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Ecological Engineering 37 (2011) 1476–1480 Contents lists available at ScienceDirect Ecological Engineering jo u r n al hom ep age: www.elsevier.com/locate/ec oleng Seasonal productivity of a periphytic algal community for biofuel feedstock generation and nutrient treatment Heather N. Sandefur, Marty D. Matlock , Thomas A. Costello Center for Agricultural and Rural Sustainability, Biological and Agricultural Engineering Department, University of Arkansas Division of Agriculture, 203 Engineering Hall, Fayetteville, AR 72701, United States a r t i c l e i n f o Article history: Received 1 July 2010 Received in revised form 28 March 2011 Accepted 10 April 2011 Available online 12 May 2011 Keywords: Algal turf scrubber Phosphorus removal a b s t r a c t Algal biomass is a promising feedstock for biofuel production. With a high lipid content and high rate of production, algae can produce more oil on less land than traditional bioenergy crops. Algal communities can also be used to remove nutrients from impacted waters. The purpose of this study was to demonstrate the ability of an algal turf scrubber (ATS) TM to facilitate the growth of periphytic algal communities for the production of biomass feedstock and the removal of nutrients from a local stream. A pilot-scale ATS was implemented in Springdale, AR, and operated over the course of a nine-month sampling period. System productivity over the nine-month operating time averaged 26 g m 2 d 1 . Total phosphorus and total nitrogen removal averaged 48% and 13%, respectively. The system showed potential for biomass generation and nutrient removal across three seasons. © 2011 Elsevier B.V. All rights reserved. 1. Introduction In recent years, algae has shown much potential as a feedstock for biofuel production (Chisti, 2007). Algal biomass offers many advantages over traditional energy crops, with 6–12 times greater annual energy production for algae than for corn or switchgrass. Algal cultivation has smaller land requirements than other crops, with a 5- to 10-fold increase in annual areal productivity over corn (Chisti, 2007; Dismukes et al., 2008). The high lipid content of algal cells make the biomass more suited for biofuel production (Bajpai and Tyagi, 2006). These lipids can constitute up to 20% of the dry weight of algal biomass, and can be used for biodiesel production (Hu et al., 2008). Algal cultivation techniques include open pond systems, pho- tobioreactors, and mesocosms (artificial streams). Open ponds involve the cultivation of suspended algae in the water column (Ugwu et al., 2007). Photobioreactors are enclosed systems and are generally used for the monoculture of microalgae, and have relatively high biomass production rates compared to other algal growth systems (Eriksen, 2008; Grobbelaar, 2000). Tubular pho- tobioreactors are considered to be the most suitable bioreactor system for commercial-scale production, but are constrained by pH fluctuations, O 2 accumulation, and decreased internal CO 2 levels. Photobioreactor scale-up is often limited, with mass production Corresponding author. Tel.: +(479) 575-2849; fax: +1 479 575-2846. E-mail address: [email protected] (M.D. Matlock). frequently relying on multiple reactor units (Eriksen, 2008). For these reasons, algal production in photobioreactor systems is often feasible only for high value algal residues. While open pond and photobioreactor systems constitute tra- ditional approaches to cultivation, mesocosm (periphytic growth) systems have also been used for the generation of algal biomass. In these systems, water is passed over an algal culture attached to some form of growth medium, simulating stream conditions at some level. Open ponds and periphytic growth systems have been shown to produce comparable biomass yields. Periphytic systems, however, are generally easier to harvest than pond sys- tems, and are less expensive to install than photobioreactors. In open ponds, the algal cells are suspended in the water column, and are difficult to remove. The attached algae in periphytic sys- tems can be harvested by mechanical means with relative ease (Hoffmann, 1998). In addition to biomass production for potential biofuel feed- stock generation, algal growth systems can also serve as tertiary treatment mechanisms for wastewater. After organic material is removed from wastewater, high concentrations of nutrients such as nitrogen and phosphorus may remain. These are the essential nutrients for algal growth, and can be removed from wastewater by algal cells (Aslan and Kapdan, 2006; Schumacher et al., 2003). Algal growth has been shown to dramatically reduce the concentrations of nitrogen and phosphorus from wastewater (Marinho-Soriano et al., 2009; Craggs, 2001), with reported phosphorus removal in excess of 90% (Hoffmann, 1998). Given the high irrigation demands of algal systems and the limited availability of freshwater resources, 0925-8574/$ see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.ecoleng.2011.04.002

