluation after 3 years showed bone healing, a complete resolution of pain, complete range of motion, good strength and complete functionality of the operated limb. CONCLUSIONS: Misdiagnosis or delayed treatment of TTAF can often result in nonunion, functional impairment, and persistent pain. For these reasons, authors believe that a stable and quick fixation associated to specialized rehabilitation are crucial for recovery. (www.actabiomedica.it)

Pressure-driven electro-dewatering applied for sludge: Economic & environmental life cycle assessment

Dewatering plays an important role in sludge minimization and reuse. In this study, pressure-driven electro-dewatering (EDW) was investigated using a lab device and various operating parameters were optimised. Furthermore, the EDW system’s economic and environmental performances were evaluated using Life Cycle Assessment. These results can be interesting for the stakeholders within the WWTP industry who are considering upgrading from the conventional mechanical dewatering to the EDW

La disidratazione elettro-assistita dei fanghi: influenza del dosaggio di polielettrolita e dei parametri operativi

In questa ricerca è stato studiato a scala di laboratorio il processo di disidratazione elettroassistita (Electro Dewatering, EDW) dei fanghi di depurazione. I campioni di fango, stabilizzati aerobicamente o anaerobicamente, sono stati prelevati da quattro impianti di depurazione intorno all’area metropolitana di Milano. Per le prove EDW sono state utilizzate due tipologie di campioni: (i) fango liquido ispessito (LI), prelevato prima del condizionamento, e (ii) fango disidratato meccanicamente (DM). Le prove EDW su fango LI hanno consentito la disidratazione dei campioni fino ad un contenuto di solido secco (SS) del 18,4-31,1%, corrispondente a un aumento compreso tra il 2,0% e il 12,7% rispetto alla disidratazione meccanica convenzionale utilizzata nei quattro impianti. In aggiunta all’aumento del tenore di secco finale, il processo ha consentito una riduzione del dosaggio di polielettrolita rispetto a quello utilizzato negli impianti. Nelle prove su fango DM si sono raggiunti valori di SS compresi tra 30,1-41,0%. Si è dimostrato che le condizioni operative, come il potenziale elettrico applicato e lo spessore iniziale del fango trattato nel dispositivo, hanno notevole influenza sull’efficienza del processo EDW, sia su fango LI, sia su fango DM. Infine, il costo del polielettrolita, il consumo di energia elettrica e il costo dello smaltimento dei fanghi associati al processo EDW sono stati confrontati con la disidratazione convenzionale utilizzata nei quattro impianti. Si è constatato che l’utilizzo del processo EDW consentirebbe di ridurre i costi di gestione dei fanghi fino al 37% all’anno per fango LI e fino al 50% per fango DM.In this research the process of electrodewatering (EDW) of sewage sludge has been studied. The sludge samples, aerobically or anaerobically stabilized, have been taken from four wastewater treatment plants (WWTPs) around the metropolitan area of Milan. For the EDW tests two types of samples have been used: (i) thickened sludge (LI), taken before conditioning and (ii) mechanically dewatered sludge (DM). The EDW tests on LI sludge allowed the dewatering of the samples up to a dry solid content (SS) of 18.4-31.1%, equal to an increase of 2.0-12.7% compared to the conventional mechanical dewatering treatments used in the four WWTPs. Together with the final DS increase, the EDW process allowed to reduce the polyelectrolyte dosage with respect to that used in the WWTPs. The tests on DM sludge achieved DS values between 30.1-41.0%. It has been shown that the operating conditions, such as electrical potential and cake thickness, have considerable influence on the efficiency of the EDW process, both on LI and DM sludge. The cost of the polyelectrolyte, the consumption of electric energy and the cost of sludge disposal associated to the EDW process have been compared to conventional dewatering used in the four WWTPs. It was found that the use of the EDW process would reduce sludge management costs by up to 37% per year for LI samples and up to 50% for DM samples

Clinical trial of laronidase in Hurler syndrome after hematopoietic cell transplantation.

BackgroundMucopolysaccharidosis I (MPS IH) is a lysosomal storage disease treated with hematopoietic cell transplantation (HCT) because it stabilizes cognitive deterioration, but is insufficient to alleviate all somatic manifestations. Intravenous laronidase improves somatic burden in attenuated MPS I. It is unknown whether laronidase can improve somatic disease following HCT in MPS IH. The objective of this study was to evaluate the effects of laronidase on somatic outcomes of patients with MPS IH previously treated with HCT.MethodsThis 2-year open-label pilot study of laronidase included ten patients (age 5-13 years) who were at least 2 years post-HCT and donor engrafted. Outcomes were assessed semi-annually and compared to historic controls.ResultsThe two youngest participants had a statistically significant improvement in growth compared to controls. Development of persistent high-titer anti-drug antibodies (ADA) was associated with poorer 6-min walk test (6MWT) performance; when patients with high ADA titers were excluded, there was a significant improvement in the 6MWT in the remaining seven patients.ConclusionsLaronidase seemed to improve growth in participants <8 years old, and 6MWT performance in participants without ADA. Given the small number of patients treated in this pilot study, additional study is needed before definitive conclusions can be made

Arginine deficiency augments inflammatory mediator production by airway epithelial cells in vitro

<p>Abstract</p> <p>Background</p> <p>Previously we showed that reduced availability of the essential amino acid tryptophan per se attenuates post-transcriptional control of interleukin (IL)-6 and IL-8 leading to hyperresponsive production of these inflammatory mediators by airway epithelial cells. Availability of the non-essential amino acid arginine in the inflamed airway mucosa of patients with asthma is reduced markedly, but it is not known whether this can also lead to an exaggerated production of IL-6 and IL-8.</p> <p>Methods</p> <p>IL-6 and IL-8 were determined by ELISA in culture supernatants of NCI-H292 airway epithelial-like cells and normal bronchial epithelial (NHBE) cells that were exposed to TNF-α, LPS or no stimulus, in medium with or without arginine. Arginine deficiency may also result from exposure to poly-L-arginine or major basic protein (MBP), which can block arginine uptake. Epithelial cells were exposed to these polycationic proteins and L-¹⁴C-arginine uptake was assessed as well as IL-6 and IL-8 production. To determine the mode of action, IL-6 and IL-8 mRNA profiles over time were assessed as were gene transcription and post-transcriptional mRNA degradation.</p> <p>Results</p> <p>For both NCI-H292 and NHBE cells, low arginine concentrations enhanced basal epithelial IL-6 and IL-8 production and synergized with TNF-α-induced IL-6 and IL-8 production. Poly-L-arginine enhanced the stimulus-induced IL-6 and IL-8 production, however, blocking arginine uptake and the enhanced IL-6 and IL-8 production appeared unrelated. The exaggerated IL-6 and IL-8 production due to arginine deficiency and to poly-L-arginine depend on a post-transcriptional and a transcriptional process, respectively.</p> <p>Conclusion</p> <p>We conclude that both reduced arginine availability per se and the presence of polycationic proteins may promote airway inflammation by enhanced pro-inflammatory mediator production in airway epithelial cells, but due to distinct mechanisms.</p