The Swan Lake attraction at Brookfield Zoo is continually in a eutrophic state every year because of nutrient loading. This abundance of nutrients caused by goose droppings leads to an excess growth of duckweed and watermeal. The dissolved oxygen of the lake decreases drastically as a result of these plants covering the lake’s surface, restricting oxygen exchange between the lake and the open air and preventing sunlight from reaching underwater plants that produce dissolved oxygen, thus endangering the fish population. It is crucial to remove the duckweed to reduce nutrient levels and increase the dissolved oxygen in the lake

Aten, Camryn

Kurinsky, Max

Quan, Kyle

English

Loyola eCommons

Swan Lake Remediation and Resource Recovery SL(𝑹)𝟑Engineering Science Capstone Design ProjectMax Kurinsky | Camryn Aten | Kyle QuanSponsor: Brookfield Zoo Faculty Advisor: Dr. Gajan Sivandran MethodsNutrient Data AnalysisThe Brookfield Zoo first began removing duckweed biomass from Swan Lake in the summer of2019. System improvements in 2020 resulted in large reductions in nutrient concentrations.By increasing the amount of duckweed biomass removed from the lake, the nutrientconcentration will decrease, and the duckweed growth will become self-limiting due to lack ofnutrients. Comparing month to month nutrient concentrations from 2019 and 2020 showsignificant decrease in nitrogen concentrations once the active removal of duckweed began.Design ProcessNumerous decision-making tools were utilized when brainstorming potential designs for animproved skimming system, providing justifications for specific design choices at each stage.The team implemented the morph matrix, design criteria and justifications, Pugh Matrices,and failure modes and effects analysis to reach the ultimate skimmer design.The result of this decision-making process is the eventual design comprised of the activecollection system attached to a small boat, omni-directional intake with an intermittent wiperto prevent clogging, angled layer screen tower to separate the biomass from the lake water,gravity slide to transport duckweed between locations, and in-place composting of duckweedand watermeal for resource recovery and reuse.Prototyping and TestingModels of various design aspects were developed in SOLIDWORKS, prototype models werebuilt using available materials, and calculations were conducted to determine how to bestscale down the skimmer system for off-site testing. Additionally, a risk analysis was performedon significant modes of failure and new controls were created to minimize risk and failure.Collection Method: Active collection system attached to a boatThe collection method was simulated by calculating the amount and frequency of duckweedharvesting from Swan Lake in order to allow the plant life to self-limit its growth. UsingMATLAB, a script was developed to theoretically determine how duckweed could be used as asponge to absorb nutrients from the water that led to its growth.Intake: Omni-directional intake with intermittent wiperThe team calculated specifications for a scaled down pump, purchasing a smaller pump to usefor simulations and prototyping. A triple-plate schematic was conceived to improve skimmingcapabilities and prevent clogging. Using nuts and bolts and laser-cutting acrylic, the scaled-down pump was outfitted with the new intake design and tested in an inflatable pool withfloating pieces of debris to simulate duckweed.Filter: Angled Layer Screen TowerUsing two sheets of different sized mesh and stainless-steel framing bars, a prototype multi-layered screen tower was made to filter the duckweed out from the lake water. While thecurrent prototype holds two screens, it can be improved to manage three or four screens ofsuccessive mesh size from coarse to fine. A flow diffuser was also constructed to distributethe flow across the full area of the screen and reduce its velocity.Transport: Gravity Slide and Wheelbarrow ContainerThe angled screens and wheelbarrow containers beside the screen tower would be used totransport the duckweed between locations. Ideally, the resource recovery site would not befar from the source of collection, so hauling the wheelbarrow to the site should not be toolabor-intensive. The layers are angled to 45 degrees, so the screens become self-cleaning, andthe system becomes more autonomous as the wheelbarrows have a large capacity.Resource Recovery and Reuse: In-Place CompostingThe proposed method of resource recovery and reuse for the harvested duckweed is in-placecomposting. This involves air flow through and over a stagnant pile of biomass which wouldbe mixed with carbon sources, like woodchips and dry leaves, to balance the nitrogen-to-carbon ratio for more efficient composting.ResultsFinal DesignBuilding prototypes and conducting tests for proof-of-concept shed a light on some minorlogistical issues. Obstacles like how and where to test were solved by constructing a scaled-down prototype to test on-campus for proof-of-concept. After testing the prototype in akiddie pool, the current pump in use was outfitted with the same intake structure and testedon-site at the zoo. Another challenge was the growing season of duckweed. Since the plantdid not bloom during the time this project was conducted, materials such as Styrofoam,frozen vegetables, leaves, and old dried duckweed were used as proxies for the actual plant.Proposed Resource Recovery and ReuseThe proposed plan of in-place composting for harvested duckweed could be an entire projecton its own. The team’s proposal involves the construction of a greenhouse-type structure thatinvolves aeration tubes with blowers and biofilters based on the zoo’s old composting facility.The team has taken the compost manual from the previous facility and updated andshortened it to accommodate for duckweed and reduced equipment