PHOENIX — As Arizona faces historical water consumption and continued drought, being able to treat wastewater to be reused has become an attractive option to maintain water security.
Thursday, the Arizona Department of Environmental Quality (ADEQ) released proposed plans on how to safely turn wastewater into reliable, purified water.
The plan introduces the Advanced Water Purification (AWP) Program, which ADEQ hopes will allow stakeholders and the public to better understand and establish clear communication throughout the process.
“Earlier this year, I was excited to announce Phoenix’s first steps in creating a regional Advanced Water Purification facility that, in accordance with these new guidelines from the state, will deliver up to 60 million gallons of water per day for valley cities," Phoenix Mayor Kate Gallego said. "Along with robust conservation programming and smart development policies, Advanced Water Purification is a safe, sustainable way to bolster our water resources for generations.”
The first step in the plan is to develop a permitting process, which will function similarly to other ADEQ permits like Aquifer Protection Permits. The permits will be in place to protect public health and the environment, ADEQ said.
How does wastewater treatment work?
What the public is probably most interested in is how pathogens will be removed from wastewater.
Between flush and faucet, there are several steps that are designed to remove chemicals and pathogens that remain in sewage after it has already undergone traditional primary, secondary and sometimes tertiary treatment.
Here's how the Center for Disease Control explains the process:
Coagulation is often the first step in water treatment. This is when chemicals with a positive charge are added to the water, which neutralizes the negative charge of dirt and other dissolved particles in the water. The particles then bind with the chemicals to form slightly larger particles. Common chemicals used in this step include specific types of salts, aluminum, or iron.
Flocculation is next. Flocculation is the gentle mixing of the water to form larger, heavier particles called flocs. Often, water treatment plants will add additional chemicals during this step to help the flocs form.
Sedimentation is one of the steps water treatment plants used to separate out solids from the water. During sedimentation, flocs settle to the bottom of the water because they are heavier than water.
Once the flocs have settled, the clear water on top is filtered to separate additional solids from the water, according to the CDC. During filtration, the clear water passes through filters that have different pore sizes and are made of different materials (such as sand, gravel, and charcoal). These filters remove dissolved particles and germs, such as dust, chemicals, parasites, bacteria, and viruses. Activated carbon filters also remove any bad odors.
Water treatment plants can use a process called ultrafiltration in addition to or instead of traditional filtration. During ultrafiltration, the water goes through a filter membrane with very small pores. This filter only lets through water and other small molecules (such as salts and tiny, charged molecules).
Reverse osmosisexternal icon is another filtration method that removes additional particles from water. Water treatment plants often use reverse osmosis when treating reused water or salt water for drinking.
After the water has been filtered, water treatment plants may add one or more chemical disinfectants (such as chlorine, chloramine, or chlorine dioxide) to kill any remaining parasites, bacteria, or viruses. To help keep water safe as it travels to homes and businesses, water treatment plants will make sure the water has low levels of the chemical disinfectant when it leaves the treatment plant. This remaining disinfectant kills germs living in the pipes between the water treatment plant and your tap.
How safe will the water be to drink?
According to ADEQ, water treated through their process will meet or exceed standards of the Safe Drinking Water Act (SDWA). Removal of pathogens will be done by using multiple-barrier treatment with monitoring of critical control points.
Operational requirements for treatment facilities will be closely monitored to ensure potable water meets all standards. Treatment plants will have to have the following before being able to go into operation:
- Full-Scale Verification Testing Plan – A plan identifying the steps necessary to complete performance testing of each component of the AWTF treatment train, to be submitted by the AWP applicant at the time of application.
- Operations Plan – A plan describing the activities that will be conducted to operate and maintain AWP facilities, to demonstrate that they are performing as designed, and to provide contingency plans for emergency situations.
- Response to Off-Specification Water– A plan for responding to treated water that does not meet standards.
ADEQ is also proposing a new certification, called the Advanced Water Treatment Operator (AWTO) certification, to be sure plants will have the knowledge and skills to operate safely and be able to provide purified water to the public.
ADEQ wants feedback on plan
ADEQ hopes to have a permanent plan in place by the end of the year and is seeking input on this proposed roadmap. Comments and feedback can be e-mailed to reuserulemaking@azdeq.gov from Nov. 2 until Dec. 2.
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