Microalgal Biomass for Greenhouse Gas Reductions: Potential for Replacement of Fossil Fuels and Animal Feeds

Microalgal biomass production offers a number of advantages over conventional biomass production, including higher productivities, use of otherwise nonproductive land, reuse and recovery of waste nutrients, use of saline or brackish waters, and reuse of CO2 from power-plant flue gas or similar sources. Microalgal biomass production and utilization offers potential for greenhouse gas (GHG) avoidance by providing biofuel replacement of fossil fuels and carbon-neutral animal feeds. This paper presents an initial analysis of the potential for GHG avoidance using a proposed algal biomass production system coupled to recovery of flue-gas CO2 combined with waste sludge and/or animal manure utilization. A model is constructed around a 50-MW natural gas-fired electrical generation plant operating at 50% capacity as a semibase-load facility. This facility is projected to produce 216 million k?Wh/240-day season while releasing 30.3 million kg-C/season of GHG-CO2. An algal system designed to capture 70% of flue-gas CO2 would produce 42,400 t (dry wt) of algal biomass/season and requires 880 ha of high-rate algal ponds operating at a productivity of 20?g-dry-wt/m2-day. This algal biomass is assumed to be fractionated into 20% extractable algal oil, useful for biodiesel, with the 50% protein content providing animal feed replacement and 30% residual algal biomass digested to produce methane gas, providing gross GHG avoidances of 20, 8.5, and 7.8%, respectively. The total gross GHG avoidance potential of 36.3% results in a net GHG avoidance of 26.3% after accounting for 10% parasitic energy costs. Parasitic energy is required to deliver CO2 to the algal culture and to harvest and process algal biomass and algal products. At CO2 utilization efficiencies predicted to range from 60–80%, net GHG avoidances are estimated to range from 22–30%. To provide nutrients for algal growth and to ensure optimal algae digestion, importation of 53 t/day of waste paper, municipal sludge, or animal manure would be required. This analysis does not address the economics of the processes considered. Rather, the focus is directed at determination of the technical feasibility of applying integrated algal processes for fossil-fuel replacement and power-plant GHG avoidance. The technology discussed remains in early stages of development, with many important technical issues yet to be addressed. Although theoretically promising, successful integration of waste treatment processes with algal recovery of flue-gas CO2 will require pilot-scale trials and field demonstrations to more precisely define the many detailed design requirements.     

Zebra Mussel Biofouling as Function of Copper Dissolution Rate

Copper and copper alloys have proven to be highly effective in preventing zebra mussel biofouling. The present laboratory measurements reveal that the rate of copper release (mg∕m2∕day) from surfaces in flowing lake water is inversely proportional to the number of zebra mussels adhering to similar surfaces in Lake Erie. Data are shown for copper, copper-nickel alloys (90:10, 80:20, and 70:30), a copper-epoxy coating, and galvanic couples of copper connected to zinc or aluminum.     

Long-Term Dynamic Modeling Approach to Quantifying Attached Algal Growth and Associated Impacts on Dissolved Oxygen in the Lower Truckee River, Nevada

Nutrient loads enter the lower Truckee River of western Nevada, affecting the growth of attached algae (periphyton) which causes depressed nighttime dissolved oxygen (DO) levels. The lower Truckee River is home to the endangered cui-ui and threatened Lahontan cut-throat trout, with DO standards being established to in part protect these species. Hydrodynamics, nutrient concentrations, periphyton biomass, and DO data spanning August 2000–December 2001 were used to calibrate and verify a modified version of the Water Quality Analysis Simulation Program Version 5 (WASP5). Under typical loading conditions the periphyton community is nitrogen limited, however nitrogen loading from an upstream wastewater treatment facility increased greatly during the analysis period due to approved site construction activities (discharge permit excursion) causing the periphyton community to temporarily become phosphorus limited. The developed modeling approach, with limited calibration, was able to accurately track dynamic system responses. Removing the impact of the noted discharge permit excursion resulted in a minimum computed DO value of 4.13?mg/L, occurring at the downstream end of the modeling domain on August 8, 2001. Additionally removing the impact of all nutrient loads from area agriculture resulted in a predicted minimum DO value of 4.54?mg/L, while also shifting its location significantly upstream and its timing to April 26, 2001. Meeting all prescribed DO standards required establishing a minimum in-stream flow value of 1.81?m3/s (64.0?ft3/s) downstream of Derby Dam.     

