REVIEW ARTICLES Filter Media for Nutrient Removal in Natural Systems and Built Environments: I—Previous Trends and Perspectives Ni-Bin Chang,* Fahim Hossain, and Marty Wanielista Department of Civil, Environmental, and Construction Engineering, University of Central Florida, Orlando, Florida. Received: December 9, 2010 Accepted in revised form: July 6, 2010 Abstract High nitrogen and phosphorus concentrations in stormwater runoff, contaminated groundwater, landfill leachate, and domestic and industrial wastewater effluents have aggravated groundwater and surface water contamination and hindered the potential of water reuse. Elevated nutrient levels in groundwater and surface water systems may cause public health problems and may impair or destroy environmentally sensitive eco- system habitats. Multiple pollutants with cotreatment strategies have not yet been fully developed. Design philosophy is evolving to fit versatile application needs with the most cost-effective way to ensure environ- mental compliance. These nutrients can actually be reduced or even removed to a large extent by using a filter or sorption media mixture throughout the applications of low-impact development and best management prac- tices. The objective of this critical and thorough literature review was to provide a comprehensive realization of the use of sorption media mixtures for nutrient removal in a number of major environmental engineering disciplines. Classification of the disciplinary applications at a practical level provides some viewpoints of the trends and perspectives along this endeavor in the nexus of materials science, sustainable engineering, and green infrastructure. Key words: sorption media; nutrient removal; environmental remediation; green materials; green engineering Introduction M uch of environmental management in the past few decades focused on point-source pollution of industrial and municipal effluent. Not until very recent years, compa- rable effort was made to restrict the input of nitrogen (N) and phosphorus (P) from dispersed or nonpoint sources such as agricultural and urban runoff. Within these dispersed or nonpoint sources, stormwater runoff is just one possible source of nitrogen; others include septic tanks and land-based application of reclaimed wastewater or fertilizer, which can even elevate nitrate and nitrite concentrations in many aquifer systems. For example, although residents in towns and cities are served by centralized wastewater treatment facilities, >25 million homes, or 25% of the U.S. population, still use on-site wastewater treatment systems to meet their wastewater treatment and disposal needs (USEPA, 2003). To provide a more specific example, *2.5 million on-site wastewater treatment systems are currently permitted in the State of Florida alone. Because of widespread septic tank failure, an- thropogenic inputs of nonpoint pollutants, particularly N and P, have accumulated dramatically in the groundwater aqui- fer. As a consequence, it has been shown that nitrate con- centrations have increased in many Upper Floridian aquifer springs since the 1950s. Phelps (2004) reported that nitrate concentrations ranged from <0.02 to 12 mg/L, with a median of 1.2 mg/L, for 56 Upper Floridian aquifer wells sampled in Marion County during 2000–2001. Besides, nitrate concen- trations have exceeded 10 mg/L in recent years at some springs in Lake, Marion, Orange, Seminole, and Volusia Counties, according to Phelps et al. (2006) and the St. Johns River Water Management District (SJRWMD, 2008). Increas- ing trends in nitrate concentration were documented in Vo- lusia County springs, such as DeLeon and Gemini Springs (Phelps et al., 2006) and Blue Spring (SJRWMD, 2008). Thus, violation of environmental compliance of the maximum contaminant level for nitrate in drinking water, which was set at 10 mg/L nitrate-nitrogen (NO 3 -N) and 1 mg/L nitrite- nitrogen (NO 2 -N) by USEPA (1988), became an acute envi- ronmental issue. Hence, how to sustain the quality of sources of potable water with respect to high nutrient concentrations has long been a challenge in environmental engineering. Nutrient pollution is the common threat that links an array of problems from stormwater to groundwater, wastewater, and drinking water all over the world. These nutrient species have direct and indirect effects on human health and the aquatic ecosystem. To deal with this issue, environmental *Corresponding author: Department of Civil, Environmental, and Construction Engineering, University of Central Florida, 4000 Cen- tral Florida Blvd., Orlando, FL 32816. Phone: 407-823-1375; E-mail: [email protected]ENVIRONMENTAL ENGINEERING SCIENCE Volume 27, Number 9, 2010 ª Mary Ann Liebert, Inc. DOI: 10.1089/ees.2009.0415 689
Transcript
REVIEW ARTICLES
Filter Media for Nutrient Removal in Natural Systemsand Built Environments: I—Previous Trends and Perspectives
Ni-Bin Chang,* Fahim Hossain, and Marty Wanielista
Department of Civil, Environmental, and Construction Engineering, University of Central Florida, Orlando, Florida.
Received: December 9, 2010 Accepted in revised form: July 6, 2010
Abstract
High nitrogen and phosphorus concentrations in stormwater runoff, contaminated groundwater, landfillleachate, and domestic and industrial wastewater effluents have aggravated groundwater and surface watercontamination and hindered the potential of water reuse. Elevated nutrient levels in groundwater and surfacewater systems may cause public health problems and may impair or destroy environmentally sensitive eco-system habitats. Multiple pollutants with cotreatment strategies have not yet been fully developed. Designphilosophy is evolving to fit versatile application needs with the most cost-effective way to ensure environ-mental compliance. These nutrients can actually be reduced or even removed to a large extent by using a filter orsorption media mixture throughout the applications of low-impact development and best management prac-tices. The objective of this critical and thorough literature review was to provide a comprehensive realization ofthe use of sorption media mixtures for nutrient removal in a number of major environmental engineeringdisciplines. Classification of the disciplinary applications at a practical level provides some viewpoints of thetrends and perspectives along this endeavor in the nexus of materials science, sustainable engineering, and greeninfrastructure.
Key words: sorption media; nutrient removal; environmental remediation; green materials; green engineering
Introduction
Much of environmental management in the past fewdecades focused on point-source pollution of industrial
and municipal effluent. Not until very recent years, compa-rable effort was made to restrict the input of nitrogen (N) andphosphorus (P) from dispersed or nonpoint sources such asagricultural and urban runoff. Within these dispersed ornonpoint sources, stormwater runoff is just one possiblesource of nitrogen; others include septic tanks and land-basedapplication of reclaimed wastewater or fertilizer, which caneven elevate nitrate and nitrite concentrations in many aquifersystems. For example, although residents in towns and citiesare served by centralized wastewater treatment facilities, >25million homes, or 25% of the U.S. population, still use on-sitewastewater treatment systems to meet their wastewatertreatment and disposal needs (USEPA, 2003). To provide amore specific example, *2.5 million on-site wastewatertreatment systems are currently permitted in the State ofFlorida alone. Because of widespread septic tank failure, an-thropogenic inputs of nonpoint pollutants, particularly N and
P, have accumulated dramatically in the groundwater aqui-fer. As a consequence, it has been shown that nitrate con-centrations have increased in many Upper Floridian aquifersprings since the 1950s. Phelps (2004) reported that nitrateconcentrations ranged from <0.02 to 12 mg/L, with a medianof 1.2 mg/L, for 56 Upper Floridian aquifer wells sampled inMarion County during 2000–2001. Besides, nitrate concen-trations have exceeded 10 mg/L in recent years at somesprings in Lake, Marion, Orange, Seminole, and VolusiaCounties, according to Phelps et al. (2006) and the St. JohnsRiver Water Management District (SJRWMD, 2008). Increas-ing trends in nitrate concentration were documented in Vo-lusia County springs, such as DeLeon and Gemini Springs(Phelps et al., 2006) and Blue Spring (SJRWMD, 2008). Thus,violation of environmental compliance of the maximumcontaminant level for nitrate in drinking water, which was setat 10 mg/L nitrate-nitrogen (NO3-N) and 1 mg/L nitrite-nitrogen (NO2-N) by USEPA (1988), became an acute envi-ronmental issue. Hence, how to sustain the quality of sourcesof potable water with respect to high nutrient concentrationshas long been a challenge in environmental engineering.
Nutrient pollution is the common threat that links an arrayof problems from stormwater to groundwater, wastewater,and drinking water all over the world. These nutrient specieshave direct and indirect effects on human health and theaquatic ecosystem. To deal with this issue, environmental
*Corresponding author: Department of Civil, Environmental, andConstruction Engineering, University of Central Florida, 4000 Cen-tral Florida Blvd., Orlando, FL 32816. Phone: 407-823-1375; E-mail:[email protected]
ENVIRONMENTAL ENGINEERING SCIENCEVolume 27, Number 9, 2010ª Mary Ann Liebert, Inc.DOI: 10.1089/ees.2009.0415
689
engineers oftentimes integrate physical, chemical, and bio-logical treatment methods in a complex regulatory frame-work to control and remediate the corresponding pollutionimpacts. It is an emerging field that promotes water treatmentefficiencies and effectiveness, creating a new dimension ofmaterial design and synthesis for green infrastructure in en-vironmental engineering science. In fact, engineered, func-tionalized, and natural sorption media can be used to treatstormwater runoff, wastewater effluents, groundwater flows,landfill leachates, and sources of drinking water for nutrientremoval via both physicochemical and microbiological pro-cesses. This approach for stormwater and wastewater treat-ment has ‘‘green’’ implications because of the inclusion ofrecycled materials as part of the material mixture, promotingtreatment efficiencies and effectiveness. The improvement ofsuch filter materials that may remove particular types of nu-trient pollutants has not yet been fully studied, although somelaboratory and field works have been completed.
