To protect aquatic life in treated wastewater receiving streams, regulators across North America are reducing the allowable ammonia concentrations in wastewater effluent. While some lagoon-based systems provide adequate ammonia reduction during the summer months, low winter temperatures inhibit the biological nitrification process, resulting in treatment performance that is out of compliance with regulations in many regions.
The Submerged Attached Growth Reactor (SAGR®) is an ideal ammonia control module, which can be incorporated into the overall OPTAER® wastewater treatment process. A key advantage is that a wide range of lagoon types, (aerated or facultative) sizes, or shapes can be utilized, often without modifications to the existing lagoons. Since the SAGR® can reliably nitrify at water temperatures below 0.5°C, insulated covers are not required to nitrify cold temperature lagoon effluent.
The patented SAGR® consists of a clean stone bed that is fully aerated using the patented LINEAR FBA™ aeration system. Water flows through the substrate horizontally or vertically. A layer of insulating mulch on the surface prevents ice formation in the bed, allowing the system to treat wastewater that is near freezing (<0.5°C).
The horizontal flow SAGR® is designed as a post lagoon nitrification module that performs well in all climates but is particularly effective in cold to moderate climates. It can also be used for final nitrification prior to discharge following any other secondary treatment system. The SAGR® provides excellent ammonia removal, while offering BOD and TSS polishing in addition to total coliform, fecal coliform and e-coli removal. Effluent from the SAGR® is suitable for direct discharge in many cases and suitable for UV disinfection where lower total/fecal coliform and E-Coli levels are required.
Where upgrades are required and space is limited, the SAGR® can often be installed within the layout of an existing lagoon treatment system, providing cold climate ammonia removal without significantly altering the lagoon footprint. Generally, the hydraulic retention time in lagoons can be reduced when adding a SAGR®.
Ammonia reduction rates (nitrification) of more than 90 percent can be consistently and reliably achieved at water temperatures below 0.5° C in climates where primary and secondary lagoons are ice-covered for much or all of the winter. Providing treatment with very low water temperatures eliminates the need for insulating, deepening, or shortening the retention time of lagoon cells to retain heat.
The SAGR® can follow a wide range of lagoon systems including continuous discharge or controlled discharge facultative or aerated lagoons. It can handle a wide range of influent water qualities without upset, allowing the SAGR® to be used as a final BOD and TSS polishing technology in addition to nitrification for lagoons that are exceeding their original design loads and flows. Utilizing existing facultative lagoons as secondary treatment reduces the overall energy requirements needed to provide treatment to tertiary levels.
Municipal Effluent Quality at <0.5°C water temperature:
Vertical flow SAGR® systems provide BOD and TSS removal. Typical applications include on-site treatment for residential subdivisions or commercial properties, as well as aircraft deicing fluid contaminated stormwater. The SAGR® is well suited for airport stormwater treatment since biomass remains present in the attached growth system between stormwater runoff events. The SAGR® also offers fast biological "ramp up" to handle large organic load spikes and to reliably provide CBOD removal at very cold water temperatures. Operating below grade in a submerged mode, there is no free water surface to attract birds and waterfowl and interference with aircraft operation at the site is minimized. CBOD reduction rates of more than 95 percent can be obtained with intermittent flow when treating glycol contaminated airport runoff.