Electroflotation clarifier to enhance nitrogen removal in a two-stage alternating aeration bioreactor.

Stringent water treatment criteria and rapidly growing pollutant loads provoke the demand for retrofitting wastewater treatment plants towards a higher capacity. In this study, we assess a two stage alternating aeration (AA) bioreactor equipped with electroflotation (EF) clarifier, for nitrogen removal within a short hydraulic retention time (HRT). The EF under steady solids loading required a minimum unit height and gas: solids ratio of 0.

Continuous clarification and thickening of activated sludge by electrolytic bubbles under control of scale deposition.

Electroflotation (EF) was investigated as a final clarification of an activated sludge process, to intensify its novel clarification and thickening efficiency. During operation of a biological reactor combined with an EF clarifier, deterioration of clarification efficiency was observed. Scale deposition on electrodes caused a coarse electrode surface, significantly increasing the size of the electrolytic bubbles.

Alteration of sediment organic matter in sediment microbial fuel cells.

The alteration of physico-chemical properties of sediment organic matter (SOM) incubated under current-harvesting conditions as well as no-current producing conditions over 120 days using sediment microbial fuel cell systems was examined. The SOM was microbially oxidized under anaerobic conditions with an electrode serving as a terminal electron acceptor. It was found that SOM around the electrochemically-active electrodes became more humified, aromatic, and polydispersed, and had a higher average molecular weight, along with its partial degradation and electricity generation compared to that for the original sediment.

Experimental evaluation of influential factors for electricity harvesting from sediment using microbial fuel cell.

The aim of this study was to evaluate limiting factors affecting electricity output from sediment microbial fuel cells (sediment MFCs). In laboratory tests, various factors likely to be encountered in field application were divided into controllable and uncontrollable ones. Based on the findings, it could be suggested that the sediment MFCs can be operated with an anode to cathode area ratio of at least 5:1 and at high external loads (1000 ohms) when the cathode is closely placed to the anode, though DO concentration at the cathode must be kept above 3 mg/l.

A simple image analysis algorithm for evaluation of extended filaments length based on the enhanced digitized image.

An automated image analysis procedure was developed to determine extended filaments length and floc area to evaluate settling characteristics of activated sludge. Digitized image obtained by Gram staining granted the first step of algorithm, segmentation, to be extremely clear and simple. The image analysis work could become more accurate and less time consuming one to be required only 1 minute of operation time per image.

Responses from freshwater sediment during electricity generation using microbial fuel cells.

In a two-electrode system, freshwater sediment was used as a fuel to examine the relationship between current generation and organic matter consumption with different types of electrode. Sediment microbial fuel cells using porous electrodes showed a superior performance in terms of generating current when compared with the use of non-porous electrodes. The maximum current densities with thicker and thin porous electrodes were 45.

Improvement of activated sludge dewaterability by humus soil induced bioflocculation.

Effects of humus soil particles on the dewaterability of activated sludge were investigated. Cations leaching increased proportionally with the dosage of humus soil, and the leaching was not significant after 2 h. Divalent cations, Ca2+ and Mg2+, leaching from the humus soil played an important role in improving dewaterability of the biological sludge.