Energy and carbon footprints of sewage treatment methods.

The paper presents energy and carbon footprints of sewage treatment plants (STPs) operating at different scales and using different technology options based on primary data from 50 STPs operating in India and the UK. The study used a combination of fundamental mass-balance approach for energy consumption and the methodology defined by IPCC for the carbon emissions. Small-scale institutional STPs consume twelve times the energy consumed by large-scale municipal STPs, the corresponding energy intensities being 4.

Fate of Trace Metals in Anaerobic Digestion.

A challenging, and largely uncharted, area of research in the field of anaerobic digestion science and technology is in understanding the roles of trace metals in enabling biogas production. This is a major knowledge gap and a multifaceted problem involving metal chemistry; physical interactions of metal and solids; microbiology; and technology optimization. Moreover, the fate of trace metals, and the chemical speciation and transport of trace metals in environments--often agricultural lands receiving discharge waters from anaerobic digestion processes--simultaneously represents challenges for environmental protection and opportunities to close process loops in anaerobic digestion.

Determination of changes in wastewater quality through a treatment works using fluorescence spectroscopy.

Fluorescence spectroscopy was used to characterize municipal wastewater at various stages of treatment in order to understand how its fluorescence signature changes with treatment and how the signal relates to biochemical oxygen demand (BOD) and chemical oxygen demand (COD). The impact of size fractionation on the fluorescence signal was also investigated. Fluorescence measurements were taken for unfiltered and filtered (0.

Velocity gradient as a tool to characterise the link between mixing and biogas production in anaerobic waste digesters.

Whilst the importance of mixing in anaerobic digesters to enhance process performance and gas production is well recognised, the specific effects of mixing regime on biogas production are not clear. Here, the velocity gradient is used to demonstrate the importance of minimally mixed zones in a digester, with computational fluid dynamics (CFD) models indicating that 20-85% of a laboratory-scale digester experiences local velocity gradients of less than 10 s⁻¹, dependent on mixing speed. Experimental results indicate that there is a threshold above which increased mixing speed (and hence velocity gradient) becomes counter-productive and biogas production falls.

A novel laboratory method to determine the biogas potential of iron-dosed activated sludge.

Sludge biogas potential is often reduced by iron-dosing, the extent of the reduction being related to the nature of the sludge and the dosing process. The aim of this research was to develop a rapid laboratory method to measure the impact of iron-dosing on the biogas potential of activated sludge, taking into account the mechanisms that may be decreasing biogas yield. To validate the method, sequential extraction (SE) was used to fractionate iron and phosphorus in the sludge before and after iron-dosing.