Efficacy of methanogenic biomass acclimation in mesophilic anaerobic digestion of ultrasound pretreated sludge.

Methanogenic biomass plays a key role with regard to methane production during anaerobic bioconversion of organic substrates. In this study, the effect of two different acclimated inocula on digestion performances was investigated by means of anaerobic batch tests on untreated and sonicated waste-activated sludge. Organics solubilization and removal kinetics, the abundance and physiological conditions of archaeal cells on ultimate methane yield were evaluated. The simultaneous presence of Methanosarcina and Methanosaeta in the archaeal biomass, the higher initial archaeal cells relative abundance and their occurrence in the aggregated forms were the main factors positively affecting the conversion into methane. The presence of the acclimated inoculum at the start-up influenced positively the methane improvement due to sonication, and the methane-specific production increased from 0.335 ± 0.03 to 0.420 ± 0.05 Nm3/kg VSfed. Moreover, the better physiological state of methanogens permitted to appreciate the effect of hydrolysis improvement by ultrasound pretreatment.

Biomethane potential of food waste: modeling the effects of mild thermal pretreatment and digestion temperature.

In order to enhance anaerobic biodegradability of food waste (FW), thermal pretreatment was applied. The effectiveness in terms of biodegradability extent and process rate improvement was investigated. To this aim, Biomethane Potential tests were carried out under mesophilic and thermophilic conditions. The IWA anaerobic digestion Model 1 (ADM1), a powerful tool for modeling the anaerobic digestion (AD) of different substrates, was implemented to predict the methane production. Disintegration constant (k_dis) and maximum acetate uptake rate (km_ac) were identified as the most sensitive parameters and were calibrated over the observed methane production. Pretreatment improvement was more evident in enhancing parameters related to the process rate, such as solubilization extent (+153%) and disintegration constant (+18%), rather than increasing substrate biodegradability. Thermophilic conditions proved to be effective in speeding up the whole AD process, since all the kinetics were significantly improved (disintegration rate increased up to fivefold). Furthermore, it was demonstrated that, after k_dis and km_ac calibration, default thermophilic ADM1 parameters can be suitable to model FW digestion.

Microbial diversity in innovative mesophilic/thermophilic temperature-phased anaerobic digestion of sludge.

Anaerobic digestion (AD) is one of the few sustainable technologies that both produce energy and treat waste streams. Driven by a complex and diverse community of microbes, AD may be affected by different factors, many of which also influence the composition and activity of the microbial community. In this study, the biodiversity of microbial populations in innovative mesophilic/thermophilic temperature-phased AD of sludge was evaluated by means of fluorescence in situ hybridization (FISH). The increase of digestion temperature drastically affected the microbial composition and selected specialized biomass. Hydrogenotrophic Methanobacteriales and the protein fermentative bacterium Coprothermobacter spp. were identified in the thermophilic anaerobic biomass. Shannon-Weaver diversity (H') and evenness (E) indices were calculated using FISH data. Species richness was lower under thermophilic conditions compared with the values estimated in mesophilic samples, and it was flanked by similar trend of the evenness indicating that thermophilic communities may be therefore more susceptible to sudden changes and less prompt to adapting to operative variations.

Quality assessment of digested sludges produced by advanced stabilization processes.

The European Union (EU) Project Routes aimed to discover new routes in sludge stabilization treatments leading to high-quality digested sludge, suitable for land application. In order to investigate the impact of different enhanced sludge stabilization processes such as (a) thermophilic digestion integrated with thermal hydrolysis pretreatment (TT), (b) sonication before mesophilic/thermophilic digestion (UMT), and (c) sequential anaerobic/aerobic digestion (AA) on digested sludge quality, a broad class of conventional and emerging organic micropollutants as well as ecotoxicity was analyzed, extending the assessment beyond the parameters typically considered (i.e., stability index and heavy metals). The stability index was improved by adding aerobic posttreatment or by operating dual-stage process but not by pretreatment integration. Filterability was worsened by thermophilic digestion, either alone (TT) or coupled with mesophilic digestion (UMT). The concentrations of heavy metals, present in ranking order Zn > Cu > Pb > Cr ~ Ni > Cd > Hg, were always below the current legal requirements for use on land and were not removed during the processes. Removals of conventional and emerging organic pollutants were greatly enhanced by performing double-stage digestion (UMT and AA treatment) compared to a single-stage process as TT; the same trend was found as regards toxicity reduction. Overall, all the digested sludges exhibited toxicity to the soil bacterium Arthrobacter globiformis at concentrations about factor 100 higher than the usual application rate of sludge to soil in Europe. For earthworms, a safety margin of factor 30 was generally achieved for all the digested samples.

