Environmental Science & Engineering Magazine 20 | Summer 2011 Wastewater Treatment Wetland systems are larger than me- chanical systems. There is a trade-off be- tween mechanical complexity and land. Wetland systems don’t need as much at- tention, or care, as their mechanical coun- terparts, are typically constructed on-site by civil contractors, and have few, if any, moving parts. Historically, the question of how to quantify performance has been left to statistics and heuristics. Recent im- provements in the engineering of wet- lands have helped increase predictability. Engineers have borrowed the biology, chemistry, and hydraulics of the waste- water industry and are employing them successfully to create treatment systems that perform like sewage plants but look more like … a field of plants. Inclusion of aeration in subsurface wetlands has greatly advanced the ability of the systems to degrade hydrocarbons and ammonia reliably. This is critical for the design of wetland systems used for spent de-icing fluids at airports, contam- inated groundwater, or tailings water from gold mines. And, by using proven B ringing a demonstration facil- ity to the doorstep of a client is always an effective way to provide proof that a treatment system works. Some vendors offer the service by trucking a test unit to the site and running the treatment system on the actual wastewater needing treatment. Treatment wetlands are in a grey area be- tween vendor technology and a consult- ing engineer’s “solution,” so no sales representative is going to show up with a wetland on a flatbed. However, there are facilities, such as the Centre for Alternative Wastewater Treatment (CAWT) at Fleming College in Lindsay, Ontario, that routinely test wetland systems. Another example is New Brunswick’s NATECH, which is currently testing the suitability of wet- land treatment technology on byproducts of the local natural gas industry. Experi- ence from these facilities has played an important role in taking the science of wetlands and using it for the engineering of projects. hydraulic and thermodynamic principles, designers are creating wetland “reactors” that are stable and more reasonably sized. These reactors increase the reliability and performance over past systems by ensur- ing proper reactor kinetics and complete use of the wetland, with minimal short- circuiting. Dr. Jim Higgins of Stantec, an early leader in treatment wetlands, piloted a number of systems at the University of Guelph’s Campus d’Alfred. The work was carried out to support development of kinetic variables that can be used to scale up systems from pilot to full scale. For example, Buffalo Niagara Inter- national Airport decided to pilot-test an aerated wetland to examine the rate at which de-icing fluid in cold stormwater could be degraded. The only way to go forward with confidence in this case was to build a model, put it in a walk-in freezer, and give it a test run. The results more than proved out the concept and were ultimately used to size the system now being operated at the airport. Engineering treatment wetlands for various wastewater streams By Mark O. Liner
Wetland systems are larger than me-chanical systems. There is a trade-off be-tween mechanical complexity and land.Wetland systems don’t need as much at-tention, or care, as their mechanical coun-terparts, are typically constructed on-siteby civil contractors, and have few, if any,moving parts. Historically, the question ofhow to quantify performance has beenleft to statistics and heuristics. Recent im-provements in the engineering of wet-lands have helped increase predictability.
Engineers have borrowed the biology,chemistry, and hydraulics of the waste-water industry and are employing themsuccessfully to create treatment systemsthat perform like sewage plants but lookmore like … a field of plants.
Inclusion of aeration in subsurfacewetlands has greatly advanced the abilityof the systems to degrade hydrocarbonsand ammonia reliably. This is critical forthe design of wetland systems used forspent de-icing fluids at airports, contam-inated groundwater, or tailings waterfrom gold mines. And, by using proven
Bringing a demonstration facil-ity to the doorstep of a clientis always an effective way toprovide proof that a treatment
system works. Some vendors offer theservice by trucking a test unit to the siteand running the treatment system on theactual wastewater needing treatment.Treatment wetlands are in a grey area be-tween vendor technology and a consult-ing engineer’s “solution,” so no salesrepresentative is going to show up with awetland on a flatbed.
However, there are facilities, such asthe Centre for Alternative WastewaterTreatment (CAWT) at Fleming Collegein Lindsay, Ontario, that routinely testwetland systems. Another example isNew Brunswick’s NATECH, which iscurrently testing the suitability of wet-land treatment technology on byproductsof the local natural gas industry. Experi-ence from these facilities has played animportant role in taking the science ofwetlands and using it for the engineeringof projects.
hydraulic and thermodynamic principles,designers are creating wetland “reactors”that are stable and more reasonably sized.These reactors increase the reliability andperformance over past systems by ensur-ing proper reactor kinetics and completeuse of the wetland, with minimal short-circuiting.
Dr. Jim Higgins of Stantec, an earlyleader in treatment wetlands, piloted anumber of systems at the University ofGuelph’s Campus d’Alfred. The workwas carried out to support developmentof kinetic variables that can be used toscale up systems from pilot to full scale.
For example, Buffalo Niagara Inter-national Airport decided to pilot-test anaerated wetland to examine the rate atwhich de-icing fluid in cold stormwatercould be degraded. The only way to goforward with confidence in this case wasto build a model, put it in a walk-infreezer, and give it a test run. The resultsmore than proved out the concept andwere ultimately used to size the systemnow being operated at the airport.
