Methods and systems for reducing the concentration of selenocyanate in water. In the methods and systems, water containing selenocyanate is treated an oxidant to provide oxidant-treated water, which is then contacted with a zero-valent iron treatment system comprising (a) a reactive solid comprising zero-valent iron and one or more iron oxide minerals in contact therewith and (b) ferrous iron.

A system and method of treating sour water, including providing sour water having hydrosulfide ions and a carbon-containing compound to an anodic chamber of an electrolyzer vessel, converting the hydrosulfide ions into sulfate ions in the anodic chamber via an oxido half-reaction of a first oxido-reduction reaction and generating carbon dioxide in the anodic chamber via an oxido half-reaction of a second oxido-reduction reaction associated with the carbon-containing compound. The technique includes reacting the carbon dioxide with hydroxide ions in the anodic chamber to generate bicarbonate ions. The technique includes discharging an anodic chamber solution having the sulfate ions and the bicarbonate ions from the electrolyzer vessel from the anodic chamber.

Disclosed are systems and processes for the removal and conversion of pollutants in water. A system includes a set of electrodes with at least one electrode having an integrated catalyst material. The system is operatable in a first, electrodialysis mode in which one or more pollutants are separated from a feedwater stream, and a second electrolysis mode in which the separated pollutant(s) are catalytically converted into benign products by way of the catalyst material of the electrode. Electrodialysis and electrolysis are therefore carried out using the same unit.

A method for treatment of mixed electroplating wastewater without a cyanide and a phosphorus-containing reductant without a cyanide and a phosphorus-containing reductant. A ferrous chloride solution is added into electroplating wastewater without a cyanide and a phosphorus-containing reductant. The pH of wastewater is adjusted to 10.5-12. Pollutants such as sodium cyanide and hydroxyl-containing organic amine complexants are oxidized with sodium hypochlorite. Carboxyl-containing organic acid complexants are precipitated. Hexavalent chromium is reduced to trivalent chromium to form chromium hydroxide precipitate. Precipitate is removed by filtering and wastewater is adjusted to pH 4.5-5.5. Heavy metal ions are precipitated with sodium dimethyldithiocarbamate or sodium diethyldithiocarbamate. Precipitate and heavy metal capturing agents are adsorbed with activated carbon followed by removal of precipitate. Wastewater is adjusted to pH 6-8. Aliphatic polyamine complexants are destroyed using an available biological degradation technique to reduce chemical oxygen demand.

The object is to provide a wastewater treatment method and a wastewater treatment system that reduce the total selenium concentration of treated water while reducing cost compared to conventional methods of removing selenium by oxidation. In the wastewater treatment method according to the present disclosure, an iron agent is added to waste water containing selenium and cyanogen to form a first coagulated substance, the first coagulated substance is removed by solid-liquid separation to obtain first treated water, a second iron agent is added to the first treated water, an acid is added to the first treated water to obtain acidic water, an oxidizing agent is added to the acidic water to oxidize the selenium, a coagulant is then added to form a second coagulated substance, and the second coagulated substance is removed by solid-liquid separation to obtain second treated water.

Methods and systems for reducing the concentration of selenocyanate in water. In the methods and systems, water containing selenocyanate is treated an oxidant to provide oxidant-treated water, which is then contacted with a zero-valent iron treatment system comprising (a) a reactive solid comprising zero-valent iron and one or more iron oxide minerals in contact therewith and (b) ferrous iron.

A method for the treatment of wastewaters including a cyanide compound and a metallic compound, wherein the wastewaters are subjected to a single oxidation step during which cyanides compounds are converted into carbon dioxide and nitrogen, this oxidation step including the mixing of wastewaters with a chlorine solution and an alkaline agent so as to obtain a mixture, the alkaline agent being added in such a quantity so as to maintain the pH of said mixture between 8.8 and 9.5 and the chlorine solution being added in such a quantity so as to maintain the oxydo-reduction potential of the mixture between 150 and 450 mV.

A system and method of treating sour water, including providing sour water having hydrosulfide ions and a carbon-containing compound to an anodic chamber of an electrolyzer vessel, converting the hydrosulfide ions into sulfate ions in the anodic chamber via an oxido half-reaction of a first oxido-reduction reaction and generating carbon dioxide in the anodic chamber via an oxido half-reaction of a second oxido-reduction reaction associated with the carbon-containing compound. The technique includes reacting the carbon dioxide with hydroxide ions in the anodic chamber to generate bicarbonate ions. The technique includes discharging an anodic chamber solution having the sulfate ions and the bicarbonate ions from the electrolyzer vessel from the anodic chamber.

A system for treating printed circuit board wastewater (PCB) includes a production system, a pretreatment system, a biochemical system, a recovery system and a concentrated water treatment system. The production system is configured for producing process water and auxiliary water from tap water. The pretreatment system is configured to pretreat different wastewater samples separately. The biochemical system is configured to decompose the pretreated wastewater. The recovery system is configured to treat wastewater from the pretreatment system and the biochemical system to obtain process water and feed concentrated water to the concentrated water treatment system. The concentrated water treatment system is configured to treat the concentrated water to meet a discharge standard. A treatment method for the PCB wastewater is also provided.

A process of treating a waste stream comprising organic amine compounds complexed with heavy metal ions. The process includes the steps of: (1) adjusting the pH of the waste stream to between about 4 and about 10; (2) b) adding a chloride salt to the waste stream to produce a concentration of chloride ions in the waste stream; and (3) circulating the waste stream through an electrochemical reactor. The electrochemical reactor comprises an array of electrodes comprising alternating anodes and cathodes. The waste stream is circulated through the electrochemical reactor for a period of time sufficient to hydrolyse amine compounds in the waste stream.