Arsenic is found in waters in many parts of the UK and mainland Europe, Asia and the USA. The arsenic comes from the underground rocks through which the ground water percolates. The legal limit for arsenic has recently been reduced to 10µg/l. The arsenic can be removed with specially formulated filter media.
Why Remove it?
Arsenic compounds are toxic even at low levels. They can cause skin and liver disorders, circulatory problems and can be life threatening. The European Union has looked at the Arsenic levels in water and reduced the allowable limit to below 10ug/l (from 50ug/l). Arsenic is present in underground rocks and percolates in to the ground water and then up through boreholes or springs into the water supply.
Bayoxide Arsenic Removal Media
Severn Trent Water worked with Bayer As to develop an arsenic removal media; Bayoxide. This dry crystalline media is similar to amorphous iron hydroxide but specifically formulated to give a high arsenic removal capacity. The media is strong, reliable and easy to handle. Bayoxide is regulation 31 approved for use in both Municipal and Private water use.
These systems give long operating cycles and low operating costs. The exhausted media is non-hazardous and can generally be sent to landfill (local conditions do apply).
Service flow: 15-18m/h Backwash flow 25m/hr Backwash frequency: 14-28 days
Requested raw water conditions Iron:<200µg/l pH: 6.5 - 8.5 Manganese: <50µg/l SiO2: <40mg/l Suspended solids: < 10mg/l PO4: <200µg/l Water outside the above must be pre treated.
How Does it Work?
Water flows into the valve at the top, down through the media and then up through the riser tube in the middle of the vessel. As the water travels through the media the arsenic is removed and held within the system. There are timer options that can be set to automatically self clean (backwash) and wash away any of the accumulated sediment but hold on to the accumulated arsenic. When the media becomes full it can easily be replaced with fresh media (typically every couple of years or so depending on arsenic levels and local conditions).
Arsenic filters can also be used in conjunction with other filters such as sand filters, if the water has high turbidity, iron and manganese reducing filters or pH correction filters if the pH of the water very low.