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Recently, wastewater lagoons are experiencing lowered phosphorus discharge limits. Apart from nitrogen, phosphorus also can cause eutrophication. Phosphorus input is more critical than nitrogen since phosphorus is a growth-limiting nutrient for the growth of organisms and can limit the primary use of a body of water. Although a small portion of phosphorus is removed naturally through regular lagoon biological treatment, it is difficult to meet the restrictive effluent standard only with the natural processes. So additional treatment within the lagoon is necessary.
The WCS Bio-Dome is the cost-effective solution for lagoons to reach their new phosphorus permit limits. Bio-Dome’s low capital cost is also combined with monthly operation and maintenance expenses.Wastewater Compliance System (WCS) manufactures and sells patented submergible aerated fixed-film (biofilm) reactors under the trade name Bio-Dome that was developed at the University of Utah. This system provides a large aerated surface and unique aeration pattern on a small footprint, accelerating the ability of beneficial bacteria to grow and breakdown undesirable pollutants to provide cleaner water. As the figure shows on the right, each Bio-Dome consists of an assembled 4-dome set that contains 4,400 ft2 of an aerated surface, utilizing patented 73:1 surface enhancing packing material to support the fixed-film growth.
Bio-Domes are positioned on the floor of a lagoon. The Bio-Dome system consists of concentrically nested domes that are infused with air from the bottom. They sit on the floor of a lagoon and are completely submerged. As the air and water flow through them, bottom-to-top, beneficial bacteria effectively reduce contaminants in the water. The figure on the right shows the aeration pattern of the Bio-Dome. Because of the unique design of Bio-Domes, the lagoon system can meet increased population sizes, loading, and even more stringent effluent requirements with minimum expense.
Phosphorus (P) in municipal wastewater exists in three forms: (1) orthophosphate, (2) polyphosphate, and (3) organically bound phosphorus. The phosphorus is removed from the wastewater usually by chemical or biological methods.
Chemical P Removal with Bio-Dome
The chemical P removal is brought about by the addition of salts of multivalent metal ions that form precipitations. These metal ions generally include calcium (II), Aluminum (III) and iron (III). Polymers have been used effectively in conjunction with alum and lime as flocculent aids. The metal ions are usually applied before/or following biological treatment. Based on previous performance, Bio-Domes have demonstrated the ability to remove organics, solids, ammonia and P. If the metal ions are applied within or after the treatment of Bio-Dome, the effluent will contain less P under the lower cost and chemical dosage.
Biological P Removal with Bio-Dome
Biological phosphorus removal usually occurs through enhanced Bio-P removal (EBPR) to reduce phosphorus in the water. The common element in EBPR implementations is the presence of an anaerobic tank (nitrate and oxygen are absent) prior to the aeration tank. Under these conditions a group of heterotrophic bacteria, called polyphosphate-accumulating organisms (PAOs) are selectively enriched in the bacterial community. Under the anaerobic and aerobic conditions, PAOs can take up more inorganic phosphate than their metabolic demand and store it as polyphosphate. Previous research determined that fixed-film systems can perform biological nitrogen and phosphorus removal with nitrifying PAOs, which produced less sludge.
Bio-Dome P Removal Results
SBIR Phase I Pilot
WCS was awarded a USDA SBIR Phase I grant to run a pilot study to verify its Bio-Dome system can remove N and P from wastewater. The pilot was operated during the 2010-2011 winter in Central Valley Water Reclamation Facility (CVWRF, UT). The picture shows the test units that were used in this pilot. One tank holds the six Bio-Domes, and the other is a Control that consists of six bubble release tubes only on the bottom of the tank in the same position as the bubble release tubes under the Bio-Domes (BD). Both tanks were operated under the same condition.
Results from CVWRF pilot test tank (figure below) show a removal of about 2 mgP/L, indicating the possibility of better P removal in lagoons with refined operational techniques (water flow and air cycle management). The CVWRF test was conducted with the equivalent surface area of one Bio-Dome at a hydraulic retention time (HRT) of 8 days.
Wellsville, UT Installation
The Wellsville Water Reclamation Facility (WWFR) has a four cell facultative lagoon system, with effluent discharging to the Little Bear River. WWFR has received a renewal permit for limiting P concentration in the final effluent. WWFR is the only lagoon system in Utah to have P limitations in their UPDES permit, due to the TMDL impairment of P into the Little Bear River.
WCS proposed a scaled implementation at Wellsville starting with 35 Bio-Domes for initial research purposes. After the 35 units were installed in late 2009, field data indicate the Bio-Domes were removing about 0.25 mg/L of P from the water prior to discharge. Wellsville decided to increase the number of domes from 35 to 75 and installed the additional 40 in June, 2011. During the year of 2015, these 75 units of Bio-Domes removed 3.78mgP/L. The chart below shows the effluent concentrations taken quarterly from 2009 to 2015. In this installation, it was also observed that TN was removed simultaneously with TP. These Bio-Domes removed ortho-P (PO43–P) and TP at 0.08 and 0.14 lb P/d/unit (with 0.04 lb TN /d/unit), respectively
Glacier National Park, MT Installation
The Many Glacier area has one wastewater treatment lagoon in operation, and has a typical operational season of May through October. Over the last few years, this lagoon had odor problems, as well as high levels of BOD and ammonia in the effluent. Among other upgrade options, WCS’ Bio-Dome system was chosen because it was reliable and the most cost-effective alternative. In the fall of 2011, WCS installed 50 Bio-Domes in this lagoon. Ten of the Bio-Domes consisted of the 7-shell units to reduce BOD and TSS, and remaining 40 were 4-dome units to remove ammonia. The new system only required a 5hp blower to operate, cutting their energy consumption by over 80%.
While the Bio-Dome system started operating from 2012, the odor issue was completely eliminated and the effluent met permit requirements. Although this update was not for P reduction, the wastewater lagoon showed significant TP removal. The chart below shows the influent and effluent TP concentration during the operational seasons from 2012 to 2015. In this installation, it was also observed that simultaneous N and P removal took place. These Bio-Domes removed 0.05 lb/d/unit of TP (with 1.35 lb TN /d/unit).
Conclusion: When considered alongside the effective treatment of P, the WCS’s Bio-Domes begin to display an all-around value for improving the water quality of the treated effluent in a wastewater lagoon. If you are interested in learning more about Bio-Domes or would like us to put together a proposal for you, please contact us using the contact information below. If you would like to speak with any of the communities mentioned in this article, please feel free to do so using the contact information found on our website. They have all agreed to answer questions.
For more information, call WCS at (801)999-8271, or visit our website at www.wastewater-compliance-systems.com.