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Pages 34-54

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From page 34...
... 34 C H A P T E R 3 Identifying Deicer Treatment Technologies 3.1 Classification System for Deicer Treatment Many technologies are capable of removing deicers from stormwater. Classification of deicer treatment provides insight into the process of implementing deicer treatment systems.
From page 35...
... Identifying Deicer Treatment Technologies 35 • Providing a more predictable effluent quality, and • Providing more consistent costs and operations. All biological treatment systems are designed to create a contained environment that supports contact between the bacteria and the organic pollutants, allowing the living organisms to flourish and resulting in reduction of the concentrations of the oxygen-demanding pollutant (measured as BOD, COD, etc.)
From page 36...
... 36 Guidance for Treatment of Airport Stormwater Containing Deicers Advantages to biological technologies for treatment of deicer-affected stormwater include: • Compared to chemical oxidation and physical treatment technologies, biological treatment technologies generally have lower capital and operating costs, especially for stormwater with BOD5 concentrations of less than 10,000 mg/L. • They are better suited to treat mixtures of organic compounds (e.g., PG, EG, acetate, formate)
From page 37...
... Identifying Deicer Treatment Technologies 37 can be effectively added, but in practice the regularity and extent of nutrient addition in some deicer treatment systems has been less than optimal. • The health of the microorganisms is difficult to measure directly, so a variety of indirect measures are used.
From page 38...
... 38 Guidance for Treatment of Airport Stormwater Containing Deicers Treatment Tips Anaerobic Aerobic Better effluent quality Fewer nutrient requirements Less reactor volume/footprint Faster response at start-up Less energy use Less sludge production Methane by-product may be used as fuel source Ability to treat at lower temperatures without heat addition Less complex operation Anaerobic Versus Aerobic Biological Deicer Treatment to changing deicing conditions. This is most significant in regard to cold-weather operation, when low water temperatures reduce the efficacy of facultative treatment processes.
From page 39...
... Identifying Deicer Treatment Technologies 39 nanofiltration, ultrafiltration, and microfiltration. Reverse osmosis is the only membrane filtration technology that can separate glycol molecules from water.
From page 40...
... 40 Guidance for Treatment of Airport Stormwater Containing Deicers See Fact Sheet 109 for public wastewater treatment facilities.
From page 41...
... Identifying Deicer Treatment Technologies 41 3.2.1 Biological Treatment Technologies 3.2.1.1 Activated Sludge Activated sludge is one of the oldest and most widely used suspended-growth biological treatment technologies to treat wastewater. The activated sludge process, as used for deicer treatment, has two main components: an aerated basin where most of the BOD reduction occurs and a clarifier where biological solids are separated.
From page 42...
... 42 Guidance for Treatment of Airport Stormwater Containing Deicers whereby the tank goes through successive filling, reacting (aeration) , and solids-separating steps.
From page 43...
... Identifying Deicer Treatment Technologies 43 The following airport summaries in Appendix D feature some variation on aerated gravel beds: • Buffalo Niagara International Airport. • Wilmington Airpark.
From page 44...
... 44 Guidance for Treatment of Airport Stormwater Containing Deicers • Excess methane gas captured from the treatment reactors can provide energy savings by use for heating the treatment building and other processes in need of heat, • Resiliency to upsets caused by variation in stormwater characteristics, • Effluent COD concentrations in a predictable range when operated as required, • Low operating cost, • Can be shut down for the summer months and restarted without seeding, and • Because the anaerobic bacteria grow at a slower rate than aerobic bacteria in technologies like activated sludge and aerated lagoons, the quantities of biological solids generated in an AFBR are up to 10 times lower than the biological solids resulting from some aerobic treatment processes. Disadvantages of the AFBR compared to other deicer treatment technologies include: • More complex operation, with multiple support systems to manage together, • The maximum flow rates that can be treated are limited by process constraints, • Longer start-up periods due to the slower-growing bacteria, • Longer and more complex construction, • More equipment to maintain, and • More process data to collect and assess.
From page 45...
... Identifying Deicer Treatment Technologies 45 3.2.1.5 Moving Bed Biofilm Reactors The MBBR technology incorporates both activated sludge (suspended bacteria) and attached biological growth (fixed bacteria on media)
From page 46...
... 46 Guidance for Treatment of Airport Stormwater Containing Deicers • Less maintenance, and • Can use land areas (such as infield areas for taxiways and runways) that are otherwise unusable for development.
From page 47...
... Identifying Deicer Treatment Technologies 47 deicer-affected stormwater to be separated into two separate effluent streams. The two streams consist of a higher-concentration glycol concentrate stream and a lower-concentration glycol distillate stream.
From page 48...
... 48 Guidance for Treatment of Airport Stormwater Containing Deicers There are few airports that spray and recover enough ADF to justify installation of an on-site distillation system. Distillation technologies applied at an airport are well suited for the following applications: • High-concentration fractions from deicing pads or systems that segregate water by concentration.
From page 49...
... Identifying Deicer Treatment Technologies 49 • Other situations where recycling is desirable. • Situations where it is desirable to create a more concentrated stream and a dilute stream for further processing.
From page 50...
... 50 Guidance for Treatment of Airport Stormwater Containing Deicers Space requirements and the need to further optimize the balance between deicer treatment and algal production are potential impediments to the use of algal technology for deicer treatment. It is recommended that any airport considering algal treatment perform a pilot-scale test prior to design.
From page 51...
... Identifying Deicer Treatment Technologies 51 The MBR has the following potential advantages for deicer treatment: • Produces a higher-quality effluent for discharge. • The plant footprint is potentially 70% smaller than conventional aerated lagoons and activated sludge systems because of reduced aeration basin size and elimination of the clarifier.
From page 52...
... 52 Guidance for Treatment of Airport Stormwater Containing Deicers UASBs have been used primarily in industries with high-strength wastewater such as breweries and food production facilities. The UASB has many similarities to the AFBR in terms of ability to treat high-strength wastewater efficiently, isolation from weather, and production of methane that can be used as a fuel source.
From page 53...
... Identifying Deicer Treatment Technologies 53 is a good fit for deicer-affected stormwater because (a) the operating costs are greater than other technologies, and (b)
From page 54...
... 54 Guidance for Treatment of Airport Stormwater Containing Deicers • A 3-year pilot study of the reciprocating gravel bed technology at the Wilmington Air Park was conducted to set design degradation rates. It was also determined from this testing that addition of wetland plants to the gravel beds yielded no additional treatment compared to a gravel bed without plants.

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