Wastewater Treatment Resources

Criteria for Sewage Works Design (Orange Book)

The Criteria for Sewage Works Design serves as a guide for the design of sewage collection, treatment, and reclamation systems. It provides guidance to municipal wastewater collection and treatment facilities, including engineering report requirements. It is intended for use by municipal design engineers and consulting engineers.

Permit Guidance, Data, and Forms

This page contains links to information on the Wastewater Discharge Permit program, guidance documents, permit applications, and tools used by Ecology permit writers and permittees.

Whole Effluent Toxicity (WET) Testing

WET tests are required in some wastewater discharge permits in order to measure the potential toxicity of effluents to the rivers, lakes, bays, and ocean waters of the state. WET testing is sometimes called "biomonitoring" or "bioassay testing."

Ground and Surface Water Quality Standards

Water quality standards provide protection and preservation of the waters of the state. These standards are implemented through a variety of permits.

Permit Fees

The Department of Ecology is authorized by state law, RCW 90.48.465 - Water Pollution Control, to adopt rules to fund the operation of the Water Quality Wastewater and Stormwater Discharge Permit Programs. Domestic wastewater treatment plants operated by government jurisdictions are required to have wastewater discharge permits and pay the required fees.

Nutrient Removal Evaluation

Studies have shown that municipal sewage treatment plants are significant contributors to these problems. This report presents an evaluation of two approaches to reducing treatment plant discharge of nutrients to surface water: