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Ferrate (FeO2- ) is believed to have a dual role in water treatment, both as oxidant and coagulant. Few studies have considered the coagulation effect in detail, mainly because of the difficulty of separating the oxidation and coagulation effects. This paper summarises some preliminary results from laboratory-based experiments that are investigating the coagulation reaction dynamically via a PDA instrument, between ferrate and humic acid (HA) at different doses and pH values, and comparing the observations with the use of ferric chloride. The PDA output gives a comparative measure of the rate of floc growth and the magnitude of floc formation. The results of the tests show some significant differences in the pattern of behaviour between ferrate and ferric chloride. At pH 5 the chemical dose range (as Fe) corresponding to HA coagulation was much broader for ferrate than ferric chloride, and the optimal Fe dose was greater. Ferrate oxidation appears to increase the hydrophilic and electronegative nature of the HA leading to an extended region of charge neutralisation. A consequence of the ferrate oxidation is that the extent of HA removal was slightly lower (~5%) than with ferric chloride. At pH 7, in the sweep flocculation domain, ferrate achieved much greater floc formation than ferric chloride, but a substantially lower degree of HA removal. [ABSTRACT FROM AUTHOR]4 ) is believed to have a dual role in water treatment, both as oxidant and coagulant. Few studies have considered the coagulation effect in detail, mainly because of the difficulty of separating the oxidation and coagulation effects. This paper summarises some preliminary results from laboratory-based experiments that are investigating the coagulation reaction dynamically via a PDA instrument, between ferrate and humic acid (HA) at different doses and pH values, and comparing the observations with the use of ferric chloride. The PDA output gives a comparative measure of the rate of floc growth and the magnitude of floc formation. The results of the tests show some significant differences in the pattern of behaviour between ferrate and ferric chloride. At pH 5 the chemical dose range (as Fe) corresponding to HA coagulation was much broader for ferrate than ferric chloride, and the optimal Fe dose was greater. Ferrate oxidation appears to increase the hydrophilic and electronegative nature of the HA leading to an extended region of charge neutralisation. A consequence of the ferrate oxidation is that the extent of HA removal was slightly lower (~5%) than with ferric chloride. At pH 7, in the sweep flocculation domain, ferrate achieved much greater floc formation than ferric chloride, but a substantially lower degree of HA removal. [ABSTRACT FROM AUTHOR]

In this study, a novel microbial fuel cell, i.e. upflow air-cathode membrane-free microbial fuel cell (UAMMFC) was reported and its performance in electricity generation from original leachate was examined. The experimental results demonstrated that the UAMMFC could continuously generate electricity from leachate (0.3V; REX = 150Ω) for an operational period of time (50 h). The maximum volumetric power reached 12.8W/m³ at current density of 41 A/m³ (93Ω). NH4+-N elimination from the leachate was shown to be a consequence of electrochemistry-independent oxidation occurred in the MFC. Increasing organic loading rate from 0.65 to 5.2 kgCOD/m³ d resulted in a decrease of overall Coulombic efficiency (CE) from 14.4% to 1.2%. The low CE obtained here should be attributed to severe oxygen diffusion from the open-to-air cathode. [ABSTRACT FROM AUTHOR]

Evaluates the technologies used in removing arsenic from groundwater. Oxidation of arsenic; Coagulation-precipitation process; Arsenic removal by adsorption.