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Ecological Engineering 37 (2011) 1476– 1480

Contents lists available at ScienceDirect

Ecological Engineering

jo u r n al hom ep age: www.elsev ier .com/ locate /ec oleng

easonal productivity of a periphytic algal community for biofuel feedstockeneration and nutrient treatment

eather N. Sandefur, Marty D. Matlock ∗, Thomas A. Costelloenter for Agricultural and Rural Sustainability, Biological and Agricultural Engineering Department, University of Arkansas Division of Agriculture,03 Engineering Hall, Fayetteville, AR 72701, United States

r t i c l e i n f o

rticle history:eceived 1 July 2010eceived in revised form 28 March 2011ccepted 10 April 2011

a b s t r a c t

Algal biomass is a promising feedstock for biofuel production. With a high lipid content and high rate ofproduction, algae can produce more oil on less land than traditional bioenergy crops. Algal communitiescan also be used to remove nutrients from impacted waters. The purpose of this study was to demonstrate

TM

vailable online 12 May 2011

eywords:lgal turf scrubberhosphorus removal

the ability of an algal turf scrubber (ATS) to facilitate the growth of periphytic algal communities forthe production of biomass feedstock and the removal of nutrients from a local stream. A pilot-scale ATSwas implemented in Springdale, AR, and operated over the course of a nine-month sampling period.System productivity over the nine-month operating time averaged 26 g m−2 d−1. Total phosphorus andtotal nitrogen removal averaged 48% and 13%, respectively. The system showed potential for biomassgeneration and nutrient removal across three seasons.

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. Introduction

In recent years, algae has shown much potential as a feedstockor biofuel production (Chisti, 2007). Algal biomass offers manydvantages over traditional energy crops, with 6–12 times greaternnual energy production for algae than for corn or switchgrass.lgal cultivation has smaller land requirements than other crops,ith a 5- to 10-fold increase in annual areal productivity over corn

Chisti, 2007; Dismukes et al., 2008). The high lipid content of algalells make the biomass more suited for biofuel production (Bajpaind Tyagi, 2006). These lipids can constitute up to 20% of the dryeight of algal biomass, and can be used for biodiesel production

Hu et al., 2008).Algal cultivation techniques include open pond systems, pho-

obioreactors, and mesocosms (artificial streams). Open pondsnvolve the cultivation of suspended algae in the water columnUgwu et al., 2007). Photobioreactors are enclosed systems andre generally used for the monoculture of microalgae, and haveelatively high biomass production rates compared to other algalrowth systems (Eriksen, 2008; Grobbelaar, 2000). Tubular pho-obioreactors are considered to be the most suitable bioreactor

ystem for commercial-scale production, but are constrained by pHuctuations, O2 accumulation, and decreased internal CO2 levels.hotobioreactor scale-up is often limited, with mass production

∗ Corresponding author. Tel.: +(479) 575-2849; fax: +1 479 575-2846.E-mail address: [email protected] (M.D. Matlock).

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925-8574/$ – see front matter © 2011 Elsevier B.V. All rights reserved.oi:10.1016/j.ecoleng.2011.04.002

© 2011 Elsevier B.V. All rights reserved.

requently relying on multiple reactor units (Eriksen, 2008). Forhese reasons, algal production in photobioreactor systems is ofteneasible only for high value algal residues.

While open pond and photobioreactor systems constitute tra-itional approaches to cultivation, mesocosm (periphytic growth)ystems have also been used for the generation of algal biomass.n these systems, water is passed over an algal culture attachedo some form of growth medium, simulating stream conditionst some level. Open ponds and periphytic growth systems haveeen shown to produce comparable biomass yields. Periphyticystems, however, are generally easier to harvest than pond sys-ems, and are less expensive to install than photobioreactors. Inpen ponds, the algal cells are suspended in the water column,nd are difficult to remove. The attached algae in periphytic sys-ems can be harvested by mechanical means with relative easeHoffmann, 1998).