Grazer Control of Stream Algae: Modeling Temperature and Flood Effects

A computer model for epilithic algae and grazer biomass in streams is modified to better predict the effects of temperature and is calibrated for diatoms and mayflies. Mayflies are predicted to maintain low diatom biomass provided that (1) temperatures remain within their preferred range (10–20°C); and (2) mayfly populations are not adversely affected by floods. Algal blooms are predicted to occur in mayfly-dominated streams above 20°C—temperatures common in pasture streams over summer. We hypothesize that mobile bed streams are susceptible to blooms during summer low flows following floods because (1) they usually lack temperature tolerant snail grazers; and (2) mayfly recovery lags behind algal regrowth, and there is a short period when algae escape from “top-down” grazer control.     

Mathematical Modeling as a Tool in Aquatic Ecosystem Management

The capacity of an existing model to simulate the growth (biomass) of a reed [Phragmites australis (Cav) Trin. ex Stuedel] in fresh water habitats using published field data and the incorporation of a submodel to estimate seasonal variation in reed mineral–nutrient content was investigated. This new feature also enabled one to estimate plant removal of mineral–nutrients from sediments. Model-predicted and observed shoot, rhizome, and root biomass showed concordance correlation coefficients of 0.97, 0.52, and 0.99, respectively. The nutrient analysis study showed that the annual uptakes of nitrogen and phosphorus from sediment by P. australis in the Denmark Vejlerne Nature Reserve were 143.9 and 16.1 kg?ha?1, respectively. The simulated results also showed that at the time of peak standing stock of minerals, shoots contained 40 and 22.5% of whole plant N and P, respectively. This suggested that the use of the common reed in wastewater treatment plants allows removal of nitrogen more easily than phosphorus, because a higher percentage of nitrogen is bound with the easily removable shoot parts.     

Characteristics and Reactivity of Algae-Produced Dissolved Organic Carbon

Algae (green, blue–green, and diatom) grown in inorganic media produced particulate and dissolved organic carbon (DOC). DOC produced by a green-alga contains 25% hydrophobic acids. DOC from all algae had specific ultraviolet absorbance values less than 2.0?m?1?(mg/L)?1. Algae-produced DOC was biologically labile; greater than 60% degraded in bioreactors within 5 days. The biodegradable material likely included carbohydrates, amino acids, and amino sugars, which were present in hydrophobic acid isolates. Chlorination of algal DOC formed disinfection by-products; DOC from the green alga, Scenedesmus quadricauda, produced chloroform [0.53?micromole?per?mg?carbon?(μmol/mg?C)], dichloroacetic acid (0.27?μmol/mg?C), and trichloroacetic acid (0.14?μmol/mg?C). This work complements other studies, which focused on algal total organic carbon (DOC and cellular material), and clearly demonstrates the importance of identifying algae-derived sources of DOC in water supplies and removing such DOC in water treatment plants prior to chlorination.     

Image Analyses-Based Nondisruptive Method to Quantify Algal Growth on Concrete Surfaces

A global ban on the use of tributyltin has resulted in the need to screen new antifouling agents to control algal growth in aquatic environments. Standard methods for the quantification of algal biomass are disruptive in nature; therefore, they are not applicable for the screening studies requiring successive observations at specified time intervals. The objective of this study was to develop a nondisruptive method to quantify algal growth on a variety of surfaces. Image analyses and chlorophyll extraction methods were used to quantify an algal biomass on a concrete surface containing different additives. For concrete samples containing single additives, the coefficient of determination between both techniques ranged from 0.74 to 0.84. However, for concrete samples containing multiple additives, the coefficient of determination of both methods ranged from 0.72 to 0.75. Results suggest that an image analyses technique can be used to accurately quantify various types of algae growing on a variety of solid surfaces.     

Effects of yttrium and phosphorus on growth and physiological characteristics of Microcystis aeruginosa

Yttrium is a main kind of rare earth elements (REEs) with wide applications in modern industry and farming. Phosphorus, an essential element of algae, is used as the nutrients and also one of the main factors of eutrophication. To investigate the effects of yttrium and phosphorus on Microcystis aeruginosa (M. aeruginosa), the growth and physiological changes were studied by lab cultured experiments. In the experiment, exogenous yttrium was tested by a concentration gradient (0.0, 0.1, 0.3, 0.5, 1.0 mg/L), meanwhile, phosphorus was tested by three concentrations (0.0, 0.02, 0.2 mg/L). The results show that the contents of chlorophyll a (chl-a) and soluble protein increase compared with the control and they have certain correlation with algal cells density. The growth status of algae is stimulated by initial yttrium concentration ≤0.3 and 0.2 mg/L phosphorus, while it is inhabited by 0.5 and 1.0 mg/L yttrium. Besides, the activity of superoxide dismutase (SOD) of algae increases with addition of yttrium dose (0–0.3 mg/L) when phosphorus dose is 0.2 mg/L. Furthermore, when yttrium dose is 0.5 and 1.0 mg/L, the vitality of SOD presents a sharp decline. The malondialdehyde (MDA) contents increase with time and addition of yttrium dose, 0.2 mg/L phosphorus weakens the accumulation of MDA.     