Innovative two-stage mesophilic/thermophilic anaerobic degradation of sonicated sludge: performances and energy balance.

This study investigates for the first time, on laboratory scale, the possible application of an innovative enhanced stabilization process based on sequential mesophilic/thermophilic anaerobic digestion of waste-activated sludge, with low-energy sonication pretreatment. The first mesophilic digestion step was conducted at short hydraulic retention time (3-5 days), in order to favor volatile fatty acid production, followed by a longer thermophilic step of 10 days to enhance the bioconversion kinetics, assuring a complete pathogen removal. The high volatile solid removals, up to 55%, noticeably higher compared to the performances of a single-stage process carried out in same conditions, can guarantee the stability of the final digestate for land application. The ultrasonic pretreatment influenced significantly the fatty acid formation and composition during the first mesophilic step, improving consequently the thermophilic conversion of these compounds into methane. Methane yield from sonicated sludge digestion reached values up to 0.2 Nm(3)/kgVSfed. Positive energy balances highlighted the possible exploitation of this innovative two-stage digestion in place of conventional single-stage processes.

Advanced anaerobic processes to enhance waste activated sludge stabilization.

The requirement for enhanced stabilization processes to obtain a more stable, pathogen-free sludge for agricultural use is an increasing challenge to comply with in the waste hierarchy. With this in mind, the Routes European project ('Novel processing routes for effective sewage sludge management') is addressed to assess innovative solutions with the aim of maximizing sludge quality and biological stability. In order to increase anaerobic stabilization performances, the sequential anerobic/aerobic process and the thermophilic digestion process, with or without integration of the thermal hydrolysis pre-treatment, were investigated as regards the effect on sludge stabilization, dewaterability and digestion performances. Thermal pre-treatment improved anaerobic digestion in terms of volatile solids reduction and biogas production, but digestate dewaterability worsened. Fluorescence in situ hybridization (FISH) quantification showed an increase of methanogens consistent with the increase of biogas produced. The aerobic post-treatment after mesophilic digestion had a beneficial effect on dewaterability and stability of the digested sludge even if was with a reduction of the potential energy recovery.

Potential of high-frequency ultrasounds to improve sludge anaerobic conversion and surfactants removal at different food/inoculum ratio.

High-frequency ultrasounds have recently gained interest as oxidative technique for sonochemical degradation of organic contaminants in water. In this study an innovative approach applying 200 kHz ultrasounds to improve both sludge anaerobic biodegradability and decontamination is proposed. Digestion tests were performed on batch reactors fed either with untreated or sonicated sludge, at different food/inoculum (F/I) ratio, in the range 0.3-0.9. First order kinetic highlighted a decreasing trend of the hydrolysis rate by increasing F/I, both for untreated and sonicated sludge. Positive effect of ultrasounds on specific biogas production was evident, but the conversion rate for pretreated sludge was strongly affected by F/I, and decreased by increasing F/I. Anionic surfactants anaerobic removal occurred in all tests, but the effect of ultrasounds was significant only at F/I=0.3. By pretreating sludge with high frequency ultrasounds, low F/I was the ideal ratio improving both sludge anaerobic digestion and decontamination.

High-frequency ultrasound treatment of sludge: combined effect of surfactants removal and floc disintegration.

Ultrasounds represent an effective technology in many research fields. In sewage sludge treatment, low-frequency ultrasound, particularly at 20 kHz, are widely used for sludge disintegration before the anaerobic digestion, while in the last years novel application of high-frequency ultrasound regards the decontamination of water and wastewater through sonochemical reactions. The innovative approach presented in this paper is the treatment of sewage sludge with ultrasound at 200 kHz for obtaining efficient sludge disintegration and the removal of the linear alkylbenzenesulphonates (LAS) at the same time. Results of the sonolysis experiments showed that native LAS degradation up to 40% can be achieved with low power input in less than 1h. The degradation pattern was different for each LAS homologue (from C10 to C13), because of their physical-chemical properties, in particular as regards the alkyl chain length. This high-frequency ultrasound irradiation resulted effective also in terms of floc disintegration and soluble organic matter release, in particular for energy inputs higher than 30,000 kJ/kg TS. The disrupting effect of the 200 kHz treatment was also evaluated by microscope analyses and determination of the extracellular polymeric substances release in the liquid phase.