and labor requirementfor the proposed plan. A potentially expensive undertaking, the idea can also be simplified tojust a roof over the pile of biomass but could require more manual labor to ensure that thereis enough airflow and no pungent odors that can be emitted during the composting process.AcknowledgementsChicago Zoological Society and Brookfield Zoo• John Kanzia, Environmental Quality Manager• Dr. Tom Meehan, VP of Veterinary Services• Ron May, Director of Facilities Management• Melissa Lewkowich, VP of Risk & Facilities Management• Dave Derk, Lead Life Support/Water QualityLUC Faculty• Dr. Gajan Sivandran, Assistant Clinical Professor• Dr. Gail Baura, Director of Engineering Science andProfessorInternational Lemna Association• Tamra Fakhoorian, Founder• Paul Fourounjian, PresidentFamily and FriendsIntroductionBackgroundBrookfield Zoo (BFZ), managed by the Chicago Zoological Society (CZS), is home to over 450different species of animals on more than 200 acres of land, providing a family-friendlyatmosphere for education and adventure to people throughout the Midwest. The mission ofCZS is to inspire conservation leadership by people and communities with wildlife and nature.One attraction found at BFZ is Swan Lake. Swan Lake is a 4-acre lake that is home to geese,ducks, turtles, and swans and has a peaceful nature trail around its perimeter.What is Duckweed?• Scientific name: lemnoideae minor• World’s smallest flowering plant• Grows on the surface of water, grows wide rather than deep• Capable of doubling its biomass in 24 hours under ideal conditions• Requires sun exposure, eutrophic water conditions, and stagnant water to thrive• Blooms from May to October in Illinois• Can grow to be about 2-5mm long and 1.5-3.5mm wide• Prevents oxygen exchange, therefore decreasing dissolved oxygen levels in the waterSystem DescriptionThe system used to skim duckweed from the lake’s surface is broken down to five mainsections: collection method, intake, filter, transport, and reuse. The system is made up ofmultiple components, including the intake, pump, inflow, filter, catch container, and outflow.Figure 3: System Diagram of Swan Lake skimmer system detailing the flow of debris, water, and duckweedScope of WorkPhase 1: Collection System Improvements• Analyze current system’s harvesting capabilities, storage capacity, ease of use, and long-term sustainability​• Analyze lake water quality to determine current and target water conditions​• Design an improved duckweed collection system​• Build a benchtop prototype of collection system design solution​• Conduct a lifetime cost analysis of proposed solution​• Research key water regulations which constrain the design and device operationPhase 2: Resource Recovery and Reuse• Examine the current treatment system to determine feasibility of resource recovery​• Analyze existing resource recovery technologies​• Research potential applications of recovered resources from harvested biomass• Design a resource recovery and reuse system• Conduct a lifetime cost analysis of proposed solution​• Research key water regulations which constrain the designAbstractThe Swan Lake attraction at Brookfield Zoo is continually in a eutrophic state every year as aresult of nutrient loading. This abundance of nutrients caused by goose droppings leads toan excess growth of duckweed and watermeal. The dissolved oxygen of the lake decreasesdrastically as a result of these plants covering the lake’s surface, restricting oxygen exchangebetween the lake and the open air and preventing sunlight from reaching underwater plantsthat produce dissolved oxygen, thus endangering the fish population. It is crucial to removethe duckweed in order to reduce nutrient levels and increase the dissolved oxygen in the lake.Figure 1: Current lake status in the summer when covered in duckweedFigure 2: Close-up look at texture of duckweed and watermealDiscussionLessons LearnedThis project taught the team a lot about project management, decision-making processes,and duckweed control. Documentation of files like timesheets and meeting minutes werecrucial to keeping everyone on task and accountable, as well as the importance of ensuring alldocuments are backed up to the cloud in case of emergency. A lot of different decision-making tools and strategies were used to help make quantified and justifiable choices in thedesign process.Next Steps• Expand on resource recovery and reuse to further uphold the zoo’s mission statement• Improve upon the proposed composting system• Zoo-wide composting would divert food waste, animal droppings, and more from landfills• Opportunity for patron education• Implement signage to teach visitors about proper composting, its environmental benefits, and ease of application at homeTeam SLR^3Figure 6: Bar graph depicting difference in nitrogen levels between 2019 and 2020 after skimming duckweed from Swan LakeFigure 7: Box plot depicting difference in nitrogen concentrations between 2019 and 2020 after skimming duckweed from Swan LakeFigure 4: Current filtering system involving a hose, mesh, and catch containerFigure 5: Proposed resource recovery and reuse greenhouse blueprintFigure 8: Scaled-down prototype pump and intakeFigure 9: SOLIDWORKS diagram of angled layer screen tower for filteringFigure 10: On-campus testing setup with scaled prototypesFigure 11: Full-size shredder pump with multi-plate intake attachedFigure 12: Full-size shredder pump with prototype pool-noodle buoyancy deviceFigure 14: Team members Max and Camryn working with sponsor John to modify current filtering systemFigure 13: Pathway leading up to Swan Lake and the Forest Preserve Nature Trail

Swan Lake Remediation and Resource Recovery

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Swan Lake Remediation and Resource Recovery

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