In membrane separation, semi-permeable membranes allow certain molecules or ions to pass through by diffusion and, occasionally, by specialised "facilitated diffusion". The rate of passage depends on the pressure, concentration and temperature of the molecules or solutes on either side, as well as the permeability of the membrane to each solute. This depends on solute size, solubility properties, or chemistry.
The family of membrane processes is generally classified as microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO). Membrane configurations include spiralwrap, tubular, flatsheets and capillary.
MEMBRANE SEPARATION PROCESSES ARE USED FOR:
- Desalination of seawater
- Production of process and potable water
- Polishing and demineralisation of boiler feedwater and pharmaceutical water
- Rehabilitation and recycling of process and municipal effluent
- As part of an integrated zero liquid discharge process
Membrane processes such as seawater desalination are finding a strong market in the South African municipal sector, while zero liquid discharge installations are saving industrial clients money by recycling their process water and limiting their production and dumping of waste and waste by-products.
- Biosep Membrane bioreactors
- Hydrex chemicals
Membrane separation processes cover the entire spectrum of:
- Microfiltration (MF)
- Ultrafiltration (UF)
- Nanofiltration (NF)
- Reverse osmosis (RO)
We have extensive experience in the following membrane applications:
- Desalination of seawater and industrial process streams
- Production of potable water from brackish supply
- Recycling of water and separation of effluent streams
- Recovery of valuables from effluent and process streams
- Removal of sulphate from injection water in off-shore oil production.
- Concentration of inorganic and organic constituents in waste streams for recovery or disposal
- Removal of COD / BOD from effluent streams
MEMBRATEK TUBULAR MEMBRANE RANGE:
Membratek also offers a tubular membrane range with its manufacturing facilities geared toward the production of these membranes and modules.
Tubular membrane range:
- Reverse Osmosis (RO) membranes
- Ultrafiltration (UF) membranes
Tubular modules offer great flexibility, as the internal tube connections are optimised to suit the application. Connections may be parallel, in series or in a parallel/series combination. For applications that demand a particularly robust system, the following types are specified:
Veolia Technologies and Membranes
BIOSEP Membrane Bioreactor
Veolia South Africa uses the innovative, patented BIOSEP process, developed by its parent company Veolia. BIOSEP is a high performance solution that combines aerobic biological treatment using activated sludge and membrane filtration for the treatment of municipal and industrial effluent. The filtration step can use immersed membranes or external, pressurised membrane filtration. The process ensures a high reduction of carbon, nitrogen and phosphorus pollution, as well as exceptional bacterial removal. BIOSEP combines an aeration tank and a membrane system where the membranes are grouped into modules. After treatment, such as screening, raw water enters the aeration tank where carbon, nitrogen and phosphorus are removed.
Membrane filtration then separates the purified water from the activated sludge. Submerged membranes typically deployed in capillary configuration and positioned vertically, with filtrate being drawn through the membranes under slight vacuum. Pressurised membranes, on the other hand, operate on a cross-flow principle. The treated water is pumped out and excess sludge is directly removed from the tank for dewatering.
Benefits over conventional activated sludge:
- Exceptional treated water quality
- Highly compact system
- No final clarification
- High COD removal
- Reduced reagent levels in phosphorus elimination
- Thickener may also be removed
- Reduced sludge production
The BIOSEP immersed membrane bioreactor is compact in design and environmentally safe, offers reliable biological treatment and delivers high quality, treated effluent. The process is especially suited to applications such as municipal water treatment, food and beverage production, pharmaceutical manufacturing, paper and pulp, and chemical plants, where effluent with organic pollutants needs to be treated. It has the potential to help Veolia in Southern Africa to gain increased market share in the biological treatment of domestic sewage and industrial effluents and will aid the company in upgrading wastewater for re-use, thus bringing long term benefits to the environment.
Approved by leading international membrane manufacturers, the Hydrex™ 4000 range offers specifically formulated chemicals that keep membranes free of scale and bacterial growth, and aid in extending membrane life. Suitable for any membrane process, these chemicals play an important role during each stage of a plant's life cycle, from pre-treatment to preservation.