Treating Greywater Cost Effectively While Protecting the Public’s Health

States that implement a Tiered Greywater Permitting Approach (Arizona, California, New Mexico, Washington and Oregon)

The states that have developed a tiered approach to permitting and regulating greywater have developed significantly different approaches in terms of water quality, permitting, and tiers. Arizona, New Mexico and California have developed a permit-by-rule standard with best management practices to be followed in order to protect the environment for small flows. Some of the common best practices include NOT storing greywater for more than 24 hours, requiring subsurface irrigation, and minimizing exposure to the public. Attempts to minimize health risks for large flows are adopted by enforcing flow limit specifications. If these flows are exceeded, the system requires a permit and departmental approval. There are differences between states in terms of quantity of flows. Arizona does not require a permit on systems less than 400 gpd and New Mexico does not require a permit on systems less than 250 gpd. California has gone further and created a tiered approach that is dependent on the source of greywater. Although, laundry connections are the only systems that do not require a permit, any system that uses other types of greywater requires department approval. Since Arizona, New Mexico and California do not require a permit; maintenance is entirely dependent on the homeowner’s abiding by Best Management Practices. With the goal of reducing the high exposure scenarios, a common approach is to require a permit on systems for multi-residential, commercial buildings and for “higher exposure” categories such as toilet flushing. Therefore, in populated regions where greywater is used for toilet flushing, all these states require a formal permitting process with specific water quality requirements. However, the way each state regulates toilet flushing varies and each state approaches the requirements for larger systems differently. Oregon requires any system over 300 gpd to achieve advanced secondary treatment (10 mg/l BOD and 10 mg/l TSS) which is more demanding than the national standards for secondary treatment and a total coliform count of 2.2 MPN/100ml. Whereas California does not require any biological treatment, it requires greywater to be treated to 2.2 MPN/100ml of total coliform. The state of Washington has adopted the International Plumbing Code for treatment and use of toilet flushing greywater which requires filtration and disinfection only. Arizona, New Mexico, and California do not include kitchen wastewater in their definition of greywater. Oregon and Washington have included kitchen wastewaters in their definition, but require an advance form of treatment. Washington defines greywater with kitchen waste as “dark greywater” that can only be used in Tier 3 applications (must be treated to NSF 350-1 standards for irrigation).  Oregon requires any kitchen water to pass through a form of physical treatment (i.e. filters) prior to being used.