Retention of Sediment and Nutrient Loads with Peak Runoff Control

The purpose of this research was to evaluate peak runoff control as a water protection method to reduce sediment and nutrient loads. Increased eutrophication of surface waters and risk of floods demands cost effective methods to reduce pollutant input and risks of flooding. With the peak runoff control it is possible to cut the main peaks and store the runoff water temporarily in ditches. The method decreases the suspended solids (SS) and nutrient loads by reducing flow velocities, and improving the settling of sediment particles. The method was tested in two heavily drained adjacent peat harvesting areas suffering considerable erosion. The peak flows were cut by 27–87%, the SS load by 61–94%, the total nitrogen (Ntot) by 45–91%, and the total phosphorus (Ptot) load by 47–88%. The peak runoff control method operated most effectively during extreme events when most of the SS load is transported. A detailed particle analysis of runoff water showed that water detention reduced the median particle size of SS load as the largest particles settle. The results clearly indicate that the peak runoff control is an effective method to control the sediment loads and peak flows from peatland drainage.     

Equilibrium Model for Cadmium Adsorption by Green Algae in a Batch Reactor

This paper reports the results of a study on the equilibrium behavior of cadmium adsorption by a tropical, indigenous single-cell algal species, identified as Oocystis sp., in a static reactor. An exponential equation, in the form of Ce/C0 = α?exp(βM/C0), was found to be statistically significant in expressing the relationship between the ratio of equilibrium cadmium (Cd) concentration in solution (Ce) to the initial cadmium concentration (C0) and the ratio of algal biomass (M) to initial cadmium concentration (C0) for both living and dead algal biomass. Based on the above equation and the mass balance of cadmium in the system, another two equations were developed and verified by a series of batch experiments. One equation, in the form of x/m = [1?α?exp(βM/C0)]/(M/C0), describes the relationship between the cadmium content per unit algal biomass (x/m) and the ratio M/C0. The other equation takes the form of x/m = β(1?Ce/C0)/ln(Ce/αC0) and describes the relationship between the ratio of equilibrium cadmium concentration to initial cadmium concentration and cadmium content per unit algal biomass. The above models for Cd adsorption were found to be applicable over a pH range of 4.5–10.5 even though it was found that pH affects the Cd adsorption potential significantly.     

Estimating Nonpoint Source Pollution in the Upper Yangtze River Using the Export Coefficient Model, Remote Sensing, and Geographical Information System

Recently, increasing nutrient (i.e., nitrogen and phosphorus) concentrations have been observed in the surface water of many countries and this nonpoint source (NPS) pollution has become an important factor in the deterioration of water quality in the upper reach of the Yangtze River Basin. In this paper, the NPS pollution loads in the upper reach of Yangtze River Basin in the year 2000 were estimated using export coefficient model and remote sensing techniques. The spatial distributions of the NPS loads within the watershed were then displayed using geographical information system. Results indicated that the total nitrogen load was 1.947×106?t and the total phosphorus load was 8.364×104?t. Important source areas for the nutrients were croplands in the Jinsha R. and Jialing R. watershed, as well as the Chongqing municipality.     

Dual Discharge Approach to Accessing Assimilative Capacity: Probabilistic Analysis and Management Application

A dual discharge strategy has been proposed for management of the effluent from the Syracuse Metropolitan Treatment Plant (Metro). The approach involves routing the discharge to the Seneca River when assimilative capacity is available there and to Onondaga Lake when it is not. Application of a deterministic modeling approach has demonstrated that the dual discharge strategy is effective in meeting water-quality standards/goals in both the river [dissolved oxygen (DO)] and the lake [total phosphorus (TP)] under summer average conditions of river flow and upstream boundary condition DO. Here, that analysis is extended to include a probabilistic treatment of the impact of natural variability in river flow and DO boundary conditions on the feasibility of this management option. Model simulations, incorporating these key sources of system variability, indicate that the dual discharge strategy will meet the lake management goal for TP ～ 94% of the time, with no attendant violation of river DO standards. Excursions from the lake TP goal, occurring ～ 6% of the time, range from 1–5?μg?L?1, are within the range of uncertainty in indicators applied in identifying trophic status. This novel management option is compared with an in-lake discharge alternative in terms of technical and economic feasibility and public acceptance of resultant water quality. Additional management actions, recommended to accompany implementation of the dual discharge strategy, are discussed.     