In addition to biomass production for potential biofuel feed-tock generation, algal growth systems can also serve as tertiaryreatment mechanisms for wastewater. After organic material isemoved from wastewater, high concentrations of nutrients suchs nitrogen and phosphorus may remain. These are the essentialutrients for algal growth, and can be removed from wastewater bylgal cells (Aslan and Kapdan, 2006; Schumacher et al., 2003). Algalrowth has been shown to dramatically reduce the concentrations

f nitrogen and phosphorus from wastewater (Marinho-Sorianot al., 2009; Craggs, 2001), with reported phosphorus removal inxcess of 90% (Hoffmann, 1998). Given the high irrigation demandsf algal systems and the limited availability of freshwater resources,

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he use of wastewater for algal cultivation can be advantageousSchenk et al., 2008).

Algal turf scrubber (ATS)TM technology involves a periphyticrowth system for the cultivation of an attached algal turf. TheTS acts as a mechanism for the removal of nitrogen and phos-horus from wastewater. Algal turf scrubbers generally involvehe polyculture of macroalgae. These controlled stream mesocosmsre modeled after coastal ecosystems, utilizing the surging motionf water to increase algal productivity by breaking down diffu-ion boundary layers and increasing nutrient uptake (Adey, 1982).

hile ATS systems are traditionally used as a method of waterreatment, they are also capable of generating high biomass yieldsp to 35–60 g m−2 d−1 (Adey et al., 1993; Craggs et al., 1996a,b;raggs, 2001).

Few data have been published on the application of periphyticlgal growth technology in colder climates. The objectives of thistudy were to: (1) design and install a test bed ATS system inhe Mid-South region of the U.S. using stream water as the inflowource, (2) to measure and evaluate the potential for the system toroduce algal biomass from periphytic polyculture across seasonallimate variations, and (3) to evaluate the potential of the system toemove nitrogen and phosphorus from a stream with high nutrientoads.

. Materials and methods

The ATS system designed and installed consisted of a 90 m longy 0.3 m-wide wooden trough sealed with silicon and lined with

mm polypropylene mesh. The trough was set at a 2% slope andedded in fill-dirt for thermal protection. Stream water was deliv-red in a surging mode, with roughly 19 L discharged into therough every 15 s (see Fig. 1). The surger was a modified version ofhe discharge mechanism used by Fulhage (1997) to deliver flushater in swine housing. The ATS was an outdoor system that uti-

ized ambient sunlight and was operated continuously from Marcho November 2009. The irrigation source for the system was thepring Creek in Springdale, AR (36◦12′N/94◦10′W). The ATS intakeas located directly downstream of a wastewater treatment plant

ffluent discharge site. Historic nutrient concentrations in Springreek were high, with average total phosphorus and total nitro-en concentrations of 0.249 mg L−1 and 4.06 mg L−1, respectivelyMatlock et al., 2009).

Wetland Area

Algal Growth SurfaceWater

ReservoirSurge Device

WaterWaterReservoir

Spring Creek

ig. 1. ATS growth system. Streamwater was pumped from the Spring Creek into reservoir and surge device. The water was then surged down the flow-way andver the attached algal community. Water was collected at the flow-way outflownd discharged into an adjacent wetland.

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The desired algal community was one dominated by filamen-ous green algae that would act as a supporting structure for thelgal turf. During the system startup phase, the ATS was seededsing filamentous algae from the genus Cladophora. The algaeas taken from streams within the local watershed, tied to stones

approximately 10 cm in diameter), and then placed onto the flow-ay in 1 m intervals. After the initial seeding with filamentous

lgae, no attempt was made to control the culture beyond theurging mechanism and mechanical harvesting regime.

The ATS sampling regime consisted of weekly monitoring ofhe system biomass production and water quality. A set of multi-arameter water quality monitoring instruments (YSI, Inc.) at the

nflow and outflow of the ATS were used to continuously mon-tor pH, water temperature, specific conductivity, and dissolvedxygen concentrations, recorded in 10-min intervals during theay and night. Grab samples were taken halfway between har-ests from the system intake and outflow around mid-morning.ater samples were analyzed for total phosphorus, total nitro-

en, orthophosphate, and combined nitrate and nitrite (Greenberg,992; Houba et al., 1987; Kroon, 1993; EPA, 1997).

