Dirtbags

Dirtbag 1There are times when you have no option but to pump out silty water, leaving you with no alternative but to treat it to remove the silt before you discharge it to a watercourse or sewer (with the relevant consents or permits, of course!). If your need is large enough, you can use settlement lagoons, or pieces of specialist plant, but sometimes what you need to do will be so minor that it doesn’t really warrant the expense and effort. Dirtbags offer a simple filtration solution that takes very little space – a large geotextile envelope that you pump the water through, leaving the suspended solids in the bag. The standard bag is 1.5m square, and according to the manufacturers, it can handle flow rates up to 4600 litres per minute. As the bags are manufactured in the UK, Dirtbags can be custom-made to suit site conditions or flow rates.

In my mind, they are a really useful primary control technique, removing the easily filtered particles, but secondary treatment (settlement, flocculation, etc) may be necessary to improve the water sufficiently to meet any suspended solids requirements of an offsite discharge consent. (The manufacturers have a separate webpage showing Dirtbags in use for primary filtration inside standard settlement tanks) They’re also really useful where you’re discharging to elsewhere on your site as part of a general silt management strategy to help you keep the discharge area clear of mud.

UtilityBagAnd if you’re in the utilities business, and you regularly face the challenge of dewatering ducts full of silty water before you can carry out your work, Dirtbags also make “Utilitybags” – a smaller sausage-shaped Dirtbag to fit over the end of the discharge hose to at least take out the larger solids before discharge to a road gully.

(To visit the Dirtbags website, click on any image)