Cost-Effective Lagoon Ammonia Compliance

Ammonia in waterways can wreak havoc on the environment—disrupting aquatic ecosystems, aggravating and killing fish, and creating dead zones—so it makes sense that the EPA is seeking to regulate it. (See our article, Why Lagoon Ammonia Matters: 3 Reasons the EPA is Regulating Lagoon Ammonia Effluent, for this topic in detail.) However, for smaller municipalities especially, this can create a tremendous financial burden as they seek to comply with these new limits with wastewater lagoon systems that just weren’t designed to remove ammonia.

In this article, we’ll briefly describe lagoon nitrification, and then go through the pros and cons of some common lagoon ammonia removal technologies with an eye toward minimizing capital and operational expense.

What are some options for lagoon-based ammonia removal?

Biological ammonia removal relies on a process that involves nitrifying bacteria. Nitrification occurs when nitrifiers convert Ammonia (NH3-N) first in to nitrite, then into nitrate. These bacteria occur naturally in wastewater, but they are sensitive, requiring specific conditions in which to effectively nitrify. The trick for encouraging nitrifiers to do their work is to create an environment that makes them happy. The following upgrade alternatives take different approaches to facilitating nitrification within a lagoon context.

Download our Lagoon Ammonia Removal Whitepaper for a more in-depth look into the different factors that affect nitrification in lagoon systems.

Upgraded Lagoon Aeration System

Lagoon nitrification requires three times more dissolved oxygen than for BOD removal alone—4.6 lb/O2 per pound of ammonia versus 1.5 lb/O2 for BOD. A typical aeration system was simply not designed to provide enough oxygen to meet the demands of lagoon ammonia removal.  Moreover, many wastewater lagoon facilities have old, worn down, and outdated lagoon aeration equipment that is struggling to provide even enough oxygen and mixing for BOD removal, let alone lagoon ammonia treatment. Lack of properly sized or functioning equipment could result in myriad problems for the wastewater lagoon. For example, broken laterals on a diffused aeration system, or surface aerators that require frequent maintenance, could result in DO levels that are too low to properly treat ammonia.

Pros

  • Provides DO for nitrification
  • Will lower BOD
  • Relatively inexpensive
  • Simple
  • Increased efficiency with lower O&M costs

Cons

  • Nitrification will not be achieved when lagoon water temperatures dip below 50–55° F
  • May not provide enough surface area for attached-growth nitrifiers

Lagoon Covers & Polishing Reactor

Wastewater lagoon covers retain heat by insulating the surface of lagoons, keeping the water warm enough to achieve nitrification in the winter and year round. However, you must be certain that there is an adequate aeration system to keep DO levels and mixing high enough to treat BOD, and thus allow for nitrification. A polishing reactor is the final step: The reactor uses UV-resistant PVC media and a complete-mix environment to promote growth of nitrifying bacteria. This allows the system to control both BOD and ammonia, despite cold weather.

Pros

  • Very reliable at cold temperatures
  • Ideal for strict limits
  • Minimal extra land requirement
  • Proven performance
  • Treats BOD and NH3-N

Cons

  • Requires redoing entire system: capital cost
  • High operating costs
  • Maintenance is difficult and costly

Aerated Rock Filter

lagoon ammonia compliance

Aerated Rock Filters can be an effective method of lagoon ammonia removal despite cold water temperatures.

A submerged aerated rock filter is typically added as an effluent polishing measure. Effluent flows through gravel media that collects a mass of nitrifying bacteria over time, making lagoon ammonia treatment more efficient. The aeration aspect of this system assures that the necessary oxygen levels are met for nitrification. The system is usually placed in the ground and covered in a layer of insulating mulch.

Pros

  • Very reliable at cold temperatures
  • Ideal for strict effluent limits
  • Simple to operate
  • Proven winter performance

Cons

  • High capital cost
  • Extra land requirement
  • Potential breaches during seasonal transitions
  • Unknown long-term cleaning requirements

NitrOx Process: Cost-Effective Lagoon Ammonia Compliance

NitrOx lagoon ammonia compliance

Triplepoint’s NitrOx provides cost-effective lagoon ammonia compliance.

The NitrOx™ Reactor was designed to be incorporated into an existing system for the sole purpose of ammonia removal. A typical NitrOx system is added near the end of the treatment process, prior to discharge. Effluent flows through two complete-mix aeration cells that have a dense concentration of nitrifiers allowing for rapid nitrification in a small footprint. The NitrOx system, through controlled thermal regulation, biomass, mixing, and aeration, can nitrify in any weather.

Pros

  • Works within existing lagoon system
  • Low capital costs
  • Easy operation
  • Proven performance
  • Can treat BOD and TN

Cons

  • Requires some additional land
  • May require additional utility connections for thermal regulation

Most lagoon systems in cold-weather climates will require a capital investment to meet the new ammonia effluent limits. The challenge is to ensure compliance in the most cost-effective way possible.

The NitrOx System, through controlled thermal regulation, biomass, mixing, and aeration, optimizes conditions for nitrification, even in cold weather. It was designed to be incorporated into an existing system for the sole purpose of ammonia removal, helping to keep capital costs low—at 2/3 the cost of existing nitrification options—and minimize the financial burden of plant upgrades.

Download the NitrOx Technical Information for more information on cost-effective Lagoon Ammonia Removal.

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