From The Editor | October 26, 2017

What The MWRD Has Learned About Wastewater Treatment

Peter Chawaga - editor

By Peter Chawaga, Associate Editor, Water Online

What The MWRD Has Learned About Wastewater Treatment

The Metropolitan Water Reclamation District of Greater Chicago (MWRD) operates perhaps the country’s best-known and highest-caliber wastewater treatment facility. The Stickney Water Reclamation Plant, located in Cicero, IL, is the world’s largest such facility and one that has been at the forefront of the nation’s efforts to recover wastewater resources and reduce nutrient pollution.

As such, the plant has been no stranger to headlines in its history and was in the news once again recently as it received a “Project Excellence Award” from the Water Environment Federation (WEF) for its ability to reduce downstream phosphorus charges and protect source water as far as the Gulf of Mexico.

Stickney’s journey to become one of the world’s preeminent resource recovery projects is well documented. It utilized Ostara Nutrient Recovery Technologies and design/build services from Black & Veatch to go online in late 2016. The plant has a peak capacity to handle 1.4 BGD and averages about 700 MGD. Its reactors have capacity to treat 7,900 pounds of nutrients per day. The MWRD has the potential to recover as much as 7,500 tons of fertilizer product per year, which it markets and sells as “Crystal Green.” It also boasts its own bulk loading capabilities, transferring the fertilizer directly into 20-ton trucks.

Despite the incredible capacity and awards, the MWRD has plans to keep improving its process. For starters, it is exploring the use of an Ostara technology called Waste Activated Sludge Stripping to Recover Internal Phosphorus (WASSTRIP).

“By implementing WASSTRIP as part of the overall nutrient recovery program, the MWRD will reduce impairment to biological phosphorus sludge dewatering,” said an MWRD spokesperson. “This will decrease the amount of polymer demand in the dewatering process. WASSTRIP should also improve the reliability and efficiency of phosphorus removal and will double the overall recovery of nutrients from the waste stream. This should also lower the phosphorus value in our biosolids compost, giving the ‘P to N’ ratio better composting characteristics.”

The MWRD also learned some critical lessons when first getting this project online, ones that may help other projects around the country and will certainly inform Chicago’s decisions in the future.

“The MWRD used a design-build format in delivering this project; this approach is new to the MWRD and brings its own learning opportunities,” the spokesperson said. “The standard Ostara reactor design was too small for this facility, so the Ostara team had to go to the drawing board and design a new reactor that could accommodate the scale of the Stickney WRP.”

The MWRD also learned a lesson courtesy of a pesky mineral as it tried to get this project up and running.

“Struvite buildup in the pumps and pipes also provided opportunities for learning,” said the spokesperson. “We are installing an automated acid wash system to care for the pumps and a CO2 pH system to address the issue”

Addressing struvite — which forms as a combination of magnesium, ammonia, and phosphate in wastewater and can be recovered for use as fertilizer — also presents an opportunity that the MWRD sees for smaller plants to follow its large-scale lead.

“Struvite removal should be scalable for the largest plant in the world and for the smallest,” the spokesperson said. “Removing phosphorus in a plant’s original footprint is possible and affordable using struvite recovery in a plant. Implementing enhanced biological phosphorus removal (EBPR) without struvite would have cost $750 million-plus in the Stickney facility. EBPR was stabilized and successful at a fraction of this cost and can be duplicated in smaller plants around the world.”

Finally, the MWRD is looking to evolve by setting the ambitious goal of full energy neutrality by 2023. It is upgrading its primary tanks and finding ways to implement new technology throughout operations. It is pursuing the sale of its treated water for industrial applications.

“The Stickney WRP will continue to develop a robust resource recovery model built on the beneficial reuse of energy, water, biosolids, phosphorus, and other nutrients,” said the spokesperson. “The available digester capacity at Stickney is being explored for the addition of food organics and will help us reach [our] energy neutrality goal.”

Though it has received national recognition and industrial acclaim, the MWRD’s Stickney facility has overcome obstacles and outlined future goals just like any other wastewater service provider in the country. Hopefully its past, present, and future offer something of value to the utilities that are watching.

Image credit: "Aerial view of Stickney Wastewater Treatment Plant," U.S. Army Corps of Engineers Chicago District, 2014, used under an Attribution 2.0 Generic license: https://creativecommons.org/licenses/by/2.0/