Sand Polishing Filters SPF have become popular in Ireland in recent years. Prior to this there were a few mostly for commercial use installed throughout the country.The construction was mostly with regular graded sand and usually preceded a Septic tank and hence were of large sizing.
Systems now use graded sands which are included in a few mentions in the most recent EPA Code of Practice 2009, this did clarify a few issues regarding type of sand to be used and construction methods. Research was carriad out on the SPF By Trinity College Dublin and the results for effluent quality etc were very good.
SPF are now used preceding a secondary treatment unit with mechanical and biological treatment with 95% reduction in key effluent parameters such as BoD, Suspended Soilds and nutrient reduction (nitrates etc). The filters are built in layers (stratified) to deal with the different components of final polishing. The top layer is a coarse sand acts a media which accomadates natural bio-organism interaction or adsorption with effluent reducing key contaminents, lower layers include layers of ventilated coarse gravels to introduce oxygen and layers of fine Sand to polish out any remaining soilds etc.
Sand polishing filters Spf are proving very effective Tertiary treatment systems where sites;
- Have bad or no soil, this would normally be a soil polishing filter entail importing of maybe 10 loads of percolation soil which will be more expensive and take up more room
- Where high effluent is required for discharge licence conditions
- Small footprint , example a regular domestic unit will only take up to 20m2 space in the garden
- Can be supplied and fitted as a complete system with full documentation
One of the most important components of the unit is the sand itself. This must be processed to achieve the right grade.
Grading is by mathematical effective particle sizing or D10, which is often confused with simple sand grading often by suppliers or builders who use regular washed sand from pits.
Tpw systems have led the development of fully fitted SPF throughout the country after many years research and development or present model is the most advanced on the Market. We place high emphasis on selecting the right treatment unit ,pump system, and installation with many added features not “in the book”. Fantastic deals on full system supply and installation.
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