Typical recycling, reuse and process water systems use Reverse Osmosis (RO) technology as the method of decreasing the level of ions in process water. RO recovery rates normally range from 50-75%, therefore 25-50% of the RO feed water is discharged as wastewater. With the increasing cost of water and waste discharge, more companies are looking to recover and reuse RO reject water.
While it is possible to reuse the reject water from an RO system by feeding it directly into a 2nd RO unit, the likelihood of scaling or fouling the 2nd RO without pretreatment is rather high.
A Porex Tubular Membrane Filter (TMF™) system coupled with lime softening will reduce scaling and enhance the operation of the 2nd RO. Lime softening along with TMF provides very efficient softening, silica reduction and solids removal within a single process scheme.
Using this treatment technique, recovery rates can be greater than 95% while assuring substantial reduction of scaling to the RO units. This is an efficient and cost effective method for either retrofitting existing RO systems or incorporating the process into newly designed systems.
The diagram above shows a typical process flow for a TMF system used in conjunction with lime softening. The solids concentration is kept at 3-5% with the excess solids sent through a filter press for de-watering and disposal. The number of TMF modules required is dependent upon the total flow rate of the system. The modules are typically placed in series, or train, of up to 12 modules and systems are usually designed to allow at least one train of modules to be independently taken off line for routine maintenance cleaning. To support system design, a small pilot test system can be used to determine the ideal flux rates through the modules and identify any issues, such as colloids, that might require further module cleaning.
RO Reject Reclaim- the diagram below, shows a TMF system used as pretreatment to a 2nd Stage or Reject Reclaim RO system. Such feed water typically contains very high levels of hardness, ions, organics and silica. The reject is fed to Reaction Tank #1 where chemicals are added to enhance particle flocculation. The water is then fed to Reaction Tank #2 where additional chemicals are added to promote the precipitation of hardness and silica. The water is then sent to a Concentration Tank to be treated by the TMF system. The concentrate is pumped through the membrane modules with the solids returning to the concentration tank, and the filtrate passing through the membranes. Solids concentration is kept at 3-5% with the excess solids sent to a filter press for de-watering and disposal.
Porex Filtration provides high quality membrane filter modules for use in water and wastewater treatment systems. We work with qualified distributors and OEM system builders who can provide complete systems.Click here for