Removal of ammonia, nitrite, nitrate, and phosphorus canbe achieved collectively or independently using sawdust(Kim et al., 2000; Gan et al., 2004; Schipper et al., 2005), tirecrumb (Shin et al., 1999; Lisi et al., 2004; Smith et al., 2008), sand(Harris et al., 1996; DeBusk et al., 1997; Clark et al., 2001; Birchet al., 2005; Forbes et al., 2005; Gungor and Unlu, 2005; Hsiehand Davis, 2005; Seelsaen et al., 2006), clay (Gisvold et al., 2000;Galvez et al., 2003), zeolite (Clark et al., 2001; Li, 2003; AEC,2005; Birch et al., 2005; Seelsaen et al., 2006), sulfur (Zhang,2002; Ray et al., 2006), limestone (Kim et al., 2000; Zhang, 2002;Sengupta and Ergas, 2006), etc., which are deemed as multi-functional materials applicable to natural systems and builtenvironments, improving both physicochemical and micro-biological processes.
The adsorption, absorption, ion exchange, and precipita-tion processes are actually intertwined with the overallphysicochemical process when removing nutrient via so-called ‘‘green sorption media.’’ Pollutants removed by theadsorption process in green sorption media may subse-quently desorb. If there are organic sources in the environ-ment, hydrolysis converts particulate organic N to solubleorganic N, and ammonification in turn releases ammonia intothe water bodies. Ammonia may be sorbed by clay in bior-etention filters filled with sorption media. However, nitrate,which is quite soluble, may be sorbed first and then leachedfrom the clay during subsequent storm events, rejuvenatingthe sorptive capacity for subsequently incoming nutrients. Inaddition to ammonification, important biochemical transfor-mation processes include nitrification and denitrification.They result in the transformation of nitrogen between am-monia, nitrite, and nitrate forms via oxidation and reductionreactions in microbiological processes. Nitrification is a mi-crobiologically mediated process that occurs under aerobicconditions, resulting in the formation of nitrate, whereas de-nitrification is also a microbiologically mediated process,but occurs under anaerobic (oxygen depleted) conditions,resulting in the formation of gaseous forms of nitrogen. Inreduction–oxidation chemistry, nitrification is a process inwhich ammonium is oxidized and denitrification is a processin which nitrate is reduced. Denitrification also requires thepresence of an electron donor, which may commonly includeorganic carbon, iron, manganese, or sulfur, to bring aboutthe reduction. Without these electron donors, denitrification isinfeasible even in anaerobic environments. Although these
physicochemical and microbiological processes have beenwell studied, the following critical questions have not beenfully answered in the literature: (1) What are the underlyingintegrated processes and their function, effectiveness, andlongevity associated with different mixtures of sorption me-dia? (2) How such systems are designed, installed, main-tained, controlled, and replaced for various nutrient controlgoals? (3) What methods are available for the comparison ofcost-effectiveness of the performance of green sorption mediain engineering processes?
The objective of this thorough literature review was toprovide a comprehensive realization of the use of sorptionmedia mixtures for nutrient removal in a number of majorenvironmental engineering disciplines (e.g., stormwatertreatment, groundwater remediation, wastewater treatment,and drinking water treatment) (Harris et al., 1996; DeBusket al., 1997; Kim et al., 2000; Clark et al., 2001; Gan et al., 2004;Birch et al., 2005; Forbes et al., 2005; Gungor and Unlu, 2005;Hsieh and Davis, 2005; Schipper et al., 2005; Seelsaen et al.,2006). The removal efficiency of a variety of systems withdifferent materials, design ideas, and associated environ-mental benefits are identified and summarized based on bothfunctional and chronological aspects. Key media characteris-tics with application potentials are discussed based on theresults with several selected recipes for the purpose of dem-onstration. This leads to examine some of the aforementionedkey questions in regard to assessing an integration of theplanning, design, siting, installation, maintenance, and man-agement functions as a companion paper, to aid in futuredesign work of green engineering infrastructure holistically.
Review of State-of-the-Art Environmental Technologiesfor Nutrient Removal
Agricultural and urban runoff contains pollutants includ-ing nutrients, sediment, animal wastes, salts, and pesticides.Many best management practices (BMPs) that have beenproved effective can be used to control runoff and reduce theerosion and transport of sediment from urban settings andagricultural fields. For agricultural fields, these practices in-clude conservation tillage, contour strip-cropping, terraces,filter strips, sediment retention ponds, and grade stabilizationstructures where sorption media may be deployed at strategicpoints to remove the nutrients. As for urban structural BMPs,such as infiltration devices, ponds, filters, and constructedwetlands, a variety of arrangements may be designed toaccommodate various sorption media applications. Evennonstructural BMPs and low-impact development (LID)practices, such as rain gardens, bioswales, and permeablepavements, may be included for the applications of varioussorption media.
Treating contaminated stormwater through either or bothphysicochemical or microbiological principles is an integralpart of BMPs and LID when nutrient levels may be a majorconcern (Ray et al., 2006). Nutrients in stormwater can be re-moved by using physicochemical processes, such as activatedcarbon adsorption, ion exchange with synthetic resins, reverseosmosis, and electrodialysis. For example, phosphorus re-moval from stormwater may be achieved by both precipita-tion and adsorption processes. Some functionalized sorptionmedia for phosphorus removal are sand rich in Fe, Ca, ormagnesium (Mg); gravel; limestone (a sedimentary rock
690 CHANG ET AL.
largely composed of calcium carbonate [CaCO3]); shale (finegrained sedimentary rock, mostly clay minerals); lightweightaggregates; zeolite (natural mineral or artificially producedalumino silicates); pelleted clay (along or in combination withsoils); opaka (a siliceous sedimentary rock); pumice (a volca-nic rock and natural porous mineral); wollastonite (a mineralcontaining calcium and ferrous metasilicate); fly ash (a resi-due generated from the combustion of coal); blast furnace slag(BFS—a porous nonmetallic coproduct in the iron and steelindustry); alum (a hydrated aluminum potassium sulfate);goethite (a hydrous ferric oxide); hematite (a mineral form ofiron(III) oxide [Fe2O3]); dolomite (a sedimentary carbonaterock or mineral composed of calcium magnesium carbonate[CaMg(CO3)2]); and calcite (a carbonate mineral) (Korkusuzet al., 2007). Mixtures of these materials as an integral part ofthe green sorption media would be very promising. Yet theleaching property of those materials is also of critical concernin environmental management.
Bioinfiltration, which is becoming one of the most fre-quently used stormwater management tools in urbanizedwatersheds, may be designed to facilitate microbiologicalprocesses with different filter media. These BMPs would becost-effective when distributed over a site and incorporatedinto the stormwater collection system as part of the corner-stone of LID designs such as rain garden, bioinfiltrationswales, bioinfiltration pond, and infiltration traffic island.Within the context of bioinfiltration, two important processesthat result in the transformation of ammonia to nitrogen gasare nitrification by autotrophic bacteria and denitrification byeither autotrophic or heterotrophic bacteria. For denitrifica-tion to occur, there is a need to ensure (1) the presence ofnitrate and nitrite, which are the final products of nitrificationand serve as the electron acceptor in denitrification, (2) theabsence of dissolved oxygen (DO), (3) a facultative bacterialmass to use nitrate instead of oxygen as the electron acceptor,and (4) the presence of a suitable electron donor, such as thecarbonaceous energy source for denitrification, which caneither be internal (e.g., sawdust in sorption media, organicmaterial present in wastewater) or external (methanol addedto the treatment stage of denitrification).
Filter media can act as a harmless internal carbon sourceand supporting element for microbial colony development inany of the above BMPs and LID designs. However, additionaltreatment of the effluent may be required for those chemicals.The ultimate removal of N and P can be considered as part ofthe natural N and P cycles. Instead of relying on sorptionmedia, however, some biological nutrient reduction waste-water treatment processes embedded in wastewater treat-ment plants are intended to remove nutrients by the followingsimilar principles: mainly (1) the five-stage Bardenpho bio-logical wastewater treatment system, which was developedfor removing carbon, nitrogen, and phosphorus simulta-neously; and (2) the anaerobic ammonia oxidation (ANA-MMOX) process. The former is a biological heterotrophicprocess, whereas the latter is a biological autotrophic processin which ammonia is converted to nitrogen gas in the presenceof nitrite under anoxic conditions using special microbes. InANAMMOX, nitrite acts as an electron acceptor and no ex-ternal carbon source is needed for denitrification as the bac-teria are autotrophs (WEF et al., 2005). The ANAMMOXprocess is known to be active at temperatures between 68Cand 438C and in the pH range of 6.7–8.3 (optimum is 8) (WEF
et al., 2005). Under optimum conditions, the maximumspecific ammonium consumption rate is 99.00 mg NH4
þ/gprotein/min (WEF et al., 2005).
Phosphorus can also be removed by phosphorus-accumulating organisms in a biological treatment processwith an aerobic stage. These phosphorus-accumulating or-ganisms can accumulate an excess of phosphorus as poly-phosphates in their cells. The system performance is generallygood at a DO concentration of *1.0 mg/L and at pH >6.5.The system should have enough Mg, Ca, and K. Generally,municipal wastewaters have enough cations such as these. Asystem designed for nitrification cannot support biologicalphosphorus removal because of the presence of nitrate in thesystem. Hence, a denitrification system should be includedin a separate chamber when biological phosphorus removal isan issue. In an anaerobic stage, the stored phosphorus isgenerally released (WEF et al., 2005).
Although nitrification and denitrification are popular forstormwater and wastewater treatments, they are also beingused for drinking water treatment in Europe and elsewhere.Riverbank filtration (RBF) is an environmentally sustainableand cost-effective water treatment technology, which hasbeen used for centuries to remove pollutants and microor-ganisms from surface water (Tufenkji et al., 2002). The hy-draulic and hydrochemical processes of the RBF techniquealso follow essential physicochemical and microbiologicalprinciples. Understanding the mass balance of the catchmentarea based on transient river stages and recharge, geologicalfactors, and spatial changes in the water chemistry is requiredto determine the quantity of bank filtrate that could be in thenexus of the sorption media. Groundwater and landfillleachate treatment processes are similar to stormwater andwastewater treatment processes, respectively.