Development of a Simple Phosphorus Model for a Large Urban Watershed: A Case Study

Often, the initiation of a total maximum daily load (TMDL) program is delayed until intensive monitoring data can be collected—even in watersheds where large historical data sets exist. This paper provides a case study of a modeling effort that utilizes available historical data to fulfill an intermediate goal of a TMDL program for the Passaic River Basin. The subject model is developed to simulate total phosphorus concentrations (and loads) within the basin’s effluent-dominated streams. The model is based on the assumption that the primary process controlling in-stream total phosphorus concentrations is the dilution of the cumulative upstream effluent load—which was computed on a continuous (daily) basis. Model comparisons indicate a generally good fit to long-term river-monitoring data at several key sites. Model results, and data analyses, suggest that secondary processes have a relatively minor impact on total phosphorus (TP) concentrations in this relatively large, urbanized system. This finding is consistent with a previous QUAL2E model study of the system, and consistent with the relatively conservative behavior of TP reported in many medium-to-large river systems throughout the United States. Model results are used to facilitate TMDL planning efforts for a major water supply reservoir in the basin.     

Growth of Floating Aquatic Macrophytes in Alkaline Industrial Wastewaters

Ponds holding industrial wastewater can quickly develop algal blooms, which in turn results in high pH excursions. Such deterioration in water quality is experienced in Portland Aluminium's retardation pond. A covering of floating aquatic plants, such as Azolla filiculoides and Lemna minor, will reduce the light entering the water body, in turn reducing algal production and lowering pH levels. In the case of Portland Aluminium's retardation pond, the initial installation of such a system has to be established under alkaline conditions and in high fluoride concentrations (up to 10 mg∕L). The survival and growth of A. filiculoides and L. minor under alkaline conditions (pH levels of 7–9.5) and under different fluoride concentrations (0–10 mg∕L) were assessed in the laboratory and in field conditions. L. minor grew well under alkaline and high fluoride conditions in short-term laboratory tests, but appeared unable to compete with itinerant algae in the field. A. filiculoides survived only in media of pH 7 and 0-mg∕L fluoride in the short-term laboratory tests, but grew very well in the long-term field experiments. A. filiculoides was also observed to inhibit algal growth in the field. Both species absorbed fluoride. Fluoride concentrations in the plants rose and fell in relation to the fluoride concentrations in the pond, suggesting that the fluoride was readily desorbed and that the absorption itself was by a passive mechanism.     

Real-Time Hydraulic and Hydrodynamic Model of the St. Clair River, Lake St. Clair, Detroit River System

The Huron-Erie Corridor serves as a major waterway in the Great Lakes and is the connecting channel between Lake Huron and Lake Erie. The system consists of the St. Clair River, Lake St. Clair, and the Detroit River, and serves as a recreational waterway, source of drinking water for Detroit and surrounding cities, as well as the only shipping channel to Lakes Huron, Michigan, and Superior. This paper describes a three-dimensional unsteady model of the combined system and its application to real-time predictions of physical conditions over the corridor. The hydrodynamic model produces nowcasts eight times per day and 48 h forecasts twice a day. Comparisons between model simulations and observed values show average differences of 3 cm for water levels and 12 cm/s for along-channel currents in the St. Clair River (compared to mean current values of 1.7 m/s) for the period of September 2007 to August 2008. Simulations reveal a spatially and temporally variable circulation in Lake St. Clair as well as significant changes in flow rate and distribution through the St. Clair Delta not accounted for in previous models.     

Influence of Lanthanum on Phosphorus Uptake and Its Chemical Fractions in Rice Crop （Oryza Sativa）

Plantgrowthisrelatednotonlytothetotalphos phoruscontentinplantbutalsotoitschemicalfrac tions .Someresearchersbelievedthatdifferentchemi calfractionsplayeddifferentrolesinplantgrowth ,andthatplantwithlowerinorganic Pcontenthashigherphosphorusmetabolicpotential[1] .Wang[2 ] foundrareearthelements nitrateincreasesphosphorusuptakebywheat (TritcumaestvicumL .)inHoaglandnutrientsolutionculture .Wahidetal .[3] showedthatrareearthelementsappliedinsoildecreasesphosphoruscontentofcoconutseedlings .Dia…     

Pentachlorophenol accumulation in the freshwater mussels Anodonta anatina and Pseudanodonta complanata, and some physiological consequences of laboratory maintenance

