Rate of rotation was the only statistically significant factor affecting RABR performance. Introduction Produced water defined by the U. EPA as reported in 40 CFR Part is the water brine brought up from the hydrocarbon-bearing strata during the extraction of oil and gas.
Approximately 14 billion barrels of the water are produced annually [Reynolds, ; Veil, et al. On average seven barrels of produced water are generated for every one barrel of crude oil generated [Arthur et al.
Academia Letters, Article Currently the industry does not treat the water and instead reinjects it back into the land from which it was drawn, so there is a risk of drinking water contamination Lyman, et al. The problem is that current disposal and treatment methods are expensive. This high cost is due to the lack of cost-effective methods of wastewater treatment. The high costs of disposal along with the large amount of produced water to dispose is what provided the basis for the development of a microalgae cultivation system that integrated produce water treatment with bioproduct production in this project.
Wood, et al. Christensen and Sims used a RABR to evaluate the en- ergy required to produce microalgae cultivated on municipal wastewater which indicated that a suspended treatment system required more energy than the RABR system 1. Biocrude was produced from municipal and dairy wastewater cultivated microalgae using the RABR technology Barlow, et al. The RABR is a biofilm technology that rotates a substratum for microalgae cultivation into colored and turbid wastewater to uptake microalgae nutrients nitrogen and phosphorus and then into the atmosphere to receive energy as sunlight and carbon dioxide Wood et al.
In the research reported here, produced water was used as a medium to evaluate power and energy requirements for cyanobacteria microalgae cultivation in RABRs, the effect of operation in terms of revolutions per minute, and the energy conserved in the transformation of microalgae biomass to biofuel as biocrude. Materials and Methods Produced water. Microalgae biomass. Two strains of filamentous cyanobcateria capable of growth on pro- duced water were combined into one mixed culture for inoculation of the RABRs.
RABR construction and operation. RABRs were located in a greenhouse to prevent precipi- tation and windblown dust from entering the produced water. Microalgae was harvested by mechanical scraping. Voltage meters were used to monitor power consumption required for the cultivation of the biomass. Environmental parameters. Average values for temperature and pH were Average photosynthetically active radiation PAR inside the greenhouse was Statistical analysis.
A test of 1. Factors evaluated included: 1 combination of east facing vs. Following this analysis, additional values of 0. Hydrothermal Liquefaction HTL. Harvested biomass was converted into biocrude using a ml HTL pressure reactor with pressure at After drying the solid phase was resuspended in dichloromethane, centrifuged, decanted, and filtered twice more to ensure biocrude recovery.
Further testing at 0. Power requirement for biomass harvesting by mechanical scraping after 30 days was consid- ered insignificant and was not included. Yield of biomass is a critical parameter in assessing biomass production for biofuels pro- duction.
Results are shown in Table 1. A rotation rate of 2. Based on the results of this testing, the highest yield per unit of power input occurred at 2. Conversely, power required to produce one unit 1 gm of algae is the reciprocal of the values presented in Table 1.
For 2. Clearly, rotation rate has an influence on both biomass yield and power requirements regarding biofilm biomass cultivation, but not a linear relationship. Therefore, with this in turn are grazed by zooplankton Pr leaching of fertilizers, and untreated in focus, a survey and analyses of literature specifically leading to a typical food web.
The major forms of N such as implications of its components and their role in nutrient nitrate, ammonia and nitrite are assimilated and recycled recycling was undertaken. This Review also provides an by organisms present at different trophic levels for effi- overview of promising algae-based wastewater treatment cient functioning of the foodweb Figure 1.
Among the technologies and their potential to generate biomass for or biofuel applications in future. A bacteria bacteria Wastewaters represent aquatic eco- Nitrate Nitrite Ammonia Phosphorus pool systems, wherein many types of Nitrogen pool phytoplankton microalgae and cyanobacteria and zooplankton, Denitrifying bacteria along with other macroscopic organisms, reside together form- ing different types of associations, which is reflected in their metabolic Atmospheric Domestic and industrial Weathering of N2 wastewater and agricultural and physiological diversity [19—22].
Nutrient dynamics in aquatic wastewater ecosystems. A Nitrogen; and ciations, can be helpful to combat B phosphorus. Solid arrows indicate outputs and dashed arrows indicate inputs into the challenges, often faced with the use nutrient pool.
