Abstract: A fast AC voltage detector includes a bridge rectifier connected to an AC power source, a threshold detector connected to an output of the bridge rectifier, a voltage isolation circuit connected to the threshold detector, a continuous voltage averager connected to an output of the voltage isolation circuit, and a Schmidt trigger connected to the continuous voltage averager. The Schmidt trigger is operable to output a first voltage level when a load is preset on said AC power source and a second voltage level when no load is present on said AC power source.

Abstract: In a method of treating a gas stream, an aqueous scrubbing liquor is circulated through an essentially closed loop (20) comprising an electrochemical unit (48) for reducing the acidity of the liquor. A portion of the circulating liquor is diverted away from the closed loop (20) to a gas scrubbing unit (10). The gas stream enters the scrubbing unit (10), wherein an acid, for example HF and solid particulates, for example SiO2 particulates, within the gas stream dissolve in the diverted liquor. The diverted liquor is subsequently returned to the closed loop (20), and is replenished in the scrubbing unit (10) by fresh liquor diverted from the closed loop (20). A device (46) is provided for monitoring the acidity of the liquor at a location within the closed loop (20). The reduction in the acidity of the liquor by the electrochemical cell (48) is controlled depending on the monitored concentration.

Abstract: A fast AC voltage detector includes a bridge rectifier connected to an AC power source, a threshold detector connected to an output of the bridge rectifier, a voltage isolation circuit connected to the threshold detector, a continuous voltage averager connected to an output of the voltage isolation circuit, and a Schmidt trigger connected to the continuous voltage averager.

Abstract: A method of treating a liquid waste containing target species is described, in which the liquid is first conveyed through a housing containing a catalyst for removing either a reducing agent or an oxidising agent from the liquid, The liquid is then conveyed to a reverse osmosis or nanofiltration membrane to obtain a retentate rich in the target species and a permeate lean in the target species. The retentate is returned to the liquid upstream from the membrane, whilst the permeate may be subject to further treatment, for example in a neutralisation plant.

Abstract: In a method of treating a gas stream, an aqueous scrubbing liquor is circulated through an essentially closed loop (20) comprising an electrochemical unit (48) for reducing the acidity of the liquor. A portion of the circulating liquor is diverted away from the closed loop (20) to a gas scrubbing unit (10). The gas stream enters the scrubbing unit (10), wherein an acid, for example HF and solid particulates, for example SiO2 particulates, within the gas stream dissolve in the diverted liquor. The diverted liquor is subsequently returned to the closed loop (20), and is replenished in the scrubbing unit (10) by fresh liquor diverted from the closed loop (20). A device (46) is provided for monitoring the acidity of the liquor at a location within the closed loop (20). The reduction in the acidity of the liquor by the electrochemical cell (48) is controlled depending on the monitored concentration.