Engineering treatment wetlands for various wastewater streams By Mark O. Liner
Summer 2011 | 21www.esemag.com
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At Fleming College’s CAWT, Dr. Brent Wootton, directorand senior scientist, leads a team of researchers who study in-novative forms of wastewater treatment. The centre has carriedout extensive research on constructed wetlands and alternativeforms of wastewater treatment technology, such as anaerobicbioreactors for metal removal, and floating wetlands for use instormwater ponds. The CAWT has state-of-the-art facilities, in-cluding six outdoor research rest cells for wetland studies, 20ponds, an indoor greenhouse research facility, climate-con-trolled environmental chamber, and a fully equipped analyticallaboratory. 1. Airport de-icing glycol. Buffalo Airport uses over 200,000gallons of glycol-based product for aircraft and pavement de-icing annually. Spent de-icing compounds are collected withinthe airport’s stormwater collection system and require treatmentprior to discharge. To evaluate the ability of an aerated gravelbed to treat the stormwater on-site, a treatability study was con-ducted on a pilot-scale treatment system at Campus d’Alfred.
Results from the testing demonstrated 95% treatment andwere used as a basis for sizing the full-scale 10,000 pounds-BOD5/d treatment system. Then Naturally Wallace Consulting(NWC) was selected to take the pilot results to full-scale design.2. Gold-mine tailings. A remote gold mine in South Americawas in need of a low O&M system to treat ammonia from thecyanide-laden water in the tailings pond. Over 16,000 m3/dayof water required treatment prior to discharge to the adjacent
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river. A treatability test was conducted todetermine the rates of ammonia removaland to support the sizing of the wetlandsystem.
Testing was done in three phases. Inthe initial phase, artificial leachate wasformulated and tested in a wetland reac-tor located at Campus d’Alfred. Duringthe second phase of testing, actual waterfrom the site was shipped to the labora-tory for testing in the same reactor. Dur-ing the final phase of testing, a reactorwas constructed and tested on-site. Re-sults from the testing demonstrated suc-cessful removal of ammonia, with noinhibition of nitrification. 3. Refinery wastes. A pilot scale sub-surface vertical-flow wetland was con-structed at the former BP refinery inCasper, Wyoming, to determine degrada-tion rates for chlorinated organics. In par-ticular, the water required treatment forbenzene, toluene, ethylbenzene, andxylenes in cold weather.
The four-cell pilot system, operated in2002, provided insight into the value ofutilizing aeration within the wetland sys-tem to expedite the rate of treatment. The
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Cells at Haliburton hatchery being planted by students.
value of a mulch cover for bed insulationwas also investigated. Treatment ratesfrom the pilot work were used to design afull-scale system capable of treating upto 11,400 m3/d of gasoline-contaminatedgroundwater. The full-scale system,which was designed by NWC, achievedcompliance levels within one week ofstartup. 4. Aquaculture. Sedimentation andscreening are primarily used for solids re-moval in flow-through aquaculture facili-ties. These physical treatment methodsremove settleable solids and particulate-bound nutrients from the wastewater. Butthey do not treat the dissolved fractionssuch as total ammonia nitrogen, phos-phate and biochemical oxygen demand(BOD5), that can harm the receivingaquatic environment.
A constructed wetland was installedafter a septic tank at the Haliburton High-lands Outdoors Association in Halibur-ton, Ontario, which operates a 300m3/dayflow-through salmonid hatchery. Inten-sive monitoring examined the ability of asubsurface flow constructed wetland to
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Haliburton wetland one year after planting.continued overleaf...
treat the concentrated wastewater flowthat is produced during daily vacuumingof the hatchery’s raceways. The wetlandwas operated for a year as a saturated hor-izontal flow system and has just beenswitched to a partially unsaturated verti-cal flow system for comparison purposes.
The saturated horizontal flow config-uration successfully treated concentratedwastewater even in extreme cold condi-tions. It is anticipated the unsaturated ver-tical flow configuration will increase
treatment performance. 5. College wastewater. An integratedtreatment system, which combines an en-gineered wetland and PhosphexTM tech-nologies (EW-Phosphex), was installed tostudy treatment efficacy of college waste-water. The system configuration con-sisted of a conventional septic system,followed by a horizontal wetland, then bya forced aeration engineered wetland cell,and ending in a Phosphex polishing unit.The Phosphex polishing unit contained
Wastewater Treatment
steel slag intended for removal of phos-phorus and pathogens.
The integrated system was monitoredin the winter of 2010 to determine treat-ment efficiency, including removal ofphosphorus, ammonia, nitrate, BOD5, totalcoliform, E. coli, metals, metalloids andpharmaceutical compounds. Most of thecontaminants monitored were effectivelyremoved by the treatment system. Ammo-nia removal was as high as 79%, whilephosphate, BOD5, total coliform and E.coli were greater than 99%. Pharmaceuti-cal removal ranged as high as 98%.
Treatment wetlands are now beingused over a wide spectrum of applica-tions. Their success depends greatly onthe front-end pilot work and the peopleand companies doing it. Pushing scienceto the limits, the pilots allow full-scaleengineering of wetland projects. And, allthis work can be done at a number ofCanadian facilities, without having to puta wetland on the back of a truck.
Mark O. Liner is with Naturally Wallace Consulting. E-mail:
