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4. NAW

DIN Standards Committee Water Practice

Procedure

VN

Overview

The purpose of this Technical Specification is to outline the management of sludges both upstream and downstream of the treatment process to ensure that it is suitable for the outlets available. Sludge is the inevitable residue of treating raw and potable water and municipal and industrial wastewaters. This Technical Specification refers to all types of sludge covered by Technical Committee CEN/TC 308 including sludges from treating industrial wastewater similar to urban wastewater and from water supply treatment work plants. In considering the likely quality of sludges, it should be remembered that municipal wastewater sludges are composed of materials that have already been disposed of and are consequently likely to be more variable than many industrial sludges that arise from sourced materials or water treatment sludges arising from surface water or groundwater. The quality of the sludge should match the requirements of the outlets whether that be to land, thermal processing or as a last resort landfill. As a general rule a high quality sludge is likely to be acceptable to a large range of outlets giving greater operational flexibility. The management of sludges will become increasingly more complex as environmental standards become more stringent and outlets become more constrained by legislation and public attitudes. Sludge quality is central to the development of good practice for sludge production in relation to its destination (use or disposal). Sludge quality depends on the composition of the upstream materials and the type of treatment including post treatment storage. Sludge quality can be characterised by different biological, chemical and physical properties: - biological properties include the microbiological stability of the organic matter in the sludge, odour and hygienic characteristics; - chemical properties include: - content of potentially toxic substances (PTSs) which include inorganic (metals, metalloids, and other minerals), and organic pollutants;- concentrations and form (availability) of plant nutrients and the main components of the sludge; - physical properties include whether liquid, semi-solid (pasty-like) or solid, and aesthetic factors associated for instance with removal of unsightly debris by effective screening. Calorific value is a quality criterion if the sludge is to be incinerated or used as a fuel. Other physical properties include, thickenability and dewaterability. The consistency of these different properties is also a critical aspect of the sludge quality and of the ability to determine its end destination (use or disposal). Standard methods should be used where these are available to measure the quality parameters of sludge. There is a continuing need to develop a full set of standardised and harmonised methods which the manager and operator can use to evaluate the quality of sludge for treatment process design and operational purposes. This Technical Specification considers the management of sludges against the waste hierarchy, the management of sludge quality and an option evaluation process to determine the options available.

Document: references other documents

Responsible national committee

NA 119-01-02-06 UA - Sludge management  

Responsible european committee

CEN/TC 308 - Characterization and management of sludge