In regard to nitrogen removal, the higher surface area ofclay in natural soil might be able to provide more contact areafor the solid to absorb and more space for the bacterial colonyto develop. Most filter media may improve solid–liquid con-tact with higher surface area, prevent channeling with a betterparticle distribution, and provide a better ion exchange ca-pacity to support absorption/adsorption, a better retainingcapability for adsorbed nutrient, and more surface area for thebacterial colony to develop. Thus, filter media can supportboth physical and biological processes simultaneously. Inregard to phosphorus removal, a number of different tech-nologies are applicable, including (1) chemical precipitation,(2) biological treatment, (3) crystallization, (4) ion exchange,(5) magnetic separation, (6) adsorption/absorption, (7) ter-tiary filtration, and (8) sludge treatment (Lazaridis, 2003). Acombination of differing technologies is critical for promotingcollective removal of several pollutants.
Nitrogen and phosphorus species present in the afore-mentioned processes can appear in different forms in waterbodies. The different nutrient forms are defined and sum-marized in Appendix.
Stormwater treatment by sorption media
Before 1995, much work tried to remove nutrients pri-marily with the sand filter method. For this reason, three maintypes of sand filters were developed: (1) the Washington D.C.sand filter method, (2) the Delaware sand filter design, and (3)the Austin sand filter (USEPA, 1999). The removal efficiency
FILTER MEDIA FOR NUTRIENT REMOVAL: PREVIOUS TRENDS AND PERSPECTIVES 691
of the Delaware sand filter is solids 70.2%, total phosphorus(TP) 71.1%, NH3-N 6.7%, and total Kjeldahl nitrogen (TKN)59.9% (Bell et al., 1995). These filter methods gave promisingresults but could not remove all nutrients. Faced with thissituation, some researchers began investigating new conceptsto remove all nutrient species. Sorption media were found tobe a very good means for nutrient removal from water bodies.Table 1 summarizes the use of sorption media to treatstormwater.
Richman (1997) found that compost had good removal of90% solids, 85% oil and greases (O/G), and 82%–98% heavymetals by adsorption. DeBusk et al. (1997) used sand (withquartz), fresh organic (peat) soil, crushed lime rock (2.50 cmnominal size), and wollastonite to remove TP, copper (Cu),nickel (Ni), and cadmium (Cd) from stormwater. They foundthat wallastonite (essentially calcium inosilicate [CaSiO3]) hadvery good removal efficiency for their targeted contaminants.Wallastonite could remove about 87.8% P, 97.7% Cd, 81.4%Cu, and 80.3% Ni by adsorption. On the other hand, limerock,peat, and sand could remove 41.4%, 44%, and 41.4% of P,respectively, in the stormwater runoff. It was concluded thatwallastonite is very effective in phosphorus removal becauseit contains calcium and ferrous ions (Debusk et al., 1997).Calcium and ferrous ions can remove phosphorus by pre-cipitation or adsorption.
Kim et al. (2000) used different kinds of filter media, such asalfalfa, leaf mulch compost, newspaper, sawdust, wheatstraw, and wood chips, for biological removal of nitrate fromstormwater runoff. Alfalfa, newspaper, and compost weregrouped in one experiment and sawdust, wheat straw, andwood chips were in the other. The particle size of the media isshown in Table 1. A total of eight columns (40 cm long, 6.4 cminner diameter) were used. Among them, two columns wereused as controls, using only washed silica sand. All columnswere operated at a temperature of 228C� 28C. The columnswere seeded by secondary effluent sample and those seededmaterials were run for 2 days. The authors found that alfalfaand newspaper had 100% nitrate removal efficiency, butmulch compost had only 60%. They also found that sawdust,wheat straw, and wood chips had good removal efficiency(>95%), but wood chips showed consistently better perfor-mance than sawdust for nitrate removal. It was concludedthat all of these were electron donors and good carbon sourcesfor promoting denitrification. They suggested that increasingthe hydraulic retention time (HRT) may result in better re-moval. They also found that soil could only remove 7%–10%of nitrate because of its anionic form (Kim et al., 2000). Nitrateremoval is performed by other processes in combination withbiological processes. If only the biological processes wereoccurring, different media should provide different removalefficiencies. This might be a combined effect of adsorption andbiological process.
Clark et al. (2001) conducted experiments to improve thequality of stormwater runoff by using activated carbon, peatmoss, compost, and sand in aerobic and anaerobic conditions.They suggested that sorption media might not be capable ofretaining the sorbed materials under anaerobic conditions(Clark et al., 2001). There might be several reasons such as pHof the system, bonding between solids and adsorbed materi-als, and competition between ions present in the liquid phasefor desorption, which can be influenced by the retention timeand amount of media. If desorption only occurs under the
anaerobic condition, there should not be any leachate fromlandfills. Tufenkji et al. (2002) used the RBF method to removepathogenic microbes from surface water. The RBF method isalso very effective for the removal of natural organic matter(OM—dissolved and particulate humic and nonhumic or-ganic substances), odorous compounds (e.g., geosmin), fra-grance compounds (e.g., menthol, limonene, and a-terpineol),and aromatic hydrocarbons. The RBF removes the pollutantsby sorption, precipitation, redox reactions, complexation withOM, microbial degradation, and dilution. The success of RBFdepends on raw water quality, characteristics of the bedsediments, and retention time. So each site should be con-sidered separately, and success at one site will not alwaysindicate that it will be helpful for other sites. It is also men-tioned that the EPA is emphasizing bank filtration for theremoval of Cryptosporidium. The Cryptosporidium oocysts (4–6 mm) and Giardia cysts (9–12 mm) can be removed by inter-ception (i.e., the microbes will encounter a collector grainbecause of its size and moving path) and gravitational sedi-mentation (i.e., the microbes will settle on a collector grainbecause of gravitational force) (Tufenkji et al., 2002). The ef-fectiveness of RBF for nutrient removal was not assessed. Ifthe surrounding soil has clay with mineral content, it shouldbe an effective process for phosphorus removal. Soil can alsosupport the growth of nitrifiers and so it should also be ef-fective for the removal of ammonium and nitrite. But it maynot work for nitrate removal as it is known that soil particleshave little affinity for nitrate. The RBF process and sorptionmedia can be used together. In a bank filtration, filter mediacan be placed around the well to help to remove nutrients.Tshabalala (2002) also tried to remove pesticides with ligno-cellulosic materials as the media, which removed about 82%of dichlobenil, 92% of chlorothalonil, and 96% of chlorpyrifosby adsorption.
Boving and Zhang (2004) used aspen wood (Populus tre-mula) fibers to remove aqueous phase polynuclear aromatichydrocarbons (PAH) such as naphthalene (NP), pyrene, an-thracene, and fluorene from stormwater runoff in a columnstudy. The ultimate removal of anthracene was 60%, pyrenewas 89%, and fluorene was 36%. NP was poorly attractedby the wood fibers. The results implied that the sorption ofPAH by aspen wood was related to the hydrophobicity andmolecular weight of PAH. The authors also observed somedesorption phenomena, but desorption was slower than ad-sorption. The sorption rate slowed over time and smallerparticles had a greater sorption capability. Hsieh and Davis(2005) carried out experiments on urban stormwater runoff in18 columns filled with different media mixtures composed ofmulch, soil, and sand. Mulch was very effective at removingnitrate, much more than sand (i.e., about 43% of nitrate wasremoved by a mulch and sand mixture, but sand alone couldremove about 11% nitrate). However, mulch could not re-move ammonium or TP (only 4% TP removed), the reasonsfor which were not explained by the authors. For all mediamixtures tested, ammonium removal was between 2% and26% and nitrate removal was 1%–43%. They concluded thatsoils with higher silt/clay contents, higher cation (Mg/Ca/K)contents, more OM, and greater cation exchange capacitymight be very effective in nutrient removal and that coarsemedia might not be able to retain the nutrient in repetitiveloading because of the small surface area available. Good TPremoval (*41%–48%) was observed by three types of sandy
1 Sandy coastal soil Harris et al. (1996)2 Compost O/G, heavy metals Maple and elm leaf compost Richman (1997)3 Peat Cu, Cd, Ni DeBusk et al. (1997)
WollastoniteLimerockSand with quartz
4 Alfalfa D< 4 mm Kim et al. (2000)Leaf mulch compost D< 2 mmSawdust D< 2 mmWheat straw D< 4 mmWood chips D< 2 mmNewspaper D (average)< 4 mmSulfur Large particles 2–2.36 mm
and small particles0.6–1.18 mm
Limestone D¼ 0.6–1.18 mm5 Crushed piping materials Organics Li et al. (2000)6 Iron sulfide Tesoriero et al. (2000)7 Peat Cu, Fe, Pb, Zn Clark et al. (2001)
of 51% cellulose,26% hemicellulose,21% lignin, and 1% ash
Boving and Zhang (2004)
10 Lignocellulosic material Basically pine bark chips Tshabalala (2002)11 Clay Cd, Pb, Ni Lazaridis (2003)12 Zeolites Birch et al. (2005)13 Opoka Microorganisms Braun-Howland (2003)14 Waste medium density
fiberboard sawdustGan et al. (2004)
15 Mulch Lead, TSS, O/G Hsieh and Davis (2005)Soil SLSand Sand
17 Allophane AEC (2005)ChitinPumice Iron (18.2%), aluminum (13.7%),
calcium (12.7%),magnesium (7.3%),and other
Bentonite 4%–8% CaCO3
Steel slagLime stoneZeolites
18 Hard wood Mulch Cu, Cd, Cr, Zn, Pb,DCB, NP, FA, BP
Silver maple, Norway maple,red oak, and cherry mulch;size 4,760mm
Ray et al. (2006)
19 Wood fibers Zn, Cu D¼ 4 mm Seelsaen et al. (2006)SandZeolitesGlass D¼ 4 mmAshCompost
20 Iron sulfide Baeseman et al. (2006)21 Metallic iron D¼ 0.006–0.01 mm;
surface area 0.31 m2/gHuang et al. (2006)
Clinoptilolite Fe D¼ 0.18–4 mm
BP, benzopyrene; D, diameter of the media; DCB, dichlorobenzene; FA, fluoranthene; NP, naphthalene; O/G, oil and grease; SL, sandyloam; TSS, total suspended solids.