Freshwater mussels Anodanta anatina and Pseudanodonta complanata were exposed to (14C)-pentachlorophenol. The wet weight based bioconcentration factor (BCF = activity in animal per activity in water) at steady state varied from 80 to 120 for A. anatina and from 61 to 85 for P. complanata. The species did not differ significantly in their wet weight or lipid based BCFs but dry weight based values were significantly higher (40-50%) for A. anatina. The soft tissue dry weight and dry weight based condition index of A. anatina (Cl4 = soft tissue dry weight per shell length) differed significantly between natural mussel populations. In animals kept from 4 to 8 months in laboratory conditions, the soft tissue dry weight and glycogen content decreased more rapidly when mussels were maintained at 15 than at 5 degrees C. However, glycogen content in the digestive gland or adductor muscle did not differ in mussels maintained in the laboratory (5 degrees C) when compared to the natural population. The adductor muscle protein content differed between laboratory maintained animals and the natural population in Lake H?yti?nen but there was no difference in the soft tissue lipid content. Trace metal concentrations and calcium in the soft tissue were in general higher in laboratory maintained mussels. In addition, laboratory maintenance affected the reproductive cycle of A. anatina.     

Stream Classification System Based on Susceptibility to Algal Growth in Response to Nutrients

We developed a stream classification system that is based on stream’s susceptibility to algal growth using a two-step approach. The model portrays algal biomass as a result of stream’s response to nutrient concentrations and the response is governed by various stream factors. In the first step, a nutrient-chlorophyll a relationship was developed to characterize nutrient’s effects on algal biomass. Residuals of the relationship were attributed to stream’s susceptibility to algal growth in response to nutrients and referred to as “observed” susceptibility. In the second step, conditions of other contributing factors were used to explain the variation in the residuals and the developed relationship was used to generate “predicted” susceptibility. Existing data compiled from various monitoring projects of Illinois streams and rivers were used to illustrate the approach. Streams were classified into three (high, medium, and low) categories based on their observed and predicted susceptibility values, respectively. With the available data, the model showed a 40-50% success rate for classifying the streams based on three observed and predicted susceptibility categories. Model entropy also was calculated for selecting the best model. The results show the important role of both nutrients and other contributing factors in explaining the variation of algal biomass. The study also suggests ways to fine tune the model and improve its accuracy, which would make the presented model a more viable tool for stream classification for establishing nutrient criteria to prevent surface streams from eutrophication.     

Modeling Zebra Mussel Impacts on Water Quality of Seneca River, New York

The concentrations of dissolved oxygen and chlorophyll have declined in the Seneca River, New York since 1991 as a result of zebra mussel respiration and filtering. Recently measured data were used to approximate flux rates of zebra mussel respiration, filtering, and phosphorus and ammonia mobilization. A model is developed that for the first time links dissolved oxygen, phytoplankton growth, and zebra mussel respiration and filtering. Good agreement is attained between the model calculations and longitudinal profiles of both dissolved oxygen and chlorophyll measured at low flow during 1997–1999. Flux rates derived from these analyses are consistent with results from other studies when normalized on the basis of zebra mussel number and tissue dry weight. Kinetic formulations for the zebra mussels are developed that describe respiration and filtering rates as a function of density, size distribution, and dissolved oxygen concentration. Several plausible test scenarios are examined using the model that indicate that both zebra mussel numbers and size distributions have a profound effect on the water quality of the Seneca River and therefore have important management and planning ramifications.     

Development and Application of a Phosphorus Model for a Shallow Oxbow Lake

A three-dimensional numerical model was developed for simulating the phosphorus concentration in shallow lakes. In this model, the computational domain was divided into two parts: the water column and the bed sediment layer. The processes of mineralization, settling, adsorption, desorption, bed release (diffusion), growth, and death of phytoplankton were taken into account, and the concentration of organic phosphorus, phosphate, and related water quality constituents was simulated. The concentrations of adsorbed (particulate) and dissolved phosphate due to adsorption-desorption were calculated using two formulas derived based on the Langmuir equation. The release rate of phosphorus from the bed sediment layer was calculated by considering the effects of the concentration gradient across the water-sediment interface, pH, temperature, dissolved oxygen concentration, and flow conditions. The adsorption and desorption of phosphate from sediment particles, as well as its release from bed sediment, were verified using laboratory experimental data. The model was calibrated and applied to Deep Hollow Lake in the Mississippi alluvial plain. The simulated trends and magnitudes of phosphorus concentration were compared with field observations. The simulation results show that there are strong interactions between sediment-related processes and phosphorus concentration.