Chromate (chromium VI) Groundwater removal
The removal of chromate (chromium VI or CrVI) from groundwater is a common task in groundwater remediation. As a rule, these are soils contaminated by industrial sites whose contaminated sites leach into the groundwater. Due to its properties, in particular its carcinogenic properties, chromate is a substance of very high concern (SVHC) and will be banned in large parts of industry in the future. As a rule, it is also easily recognizable visually, as a clear yellow coloration appears in higher concentrations.
The remediation of anionic chromate compounds from groundwater is possible in an established standard ion exchange process using weakly basic and strongly basic anion exchangers. First, specially conditioned weakly basic anion exchangers are connected upstream, which take over the pre-purification at higher chromate concentrations due to their greater capacity. Discharge values of up to 0.05 mg/L can be achieved. However, a pH adjustment is often necessary for the use of weakly basic anion exchangers in order to achieve the best possible binding, i.e. capacity and slip. The advantage of weakly basic anion exchangers is that they can be regenerated. The ion exchangers can be regenerated externally as an ion exchanger regeneration service and are therefore suitable for reuse.
A strongly basic anion exchanger is connected after the weakly basic ones. This has only half the capacity of the weakly basic anion exchangers and cannot be regenerated. However, discharge values of up to 0.01 mg/L, the legally required discharge value, can be achieved with the strongly alkaline anion exchanger.
Some groundwater contains unfavorable constellations of competing anions that significantly impair the capacity of the ion exchangers. This is taken into account when designing the ion exchanger system.
The system is monitored analytically. This means that each stage must be executed twice in order to be able to maintain sufficient capacity at all times. As a rule, weakly alkaline – weakly alkaline – strongly alkaline – strongly alkaline are run through in series. Depending on the predicted service life, an additional replacement cartridge may be required for each anion exchanger stage to ensure uninterrupted operation. Typical volume flows for the application are between 1 – 25 m³/h.
In industrial applications, there are very similar processes for recirculating rinsing water. For those areas of application that have a permissible exemption from the chromium VI ban, there are established chemical-physical wastewater treatment methods that ensure compliance with the statutory monitoring values. This technology is also required for those industrial sectors that use the alternative process with chromium III, as chromium VI is formed as a non-isolated intermediate product during wastewater treatment.
Do you have further questions about removing chromate from groundwater? Please do not hesitate to contact us.