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0%T
P,
76.9
5%C
u,
94.4
0%C
d,
and
77.6
7%N
i3
Su
lfu
rN
itri
fica
tio
n/
den
itri
fica
tio
nN
ot
rep
ort
edK
imet
al.
(200
0)A
lfal
fa10
0%n
itra
te(i
nit
ial
con
cen
trat
ion
2.00
mg
N/
L)
Lea
fm
ulc
hco
mp
ost
60%
nit
rate
(in
itia
lco
nce
ntr
atio
n2.
00m
gN
/L
)N
ewsp
aper
100%
nit
rate
(in
itia
lco
nce
ntr
atio
n2.
0m
gN
/L
)S
awd
ust
>95
%n
itra
te(i
nit
ial
con
cen
trat
ion
2.00
mg
N/
L)
Wh
eat
stra
w>
95%
nit
rate
(in
itia
lco
nce
ntr
atio
n2.
00m
gN
/L
)W
oo
dch
ips
>95
%n
itra
te(i
nit
ial
con
cen
trat
ion
2.00
mg
N/
L)
4L
ign
oce
llu
losi
cm
ater
ials
Ad
sorp
tio
n82
%d
ich
lob
enil
(in
itia
lco
nce
ntr
atio
n0.
04m
g/
L,
for
all
case
s)T
shab
alal
a(2
002)
92%
chlo
roth
alo
nil
96%
chlo
rpy
rifo
s5
Asp
enw
oo
dfi
ber
sA
dso
rpti
on
60%
anth
race
ne
(in
itia
lco
nce
ntr
atio
n0.
05m
g/
L)
Bo
vin
gan
dZ
han
g(2
004)
89%
py
ren
e(i
nit
ial
con
cen
trat
ion
0.05
mg
/L
)36
%fl
uo
rin
e(i
nit
ial
con
cen
trat
ion
0.05
mg
/L
)6
100%
san
dA
dso
rpti
on
96%
TS
S,9
6%O
/G
,98%
lead
,85%
TP
,11%
nit
rate
,an
d8%
amm
on
ia(i
nit
ial
ph
osp
ho
rus
con
cen
trat
ion
3m
gP
/L
,n
itra
teco
nce
ntr
atio
n2
mg
N/
L,
amm
on
ium
con
cen
trat
ion
2m
gN
/L
,m
oto
ro
il20
mg
/L
,fo
ral
lca
ses)
Hsi
ehan
dD
avis
(200
5)
100%
san
d96
%T
SS
,96
%O
/G
,96
%le
ad,
10%
TP
,1%
nit
rate
,an
d15
%am
mo
nia
2%m
ulc
h,
93%
soil
,5%
san
d29
%T
SS
,96
%O
/G
,98
%le
ad,
47%
TP
,1%
nit
rate
,an
d6%
amm
on
ia2%
mu
lch
,93
%so
il,
5%sa
nd
88%
TS
S,
96%
O/
G,
98%
lead
,41
%T
P,
14%
nit
rate
,an
d24
%am
mo
nia
2%m
ulc
h,
93%
soil
,5.
00%
san
d91
%T
SS
,96
%O
/G
,98
%le
ad,
48%
TP
,8%
nit
rate
,an
d16
%am
mo
nia
91%
mu
lch
,9%
san
d86
%T
SS
,96
%O
/G
,75
%le
ad,
4%T
P,
43%
nit
rate
,an
d16
%am
mo
nia
100%
san
d96
%O
/G
,66
%le
ad,
84%
TP
,13
%n
itra
te,
and
5%am
mo
nia
3%m
ulc
h,
97%
san
d96
%T
SS
,96
%O
/G
,98
%le
ad,
61%
TP
,9%
nit
rate
,an
d9%
amm
on
ia
694
2%m
ulc
h,
21%
soil
,77
%sa
nd
66%
TS
S,
96%
O/
G,
98%
lead
,47
%T
P,
3%n
itra
te,
and
2%am
mo
nia
8%m
ulc
h,
26%
soil
,66
%sa
nd
94%
TS
S,
96%
O/
G,
98%
lead
,50
%T
P,
4%n
itra
te,
and
7%am
mo
nia
6%m
ulc
h,
32%
soil
,62
%sa
nd
93%
TS
S,
96%
O/
G,
98%
lead
,39
%T
P,
4%n
itra
te,
and
7%am
mo
nia
24%
soil
,76
%sa
nd
93%
TS
S,
96%
O/
G,
98%
lead
,39
%T
P,
2%n
itra
te,
and
5%am
mo
nia
3%m
ulc
h,
43%
soil
,54
%sa
nd
96%
TS
S,
96%
O/
G,
98%
lead
,83
%T
P,
13%
nit
rate
,an
d26
%am
mo
nia
3%m
ulc
h,
24%
soil
,73
%sa
nd
96%
TS
S,
96%
O/
G,
98%
lead
,57
%T
P,
24%
nit
rate
,an
d17
%am
mo
nia
11%
mu
lch
,19
%so
il,
70%
san
d96
%T
SS
,96
%O
/G
,98
%le
ad,
54%
TP
,27
%n
itra
te,
and
20%
amm
on
ia2%
mu
lch
,17
%so
il,
81%
san
d96
%T
SS
,96
%O
/G
,97
%le
ad,
24%
TP
,6%
nit
rate
,an
d11
%am
mo
nia
2%m
ulc
h,
72%
soil
,26
%sa
nd
92%
TS
S,
96%
O/
G,
98%
lead
,72
%T
P,
9%n
itra
te,
and
19%
amm
on
ia2.
%m
ulc
h,
49%
soil
,49
%sa
nd
92%
TS
S,
96%
O/
G,
98%
lead
,71
%T
P,
9%n
itra
te,
and
19%
amm
on
ia7
1:6
mix
ture
of
zeo
lite
(hav
ing
clin
op
tilo
lite
)an
dco
arse
,p
ure
qu
artz
itic
san
d
Ad
sorp
tio
n47
%–7
4%to
tal
Kje
ldah
ln
itro
gen
(in
itia
lco
nce
ntr
atio
n0.
54–1
.690
mg
/L
),33
%–4
0%T
N(i
nit
ial
con
cen
trat
ion
2.94
–2.4
5m
g/
L),
37%
–67%
TP
(in
itia
lco
nce
ntr
atio
n0.
27–0
.2m
g/
L),
49%
–81%
Cu
(in
itia
lco
nce
ntr
atio
n0.
013–
0.01
9m
g/
L),
88%
–98%
Pb
(in
itia
lco
nce
ntr
atio
n0.
03–0
.029
mg
/L
),�
1%–
77%
Zn
(in
itia
lco
nce
ntr
atio
n0.
19–0
.39
mg
/L
),10
%C
r(i
nit
ial
con
cen
trat
ion
0.00
37m
g/
L),�
213%
–38%
Fe
(in
itia
lco
nce
ntr
atio
n0.
15–
2.16
mg
/L
),20
%–8
8%T
SS
(in
itia
lco
nce
ntr
atio
n25
–17
mg
/L
)
Bir
chet
al.
(200
5)
8H
ard
wo
od
mu
lch
Ad
sorp
tio
n(2
hH
RT
)85
%C
u,7
5%C
d,2
1%C
r,90
%P
b,6
0%Z
n,6
3%D
CB
,63%
NP
,89%
FA
,90%
BB
P,
80%
BP
(in
itia
lco
nce
ntr
atio
n:
Cu
0.99
2m
g/
L,
Cd
1.01
6m
g/
L,
Cr
0.98
9m
g/
L,
Pb
0.99
6m
g/
L,
Zn
1.07
9m
g/
L,
DC
B0.
047
mg
/L
,N
P0.
375
mg
/L
,F
A0.
418
mg
/L
,B
BP
0.4
mg
/L
,B
P0.
815
mg
/L
)
Ray
etal
.(2
006)
Ad
sorp
tio
n(4
hH
RT
)85
%C
u,8
3%C
d,2
6%C
r,85
%P
b,7
2%Z
n,7
1%D
CB
,65%
NP
,95%
FA
,95%
BB
P,
84%
BP
Ad
sorp
tio
n(7
2h
HR
T)
85%
Cu
,86
%C
d,
68%
Cr,
92%
Pb
,72
%Z
n,
100%
DC
B,
88%
NP
,93
%F
A,
77%
BB
P,
92%
BP
9F
ine
gla
ssA
dso
rpti
on
68%
Zn
(in
itia
lco
nce
ntr
atio
n27
mg
/L
,fo
ral
lca
ses)
and
40%
Cu
(in
itia
lco
nce
ntr
atio
n5
mg
/L
,fo
ral
lca
ses)
See
lsae
net
al.
(200
6)
San
d15
%Z
nan
d30
%C
uC
ou
rse
gla
ss15
%Z
nan
d28
%C
uA
sh50
%Z
nan
d97
%C
uZ
eoli
te97
%Z
nan
d50
%C
uC
om
po
st97
%Z
nan
d90
%C
uP
ack
ing
wo
od
88%
Zn
and
84%
Cu
10C
lin
op
tilo
lite
Ion
exch
ang
e10
0%F
eH
uan
get
al.
(200
6)
BB
P,
bu
tyb
enzy
lph
thal
ate;
HR
T,
hy
dra
uli
cre
ten
tio
nti
me;
TN
,to
tal
nit
rog
en;
TP
,to
tal
ph
osp
ho
rus.
