DIN EN 14701-2:2013-07

The specific resistance to filtration is a parameter which indicates the suitability of sludge to be filtered. The value of the specific resistance to filtration has great importance in filtration processes as it can be useful for estimating the performance of full-scale filtering devices, mainly pressure filters, and comparing filterability characteristics of sludges produced in different plants. Specific resistance measurements can also give indications on both the optimal type and dosage of conditioner to be used (CEN/TR 14742). This European Standard specifies a method for determining the specific resistance to filtration of conditioned and non-conditioned sludges, provided that no sedimentation occurs during filtration (that is, single phase suspension with particles in suspension). This European Standard is applicable to sludges and sludge suspensions from: storm water handling, urban wastewater collecting systems, urban wastewater treatment plants, industrial wastewater that has been treated similarly to urban wastewater (as defined in Directive 91/271/EEC) and water supply treatment plants. This method is also applicable to sludge and sludge suspensions of other origins. This method is based on the flow of a liquid through a porous medium in accordance with Darcy's law (see Annex A). The specific resistance to filtration is determined by pouring a suitable volume of sludge into a filtering device, allowing the liquid to be filtered under constant vacuum or pressure, whilst recording the amount of filtrate over time. Considering that for sludges this parameter is affected by pressure value, this standard has been validated for the determination of specific resistance to filtration at pressure values (50 ± 5) kPa, (150 ± 10) kPa and (300 ± 15) kPa, as specifically indicated in Clause 6. If necessary, as in the case of tests intended to size or optimise industrial filters, tests may be carried out at different pressures, provided results have been validated in advance. This revised version only includes editorial changes that do not influence the original, validated method. The committee responsible for this standard is committee NA 119-01-02-02 UA "Chemische und physikalische Verfahren" ("Chemical and physical processes") of Working Committee NA 119-01-02 AA "Abfall- und Bodenuntersuchung" ("Examination of waste and soil") at the Water Practice Standards Committee (NAW) at DIN.