Improvements in biological treatment ensure robust removal of nutrients from wastewater to meet even the strictest effluent standards

Around the world, nutrient removal standards have become stricter in recent years, and it’s no mystery why. Despite a global focus on per- and polyfluoroalkyl substances (PFAS) and other emerging contaminants in wastewater, nutrient pollution may still be the most dangerous water-quality challenge the world faces.

Water with high nutrient levels is dangerous to consume, and it has caused incalculable harm at the watershed level, frequently fueling toxic algal blooms that harm human health and ecosystems. Eutrophication from nutrient overloads wipes out fisheries around the world and has grown vast “dead zones” in the Gulf of Mexico.

How are nutrient removal standards tightening to address these problems, and how can municipalities, industrial operations, and agriculture comply as regulation grows?

Stiffer Nutrient Guidelines in the US

The United States Environmental Protection Agency (EPA) is in the process of tightening nutrient standards for direct and indirect effluent discharges. For instance, the EPA has proposed a new set of regulations for the meat and poultry industries and is overseeing state progress toward adopting numeric nutrient criteria for water quality. At the state level, governments have also moved to set nutrient load reduction goals that prioritize watersheds.

The Clean Water Act has long addressed pollution from specific sources, for example, a factory. However, there’s been a growing recognition of the impact of nonpoint source pollution, such as agricultural runoff. Section 319 of the Clean Water Act provides a way to address pollution from nonpoint sources. Officials can now use this section to attach conditions to loans, requiring borrowers to take steps to reduce nutrient pollution from these sources.

Nutrient Regulation Around the World

In Europe, the European Union (EU) has put stiff fines in place for noncompliance with wastewater standards. In the United Kingdom water sector, fines for violations by water systems have risen as high as 500,000 pounds. The latest EU directive expands the scope of regulation to encompass smaller municipalities, including towns with populations as low as 1,000 inhabitants, and will necessitate increased nutrient removal by urban wastewater treatment facilities.

In Asia, there has been a general tightening of effluent standards and rising penalties for violations, for example, the codification of penalties for environmental offenses in Vietnam. In China, previous Five Year Plans reduced cumulative COD by 6.426 million tons, improving water quality across the nation and aligning with China’s ongoing push for stricter regulations.

As standards become more stringent, municipalities, commercial enterprises, and farms must look for ways to lower the nutrient load of their wastewater discharges and runoff.

Biological Treatment With Activated Sludge and Aeration

Over the past century, biological wastewater treatment, such as the activated sludge process, has been the standard for most of the world’s nutrient removal. In biological treatment, bacteria naturally remove nutrients such as nitrogen. These nitrogen-removing bacteria are aerobic, meaning that they need oxygen to thrive. Consequently, legacy biological treatment processes rely heavily on air compression to make the bubbles that support aerobic bacteria. Creating bubbles with compressed air, however, comes with a high energy requirement, which makes compliance more costly than it has to be. Most of the bubbles rise to the surface before the bacteria can use the oxygen they contain, adding to the inefficiency of the process.

MABR Nutrient Removal

There are alternatives to the activated sludge process. Fluence’s membrane aerated biofilm reactor (MABR) virtually removes the need for compressed air, cutting the energy cost for air compression in biological treatment by 90%.

Most membrane processes use membranes for filtration, but Fluence designed its MABR membrane specifically to optimize aeration. In the process, two sheets of semipermeable membrane form an envelope around a spacer that allows air to freely circulate. The membrane is then rolled up, and when it’s immersed in mixed liquor, air is pumped in at near-atmospheric pressure. The microscopic pores of the membrane allow the air to pass through into the mixed liquor efficiently without forming bubbles that could rise to the surface.

The oxygen-rich surface of the membrane forms the perfect environment for aerobic bacteria, which create a resilient biofilm that resists both chemical and temperature shocks. Around the membrane, the mixed liquor has a low enough oxygen content to support anaerobic bacteria. Together, the two forms of bacteria enable simultaneous nitrification and denitrification (SND) in a single tank, a process that once required two or more chambers.

MABR technology doesn’t sacrifice effluent quality for efficiency. It can exceed the toughest nonpotable water reuse standards in the world, including China’s Class 1A and California’s Title 22, with a smaller footprint, less noise, and less odor than legacy processes. With additional ultrafiltration treatment, MABR can transform wastewater into potable water.

Fluence MABR Wastewater Treatment Products

Fluence carries a range of products that use MABR to help both public and private enterprises meet ever-stricter effluent regulations.

• Aspiral™ Flex: Fluence Aspiral™ Flex units package wastewater treatment technology into weatherized units the size of standard shipping containers, which simplifies logistics, shipping, and installation. With Aspiral™ Flex, you have your choice of MABR, membrane bioreactor (MBR), or activated sludge treatment. Aspiral™ Flex also enables full plant design with a simplified building-blocks approach for a plug-and-play experience like never before.
• SUBRE: SUBRE units are MABR towers that are submerged in activated sludge plants for retrofits. SUBRE upgrades the effluent quality and capacity of existing plants without major construction or increased footprint. Fluence also offers SUBRE greenfield plants for those looking for a full-scale wastewater treatment plant featuring energy-efficient MABR technology.
• Nitro: Fluence Nitro units also use MABR for shortcut nitrogen removal of nutrients from sidestreams with heavy Biological Oxygen Demand, Total Nitrogen, and Total Phosphorus. Shortcut nitrogen removal saves energy by converting ammonia to nitrite and then directly to nitrogen gas, skipping the conversion to nitrate in between.

Over the years, Fluence has become synonymous with nitrogen removal, with MABR installations from the United States to China and many points in between. Our experts are here to help you navigate the complexities of compliance. Contact us to discuss your unique effluent and regulatory challenges.