Ultrafiltration is a drinking water and wastewater treatment technology in which water is passed through a membrane that physically filters out contaminants like suspended solids, bacteria and some viruses. Among membrane filtration types (e.g. microfiltration, nanofiltration, reverse osmosis) it has the second smallest pore size range – 0.1 to 0.01 microns. Its ability to remove a large proportion of microorganisms makes it useful as a disinfectant, and attractive because it does not require the addition of chemicals that form harmful by-products the way other techniques do (e.g. chlorination).
The Earth Rangers Centre onsite wastewater treatment plant, which receives water from all building drains, toilets and urinals, employs ultrafiltration as part of their membrane bioreactor (MBR). The MBR combines biologically active treatment and ultrafiltration, which results in less fouling of the membrane and improved water treatment. The system uses 20 to 30 plate-type ultrafiltration membranes which have a pore size of 0.04 microns. Following treatment in the MBR, the water is passed through a carbon filter and then disinfected with UV radiation. Effluent from the system is used to meet non-potable water demands like toilet flushing, irrigation, and cleaning of animal cages.
Wastewater treatment systems employing ultrafiltration require regular maintenance and water quality testing to ensure the safety of the building occupants and the environment. One of the most important maintenance concerns with ultrafiltration membranes is fouling – the accumulation of insoluble material on the external membrane surface or inside the pores – which compromises performance over time. Membrane fouling is best avoided by optimizing system design and by pre-treating the water, but eventually cleaning will be required. The frequency of cleaning will vary widely based on the system’s capacity and the typical contaminant levels in water that passes through the membrane.
For more information on this technology, please visit Earth Rangers Centre for Sustainable Technology’s Wastewater Treatment page.