695
loam soils; this was interpreted as caused by simple adsorp-tion or complex sorption/precipitation processes (Arias et al.,2001; Hsieh and Davis, 2005). All three of these soils hadsignificant fractions of sand (i.e., 66%–79%), clay (i.e., 12%–19%), and silt (i.e., 9%–15%). Across all media, TP removalwas highly variable (i.e., from 4% to 85%), which might berelated to properties of the sorption media used and the flowpattern of nutrient-laden water. As with the nitrogen con-taminants, OM enhanced TP removal (about 93% TP removal)and a good correlation between OM and TP removal wasestablished. They also tried to remove other chemicals suchas O/G, Pb, and total suspended solids with sand, whichprovided>96% removal of all targeted compounds. Differentmixtures of mulch, soil, and sand were also used to removethose compounds, all achieving noticeable removal. The au-thors suggested that total suspended solid removal at theupper layer or first stage of a bioretention system is veryimportant to protect the system from clogging. They alsoconducted an on-site evaluation of rainfall events. About>99% O/G, >94% Pb, 31% NO3-N, and >44% NH4-N wereremoved by the process (Hsieh and Davis, 2005). The lowremoval of nitrogen compounds suggests that either mulchimpedes the growth of nitrifiers or it cannot adsorb ammo-nium.
Birch et al. (2005) experimented with removing nitrogenspecies with a stormwater filtration basin (SIB) and flowthrough a filtration medium with a 1:6 mixture of zeolite (withclinoptilolite) and coarse, pure quartzitic sand. Their analysisrevealed the valuable removal capabilities of SIB. TKN removalwas about 47%–74% and total nitrogen (TN) removal wasabout 33%–40% (also some negative removal was observed).They found negative removal of NO2
� and NO3� by the sys-
tem. Sand was not effective in removing nitrate þ nitrite andthe denitrification capacity was not enough to support the re-moval system. On the other hand, nitrifiers may have beenconverting ammonia into nitrate so efficiently that the ultimatenitrate concentration in the effluent was increased, concealingthe effects of the denitrifiers. TP removal was about 37%–67%by SIB. Clinoptilolite has an affinity for ammonium and it re-moves TN and TKN in an ion exchange process. Therefore,biological processes were not solely responsible for TN andTKN removal in this study. Clinoptilolite may be acting as aninhibitor of denitrifiers by promoting a less anaerobic condi-tion. The pH of stormwater should be > 7 for the best removalof metals by the sorption media, otherwise the adsorbed metalions will be quickly released.
Analytical and Environmental Consultants (AEC, 2005)investigated locally available adsorption materials to removenutrient from surface and ground water. The materials testedwere (1) allophane (an amorphous hydrous aluminum silicateclay mineral with an affinity for NH4
þ, NO3�, and PO4
3�),which has a density of 2,000–2,200 kg/m3 and surface area of400–900 m2/g; (2) bentonite (an impure clay, mostly mont-morillonite, with an affinity for PO4
3�), which has a density of2,000–3,000 kg/m3 and cation exchange capabilities of 70–100 meq/100 g; (3) chitin (a long-chain polymer and a deriv-ative of glucose with an affinity for NH4
þ); (4) pumice (has anaffinity for NO3
� and PO43�), which has a density of 600–
800 kg/m3 and cation exchange capabilities of 5–8 meq/100 g;(5) zeolite (with an affinity for NH4
þ, NO3�, and PO4
3�),which has a density of about 1,700–2,100 kg/m3, surface areaof 145 m2/g, and cation exchange capabilities of 80–200 meq/
100 g; (6) steel slag (has affinity for PO43�); and (7) limestone.
After their investigation factoring in local availability, cost,nutrient removal capability, environmental impact, and ap-plicability, they identified allophane, zeolite, bentonite, steelslag, and limestone as the most suitable choices (AEC, 2005).These minerals can remove nutrients in an ion exchange andadsorption process.
Ray et al. (2006) used hardwood mulch to remove somemetals (Cu, Cd, Cr, Pb, and Zn) and organics (dichloroben-zene, NP, fluoranthene, butybenzylphthalate, and benzo-pyrene) from urban stormwater runoff. These researcherssuggested that (1) sorption capacity might be correlated withthe ionic radii and molecular weight of the metal and organiccontaminants, and (2) sorption by mulch varied with theconcentration and species of contaminants (Ray et al., 2006).This experiment proved that sorption media are also veryeffective in metal removal. However, metal removal is af-fected by pH: (1) metal ions will be dispersed in solutionunder acidic pH and (2) ions will engage in precipitation re-actions or adsorption under alkaline pH. Metal removal willbe completely via an adsorption or ion exchange processbecause there is little possibility that metals will be removedby biological processes.
Seelsaen et al. (2006) used fine glass, sand, coarse glass, ash,zeolite, compost, and packing wood to remove heavy metalsfrom stormwater. Huang et al. (2006) performed an experi-ment to remove nitrate with metallic iron, and ammonium(NH4
þþNH3) and ferrous ions [Fe(II)] with clinoptilolite.They reported that acidic pH (i.e., 2.0<pH< 4.5) was animportant factor for the removal of nitrate by Fe0, which wasvery active at removing nitrate within a short time (i.e., about30 min) in these conditions. The pH value and nitrate removalwere inversely related. Nitrate removal was also inverselyrelated to nitrate loading. It showed that when the nitrateloading was higher, there were insufficient iron surface sitesto attract more nitrates, and ultimately, the removal efficiencywas hampered. They also observed the appearance of am-monium when the nitrate was reducing in the redox sense.The removal of ammonium and Fe(II) by clinoptilolite wasobserved to depend on both pH and the F/N ratio (i.e., Fe(II)to [NH4
þ]þ [NH3]). Nitrate has a tendency to produce am-monium in the presence of Fe, which can be removed byclinoptilolite. Cliniptilolite is already well known for its am-monium removal capability, but it is too costly to use as asorption media in a small-scale facility.
The preceding discussion was presented in chronologicalorder to provide an overall picture of recent advancements inmixed media water treatment. Table 2 further summarizes thegeneral success of the sorption media mentioned for removingvarious pollutants, especially nutrients, in the stormwaterrunoff under specified conditions.
Wastewater treatment by sorption media
Nutrient removal from wastewater is accomplishedthrough adsorption and biological processes. The filter me-dium acts as a growth chamber for the microorganisms thatare inoculated in the reactors. However, the removal of nu-trient may not be accelerated by these dual effects. As themicroorganisms are attached to the surface of the media, theyreduce the surface area available for adsorption. Adsorptionmay be suppressed by biological processes in a sorption
696 CHANG ET AL.
media system if too much bacteria grow there. Thus, thegrowth of microorganisms has competing effects on watertreatment by the system. Table 3 summarizes the sorptionmedia that have been applied to wastewater treatment.
Shin et al. (1999) found that tire chips could adsorb volatileorganic carbon from wastewater by a biological process andproved that it would be a good filter media (Shin et al., 1999).Han et al. (2001) used polyurethane-based porous media in anup-flow (UF) biological aerated filter (BAF) to treat waste-water at 188C–228C. The BAF consisted of a sludge drain,wastewater and air inlets, sampling ports, and effluent outlet.The porous media (about 70% of the reactor volume was fil-led) was used for the growth of autotrophic nitrifiers anddenitrifiers. The nitrification reached nearly 100% and sig-nificant nitrogen loss was observed from the BAF. The het-erotrophic denitrifiers were not responsible for this lossbecause there was no total organic carbon available in thesystem that could serve as electron donors. Nitrosomonas were
capable of denitrification using hydrogen and ammonium aselectron donors in the absence of oxygen, but this process wasvery slow and could not solely account for the denitrificationin the BAF. The authors ultimately concluded that the deni-trification was completed by autotrophic nitrifiers and theANAMMOX reaction in an anaerobic zone (Han et al., 2001).The maintenance of this kind of system and the growth of theANAMMOX bacteria were critical.
Zhang (2002) performed an experiment to remove nitratefrom wastewater by sulfur in a limestone autotrophic deni-trification pond reactor. He assessed the effects of three vari-ables on nitrate removal: (1) aerobic (mixed) and anoxic(unmixed) conditions, (2) the effect of temperature, and (3) theinfluence of chemical oxygen demand (COD)/N ratios in thefeed. All the reactors contained sediment from a rural cattlepond and the sulfur and limestone were not covered by sed-iment. There were four types of reactors: (1) a reactor con-taining granular sulfur and limestone on sediment, (2) same
10 Masonry sand Bulk density of masonry sand is 1,670 kg/m3;porosity of masonry sand is 0.3
Forbes et al. (2005)
Expanded shale Expanded shale (SiO2 62.06%, Al2O3 15.86%,Fe2O3 5.8%, CaO 1.44%, MgO 1.68%);bulk density of expanded shale is 728 kg/m3;porosity of expanded shale is 0.59
11 OSP Powder form, 28% calcium, average particlesize 200 mm, surface area 237 m2/g
Namasivayamet al. (2005)
12 Limestone D¼ 2.38–4.76 mm Sengupta andErgas (2006)Oyster shell
Marble chips Mg(OH)2 and CaCO3
13 Soy meal hull Direct and acid dye D< 0.125 mm Arami et al. (2006)14 Clinoptilolite Hedstrom (2006)
Blast furnace slag Composed of melilite, merwinite,anorthite, and gehlenite
15 Perlite Joseph andRodier (1995)
16 Clinoptilolite D¼ 0.30–4.76 mm, density 0.88 g/cm3 Smith et al. (2008)Expanded clay D¼ 0.40–5 mm, density 0.656 g/cm3
Tire crumb D¼ 0.30–5 mm, density 0.4 g/cm3
Sulfur D¼ 2.00–5 mm, density 1.23 g/cm3
Crushed oyster shell D¼ 3–15 mm, density 1.31 g/cm3
Utelite (expanded shale) D¼ 0.4–4.5 mm, density 0.864 g/cm3
FILTER MEDIA FOR NUTRIENT REMOVAL: PREVIOUS TRENDS AND PERSPECTIVES 697
as reactor 1 but seeded with sulfur-based autotrophic deni-trifers (i.e., Thiobacillus denitrificans), (3) a control case withonly the sediment, and (4) same as reactor 1 but with 1/3 lesssulfur and limestone by volume. He observed that the nitrateremoval was about 90%–100% with alkalinity control andmixing and about 80%–85% without it; the control case hadvery low but highly variable nitrate removal. Reactor 2 wasnot used for testing the influence of temperature. Nitrate re-moval was found to increase with increasing temperature inreactors 1 and 4, but to decrease with increasing temperaturein the control case (reactor 3). The COD/N ratio had a stronginfluence on nitrate removal. It was found that if the COD/Nratio was<1.2, the nitrate removal efficiency was 85%. On theother hand, if the ratio was >3, the removal was only 30%.High concentrations of organics can promote rapid growth ofheterotrophic bacteria in the system, which, in turn, consumesthe organic carbon. This may affect the activity of autotrophicbacteria, ultimately hampering the nitrate removal.