One of Labeorohita, Catla catla, the most important factors regulating ecosystem pro- cesses are trophic cascades, reflected as reciprocal preda- Cirrhina mrigala tor—prey effects that alter the abundance, biomass and Macrofauna productivity of a population, community or trophic level across more than one link in a food web [25]. Apart from direct effects of predators on their Lemna spp. Several researchers observed that induc- spp.
Vari- Community diversity Fungi Aspergillus spp. Planktothrix mougeotii, Microcystis aeruginosa Euglena spp. Microcystis aeruginosa, Oscillatoria curviceps, belonging to Chlorophyta, Cyanophyta and Oscillatoria spp. Microalgae are observed to be associated with several Limnothrix spp. Pteridophytes, commonly used in phytoremediation, and Pseudanabaena mucicola wherein they play a key role in the nutrient sequestration h or bioaccumulating ability of these systems.
Ferdoushi et al. Bacillariophyta in which biofilters Azolla and Lemna spp. Community diversity in different wastewaters. They found the predominance P. Roselene and Paneerselvam Experimental studied the phytoplankton diversity in the heavily pol- Artificial Artificial Artificial Artificial luted Bellandur Lake [21].
Microalgal diversity study Natural Natural Natural Natural set up revealed the dominance of Microcystis spp. Among macrophytes, Wastewater from wastewater Eichornia spp. Senthil et al. Among microalgae, cyanobacteria treatment plants treatment plant treatment plant were the dominant members with a total of 42 spe- Paper mill and cies, including 14 species of Oscillatoria, which was the ND: No data.
Fish pond dominant genus, followed by Lyngbya 8 , Phormidium effluent 4 , Chroococcus 2 and Microcystis 2. Among fungi, plant Aspergillus was dominant with seven species followed future science group www. Key terms by Penicillium 2. Among bacteria, layer of amorphous polysaccharide materials are all dif- Grazers: Zooplankton in aquatic Salmonella spp. In case of a ciliate attack, Phormi- ecosystem that consume microalgae as all months throughout the study. Some microalgae types of wastewaters was stud- entangle trichomes inside the amorphic polysaccharide have defense mechanisms to avoid these grazers.
Another cyanobacterium, Micro- natural water bodies and wastewaters, nonheterocystous forms, in most cystis spp. However, Chinnasamy depending on the grazer to which it is exposed. The consumers, although in ecological terms they are primary producers. However, when protozoan flagellates Ochromo- activated sludge process , Cyanophycean members nas spp. Vasconcelos secretion of extracellular polysaccharides [42] , leading to and Pereira studied the microalgal diversity in faculta- formation of colonies and enhanced biomass produc- oo tive and maturation ponds belonging to a wastewater tion [43,44].
They reported that cya- strong pressure of Pseudomicrothorax resulted in a quicker nobacteria frequently dominated the wastewater dur- and more pronounced defense reaction in cyanobacteria ing the study period, constituting Planktothrix mougeotii, entangled in clumps, which improved their chances of Pr Microcystis aeruginosa and Pseudanabaena mucicola were survival and, thereby, increased biomass.
Badr et al. Some species on the mode of defense adopted was also recorded in of cyanobacteria, that is, Microcystis aeruginosa, Oscil- the ciliate Euplotes octocarinatus [45,46]. This organism or latoria curviceps, O. The substitution populations remain more strongly bound away from of one cyanobacteria grazer Furgasonia by another zero [25,26]. Van der Stap et al. This, in turn, can lead to the undefended flagellates, which in turn provide food for Stylonychia.
An interesting exam- to influence the growth and biomass productivity under ple of inducible defense recorded involved a phenomenon natural environments and laboratory conditions [47,48]. Bacterial diversity studies of and 13 gPm-3day-1, respectively [60]. The estimated total activated sludge in Gaobeidian wastewater treatment biomass produced expressed on the basis of volatile sus- plant in Beijing revealed the dominance of Proteobacte- pended solids [VSS] with four-, and two-times diluted ria Nitrosomonas-like and Nitrospira-like and undiluted centrifuged swine slurry was , bacteria, that is, Nitrosomas sp.
Zamora-Castro et al. Denitrifying bacteria such as Thauera sp. Evaluation of cyanobacterial class Proteobacteria and Nitzschia spp. Su et al. The profiles generated using dena- in wastewaters are viruses.
