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

Assessing the Utility of Restaurant Descriptors and Typologies for Advancing the Body of Knowledge in Restaurant Management

The study begins with a review of existing typologies in the restaurant management literature. Segment labels from three typologies are used as keywords to collect 251 empirical studies from nine relevant academic journals serving the restaurant management discipline. Content analysis of titles, abstracts, and methodology sections reveals inconsistent use of existing typologies and limited use of effective restaurant descriptors. Recommendations are offered to optimize the use of restaurant descriptors so that the content of empirical studies may be more effectively accessed, digested, and compared across, thereby enhancing the communication of advances in the restaurant management body of knowledge

Treatability of digested piggery/poultry manure by anammox bacteria

The liquid fraction of digested material is rich in ammonium and may require nitrogen removal. The aim of this research was to evaluate the applicability of the anammox process for the biological N removal from a supernatant coming from the anaerobic digestion of a mixture of piggery manure, poultry manure, and of agro-wastes. The supernatant was pre-treated in a partial nitritation pilot-scale reactor located at the farm. A batch procedure for testing the short term effect of high-strength wastewaters on anammox activity is presented. The anammox process was successfully applied for the first time to undiluted digestate, and the average N removal efficiency achieved during 350 days of experimentation in a SBR lab-scale reactor was 91%

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

Phosphorus recovery from a pilot-scale grate furnace: influencing factors beyond wet chemical leaching conditions

Phosphorus is a non-renewable resource going to exhaustion in the future. Sewage sludge ash is a promising secondary raw material due to its high phosphorus content. In this work, the distribution of 19 elements in bottom and cyclone ashes from pilot-scale grate furnace have been monitored to determine the suitability for the phosphorus acid extraction. Moreover, the influence of some parameters beyond wet chemical leaching conditions were investigated. Experimental results showed that bottom ash presented lower contamination in comparison to cyclone ash and low co-dissolution of heavy metals (especially Cr, Pb and Ni), while high phosphorus extraction efficiencies (76-86%) were achieved. High Al content in the bottom ash (9.4%) negatively affected the phosphorus extraction efficiency as well as loss on ignition, while the particle size reduction was necessary for ensuring a suitable contact surface. The typology of precipitating agents did not strongly affect the phosphorus precipitation, while pH was the key parameter. At pH 3.5-5, phosphorus precipitation efficiencies higher than 90% were achieved, with a mean phosphorus content in the recovered material equal to 16-17%, comparable to commercial fertilizers. Instead, the co-precipitation of Fe and Al had a detrimental effect on the recovered material, indicating the need for additional treatments

LTE transmission exploiting pulse width modulation in fibre optic links

Recently it has been demonstrated that pulse width modulation (PWM) can represent a viable solution for the analog optical fronthaul alternative to standard radio over fibre, which still avoids the bandwidth expansion of the digital fronthaul. The PWM encodes the analog samples at the transmitter onto the duration of the on/off keyed optical signal, splitting the sampling and quantization of the radio signal between remote radio units (RRUs) and baseband units (BBUs). In particular in this contribution we demonstrate the capabilities of optical PWM for the transport of LTE signals to support the centralized access network (C-RAN) fronthaul in fibre optic link up to 10-km of standard single mode fibre. The generation and analysis of the radio signals is provided by software modules compliant with the LTE standard which allowed to analyse performance results for the different LTE carriers, channels and services. The PWM optical signal connecting RRUs to BBUs is generated by either directly modulating a DFB laser or an externally seeded reflective semiconductor optical amplifier (RSOA). Both devices could be exploited inside a wavelength division multiplexed passive optical network (WDM PON) architecture where the various RRU-to-BBU links are pooled through virtual point-to-point connections at different wavelengths

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

Variabilidad de perturbaciones espaciales y temporales de 500hPa parasistemas tropicales y extratropicales de Sudamérica