A 10 cm2 section of the mesh growth substrate was removednce per month for the first three months of system operation.he sample was analyzed to determine the community structuref the algal turf. The inverted microscope sedimentation chambersethod was used to visually identify the dominant algal species

Utermohl, 1958). The corresponding cell density was then calcu-ated (Wetzel and Likens, 1979; Schwarzbold, 1992).

The algal biomass from the entire system was mechanicallyarvested every 5–14 days, depending on the season, using aonsumer-model shop vacuum. The system was harvested oncelgal biomass covered the system, but before major senescing tooklace in order to maximize production. The total biomass was quan-ified from three 1 m2 areas at the upper, middle, and lower sectionsf the trough. The dry weight of the biomass at each section wasetermined by drying each sample at 105 ◦C for 24 h (Greenberg,992). The slough (detached algae) coming off the system was col-

ected continuously during system operation at the ATS outflowsing a catchment lined with a 50 �m screen. The dry weight ofhe slough was determined along with the algae samples takenrom the harvest. The total rate of production of slough coming offf entire the system was added to the biomass production rate ofhe sampling sections on the flow-way during each harvest period.he mean system production was the average of the productivity ofhe sampling sections. In addition, on August 24, 2009, the systemas harvested at alternating 3-m intervals down the flow-way toeasure the variation in growth across the entire length of the ATS.Three major system shutdowns occurred during the biomass

ampling period due to power interruptions. The first shutdown (3ays) was in early May, the second shutdown (2 days) occurred athe end of May, and the third shutdown (4 days) occurred in earlyctober. Each shutdown resulted in the loss of the system’s basallgal turf, which required a one to three week startup phase to re-stablish. The standard sampling protocol was resumed as soon asower was resupplied to the system, and operation resumed.

. Results and discussion

.1. System productivity

Average monthly productivity rates are given in Table 1. Sys-

em productivity over the nine-month monitoring period averaged6 ± 16 g m−2 d−1 dry weight. In the upper, middle, and lowerampling sections, biomass production averaged 31 ± 19 g m−2 d−1,0 ± 10 g m−2 d−1, and 26 ± 15 g m−2 d−1 dry weight, respectively.

1478 H.N. Sandefur et al. / Ecological Engineering 37 (2011) 1476– 1480

Table 1Average algal turf scrubber system productivity and inflow water temperature, bymonth with standard deviations.

Month Water temp. (◦C) Productivity(g dry weight m−2 d−1)

Average S.D. Average S.D.

March 15 2 13 7April 16 2 18 12May 19 1 12 4June 22 2 29 14July 25 2 34 20August 24 2 31 18September 18 1 26 10October 17 2 24 14

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Phylum March April May

Chlorophyta 7279 10,856 866,867Cyanophyta 3639 56,452 81,269Bacillariophyta 454,889 1,042,193 1,391,728

Table 3Average nutrient removal from the algal turf scrubber system.

Month Nutrient removal

PO4 Total phosphorus NO3−–NO2

− Total nitrogen

March 26% 9%April 2% 7%May 9% 11% −19% −5%June 28% 28% 20% 17%July 56% 72% 26% 15%August 43% 53% 10% 4%September 33% 54% 5%

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imilar average annual productivity rates were reported at otherTS systems (Craggs et al., 1996a,b; Craggs, 2001). However, theaximum productivity rates reported for other systems were

igher than the maximum biomass production rates observed inhis study, where the productivity was impacted by inclementeather and system failures. Due to the growth lag in the ini-

ial startup phase in March and April, and the losses of thelgal turf in May, the system did not operate at maximum yieldotential until early summer. In addition, Northwestern Arkansasxperienced heavy rains in May, and from August through earlyctober 2009. Each storm event corresponded to a decrease

n measured biomass production. Not including the startuperiod, the measured mean productivity for periods June–Augustnd September–November were 31 ± 18 g m−2 d−1 dry weight and3 ± 11 g m−2 d−1 dry weight, respectively.