Wu and Liu used pulsed-field roidiae and Betaproteobacteria. Zhou et al. This range [55]. Their study suggested that indigenous viruses technology can be highly promising in the present sce- h are abundant and play a dynamic role in the functioning nario requiring effective algae harvesting systems and of the municipal wastewater treatment system. They suggested that cocultivation of algae and microorganisms can also contribute to nutrient two organisms, the filamentous Planktothrix spp.
Several researchers have also used consortia com- in the wastewater column, in the absence of mixing, can prising different microalgae both native and non-native be considered as one of the possible options for removing or microalgae with bacteria or microalgae with fungi to P and N from tropical wastewaters.
Chinnasamy et al. The mance of waste stabilization ponds [59]. The inoculation nitrate-N removal was Table 2. Associations of algae with other community partners and their role in nutrient removal in different types of wastewaters. Synthetic wastewater NH4-N - 45 [87] C. Coastal effluent PO4-P - 94 [53] f spp.
Planktothrix spp. Spirogyra sp PO4-P - The biomass produc- the benefit of oxygen supply by microalgae to the tion potential and lipid content of this consortium in aerobic bacteria for the degradation of organic pollut- treated wastewater varied from 9. Recently, Renuka et al. However, microalgae can have a detri- the potential of three consortia of microalgae differing mental effect on the growth of bacteria by altering in their nature of thallus organization unicellular vs fila- some factors such as pH, dissolved oxygen, tempera- mentous and source of origin native vs non-native [20].
A They observed that a consortium comprising filamen- Therefore, the interactions among the partners need tous and native microalgae mainly from Cyanophyta to be investigated in depth. The information available from available and concentration of contaminants in wastewaters. Microal- intensity. Mustafa et al. Cultivation of microalgae with the use of microalgal strains, that is, Chlorella vulgaris, Scenedesmus chemical fertilizers increases the cost of production quadricauda, Euglena gracilis, Ankistrodesmus convolutes besides raising questions regarding their environmen- and Chlorococcum oviforme [70].
This consortium was able tal impact. Therefore, wastewaters rich in nutrients to produce 2. Ryu et al. Mixed culture of wild algae Studies have been undertaken by various workers for species were successfully grown on wastewater nutrients evaluating the feasibility of different types of wastewaters and potentially scaled up to commercial production [11].
The Municipal wastewater centrate can be used as a growth unfavorable conditions of wastewaters are mainly due to medium for the cultivation of microalgae.
Comparison of increased nutrient load or uneven competition among municipal wastewater from five stages of municipal waste- the different community members.
Studies have shown water treatment plant revealed that centrate was the best that harshness of wastewaters can be decreased either medium for Chlorella vulgaris [72] , leading to the highest by dilution [19,66] or preliminary treatment with UV Pr biomass productivity of 0. Cho et al. Li et al. Chlo- Similarly, dilution of poultry litter anaerobic digester rella kessleri and C.
This consortium can [73]. However, various environmental carbohydrates However, higher biomass with high A as a cultivation medium for the oleaginous microalga lipid accumulation was feasible, using a native microalga Chlorella [68]. This microalga can produce 1. Highest biomass production of 1. Kang et al. The biomass obtained was rich in carbohy- promising as cultivation media for the alga Haematococ- drates Due cus pluvialis [69] , which is a potential source of astaxan- to the high percentage of carbohydrates in Kirchneriella thin production carotenoids with antioxidant property.
Wu et al. Chlamydomonas spp. Prospects of wastewater use for algal biomass production. Baffled hybrid flasks ml 6. Coil reactor 9l 0. Erlenmeyer flask ml 0. Prospects of wastewater use for algal biomass production cont. Tube photobioreactor ml 0. Photobioreactor 6 l 5l 0. Erlenmeyer flasks 1 l ml 0. Key terms 1. However, the part of food web, is a challenging issue lipids. Invasion by these organisms can lead to the crash of algal biodiesel production. Concentrated They also reported that biomass and lipid production cultures or undesirable growth of municipal wastewater can be used as in microalgae can be enhanced by the supplementation weed algae.
This microalga produced respectively. Sydney et al. Scaling up of this ondary treated domestic wastewater [82]. Botryococcus system in BIOCOIL reactors led to a net biomass produc- braunni was the most promising, as it was able to produce tivity of 1. When this microalga 0. These studies Chlorella spp. This could be due clearly showed that culture conditions can significantly to the wider acceptability of Chlorella in biofuel pro- influence the production of biomass and accumulation of duction.
