A process is disclosed for producing tungstosilicic acid which involves adding sodium silicate to a first solution of sodium tungstate while assuring that the pH of the resulting mixture is from about 2 to about 6, the pH adjustments being made with a cation exchange resin on the hydrogen cycle, to produce a second solution. The solids are removed from the second solution which is digested at a temperature of greater than about 50.degree. C. and then contacted with a cation exchange resin on the hydrogen cycle to produce a third solution which is essentially a tungstosilicic acid solution containing at least about 99% by weight of the starting tungsten as tungstosilicic acid.

The method essentially creates a lake, if one does not already exist, and uses this lake as a "moving" biological treating pond for contaminated soil sites. Contaminated soil from one side of the lake is dragged into the lake, the water of which is infested with contaminant-consuming micro-organisms, then is tilled at the bottom of the lake to fully expose the soil to biological treatment, and then is raked upwardly along an opposite side of the lake to form a shoreline of cleaned soil material. The earthmoving process is repeated until the lake has passed through the treated all of the contaminated soil site. The method performs all decontamination on-site and avoids the requirement for any backfilling of the side after decontamination of the site.

Method and system for removing accumulated sediment at the bottom of a waste pond or lagoon of a wastewater treatment plant for a petroleum refinery. The system comprises a primary oil separation stage for separating hydrocarbons from the wastewater stream by gravity, a secondary oil removal stage and a biological treatment stage downstream of the secondary oil removal stage. A portion of the sediment from the bottom of the waste pond or lagoon is passed to the secondary oil removal stage and/or the biological treatment stage for processing with the refinery wastewater being treated in these stages.

The present invention is a process for treatment of waste water streams having a sodium sulfate content of above 20 percent. The process is useful for treating waste water generated in the production of polyethyleneimine and cyclohexanone. The process includes the steps of removing sodium sulfate from waste water by the addition of organic solvent. The waste water having reduced sodium sulfate content is then subjected to biological treatment with activated sludge. First the waste water is subjected to pre-treatment. Pre-treated waste water is combined other waste water and treated by denitrification and nitrification.

A system and method for determining the concentration of nitrate ions in a nitrate ion-containing water sample which also contains chloride ions and bicarbonate ions is disclosed. The potentially interfacing chloride ions are suppressed by reaction with a cation exchange resin in the silver form. The potentially interferring bicarbonate ions are suppressed by reaction with a cation exchange resin in the hydrogen form. The sample, after having been treated with the two resins is passed into a conductivity cell with the conductivity being directly related to the nitrate ion concentration of the sample. The device and method find advantageous application in automated systems for monitoring and controlling water treatment facilities.