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LemTec™ Partial Mix Facultative Treatment Process

Enhancing lagoon process control and performance by introducing LET’s advanced technologies within conventional lagoon processes.

The LemTec™ Partial Mix Facultative Treatment Process (LPMFTP) is an enhanced, partial mix aerated lagoon treatment process that is capable of meeting some of the most stringent treatment parameters. Facultative lagoons are quite common in warmer climates that are more conducive to facultative lagoon treatment. The primary benefit of the LPMFTP is that it expands the capabilities of existing, large conventional facultative lagoons by upgrading the treatment process to include state-of-the-art technologies that ensure effluent limits are successfully and consistently achieved.

LemTec™ Partial Mix Facultative Treatment Process

LET’s innovative LPMFTP Process achieves year-round effluent limits as low as 10 mg/L BOD, 10 mg/L TSS and 1 mg/L NH3-N, 1 mg/l Total Phosphorus and 10 mg/l Total Nitrogen at a fraction of the cost of traditional wastewater treatment systems. Upgrading to the cost-effective, reliable LPMFTP provides a comprehensive solution that enables LET clients to maximize their treatment capabilities and successfully meet effluent requirements without unnecessarily replacing underperforming lagoons with expensive new mechanical or biological treatment systems. Each LET wastewater treatment process, including the LPMFTP, is custom designed with our Advanced Integrated Lagoon Technologies (AILT) approach. The AILT approach allows us to integrate cutting edge technologies in combination with over 30 years of proven experience to deliver guaranteed results for each of our clients’ unique needs.

Partial Mix Facultative Treatment Process

STAGE 1 – Partial Mix Aeration Process for Aerobic Treatment

The first stage of the LemTec™ Partial Mix Facultative Treatment Process (LPMFTP) is primarily an aerobic process. Its most unique feature is that it relies on a traditional facultative treatment process that is augmented by the LemTec™ Partial Mix Aeration Process which enhances BOD removal, reduces algae growth and also aides in sludge digestion.

The Aeration Process design may consist of one or several partial mix aeration cells. By creating partial mix aeration cells within the facultative environment, Lemna can expand upon the facultative process and improve the lagoon’s capabilities, providing consistent, reliable BOD removal while setting the stage for the remaining treatment objectives. Sophisticated process modeling ensures that the partial mix aeration process is maximized, designed to perform consistently and reliably even during high flow conditions or variable influent loading. The other primary function of the partial mix aeration cells is to begin the process of sludge digestion and stabilization.

By covering the settling zone of the LPMFTP with the LemTec™ Modular Insulated Cover System, the covered lagoon system eliminates algae and aquatic growth within the lagoon. Algae and aquatic growth contribute to elevated TSS levels, negatively impact BOD removal and can be the cause of nuisance odors.

STAGE 2 – Solids Management

After the aerobic process stage of the LemTec™ Partial Mix Facultative Treatment Process (LPMFTP), the next primary step is for sludge reduction and solids management including storage, separation and digestion.

The first consideration is to provide an environment conducive for solids settling. The use of the LemTec™ Modular Insulated Cover System enhances the settling process by eliminating wind and wave action on the lagoon surface. Our cover system also eliminates the stratification of temperatures and prevents pond “turn over” during changes in the season. In addition, our cover system eradicates algae or aquatic growth within the lagoon and the potential for nuisance odors.

To achieve proper sludge digestion and benthal decay, LET provides a unique aeration process within the settling zone. Doing so enhances the digestion process, minimizes the amount of sludge collected and eliminates the risk of benthal rebound. Through this unique settling design, LET can ensure the settling zone will be sized adequately to provide many years of maintenance-free service as it relates to sludge handling.

STAGE 3 – Expanded and Tertiary Treatment Components for Enhanced Process Capabilities

Depending on our customers’ individual, final treatment objectives, LET is able to include additional treatment steps immediately following the custom-designed LemTec™ Partial Mix Facultative Treatment Process (LPMFTP) settling zone.

The need to reduce ammonia, for instance, is quite common. The use of the Lemna Polishing Reactor™ (LPR) immediately downstream of the settling zone is used to achieve ammonia limits down to less than 1 mg/l. The LPR is a submerged, fixed film, attached-growth process that creates an environment conducive to the growth of nitrifying bacteria necessary for ammonia removal and BOD polishing. Further nutrient removal, beyond ammonia may be required.

The LemTec™ Phosphorus Removal System (LPRS) can be designed into the upgrade of facultative lagoons by including the system into our process design prior to the wastewater reaching the final LPR step. The LPRS is comprised of a chemical dosing system, low horsepower pumps and mixers. The phosphorus removal process precipitates phosphorus and allows contaminants to be dissolved or suspended to settle out as floc particles, achieving effluent of 1 total phosphorus for our clients.

Other steps can be added to adapt the LPMFTP and enhance its capabilities to accomplish virtually any treatment objective including Total Nitrogen (TN) removal, additional solids capture, and more. With each customized LPMFTP design, we are able to successfully deliver wastewater treatment solutions that meet every challenge from influent to effluent.


LET is committed to advancing lagoon technologies and treatment processes, including the LemTec™ Partial Mix Facultative Treatment Process (LPMFTP), by continuously improving and expanding upon our treatment designs and service offerings. Our “Circle of Innovation” philosophy ensures that the needs of our clients are met efficiently, effectively and cost-consciously as we work together with our municipal and industrial clients, protecting water resources now and for future generations.

“Since installation, we have noticed excellent odor control, algae control and our effluent test levels are remarkable. To encourage the choice of Lemna Environmental Technologies products, we welcome anyone interested to tour our facilities and/or review our weekly test results.”

J.R., Iowa – LET Client

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