Espino-Valdes et al. (2003) conducted experiments to re-move nitrogen species from wastewater by a reactor-basedbiological process. Their system was an UF bioreactor fol-lowed by a clarifier. This reactor was used as a nitrificationchamber and the air required was supplied from the bottom ofthe reactor. The first clarifier was connected with a second UFbioreactor followed by another clarifier. The UF bioreactorwas used as a denitrification chamber and methanol wassupplied from the bottom of the reactor. They used sand tosupport the growth of biomass and the reactor was inoculatedwith secondary sludge. About 81.3% of ammonia-nitrogenwas removed at 26.68C and 94.8% at 32.28C in 2.7 and 17.4 h,respectively. The final concentration was 1.20 mg/L. Nitrateand nitrite removal were also very significant in the reactor.Nitrate þ nitrite removal of about 85.6% at 28.78C and 95.3%at 33.38C was observed in 2 and 4 h, respectively. The finalconcentration was 1.6 mg/L. Nitrification and denitrificationbiomass concentrations were 365 mg volatile suspended soil(VSS)/L and 1,461 mg VSS/L. Both the effluent ammonia andnitrate concentration were within the range acceptable inMexico. The aquifer recharge standard limits for ammonia andnitrate-nitrogen are 5 and 10 mg/L, respectively, in Mexico.
Galvez et al. (2003) tried using a submerged fixed film re-actor to remove nitrogen from urban wastewater. There weretwo columns in the system. The first column was a down-flownitrification reactor running under aerobic conditions and thesecond one was an UF anoxic denitrification reactor. Air wasadded in the first column and methanol was added in thesecond one, both from the bottom. The reactor was filled withclay schists from recycled construction materials and thestudy emphasized the influence of hydraulic loading andthe air flow rate on nitrogen removal. The authors foundthat low methanol concentrations reduced the nitrate re-moval efficiency and there was a good correlation betweennitrogen removal and methanol concentration. The amount ofnitrification can be reduced by direct competition betweenheterotrophic and autotrophic bacteria for substrate. Thenitrification in the system can be enhanced by decreasing theorganic loadings. The researchers concluded that the systemcould achieve about 95% denitrification and about 75% CODwas removed (Galvez et al., 2003). When the denitrifiers weregiven less methanol to consume over time, the nitrate removaldecreased but, again, high organic loading can hamper thenitrogen removal process in the system.
Rodgers and Zhan (2004) used a vertically moving biofilmsystem to remove nitrogen species from wastewater by bio-logical processes. This small biological nutrient reductionprocess was operated at 118C and consisted of six polypro-pylene tanks (with dimensions of 0.40�0.40�0.60 m) in series,six biofilm modules (one for each tank, with a specific surfacearea of 6.48 m2), a wastewater feed mixing tank, three peri-staltic pumps (one for the feed mixing tank, one for tap water,and the third for recirculation of nitrified wastewater), and apneumatic system complete with limit switches and delaycontrollers. The delay controllers could lift and lower thebiofilm modules. The module speed was 0.2 m/s and the re-circulation ratio was about 2.54. The first two tanks wereanoxic for denitrification and filled with cubes of corrugatedPVC sheets with a surface area of 150 m2/m3, and the otherfour tanks were aerobic for nitrification, with a surface area ofmedia of 240 m2/m3. The flow rate was about 0.397 m3/day.The researchers found an overall COD removal of 94% withan initial concentration of 485 mg/L, TN removal of 82% with75 mg/L initial concentration, and NO3-N removal of 95%with 9.2 mg/L initial concentration in the system, without anyclogging. The denitrification rate was about 120.8 g/m3/dayand 6.5 g/m3/day in tanks 1 and 2, respectively. They con-cluded that nitrification might be inhibited by competition forDO between nitrifiers and heterotrophs (Rodgers and Zhan,2004). Module speed was a very critical issue in operating thesystem. The modules had to be sufficiently slow so that theyhave sufficient contact time with the liquid. If the modules aretoo fast, the biofilm layers may be washed out.
Gungor and Unlu (2005) conducted nitrate and nitrite re-moval from wastewater in a laboratory column experimentwith three types of soil. They used sandy clay loam, loamysand, and sandy loam and found significant nitrate and nitriteremoval (>90%) in all three soils. This experiment was veryimportant for nitrate removal by soil. It proved that some soilshave an affinity for nitrate but that this will vary from onekind of soil to another. Forbes et al. (2005) used lightweightexpanded shale and masonry sand for the removal of phos-phorus from secondarily treated municipal effluent. Thesystem contained three cells filled with expanded shale andthree cells filled with masonry sand. They found that sandwas a poor candidate for retaining phosphorus and expandedshale had greater removal efficiency because of its largersurface area. The chemical composition (i.e., Fe þ Al) andexcellent hydraulic efficiency of shale were also responsiblefor the removal of phosphorus (Forbes et al., 2005). Sand canremove phosphorus by adsorption if it is rich in clay and siltparticles or rich in minerals. Both of these may have beenabsent in the masonry sand tested. Namasivayam et al. (2005)used oyster shell powder (OSP) to remove phosphorus fromwastewater at 248C. They found that raw oyster shells had noaffinity for phosphorus, but about 45% of phosphorus in batchmode and 85% of phosphorus in continuous mode was re-moved by OSP. They concluded that phosphorus was re-moved by sorption as amorphous calcium phosphate on theOSP surface and then slowly transformed into the more stablehydroxyapatite (Namasivayam et al., 2005).
Sengupta and Ergas (2006) experimented to remove nitratefrom wastewater by using sulfur, marble chips, limestone,and oyster shell. In one system there were sulfur, marble, andlimestone and the other system contained sulfur, marble, andoyster shell. Their experiment revealed the significant poten-
698 CHANG ET AL.
tial of using those solids as sorption media. They found thatoyster shell (almost 98% CaCO3) could remove 80% nitrate,whereas limestone removed only 56% nitrate. The pH andalkalinity were higher for oyster shell relative to limestoneand marble chips. Oyster shell was very efficient at reducingnitrite accumulation and DO did not inhibit denitrificationwhen oyster shell was used as the filter media. It was provedthat the system containing oyster shell was followingthe sulfur-oxidizing denitrification pathway. Sulfur-oxidizingmicroorganisms generally follow aerobic autotrophic deni-trification. A first-order denitrification was observed (about0.028/h) in this study. It can be concluded that oyster shell ismuch more effective than limestone or marble chips for re-moving nitrate through sulfur-oxidizing microorganisms.Oyster shell is also a good candidate for controlling pH, whichis a limiting factor for denitrification (Sengupta and Ergas,2006).
Arami et al. (2006) studied the adsorption of direct (i.e.,DR80 and DR81) and acid (i.e., AB92 and AR14) dyes by soymeal hull (SMH) to simulate the nutrients. The surface area ofSMH was 0.7623 m2/g. In all cases, the higher the initial dyeconcentration, the lower was the dye adsorption. They ob-served that, with an initial concentration of 50 mg/L and a pHof 2, the removal efficiencies of DR80, DR81, AR14, and AB92were 98%, 97%, 86%, and 98%, respectively, after 120 min. Themaximum monolayer adsorption capacity was 178.57 mg/gfor DR80, 120.48 mg/g for DR81, 114.94 mg/g for AB92, and109.89 mg/g for AB14. The adsorption capacity of SMH in-creased when the pH decreased. SMH has various functionalgroups such as amines, hydroxyl, and carbonyl groups. Atlower pH (i.e., 2), significantly high electrostatic attractionmight exist between the positively charged surface of SMHand negatively charged dyes. At higher pH (i.e., 10), SMHadsorbed less dyes because of higher negative charge on SMHsurface. It was found that at pH 10, significant electrostaticrepulsion existed between SMH surface and dyes. They foundthat pH and dye removal were inversely related. It was con-cluded that electrostatic attraction and the organic propertiesand structure of dye molecules might influence the adsorptionprocess (Arami et al., 2006).
