Electrochemical processes are used to treat waste streams and waters before disposal and release to the environment.
The treatment mechanisms of the process vary depending on the nature of the contaminants.
For example, under direct electric current, insoluble anode and cathode separated by a membrane will generate respectively acidic (2═2╬ = ╬2 + 4═+) and alkali (2═2╬ = 2╬═- + ═2) environments. Ions of heavy metals will react with catholyte to form insoluble hydroxides in the alkali environment. Therefore, the main task of transforming dissolved contaminants into insoluble state is achieved without adding any chemical reagents. The final removal of insoluble contaminants is carried out on hydro-automatic floating filters.
Carbon steel or aluminium plates, used as an anode, will dissolve in water to generate coagulating agents for water purification in the amount required at any given moment.
Electrodes coated with iridium or ruthenium oxides, and used as an anode, will produce chlorine residuals by electrolysis of brine solution or natural chlorides in the water for disinfection purposes.
Electrochemical processes can be utilised to achieve the following objectives:
- Non-reagent change of water pH in the range 2.5-8;
- Non-reagent generation of flocculants;
- Non-reagent purification of water by means of electrochemical flotation;
- Non-reagent oxidation, reduction and destruction of various contaminants;
- Non-reagent reduction of dissolved solids in water;
- Non-reagent disinfection of water;
Electrochemical process can be applied in the purification of water from heavy metals, organic and inorganic contaminants, oil products, surface active substances and in the water softening.
If required, filtration is carried out on our hydro-automatic floating filters.
Electrochemical processes bring the following advantages:
- No chemical reagents are used in the process
- Multiple recycling of treated water as there is no increase in TDS
- Significant reduction in space requirements (by a factor of 4 to 5) in comparison to reagent-based processes
- Considerable reduction in fabrication materials requirements (by a factor of 5 to 10) in comparison to reagent-based processes
- The volume of generated sludge is reduced by a factor of 2 to 5 in comparison to reagent-based processes
- The process of water purification is regulated only by the parameters of the electric current.
Electrochemical facilities are designed for flow rates of up to 30 m3/h, whereas
the optimum flow rate is 3 to 5 m3/h. The energy requirements are typically
within the range of 1 to 3 kWh/m3.
TREATMENT OF WASTE WATERS
FROM THE ELECTROPLATING INDUSTRY
The technology is developed for the treatment of waste water from the electroplating industry with medium and high concentrations of heavy metals.
This technology has the following advantages:
- Significant reduction in the use of chemicals
- Low operational and maintenance costs
- Reduced volumes of solid waste
- Recycling of 50 to 90% of treated water
- Compact size
- Significant reduction in the bill of fabrication materials
- Significant reduction in energy consumption
- The initial concentration of heavy metals should not exceed 1.5 gram per litre.
- The initial concentration of extractable substances should not exceed 0.2-0.25 gram per litre, including oil products 0.15-0.2 gram per litre.
- It is not permissible to mix waste stream with solutions containing various complex forming agents or other additives that prevent hydrate formation.
The technology utilizes electrochemical reduction of Cr6+ when concentrations of Cr6+ do not exceed 0.1 gram per litre.
Reagents (reducing agents) are used when concentrations of Cr6+ are greater than 0.1 gram per litre.
Heavy metals are removed from waste water in the form of hydroxides, carbonates, phosphates and other low-soluble compounds by means of flotation and filtration.
If required, ELRI can be supplemented with an additional fine-purification module.
The table below demonstrates the quality of water after treatment.