En este trabajo se estudia la variabilidad espacial y temporal de los campos de circulación a través de un análisis de anomalías mensuales del nivel de 500hPa. En particular, se analizan las anomalías extremas en la región tropical y extratropical de Sudamérica oriental, y su comportamiento regional con relación al cambio climático. Se presenta también un análisis de vientos relacionados con eventos extremos, y de saltos climáticos en cada una de las estaciones. Para este estudio se utilizan radiosondeos de Argentina (Córdoba, SACO; y Ezeiza, SAEZ) y sur de Brasil (Galeáo, SBGL), cubriendo el período enero 1973-abril 2006. Ambas estaciones argentinas representan la región extratropical, mientras que la estación brasilera representa la región tropical. La variable utilizada es la altura geopotencial de 500 hPa y la metodología consiste en la aplicación de métodos estadísticos básicos, análisis de Fourier, y de cluster para la clasificación de los campos de circulación. Para detectar saltos climáticos se utiliza el test de Yamamoto. La presencia de un dipolo ubicado al sur de 30° S caracteriza a la primera componente principal en relación con la presencia de anomalías mensuales extremas en la altura de 500hPa para cada una de las estaciones analizadas. En general, eventos extremos negativos (positivos) están relacionados con mayor (menor) frecuencia e intensidad de oestes. Además, las series de anomalías presentan un salto climático en la década del ’80 para SACO y SBGL, mientras que la serie de SAEZ no presenta cambio alguno.Spatial and temporal variability ofcirculation patterns associated to extreme 500 hPa geopotential height anomalies are studied. Particularly, extreme anomalies in the tropical and extratropical region of southeastern South America are analyzed, as well as its regional behaviour related to climatic change. Wind analyses related to extreme events and climatic jumps analysis are also presented. Rawinsondes from Argentina (Córdoba and Ezeiza) and southern Brazil (Galeáo) covering the period January 1973-April 2006 are used. Both argentine stations represent the mid-latitude region, while the Brazilian one represents the tropical region. The variable used is the 500 hPa geopotential height, and the methodology consists in basic statistical methods, Fourier analysis, and a cluster analysis to classify the circulation patterns. Yamamoto test is used to detect climatic jumps. The main feature for the first principal component is the presence of a dipole located south of 30° S. The first principal component is highly related to the presence of extreme 500 hPa geopotential height monthly anomalies at each station. Negative (positive) extreme events are in general related to higher (lower) frequency and intensity of westerlies. Moreover, the series of anomalies present a climatic jump in the eighties for SACO and SBGL, but not for SAEZ.Material digitalizado en SEDICI gracias a la colaboración de la Facultad de Ciencias Astronómicas y Geofísicas (UNLP).Asociación Argentina de Geofísicos y Geodesta

Altered Env conformational dynamics as a mechanism of resistance to peptide‑triazole HIV‑1 inactivators.

Background: We previously developed drug-like peptide triazoles (PTs) that target HIV-1 Envelope (Env) gp120, potently inhibit viral entry, and irreversibly inactivate virions. Here, we investigated potential mechanisms of viral escape from this promising class of HIV-1 entry inhibitors. Results: HIV-1 resistance to cyclic (AAR029b) and linear (KR13) PTs was obtained by dose escalation in viral passaging experiments. High-level resistance for both inhibitors developed slowly (relative to escape from gp41-targeted C-peptide inhibitor C37) by acquiring mutations in gp120 both within (Val255) and distant to (Ser143) the putative PT binding site. The similarity in the resistance profiles for AAR029b and KR13 suggests that the shared IXW pharmacophore provided the primary pressure for HIV-1 escape. In single-round infectivity studies employing recombinant virus, V255I/S143N double escape mutants reduced PT antiviral potency by 150- to 3900-fold. Curiously, the combined mutations had a much smaller impact on PT binding affinity for monomeric gp120 (four to ninefold). This binding disruption was entirely due to the V255I mutation, which generated few steric clashes with PT in molecular docking. However, this minor effect on PT affinity belied large, offsetting changes to association enthalpy and entropy. The escape mutations had negligible effect on CD4 binding and utilization during entry, but significantly altered both binding thermodynamics and inhibitory potency of the conformationally-specific, anti-CD4i antibody 17b. Moreover, the escape mutations substantially decreased gp120 shedding induced by either soluble CD4 or AAR029b. Conclusions: Together, the data suggest that the escape mutations significantly modified the energetic landscape of Env’s prefusogenic state, altering conformational dynamics to hinder PT-induced irreversible inactivation of Env. This work therein reveals a unique mode of virus escape for HIV-1, namely, resistance by altering the intrinsic conformational dynamics of the Env trimerpost-print4093 K

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