Smith et al. (2008) experimented on passive (i.e., not de-pending on pumping and external aeration) nitrogen removalfrom septic tank wastewater in Florida. They used three filtersystems with the same structure. Each system had two col-umns: one was vertical and filled with stage 1 media (i.e.,saturated condition, aerobic), and the other one was hori-zontal and filled with stage 2 media (i.e., unsaturated condi-tion, anoxic). The stage 1 media were clinoptilolite (has ionexchange properties), expanded clay (increases the retentiontime and has adsorption properties), or tire crumb (has ad-sorption properties) and stage 2 media were elemental sulfur(an electron donor medium for denitrifiers), crushed oystershell (used as an alkalinity source), or utelite (expanded shalewith anion exchange properties). In system 1, the verticalcolumn (1A) was filled with clinoptilolite and the horizontalcolumn (2A) was filled with 75% sulfur and 25% oyster shell.In system 2, the vertical column (1B) was filled with expandedclay and the horizontal one (2B) with 60% sulfur, 20% oystershell, and 20% expanded shale. In the third system, the ver-tical column (1C) was filled with tire crumb and the horizontalone (2C) was filled with 45% sulfur, 15% oyster shell, and 40%expanded shale. The researchers found strong removal of
nitrogen species. TN removal was about 97.1% for 1A þ 2A,97.7% for 1B þ 2B, and 33% for 1C þ 2C. Total inorganicnitrogen (TIN) removal was about 99.8% for 1A þ 2A, 98.1%for 1B þ 2B, and 34.4% for 1C þ 2C. TN removal was about50.6% for 1A, 26.1% for 1B, and 13% for 1C. NH3-N removalwas about 99.9% for 1A, 99.9% for 1B, and 60.5% for 1C. Thedenitrification process in the system was also good, with thelowest denitrification rate in column 2C. They proposed twopossible explanations for this result: (1) as the amount ofsulfur was lowest in this column, there were not enoughelectron donors for denitrification, and (2) harmful leach-ates from the tire crumb may have been present in this col-umn. The DO concentration was 7.21 mg/L on average instage 1 columns and 0.34 mg/L on average in stage 2 columns(Smith et al., 2008). The above discussion summarizes themost recent development in this field. Table 4 details thegeneral success of using sorption media to remove variouspollutants, especially nutrients, from wastewater under theconditions shown.
Groundwater treatment by sorption media
Groundwater is the most expensive and difficult type ofwater body to treat. Most of the existing research has beendone in shallow groundwater. The main problem in workingwith groundwater is that water may change its flow pathwayduring the test. Benson and Lee (2001) used waste foundrysand to treat groundwater. Table 5 summarizes the sorptionmedia used to treat groundwater.
Schipper et al. (2005) performed an experiment with asawdust denitrification wall to remove nitrate in shallowgroundwater with an HRT of 5 days. They filled a trench(about 35 m long, 1.5 m deep, and 1.5 m wide) with Montereypine sawdust (Pinus radiata D. Don; 30% by volume) mixedwith the excavated soil. The authors suggested that the nitrateconcentration was the limiting factor to denitrification, ratherthan carbon, because the denitrification rate increased whenadditional nitrate was added to the soil. Because of the highernitrate level, the denitrifiers could grow easily and subse-quently increased the denitrification rate. No nitrate accu-mulation was observed in the soil OM and nitrate was nottransformed into ammonia. They found a nitrate-N removalrate of 1.4 g N/m3 of wall per day, which was about 97.2%of nitrate removal (Schipper et al., 2005).
Landfill leachate treatment by sorption media
Groundwater can also be contaminated by landfill leachate.Some protective measures are taken during landfill con-struction, but the condition of the system may deterioratewith time and start to pollute the groundwater. For this rea-son, it is sometimes necessary to treat the landfill leachate.Table 6 summarizes the use of sorption media in the treatmentof landfill leachate.
Jokela et al. (2002) conducted an experiment to eliminatenitrogen from municipal landfill leachate by a biologicalprocess. Nitrification was tested in three types of reactors: (1)UF nitrification filter with crushed brick as a filter medium, (2)down-flow nitrification filter with wood chips, and (3) nitri-fication in suspended carrier biofilm process (SCBP). All thenitrification reactors were inoculated by nitrifying activatedsludge collected from a sewage treatment plant. In the UF
FILTER MEDIA FOR NUTRIENT REMOVAL: PREVIOUS TRENDS AND PERSPECTIVES 699
Ta
bl
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Nu
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ffi
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Tr
ea
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t
No.
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Rem
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efer
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1T
ire
chip
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OC
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(199
9)2
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lyu
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bas
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oro
us
med
iaN
itri
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n/
den
itri
fica
tio
n10
0%am
mo
nia
and
nit
rite
(in
itia
lco
nce
ntr
atio
n50
mg
/m
3),
amm
on
ia-l
oad
ing
rate
1.8
kg
NH
4-N
/m
3/
day
Han
etal
.(2
001)
3S
ulf
ur:
lim
esto
ne
auto
tro
ph
icd
eni-
trifi
cati
on
Den
itri
fica
tio
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chem
ical
reac
tio
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00%
nit
rate
wit
hal
kal
init
yco
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ol
and
mix
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,ab
ou
t80
%–8
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itri
tew
ith
ou
tal
kal
init
yco
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(in
itia
lco
nce
ntr
atio
n30
mg
N/
Lan
dlo
adin
gra
te1
gN
O3-N
/m
3/
day
)
Zh
ang
(200
2)
4S
and
Nit
rifi
cati
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/d
enit
rifi
cati
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81.3
%am
mo
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-nit
rog
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nit
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con
cen
trat
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22.4
mg
N/
L),
85.6
%n
itra
teþ
nit
rite
(in
itia
lco
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ntr
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mg
N/
L)
Esp
ino
-Val
des
etal
.(2
003)
5C
lay
sch
ists
Nit
rifi
cati
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/d
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den
itri
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cen
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80m
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OD
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itro
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mo
val
rate
0.64
kg
N/
m3/
day
,h
yd
rau
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load
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rate
0.71
m3/
m2/
h,
HR
T1.
6h
Gal
vez
etal
.(2
003)
6B
iofi
lmm
od
ule
sN
itri
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itri
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%T
N,
95%
NO
3-N
Ro
dg
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and
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004)
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CL
Nit
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/d
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90%
nit
rateþ
nit
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mg
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LG
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(200
5)
LS
90%
nit
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nit
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itia
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.87
mg
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L)
SL
90%
nit
rateþ
nit
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(in
itia
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.87
mg
N/
L)
8L
igh
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itri
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orb
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5)M
aso
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san
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PA
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ph
osp
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rus
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atch
mo
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85%
ph
osp
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inco
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nu
ou
sm
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cen
trat
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g/
m3)
Nam
asiv
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.(2
005)
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lech
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Ad
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alam
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56%
of
nit
rate
(in
itia
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mg
N/
L)
Oy
ster
shel
l80
%n
itra
te(i
nit
ial
con
cen
trat
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40m
gN
/L
)11
So
ym
eal
hu
llA
dso
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98%
DR
80,
97%
DR
81,
86%
AR
14,
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AB
92(i
nit
ial
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L)
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mi
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.(2
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lin
op
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Nit
rifi
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/d
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rifi
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%T
N(i
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77.4
mg
/L
,fo
ral
lca
ses)
,99
.9%
amm
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cen
trat
ion
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mg
/L
,fo
ral
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ses)
Sm
ith
etal
.(2
008)
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pan
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clay
26.1
%T
N,
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%am
mo
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b13
%T
N,
60.5
%am
mo
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Cli
no
pti
loli
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(75%
sulf
urþ
25%
oy
ster
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l)97
.1%
TN
,99.
8%T
IN(i
nit
ial
con
cen
trat
ion
56.8
mg
/L
),h
yd
rau
lic
load
ing
rate
110.
42L
/m
2/
day
Ex
pan
ded
clayþ
(60%
sulf
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ster
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lþ
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and
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dra
uli
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L/
m2/
day
Tir
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15%
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ster
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40%
exp
and
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33.%
TN
,34
.4%
TIN
,h
yd
rau
lic
load
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rate
102.
27L
/m
2/
day
CO
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700
filter, nitrification efficiency was about 60%–88% in 60 days,and after 60 days it was above 90%. COD removal efficiencyranged from 26% to 62%. In the down-flow filter, the nitrifi-cation efficiency was about 90% after 70 days and no CODremoval was detected. With SCBP, the nitrification efficiencywas 75%–99% between 112 and 196 days and COD removalwas 53%–63%. They suggested that the UF nitrification modewas more efficient because of its higher HRT. Denitrificationwas tested in a landfill waste column fed by a nitrified samplefrom the SCBP. It was concluded that leachates with highCOD might inhibit denitrification by favoring the growth ofheterotrophs over nitrifiers ( Jokela et al., 2002).
Lisi et al. (2004) tested the use of granulated tires for theremoval of nitrate. They found that 48 kg of tire crumb canremove 16.2 g of NO3-N by adsorption (Lisi et al., 2004). Sa-vage and Tyrrel (2005) used wood mulch, compost, soil,broken brick, and polystyrene packaging to remove NH3-Nand biochemical oxygen demand (BOD5) from compostleachate. They concluded that wood mulch (75% removal)and compost (55% removal) had better removal efficiencies,and polystyrene (31% removal) was the least effective at re-moving NH3-N. Similarly, for BOD5, compost had a betterremoval efficiency (i.e., about 78%) and polystyrene was theleast efficient (i.e., about 34%). The researchers found thatcompost and wood mulch had a tendency to increase thepH and concluded that specific surface area, void space,permeability, media durability and strength, and absorption/adsorption capacity might influence removal efficiency(Savage and Tyrrel, 2005).
