Genotoxic effect induced by hydrogen peroxide in human hepatoma cells using comet assay

Background: Hydrogen peroxide is a common reactive oxygen intermediate generated by variousforms of oxidative stress. Aims: The aim of this study was to investigate the DNA damage capacity ofH2O2 in HepG2 cells. Methods: Cells were treated with H2O2 at concentrations of 25 μM or 50 μM for5 min, 30 min, 40 min, 1 h or 24 h in parallel. The extent of DNA damage was assessed by the cometassay. Results: Compared to the control, DNA damage by 25 μM and 50 μM H2O2 increasedsignificantly with increasing incubation time up to 1 h, but it was not increased at 24 h. Conclusions:Our Findings confirm that H2O2 is a typical DNA damage inducing agent and thus is a good modelsystem to study the effects of oxidative stress. DNA damage in HepG2 cells increased significantlywith H2O2 concentration and time of incubation but later decreased likely due to DNA repairmechanisms and antioxidant enzyme

A Comparison of the Anaerobic Filter and the Anaerobic Expanded/Fluidized Bed Processes

The anaerobic filter and the anaerobic expanded/fluidized bed processes represent advances in wastewater treatment technology for processing organic wastes. Literature data for both processes is presented and discussed. In addition, mass transport concepts are used to compare the substrate flux rates of both systems. It is concluded that the expanded/fluidized bed represents a more efficient design for anaerobic fermentation reactions.</jats:p

Anaerobic Treatment of Municipal Solid Waste Landfill Leachate: Operation of a Pilot Scale Hybrid UASB/AF Reactor

Landfill disposal is a widely used technique for solid waste management. The leachate produced, owing to moisture release and rain and snow infiltration, can cause environmental hazards if it is not properly collected, treated, and disposed. An on-site pilot plant study was carried out to assess the treatability of the leachate from a developing landfill. Details of the designed reactor and data collected during a long term run are presented, showing that a young landfill leachate is amenable to anaerobic treatment of its organic fraction, but special care should be taken with the management of the inorganic compounds, especially heavy metals.</jats:p

Evaluation of an electronic nose for the early detection of organic overload of anaerobic digesters

This study aims at the analysis of the utilization of an electronic nose (e-nose) to serve as a specific monitoring tool for anaerobic digestion process, especially for detecting organic overload. An array of non specific metal oxide semiconductor gas sensors were used to detect process faults due to organic overload events in twelve anaerobic semi-continuous reactors of 1.8 L. Three different load strategies were followed (i) a cautious organic load (1.3 gVS•L-1•day-1); (ii), an increasing load strategy (1.3 to 5.3 gVS∙L-1•day-1) and (iii) a cautious organic load with load pulses of up to 12 gVS•L-1•day-1. A first monitoring campaign was conducted with three different substrates : sucrose, maize oil, and a mix of sucrose/oil during 60 days. The second campaign was run with dry sugar beet pulp during 45 days. Hotelling's T²-value and upper control limit to a reference set of digesters fed with a cautious OLR (1.3 gVS•L-1•day-1), was used as indirect state variable of the reactors. Overload situations were identified by the e-nose apparatus with Hotelling’s T²-values at least 4-times higher in magnitude than the upper control limit of 23.7. These results confirmed that the e-nose technology appeared promising for online detection of process imbalances in the domain of anaerobic digestion

Filamentous Bulking in Massachusetts: Extent of the Problem and Case Studies

A handbook has been written for control of activated sludge bulking for wastewater treatment plant operators in Massachusetts. In order to demonstrate the principles described in the handbook for filamentous organism identification and subsequent selective control, six Massachusetts activated sludge plants experiencing bulking problems were investigated. In addition, a survey was conducted to determine the extent of the filamentous bulking problem in Massachusetts. Dominant filamentous organisms in the aeration tank mixed liquor were identified to determine the probable cause of bulking problems. Plant data and operating conditions were also studied to verify the organism-cause relationship. Based on the sample and data analysis, selective control strategies were suggested to the plant operator to control or eliminate the bulking problem.</jats:p