Composite Sampling

Water Quality Monitoring Section personnel sample discharge from wastewater treatment facilities that possess a valid Missouri State Operating Permit to verify compliance with the Missouri Clean Water Law, state regulations and the operating permit. A facility’s permit authorizes only wastewater discharges under the Missouri Clean Water Law and the National Pollutant Discharge Elimination System. Facilities to be sampled are outlined in the Water Pollution Control Program’s Quality Assurance Project Plan for compliance monitoring annually.

Data acquired from a sampling event may be used for:

  • quality assurance/quality control purposes,
  • to check the accuracy of the facility’s monthly discharge monitoring reports that are submitted to the department's regional offices,
  • to support determinations of compliance with the conditions established in the
    Missouri Clean Water law, state regulations, the operating permit, or limitations contained in an administrative order or court order.

Samples are collected and returned to the department's Environmental Services Program laboratory to be analyzed for parameters included in the facility's permit. The data collected may be used in conjunction with other findings for the purpose of enforcing the water pollution control rules and regulations.

Under normal circumstances, 24-hour timed-interval composite samples are collected using an automatic wastewater sampler.

Some parameters require a discrete grab sample. Field measurements of pH and temperature are recorded when the composite sample is collected.

Wastewater Treatment Education Guide