System productivity in the fall provides some information onTS performance in colder weather. For example, the growtheriod from October 22 to 29, 2009 biomass production averaged6 g m−2 d−1 dry weight. The average daily high and low ambientir temperatures for this period were 17 ◦C and 7 ◦C, respectively,nd the average water temperature at the inflow was 15 ◦C. Sub-equent to the formal monitoring period, the ATS continued to beperated. Sustained algae growth (data not shown) was observedven during extreme cold winter periods when night-time ambi-nt air temperature declined as low as −15 ◦C. The established turf’solerance of a wide range of ambient temperatures demonstrateshe robustness of the system, and its potential for application inreas with variable climates.

In addition to repeated sampling at the upper, middle, and lowerections, the amount of variation in growth across the entire length

f the flow-way was measured. A plot of the system profile is shownn Fig. 2. Wide variations in algal growth were observed acrosshe length of the turf scrubber. Fig. 2 shows inconsistent biomass

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mounts in the first 30 m of the flow-way, with stabilization in theid-sections, and a decrease in biomass amounts in the tailwa-

ers. These trends are consistent with the growth patterns observeduring the nine-month sampling period. The variability of growth

n the upper sections was likely the result of the colonization ofhese areas by macroinvertebrates, as well as a tendency for theurging water to cause algae to detach. Because the ATS receivednputs directly from the Spring Creek, colonization of the system by

acroinvertebrates occurred in small (less than 1 m) sections alonghe trough during the summer. This was to be expected, as theeasonal distribution of grazing insect production favors the latepring and early summer months (Georgian and Wallace, 1983).he vacuum harvesting, however, prevented major biomass lossrom the macroinvertebrates by destroying the individual insectshile disrupting the cohort production intervals within the system

Georgian and Wallace, 1983).The community structure of the algal turf changed over the

ine-month operating period (see Table 2). The system was initiallyolonized by diatoms, with the phylum Bacillariophyta accountingor 94% of algal cells counted, while Chlorophyta only accounted for%. After the startup period, the incidence of green algae increasedo account for 37% of the cells. However, diatoms continued toominate the system, making up 60% of the algae. While the sys-em was seeded with green filamentous algae, diatoms were likelyntroduced from the streamwater used to irrigate the system, andheir dominance of the algal community has been reported by othertudies including reports of systems used for tertiary wastewa-er treatment (Craggs et al., 1996a,b; Craggs, 2001). Because theommunity was made up of an assemblage of unicellular algae,he biomass sloughed off of the flow-way more easily than if theommunity had been dominated by Chlorophyta. Slough mass,owever, did not account for a large portion of the solids recovered

rom the system.

.2. Water quality

The Springdale ATS also demonstrated the ability of attachedlgal communities to reduce the concentration of nitrogen andhosphorus in the system influent. Table 3 shows the removal

f total phosphorus, orthophosphate, total nitrogen and nitrate-itrite during the nine-month monitoring period. Total phosphorusoncentrations averaged 0.165 mg L−1 at the system inflow and.095 mg L−1 at the system outflow. Total nitrogen concentrations

H.N. Sandefur et al. / Ecological Engineering 37 (2011) 1476– 1480 1479

Table 4Water quality parameters at the system inflow and outflow, averaged for the 9 month period.

Parameter Inflow Outflow

Max Ave S.D. Max Ave S.D.

Temperature (◦C) 32.8 19.2 3.9 32.8 18.9 4.7Dissolved oxygen (%) 194.9 103

pH 9.9 7.6

Specific conductivity (�S/cm) 683 491.8

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7/17/20097/16/20097/15/2009 7/20/20097/19/20097/18/2009

pH

Outflow Inflow

Fig. 3. Diurnal pH data measured at the inflow and outflow of the algal turf scrubberfrom July 15 to 20, 2009.

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ig. 4. Diurnal dissolved oxygen percent saturation measured at the inflow andutflow of the algal turf scrubber from July 15 to 20, 2009.

veraged 9.20 mg L−1 and 7.56 mg L−1 at the inflow and outflow,espectively. Orthophosphate and total phosphorus removal aver-ged 36% and 48%, respectively. Nitrate–nitrite and total nitrogenemoval averaged 13% and 12%, respectively. During the month ofay nitrogen levels were shown to increase across the system. In

ddition, during October total phosphorus levels also increased.his net increase in nutrients was likely a result of algal senescenceuring the water sampling period.