Kietlinska and Renman (2005) applied sand, BFS, and Po-lonite� (a calcinated Opoka—a siliceous sedimentary rock) toremove nitrogen species and heavy metals from landfillleachate in a column study. Peat was mixed with each of them
in a ratio of 1:4 by volume. Total inorganic nitrogen could beremoved by sand (about 4%), Polonite (18%), and BFS (8%).Kietlinska and Renman inferred that the wollastonite in Po-lonite might be responsible for the removal of nitrogen spe-cies, as wollastonite has some preference for nitrogen species,especially ammonia. Polonite could also remove 89% Mg, 99%manganese, 93% Fe, 86% Zn, 86% zirconium (Zr), 85% barium(Ba), 67% Cu, 77% titanium (Ti), 60% yttrium (Y), and 30%cobalt (Co); BFS could remove 20% Fe, 62% Zn, 63% Zr, 31%Ba, 66% Cu, 33% Co, 19% Ni, and 16% molybdenum (Mo);and sand could remove 25% Cu and 15% Mo. Polonite mightbe removing the metals by precipitation, ion exchange, andadsorption. They concluded that pH can affect the removal ofheavy metals by Polonite, and hydroxide precipitation is re-sponsible for the high removal of metals by forming insolubleprecipitates. Table 7 shows the general success of usingsorption media to remove various pollutants, especially nu-trients, in landfill leachate under the given conditions.
Drinking water treatment by sorption media
Applications of biological processes to drinking watertreatment are common nowadays, although there is a dangeron unintentional introduction of bacterial contaminants.Disinfectant should be used to reduce possible bacterial con-tamination. However, nutrients and heavy metals can be re-moved by adsorption and ion exchange processes withsorption media. For drinking water generation, the use ofsorption media is much more attractive than biological pro-cesses. As sorption media are good supports for bacterialgrowth, they should be changed frequently when treatingdrinking water. Table 8 lists the sorption media that have beenapplied to drinking water treatment.
Crushed bricks2 Tire crumb VOC Lisi et al. (2004)3 Wood chips Savage and Tyrrel (2005)
Oversized pulverized brickPolystyrene packing
4 Peat Zn, Ni, Co, Ti, Cu, Ba Kietlinska and Renman (2005)Polonite Manufactured from a cretaceous
rock Opoka (SiO2 39.4%,CaO 42%, Al2O3 4.3%, Fe2O3 2%)
Blast furnace slag SiO2 36.2%, CaO 35%,MgO 13.4%, Al2O3 10.6%
FILTER MEDIA FOR NUTRIENT REMOVAL: PREVIOUS TRENDS AND PERSPECTIVES 701
Table 7. Nutrient Removal Efficiency of Different Sorption Media in Landfill Leachate Treatment
No. Sorption media Mechanism Removal efficiency References
1 Up-flow nitrification filterwith crushed brick as afilter medium
Nitrification/denitrification
Nitrification efficiency was about 60%–88% in 60 days, and after 60 days itwas above 90%, COD removalefficiency ranged from 26% to 62%(initial concentration 60–170 mg N/Land 230–510 mg O2/L, for all cases)
Jokela et al. (2002)
Down-flow nitrificationfilter with wood chips
Nitrification efficiency was about 90%
Nitrification in suspendedcarrier biofilm process
Nitrification efficiency was 75%–99%,COD removal was 53%–63%
2 Tire crumb Adsorption 48,000 g of tire crumb can remove 16.2 gof NO3-N
2% Mg (initial concentration 101 mg/L,for all cases), 2% S (initialconcentration 124 mg/L, for all cases),25% Cu (initial concentration0.03 mg/L, for all cases), 15% Mo(initial concentration 0.02 mg/L, for allcases), 4% TIN (initial concentration105.9 mg/L, for all cases)
Kietlinska andRenman (2005)
Blast furnace slag þ peat 89% Mg, 4% S, 99% Mn (initialconcentration 0.57 mg/L, for all cases),93% Fe (initial concentration0.61 mg/L, for all cases), 86% Zn(initial concentration 0.08 mg/L, for allcases), 86% Zr (initial concentration0.003 mg/L, for all cases), 85% Ba(initial concentration 0.19 mg/L, for allcases), 67% Cu, 77% Ti (initialconcentration 0.002 mg/L, for allcases), 60% Y (initial concentration0.001 mg/L, for all cases), 30% Co(initial concentration 0.004 mg/L, forall cases), 2% Ni (initial concentration0.02 mg/L, for all cases), 8% tin
FIG. 1. Flow chart showing the methods of nitrogen species removal in chronological order of first application.
Table 9. Nutrient Removal Efficiency of Different Sorption Media in Drinking Water Treatment
No. Sorption media Mechanism Removal efficiency References
1 Shredded newspaper Denitrification 77.78% of nitrate after 30 days and 38.9%of nitrate after 120 days (initial concentration22.58 mg N/L), nitrogen removalrate 0.73 mg N/g paper/day
Volokita et al. (1996)
2 Sulfur þ limestone (1:1) Denitrification 98% nitrate (initial concentration 27 mg N/L) Darbi et al. (2002)3 Cotton Denitrification 91.5% nitrate (initial concentration 100 mg N/L) Rocca et al. (2005)
FILTER MEDIA FOR NUTRIENT REMOVAL: PREVIOUS TRENDS AND PERSPECTIVES 703
Volokita et al. (1996) used shredded newspaper for deni-trification of drinking water in a column study. Newspaper isa good source of carbon and colony support for microbialpopulations. These authors found that the system could re-move about 77.78% of the nitrate after 30 days and 38.9% after120 days. This longer time was necessary to accommodate thegrowth of sufficient denitrifying bacteria in the system. Thestudy showed that temperature and retention time have amarked effect on cellulose-based denitrification. The retentiontime can be increased by decreasing the flow or by increasingthe length of the system. The ink on newspaper also affectedmicrobial growth in the system, but was not a limiting factor.It was observed that the highest denitrification rate occurredat temperatures of 258C–328C and with unprinted newspaper(Volokita et al., 1996).
Darbi et al. (2002) assessed sulfur and limestone for nitrateremoval through autotrophic denitrification from potable wa-ter in a batch study. In this experiment, sulfur was used as anelectron donor and limestone was used to maintain the pH. Theoptimum mixing ratio of sulfur and limestone was 1:1, yieldingabout 98% nitrate removal and minimizing sulfate productionat pH 7. Sulfate production was also decreased when the nitrateremoval was increased. The authors suggested that increasingthe retention time might result in higher removal efficiency(Darbi et al., 2002). The same researchers conducted a columntest for nitrate removal from potable water (Darbi et al., 2003).In this study, there were three UF columns filled with elementalsulfur and limestone at ratios of 1:1, 2:1, and 3:1. All the col-umns were inoculated with Thiobacillus denitrificans. With 26 hHRT, the nitrate removal was about 95%–100% and nitriteconcentrations were below 1 mg NO2-N/L in all columns. Thenitrate removal and sulfate production were highest when thesulfur-to-limestone ratio was 2:1. It was noticed that sulfate(SO4
2�) production increased with increase of both volumetricloading rate and nitrate removal. About 6 mg SO4
2� was pro-duced for 1 mg NO3-N removal (Darbi et al., 2003).
Rocca et al. (2005) used cotton-supported heterotrophicdenitrification (HD) for the removal of nitrate from drinkingwater. There were two reactors: an HD reactor followed by atrickling sand filter. Cotton (the purest form of naturally oc-curring cellulose) was used as the organic carbon source and
supporting material for the growth of denitrifiers. Nitrateremoval was about 91.5% at a system temperature of 288C.Nitrate removal decreased with increasing temperature andincreased with increasing water velocity (Rocca et al., 2005).Table 9 integrates the general success of using sorption mediato remove various pollutants, especially nutrients, in thedrinking water under some given conditions.
Figures 1 and 2 illustrate the timeline of how using sorptionmedia for nutrient removal has progressed over the past 3decades. The most intensive work was performed in recentyears. This was triggered by the acute need of a regulatoryframework for nutrient control in on-site wastewater treatment,stormwater treatment, combined sewer overflow, and LID.
Conclusions
This article describes the most important research for nu-trient removal via sorption media mixtures for stormwaterreuse, wastewater treatment, landfill leachate treatment,groundwater remediation, and drinking water treatment.Media mixtures can provide a good organic carbon source ifsawdust/compost is included. They can create excellent en-vironments for the growth of microorganisms that foster bothnitrification and denitrification at the laboratory scale. Fieldapplications focusing on the practical scale-up of nutrientremoval technologies, however, remain of critical concern.Cost-effectiveness assessment for nutrient removal will be asimportant as the consideration of sustainable development.The companion paper will address the field applications by amore elaborate way to clarify some of the application chal-lenges, perspectives, and potentials.
Author Disclosure Statement
No competing financial interests exist. The authors aregrateful for all the data and reports cited and used in thisstudy. Conclusions and opinions presented in this paper arethose of the authors, and do not necessarily represent theposition of any funding agency. Mention of commercial pro-ducts, trade names or services in the paper does not conveyendorsement, or recommendation.
Sand, peat, crushed lime rock, wollastonite
1997
Activated carbon, peat moss, compost, sand
2001
Mulch, soil, sand
2005 Zeolite, pure quartzitic
sand
Lightweight expanded shale, masonry sand
Oyster shell powder
Washington DC sand filter method 1989
Delaware sand filter 1991
FIG. 2. Flow chart showing methods of phosphorus species removal in chronological order of first application.
704 CHANG ET AL.
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Appendix: Nutrient Forms Involved in This Study
(1) Nitrogen species
� Total nitrogen (TN)¼ organic N þ ammonia N þ nitrateN þ nitrite N
� Total Kjeldahl nitrogen (TKN)¼ organic N þ ammoniaN
� Organic nitrogen¼ Filtrable organic N þ nonfiltrableorganic N
� Total inorganic nitrogen (TIN)¼ ammonia N þ nitrate Nþ nitrite N
� Total oxidized nitrogen (TON)¼ nitrate N þ nitrite N� TN¼TKN þ TON
(2) Phosphorus species
� IP¼ inorganic phosphate� OP¼ orthophosphate� CP¼ condensed phosphates (also known as metaphos-
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