Technologies: Wehrle MBR-DD

The Wehrle MBR-DD (also known as the BIOMEMBRAT® plus) process is used in situations where there is direct discharge of effluent, with associated strict consents, and/or where the treated effluent will be recycled.

Compounds that are not easily removed by biological processes are often found in wastewater. In these circumstances some form of physical treatment is added as a subsequent step to biological treatment. The cost effectiveness of these processes diminishes with higher discharge standards. For example, the use of activated carbon increases when higher discharge standards must be met. In processes such as chemical oxidation, larger amounts of oxidising agents are required when lower discharge limits are set.

Low effluent concentrations and high process stability are demanded where effluent is either discharged directly to the environment or is reused as process water. The Wehrle MBR-DD process was developed to meet these demands whilst maintaining a high operating efficiency.

Wehrle MBR-DD process schematic

The Wehrle MBR-DD process comprises an MBR system with a subsequent Nanofiltration step. Non-biodegradable compounds are removed in this final step. The treated effluent (permeate) can be directly discharged or reused. The reduced-volume highly-loaded concentrate can undergo further physical treatment. After this treatment the concentrate can re-enter the biological process in the influent, thereby creating a closed system. The aim of the physico-chemical treatment is then no longer limited to just meeting the discharge consent, but also includes finding the most economic removal efficiency.

Due to extremely high concentrations and stringent discharge consents, the treatment of this highly loaded concentrate can be very efficient. For example with activated carbon, a higher loading can lead to a reduced operating cost of 50-70%. This is also the case with oxidation plants where the consumption of oxidising agents, on account of the high concentrations, is greatly reduced. Through chemical oxidation, compounds that are very difficult to biodegrade are broken up into smaller molecules that are easier to degrade in the biological system.

Wehrle MBR-DD plant for the treatment of landfill leachate (courtesy of Rems Murr Kreis)

In the case of landfill leachate treatment, the Wehrle MBR-DD process is a residual free process that removes the necessity to dispose of large volumes of concentrate. Landfill sites that dispose of treated leachate directly to watercourses place enormous demands on the final effluent quality and process stability. Significant volumes of concentrate must be disposed of at a high cost, since, in the majority of cases, returning the concentrate from these membrane plants back to the landfill site is not an option. With the Wehrle MBR-DD process it is possible to meet the demands of a high effluent quality and process stability whilst also minimising the costs incurred from the disposal of residuals.

Oxidation plant for concentrate treatment