A copper integrated electrode with a convertible oxidation state, a preparation method and an application method are provided. The preparation process is based on an electrochemically induced self-growth method. Copper foam is used as a precursor, soaked in a graphene oxide solution, dried, calcined at high temperature and annealed, and then treated with an alkali solution to obtain the copper integrated electrode with the convertible oxidation state. The working electrode prepared by the nano-catalytic material of the present invention has good denitrification performance in the environmental field, which can achieve nearly 100% nitrate removal rate, nearly 100% nitrogen selectivity and long-term stability. These properties are due to the prepared working electrode having an oxidizable copper (I, II/0, I), oxygen vacancy (O) and a one-dimensional nanowire structure. The structure can regulate the adsorption and reduction of intermediate products, resulting in nearly 100% nitrate removal rate and nearly 100% nitrogen selectivity.

The present invention relates to a method of removing chromate ions from an ion-exchange effluent, the method comprising: (i) providing an ion-exchange effluent comprising chromate ions obtained from the regeneration of an ion-exchange material, (ii) admixing the ion-exchange effluent with a source of alkali metal dithionite to form a first precipitate, and (iii) removing the first precipitate

A nitrate reduction method includes the step of reducing at least one type selected from a group of nitrates and nitrites at an active site included in a defect of graphene in a reduction reaction, wherein the graphene is a reduced product of graphene oxide, and the defect of the graphene is derived from a defect of the graphene oxide.

In a method of manufacturing a bimetallic catalyst for reductively decomposing nitrate nitrogen, a powder including a trivalent iron oxide, a powder including a trivalent iron oxyhydroxide powder or a combination thereof is mixed in an aqueous solution. A copper precursor and a palladium precursor are mixed in the aqueous solution to form a precursor mixture. The precursor mixture is dried. The dried precursor mixture is fired at a temperature from about 300° C. to about 450° C. to form a fired product. The fired product is reduced by a reducing agent. A hydrochloric acid solution is mixed in the aqueous solution, or mixed with the copper precursor or the palladium precursor.

A system and method for treating wastewater includes two or more biological reaction zones separated by chamber walls. The system and method for treating wastewater includes static recycle of a mixed liquor from a second biological reaction zone to a first biological reaction zone.

A device for purifying liquid wastewater, includes: a container suitable for retaining a granulate consisting of solid particles, and for enabling the contact between the solid particles of the granulate and the liquid wastewater flowing in the container between: an inlet for the liquid wastewater to flow into the container, and an outlet for substantially decontaminated water to flow out of the container; a community of microorganisms extending so as to be in contact with the solid particles of the granulate; at least one live benthic invertebrate whose mean size is greater than 250 μm and which is distributed in the granulate; and at least one live benthic invertebrate whose mean size is from 50 μm to 250 μm and which is distributed in the granulate, characterized in that the community of macrobenthic organism and meiobenthic organism species includes a proportion of 60% to 80% of invertebrate detrivorous organisms.

The present disclosure relates to a bacterium-alga coupled sewage treatment device based on energy recycling and a use method thereof. The device comprises a pretreatment device, a photobioreactor, an alga separation apparatus, a continuous flow bioreactor and a secondary sedimentation tank which are sequentially connected in order, the pretreatment device being connected to a municipal sewage inlet pipe, the photobioreactor being connected to a carbon dioxide gas charging device through a gas filling pipeline, one part of a sludge thickening tank being connected to the secondary sedimentation tank, the other part thereof being connected to remaining sludge of the pretreatment device, carbon dioxide generated from the sludge which flows through the thickening tank and is thermally-hydrolyzed and anaerobically-acidified being connected to the photobioreactor through a gas inlet pipeline, and the alga separation apparatus being further connected to a filter press. The present disclosure has the advantages of a rational structural design, reliable and stable operation, a low operation and maintenance cost and high automaticity and intelligence, and being suitable for the use and transformation requirements of a wide range of sewage treatment plants, etc.

This invention relates to a treatment method and apparatus directed to improving water quality, increasing net energy production, and reducing greenhouse gas emissions without employing bioreactor processing for waters containing suspended organic solids, PPCPs, PFAS, negative colloids, heavy metals, phosphates, nitrates, carbonates, silicates, chlorides and sodium ions. It employs SO.sub.2, sulfites and bisulfites to self-agglomerate suspended organic solids with sorbed PFAS and PPCPs, and acid leach heavy metals into solution. Subsequent liming filtration separates of metal hydroxides and insoluble calcium salts while chemically conditioning the separated organic solids for gasification or burning. The second filtrate is then exposed to ultra violet light for pathogen disinfection, and exciting sulfites to remove nitrates, and degrade PFAS and PPCPs to form a disinfected metal free salt balanced reclaimed wastewater with reduced PFAS, PPCPs, pathogens and negligible nitrogen and phosphorous.

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 of treating water to remove selenium and/or mercury that is dissolved in the water. The method includes adding an acid to the water to reduce the pH, adding a metal reagent to the water that is effective to reduce the selenium and/or mercury to a lower oxidation state, and then removing the reduced selenium and/or mercury from the water.