Cisplatin-paclitaxel weekly schedule in advanced solid tumors: a phase I study.

PURPOSE: The objective of our study was to determine the maximum tolerable doses (MTDs) of both paclitaxel and cisplatin when given in a weekly schedule alone or simultaneously with G-CSF in advanced solid neoplasms. PATIENTS AND METHODS: Patients with advanced cancer either chemotherapy-naive or resistant to standard treatments received paclitaxel in a three-hour infusion followed by cisplatin, with or without the addition of r-HuG-CSF (5 micrograms/kg s.c. days three to five). The starting doses of CDDP and paclitaxel were 25 mg/m2/week and 45 mg/m2/week, respectively. During the first six courses the dosages of the two drugs were alternately escalated by 20% (CDDP = 5 mg/m2/week, and paclitaxel 10 mg/m2/week) at each step until the appearance of dose-limiting toxicity (DLT) in one-third or more of the patients enrolled in that cohort. RESULTS: Fifty-five patients with cancer (16 lung, 16 breast, 11 ovarian, 7 head and neck, 1 renal, 1 esophageal, 1 cervical, 1 soft-tissue sarcoma, and 1 of unknown primary), 25 of whom were pretreated, were entered into the study. A total of 439 weekly courses were delivered. In chemotherapy-naïve patients, the MTDs of cisplatin and paclitaxel were 30 mg/m2/week and 65 mg/m2/week, respectively, in the absence of G-CSF support, which increased to 40 mg/m2/week and 85 mg/m2/week, respectively, when G-CSF was given. There were no toxic deaths in this study. Neutropenia was the main dose-limiting toxicity (100/439 courses), but was seldom severe. Neurotoxicity was quite frequent (18 of 55 patients for the total of 88 courses) but never dose-limiting. It was more frequent and clinically relevant in cisplatin-pretreated patients. Overall 18 patients (eight ovarian, five breast, three lung, and two head and neck) achieved objective responses. CONCLUSIONS: The cisplatin-paclitaxel weekly administration seems a safe, practical and effective therapeutical approach in patients with advanced solid neoplasms. Large phase II trials are warranted to accurately define the efficacy of this schedule in cisplatin-paclitaxel sensitive tumors.

Identification and screening of 416 patients with chronic hepatitis at high risk to develop hepatocellular cancer.

OBJECTIVE: The authors performed a prospective trial to screen patients with chronic hepatitis B or C virus (HBV, HCV) infections to (1) determine the incidence of asymptomatic hepatocellular cancer and (2) identify the subgroups at highest risk to develop hepatocellular cancer. METHODS: Four hundred sixteen patients with chronic hepatitis of more than 5 years' duration were evaluated (340 HCV, 69 HBV, 7 both). All underwent hepatic ultrasound and measurement of serum alpha-fetoprotein every 3 months. Liver biopsy was performed on entry into the study to determine the severity of hepatitis-related liver injury. RESULTS: Initial screening identified asymptomatic hepatocellular cancer in 33 patients (7.9%). Three additional liver cancers were detected during the 1st year of follow-up, bringing the overall incidence to 8.6%. Treatment with curative intent was possible in 22 of these patients (61.1%), whereas 14 (38.9%) had advanced disease. Thirty-five of these hepatocellular cancers occurred in a subset of 140 patients (25% incidence) with liver biopsies showing severe chronic active hepatitis, cirrhosis, or both, and one hepatocellular cancer occurred among the 276 patients (0.4%) with histologically less severe liver injury (p < 0.0001, chi square test). CONCLUSIONS: This screening study in patients with chronic HBV or HCV infection demonstrates (1) that the yield of asymptomatic hepatocellular cancer on initial screening is 7.9% and (2) that patients with severe chronic active hepatitis, cirrhosis, or both are at extremely high risk to develop hepatocellular cancer (25%). On the basis of these results and the finding of a significant number of small; treatable hepatocellular cancers (61.1%), the authors recommend hepatocellular cancer screening every 3 months for the subset of high-risk patients.