Membrane Technologies: NF & RO
Nanofiltration & Reverse Osmosis for Effluent Treatment
Membrane Technologies, such as Nanofiltration or Reverse Osmosis systems are used to separate liquids. This can be used, for instance, as a polishing step after a biological treatment step – ideally a Membrane Bioreactor due to its solid free discharge. Another application is the recovery of valuable substances from treated industrial effluents or from concentrate. In combination, different setups of Nanofiltration and Reverse Osmosis allow a high selectivity for different liquids. Depending on the treatment step at hand, either the so-called Feed & Bleed or the Christmas Tree / Pine Tree configurations are used.
NF - Nanofiltration
In applications like polishing of treated leachate after an MBR, a Nanofiltration (NF) Feed & Bleed is for the reduction of the remaining non-biodegradable COD, reduction of TN/NO3-N and multivalent ions. Then Nanofiltration ensures that strict outlet requirements can be reliably observed. Using a NF as final treatment step in leachate treatment is an effective salt sink for the overall process: it allows environmentally non-relevant salts to leave the system. This reduces the negative effects of concentrate return to the landfill considerably and ensures a long-term stable treatment process.
RO - Reverse Osmosis
Of all filtration processes, reverse osmosis can achieve the highest filtrate quality. Compared to conventional filters, the reverse osmosis membrane has no pores through which the pollutants of the wastewater can pass. It is therefore able to separate both suspended, colloidally dissolved solids as well as completely dissolved organic and inorganic components.
For this purpose, a part of the water, the so-called permeate stream, is forced through the membrane by pressurization. The retained wastewater components remain in the so-called concentrate stream. The ratio of the two streams can be influenced by the pressure level and the choice of the membrane type.
Today, a variety of different membrane types are available on the market, which differ in retention capacity for different wastewater components. WEHRLE selects the membrane type specifically depending on the cleaning performance requirements in order to ensure the highest possible permeate yield with low energy consumption.
Reverse osmosis can be used to achieve a high degree of purity in the permeate stream. The technology is traditionally used for the treatment of potable water or the generation of boiler feed water. In wastewater treatment, it is used both as a "polishing" step after a biological pre-treatment, but also for the direct treatment of highly loaded wastewater, such as landfill leachate. Since this is a purely substance-separating process, a suitable solution must be found for the whereabouts of the concentrate.
Reverse Osmosis (christmas tree / pine tree)
The Reverse Osmosis (RO) will effectively and with a high yield (> 90%) remove all impurities, remaining particles, unwanted salty components and/or toxic and harmful substances such as, for example, heavy metals or nitrates.
The RO will guarantee that the purified water can be used as potable water or can be re-used for example as boiler feed water and/or process water.
Reverse Osmosis (feed & bleed)
A Reverse Osmosis (RO) feed & bleed for the removal of the remaining non-biodegradable COD, maximal reduction of TN/NO3-N and most of the dissolved salts. The Reverse Osmosis ensures that the strict outlet requirements will be reliably observed.
Ready for use
WEHRLE supplies reverse osmosis systems pre-assembled on racks or as turnkey version installed in a sea freight container. If necessary, all components can be installed within containers so that no additional operating building is required and the system is immediately ready for operation after connecting the inlet and outlet pipes.
Flexible wastewater treatment
The amount and degree of pollution of wastewater can vary in many cases. The throughput of the reverse osmosis system can be infinitely adjusted between 30 and 100 % of the maximum hydraulic load. If there are particularly high demands on the process quality, the treatment can also be carried out in several stages. WEHRLE offers systems that produce up to 3 times filtered permeate. In times of lower throughputs, the additional steps can be bypassed in favor of lower operating costs.
Low membrane replacement costs
WEHRLE prefers to use reverse osmosis membranes in the form of spiral wound elements, as this design allows cost-effectively to accommodate the largest possible membrane surface in a small space. Spiral wound modules are now produced in large quantities by different manufacturers, so that there is no obligation towards a specific supplier when changing membranes.
High operating comfort
WEHRLE delivers reverse osmosis systems with high operating comfort that offer a higher degree of automation and ease of use compared to competing products. The systems are basically equipped with a graphical user interface, which monitors all essential process parameters and sets off all essential control functions. On request, the systems are equipped with features that further facilitate the operation of the system: remote access to the control system, fully automatic membrane cleaning, SMS notification...