A new disinfection chemistry holds environmental and financial promise

Credit: Evonik

Evonik Industries manufactures peracetic acid next door to where the firm uses it to disinfect wastewater in Memphis, Tennessee.

For decades, the city of Memphis, Tennessee, didn’t disinfect its wastewater. It stopped disinfecting in the 1980s because of concerns that residual chlorine would harm aquatic life and because of the cost of neutralizing the chlorine. It relied instead on settling, filtration, and microbial digestion for treatment. But in the first decade of this century, when its discharge permits were coming up for renewal, the city started working with environmental engineers on a new way to disinfect its discharge into the Mississippi River: peracetic acid.

In 2015, Memphis asked companies for bids to supply peracetic acid to its main wastewater plant. One of them, PeroxyChem, responded with a bigger pitch. The firm wanted to operate the city’s disinfection system and build a peracetic acid plant next door.

The city agreed. PeroxyChem built the plant and late last year started making peracetic acid on-site. The plant is large enough to supply both of Memphis’s wastewater plants as well as other peracetic acid markets, such as food safety. The deal also gives other Tennessee wastewater plants access to peracetic acid at lower costs than they could get elsewhere.

PERACETIC ACID AT A GLANCE

▸ 16,000 municipal wastewater plants in the US treat 45 billion L of sewage each day.

▸ 90% of peracetic acid’s disinfection activity happens in the first minute.

▸ Peracetic acid is a stronger oxidant than sodium hypochlorite and chlorine dioxide but weaker than ozone.

▸ In returnable containers, peracetic acid costs around $1.40–$1.80 per liter.

▸ UV light and metal contaminants strongly reduce peracetic acid stability.

▸ Most peracetic acid is sold in 15 or 22% concentrations and used at 1–2 ppm in wastewater.

Sources:  Domenico Santoro, Kati Bell, Alberto Garibi, Jacquelyn Wilson, Lenntech, Tom Warmuth.

Today, chlorine dominates the US wastewater treatment market, disinfecting sewage at more than two-thirds of the country’s 16,000 plants. But the various chlorine-based chemicals used in water treatment create disinfection by-products that can harm the environment and human health. Residual chlorine flowing out of treatment plants can kill aquatic life. Tightening regulations on disinfection by-products and residual chlorine are driving up costs for wastewater plants using those workhorse chemistries.

For some plants, peracetic acid is the answer. It isn’t known to create harmful disinfection by-products. And because peracetic acid decomposes quickly into acetic acid, oxygen, and water, there is little need to remove or neutralize it before treated water enters waterways. As more plants adopt peracetic acid, its cost is decreasing. Once a niche product, peracetic acid may soon challenge the dominance of chlorine in large swaths of the US wastewater treatment market.

The global peracetic acid market was worth $650 million in 2017 and will grow to $1.3 billion by 2026, according to the consulting firm Trends Market Research. That estimate includes other uses of peracetic acid, such as poultry processing and industrial cleaning. Peracetic acid for wastewater treatment specifically is expected to grow by 8% per year over that same time frame.

Memphis will be a big part of that growth. In November 2018, the 356 million L per day Maynard C. Stiles Wastewater Treatment Facility started using peracetic acid supplied by PeroxyChem—the world’s largest such system. In February of this year, the big German chemical maker Evonik Industries purchased PeroxyChem for $640 million, largely on the strength of its peracetic acid business. Evonik expects Memphis’s other wastewater plant, which handles 264 million L per day, to start using peracetic acid in November.

“We have a long-term contract with the city of Memphis that enabled us to invest with a bit more peace of mind in this new production facility,” says Alberto Garibi, a PeroxyChem executive who now leads Evonik’s water and wastewater treatment business. “And it reduced operating costs for the city.”

Memphis’s wastewater stream is challenging, Garibi explains, because it contains a lot of industrial wastewater in addition to the municipal flow. The amount of chlorine required to meet the disinfection targets would be cost prohibitive, he says.

SOURCE

New WEF Handbook Aims to Bridge Peracetic Acid Knowledge Gap

WEF technical publication, Peracetic Acid Disinfection: Implementation Considerations for Water Resource Recovery Facilities, aims to bridge the knowledge gap about the value of peracetic acid as a wastewater and stormwater disinfectant. The handbook's lead author, Dr. Kati Bell, offers insights.

Why did the authors write this publication?
KB: Although peracetic acid (PAA) has been used for wastewater effluent disinfection or over two decades in Europe, it only recently has been applied for municipal wastewater disinfection, and in only a handful of facilities in North America. While the first commercial PAA product approved for use in the United States by the EPA was in 2006, with the first application in 2012, this technology has been out of reach for most utilities in North America. Seeing the need to fill a knowledge gap in our industry, I proposed development of this document, in partnership with other experts in the field to inform utilities, regulators, engineers, operators and regulators about the applicability of the technology along with the challenges that must be overcome for more widespread implementation of PAA.

What do you want the water sector to know about this publication?
KB: This publication was a collaboration among utilities, engineers, operators, PAA manufacturers and regulators and reflects a breadth of perspectives and represents a wealth of knowledge that has been compiled in a single document. While there is still a need to build upon the information provided in this document, it is a major step forward in the collection of practical experience and case studies on the testing, design, permitting, construction, and operations of a PAA system for wastewater disinfection compliance. It was an honor to work with the authors, reviewers and WEF editorial staff on this document to help advance use of this important technology.

What advice can you provide to readers?
KB: Peracetic acid is not a silver bullet for addressing all wastewater disinfection applications, but it is a valuable tool that we have in our toolbox that can be used under the appropriate circumstances. For some wastewater resource recovery facilities where other, more mature technologies like chlorination/chloramination or UV cannot be applied. In some facilities, chlorination/chloramination can yield challenges with disinfection by-products with discharge limits that are increasingly stringent; and in some facilities low UV transmittance or suspended solids above 10 mg/L can limit use of the technology. In these cases, PAA could address these challenges while being economically competitive. The document can be used to help guide an informed discussion on whether PAA could be a viable solution when site-specific factors are considered.

For more information on  Peracetic Acid Disinfection: Implementation Considerations for Water Resource Recovery Facilities ,  visit WEF’s online store . 

Taxonomy

• Chlorine Dioxide
• Chlorination
• Chlorine Dioxide Treatment