Most of the phosphorus removal was in the form of soluble reac-ive phosphorus, which was similar to the phosphorus removaleported at other ATS systems and suggests that the removal washe result of both assimilation and precipitation. Phosphorus pre-ipitation has been shown to occur between pH values of 8.9 and 9.5Craggs et al., 1996a,b). Table 4 gives maximum and average pH, dis-olved oxygen, water temperature, and specific conductivity levelsver the nine-month harvesting period. Fig. 3 shows typical diurnalrends in pH recorded during the harvest period from August 19,009 through August 24, 2009. Diurnal monitoring at the Spring-ale ATS showed frequent increases in effluent pH to between 9nd 10 (see Table 4 and Fig. 3). This was likely to have drivenhosphorus precipitation with cations. The pH spikes occurredhen dissolved oxygen was elevated at mid-day (see Fig. 4), corre-

ponding presumably to high photosynthetic reaction rates, during

hich the algae were absorbing CO2 (Small and Adey, 2001). Futureesigns with increased flow-way lengths, and increased retentionimes, could lead to further cumulative CO2 uptake and increasedH—resulting in increased phosphorus precipitation.

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25.8 320.7 114.6 47.10.3 10.8 8.14 0.7

107.2 738 461.8 129.84

In addition, the dissolved oxygen levels within the system wereenerally supersaturated during peak times. The maximum dis-olved oxygen content recorded was 320.7% saturation. This waseasured in July at the peak of photosynthetic activity. Fig. 4 shows

n example of the diurnal trends in percent saturation. During theay, photosynthesis frequently drove the dissolved oxygen satu-ation above 200%. It is likely that very high DO concentrationsnhibited growth, if by no other process than by stripping out CO2rom solution, depriving algae of their carbon source during theseeriods.

. Conclusions

The purpose of this study was to evaluate the potential forn attached algal community to operate in locations with vari-ble climates to produce biomass while removing nutrients frommpacted waters. On average the ATS produced biomass at the ratef 26 ± 16 g m−2 d−1 while removing an average of 48% and 12% ofotal phosphorus and nitrogen, respectively. The pilot-scale algalurf scrubber system in Springdale, AR, shows potential for use iniomass production and the removal of nutrients, but improve-ents to the system could be made. It will be important for future

ystems to ensure constant flow, and to avoid shutdowns wheneverossible. Because of the time required to reestablish the algal turf,hutdowns proved to be devastating to the temporal productivityf this system. In addition, heavy rainfall proved to be detrimen-al to the operation of the system, and should be considered whenelecting a location for an outdoor algal growth system. In all, thebility of the ATS to continue biomass production during periods ofow temperatures, combined with the relative ease of biomass cul-ivation, harvest, and nutrient removal, show potential for attachederiphytic algal growth technologies to be used as a method of algaleedstock generation and nutrient removal.

cknowledgements

This study was supported by the Lewis Foundation of Clevelandnd the Smithsonian Institution. The authors would like to thankr. Walter Adey for his input and support, as well as Jeffrey Hickle,yan Johnston, Nathan Jones, Benjamin Kennedy and Steve Green

or help with system installation and operation.

eferences

dey, W.H., 1982. Algal turf scrubber. U.S. Patent 4,333,263, June 8.dey, W., Luckett, C., Jensen, K., 1993. Phosphorus removal from natural waters

using controlled algal production. Restor. Ecol. 1, 29–39.slan, S., Kapdan, I.K., 2006. Batch kinetics of nitrogen and phosphorus removal from

synthetic wastewater by algae. Ecol. Eng. 28 (1), 64–70.ajpai, D., Tyagi, V.K., 2006. Biodiesel: source, production, composition, properties

and its benefits. J. Oleo Sci. 55, 487–502.histi, Y., 2007. Biodiesel from microalgae. Biotech. Adv. 23, 294–306.

raggs, R.J., 2001. Wastewater treatment by algal turf scrubbing. Water Sci. Technol.

44, 427–433.raggs, R.J., Adey, W.H., Jenson, K.R., St. John, M.S., Oswald, W.J., 1996a. Phosphorus

removal from wastewater using an algal turf scrubber. Water Sci. Technol. 33,191–198.

