S4.1.1 Where it is necessary to take samples in order to ascertain the characteristics of any discharge or of any ingredient of any discharge pursuant to or for the purposes of any provision of this Bylaw, the provisions of the this schedule shall apply.
S4.1.2 ISO 5667 Part 1 shall be used as a guide to the design of sampling programmes.
S4.1.3 In this Schedule:
'A grab sample' means a discrete sample taken randomly (with regard to time and/or location) from the trade waste.
'A composite sample' means 2 or more samples or sub-samples, mixed together in appropriate known proportions (either discretely or continuously), from which the average result of a desired characteristic may be obtained. The proportions are usually based on time or flow measurements.
S4.2.1 Sample containers and sampling equipment shall be chosen and prepared for use having regard for the nature of the wastewater to be sampled, the characteristic to be tested and the accuracy required of the test. Guidance in this shall be sought ISO 5667 Part 3.
S4.2.2 Samples of turbulent flow or from the surface shall be taken using techniques that comply with ISO 5667 Part 2 and Part 10.
S4.3 Sampling methods for trade waste
Samples shall be either grab samples, composite samples or a sequence of composite samples.
S4.3.1 An anstantaneous composite sample
Three grab samples of the discharge shall be taken at intervals of not less than 1 minute nor more than 5 minutes. The three grab samples shall be combined using equal volumes of all three samples to obtain the instantaneous sample.
S4.3.2 A four-hour average composite sample
- No less than 12 grab samples shall be taken from the discharge over a continuous four-hour period. The samples shall be taken at reasonably even intervals over the whole period. The intervals between the samples shall not be less than 5 minutes nor more than 30 minutes. The samples shall be mixed using equal volumes of all samples to obtain the four hour average sample.
- The four-hour flow period used when taking a four-hour average sample shall be a continuous period of four hours during which the discharge is occurring and:
- shall as far as practical be representative of the discharge occurring on a typical working day
- may include periods of decreased discharge prior to or after the days operations.
S4.3.3 A twenty-four hour flow proportionate sample
- No less than 18 grab samples shall be taken from the discharge over a continuous twenty-four hour period. The samples shall be taken at reasonably even intervals over the whole period. The intervals between the samples shall not be less than 5 minutes nor more than 60 minutes. Whenever more than one sample is taken within a 60 minute period the samples shall be of equal quantity and may be stored with other samples taken during that 60 minute period in a common container.
- The twenty-four hour flow proportionate sample is then obtained by taking a part of the contents of each container and mixing all such samples together. The size of the part of each container sample that is used shall be in direct proportion to the volume of discharge that occurred from the time a sample was first placed in the particular container to the time a sample was first placed in the next container.
S4.4 Sample preservation, transportation and storage
S4.4.1 The preservation and storage of samples shall be in accordance with ISO 5667 Part 3.
S4.4.2 Sample storage
- When samples are stored prior to analysis, they shall be kept in a manner which as far as possible preserves the samples' characteristics.
- When it is not possible to preserve a particular characteristic of a sample, then analysis of the sample to determine that characteristic shall begin promptly upon receipt of the sample.
S4.5 Sample identification and records
A printed form for the sampling report should as a minimum include at least the following information:
- name of the trade premises
- consent number
- sampling point
- date, start and stop of sampling
- time, start and stop of sampling
- duration of the sampling period
- details of the sampling method
- preservation method
- details of any field tests
- name of the person who carried out the sampling.