This part of ISO 5667 gives guidance on the sampling of sludges from wastewater treatment works, water treatment works and industrial processes. It is applicable to all types of sludge arising from these works and also to sludges of similar characteristics, for example septic tank sludges. Guidance is also given on the design of sampling programmes and techniques for the collection of samples. This part of ISO 5667 is applicable to sampling motivated by different objectives, some of which are to: — provide data for the operation of activated sludge plants; — provide data for the operation of sludge treatment facilities; — determine the concentration of pollutants in wastewater sludges for disposal to landfill; — test whether prescribed substance limits are contravened when sludge is used in agriculture; — provide information on process control in potable and wastewater treatment, including: a) addition or withdrawal of solids; b) addition or withdrawal of liquid; — provide information for legally enforceable aspects of the disposal of sewage and waterworks’ sludges; — facilitate special investigations into the performance of new equipment and processes; — optimize costs; for example for the transport of sludges for treatment and/or disposal. NOTE When designing a sludge sampling programme, it is essential that the objectives of the study be kept in mind, so that the information gained corresponds to that required. In addition, the data should not be distorted by the use of inappropriate techniques, such as inadequate storage temperatures or the sampling of unrepresentative parts of a treatment plant.