1 l Engin

C

D

E

F

G

G

G

H

H

H

K

M

M

M

S

S

S

S

480 H.N. Sandefur et al. / Ecologica

raggs, R.J., Adey, W.H., Jessup, B.K., Oswald, W.J., 1996b. A controlled stream meso-cosm for tertiary treatment of sewage. Ecol. Eng. 6, 149–169.

ismukes, G.C., Carrier, D., Bennette, N., Ananyev, G.M., Posewitz, M.C., 2008. Aquaticphototrophs: efficient alternatives to land-based crops for biofuels. Curr. Opin.Biotechnol. 19, 1–6.

riksen, N.T., 2008. The technology of microalgal culturing. Biotechnol. Lett. 30,1525–1536.

ulhage, C.D., 1997. Manure management considerations for expanding dairy herds.J. Dairy Sci. 80, 1872–1879.

eorgian, T., Wallace, J.B., 1983. Seasonal production dynamics in a guild ofperiphyton-grazing insects in a southern Appalachian stream. Ecol. Soc. Am.64 (5), 1236–1248.

reenberg, A., 1992. Standard Methods for the Examination of Water and Wastew-ater, 18th ed. American Public Health Association.

robbelaar, J.U., 2000. Physiological and technological considerations for optimizingmass algal cultures. J. Appl. Phycol. 12, 201–206.

ouba, V.J.G., Novozamsky, I., Uittenbogaard, J., van der Lee, J.J., 1987. Automaticdetermination of total soluble nitrogen in soil extracts. LandwirtschaftlicheForschung 40, 295–302.

offmann, J.P., 1998. Wastewater treatment with suspended and nonsuspendedalgae. J. Phycol. 34, 757–763.

u, Q., Sommerfeld, M., Jarvis, E., Ghirardi, M., Posewitz, M., Seibert, M., Darzins, A.,

2008. Microalgal triacylglycerols as feedstocks for biofuel production: perspec-tives and advances. Plant J. 54, 621–639.

roon, H., 1993. Determination of nitrogen in water; comparison of a continuousflow method with on-line UV digestion with the original Kjeldahl method. Anal.Chim. Acta 276, 287–293.

U

U

W

eering 37 (2011) 1476– 1480

arinho-Soriano, E., Nunes, S.O., Carneiro, M.A.A., Pereira, D.C., 2009. Nutrients’removal from aquaculture wastewater using the macroalgae Gracilaria birdiae.Biomass Bioenergy 33, 327–331.

atlock, M.D., Haggard, B.E., Brown, A.V., Cummings, E., Yates, L.C., Parker, D.G.,2009. Water Quality and Ecological Assessment: Osage and Spring creeks. Uni-versity of Arkansas Center for Agricultural and Rural Sustainability, Fayetteville,AR.

ethods for the Determination of Organic and Inorganic Compounds in DrinkingWater, 1997. Volume 1 (EPA/815-R-00-014).

chenk, P.M., Thomas-Hall, S.R., Stephens, E., Marx, U.C., Mussgnug, J.H., Posten,C., Kruse, O., Hankamer, B., 2008. Second generation biofuels: high efficiencymicroalgae for biodiesel production. Bioenergy Res. 1, 20–43.

chumacher, G., Blume, T., Sekoulov, I., 2003. Bacteria reduction and nutrientremoval in small wastewater treatment plants by an algal biofilm. Water Sci.Technol. 47, 195–202.

chwarzbold, A., 1992. Efeitos do regime de inundac ão do rio Mogi-Guac u (SP) sobrea estrutura, diversidade, produc ão e estoques do perifíton de Eichornia azurea(Sw) Kunth da Lagoa do Infernão. Tese de Doutorado, Universidade Federal deSão Carlos, São Carlos, 237p.

mall, A.M., Adey, W.H., 2001. Reef corals, zooxanthellae and free-living algae: amicrocosm study that demonstrates synergy between calcification and primaryproduction. Ecol. Eng. 16 (4), 443–457.

gwu, C.U., Aoyagi, H., Uchiyama, H., 2007. Photobioreactors for mass cultivation ofalgae. Bioresour. Technol. 99, 4021–4028.

termohl, H., 1958. Zur vervollkommung der quantitativen phytolankton-methodik. Mitt. Int. Verein. Limnol. 9, 1–39.

etzel, R.G., Likens, G.E., 1979. Limnological Analysis. Saunders, Philadelphia.