In general, a wide range of variation, from Pr lipids by microalgae grown in wastewater. The utility of 0. This variation [79] , which illustrated that it could be recycled twice with could be due to the following reasons: nature of micro- the addition of sufficient nutrients.
Algae cultivation in open ponds is a challeng- A for growth in carpet mill wastewater and lipid content ing task due to invasion of weed algae as contaminants for biodiesel production [16]. Strains of Botryococcus and other inputs from the environment, which include braunii, Dunaliella tertiolecta, Pleurochrysis carterae and bacteria, fungi, protozoa, zooplankton and insects [84].
Also, 1. Hence, the higher cost soil conditions and local regulations. Figure 2 shows the incurred for the maintenance of unialgal cultures in the picture of a high rate algal pond operating in the USA. HRAPs are considered to be the most This type of expensive cultivation practices may not be cost effective reactors available for wastewater treatment a viable option for production of high volume low value as they depend on solar radiation for energy.
However, products such as biofuels [89]. In open ponds, biomass production is deter- The performance of a 5-ha demonstration scale mined by two factors, that is, bottom-up control of HRAP system for treating primary treated sewage at production by resource supply rate and the top-down Christchurch in New Zealand comprising four 1. The ponds were dominated compared with the communities showing low diversity by Micractinium spp.
Multispecies or polyalgal cultures in open ponds biomass productivity observed was 4. The top of algae [81]. Hence, diverse microalgal communities are portion of the pond is always maintained under aerobic or very good for removing pollutants from wastewaters. The suspended solids in the effluent settle in Knowledge on algal physiology, ecology, limnology and the sedimentation pit or the in-pond digester and the pol- ecological stoichiometry is considered very important to lution load of the effluent is reduced through anaerobic design, operate and maintain commercial-scale algae h production systems for wastewater treatment [90].
The algal biomass produced through wastewater treatment is low in lipids. However, it can be effectively utilized ut for the production of biocrude and biogas through thermochemical and biochemical conversion processes, respectively. A High-rate algal pond Compared with conventional energy intensive waste treatment technologies for nutrient removal, algae medi- ated bioremediation techniques offer significant advan- tages in terms of energy, cost and performance.
In s, Oswald demonstrated the use of algae in wastewater treatment using high-rate algal ponds HRAP that are raceway type ponds [93]. Compared to conventional facultative ponds, HRAPs are shallow 0.
They are continuously mixed with paddle wheels to facilitate maximum light capture by algae and have short hydraulic retention time; that is, approximately Figure 2.
The ponds can be future science group www. Biogas generated from the settled sol- Algal turf scrubbers ids is effectively captured for energy production through Realizing the importance of low-cost technologies for a novel design [96].
As the surface layer is maintained wastewater treatment, ecologically engineered algae- under aerobic conditions, odor pollution due to sulfur based systems such as algal turf scrubbers ATS were compounds present in the biogas is reduced drastically.
Oxygen released by the algae through photosynthesis and a screen to promote the growth of an attached is utilized by bacteria that oxidize most of the BOD and algal community constituted by strains of robust cya- release CO2 to promote algal growth for nutrient removal nobacteria, green algae and diatoms, which results in the wastewaters.
Algal biomass is removed periodically in a thick biofilm mat. Figure 3 shows ATS located in by sedimentation in a settling pond. The algal commu- f water from settling ponds is discharged after keeping nity present in the biofilm mat oxygenates the waste- it in maturation ponds for 10—15 days. The net energy water through photosynthesis and absorbs inorganic oo requirement of AIWPS system designed by Oswald and nutrients like nitrogen and phosphorus to reduce the Green, LLC, is approximately 0.
At the end of the flow way, the treated removed, which is significantly lower than conventional water is discharged, which meets the pollution control mechanical aeration treatments which require approxi- norms.
The nutrients removed from the wastewater and mately 0. The stud- carbon fixed through photosynthesis is stored in the Pr ies conducted by Green indicated that approximately algal biofilm mat which is harvested once in a week. A yearly mean algal productivity of 35 gm-2d-1 in the pilot-scale ATS tertiary wastewater treatment or A B system handling secondary treated sewage in Patter- son, California was reported by Craggs et al.
ATS h treating sugar farm wastewater produced 33—39 gm-2d-1 of dry algal biomass and removed 0. Based on various studies, it has been ut estimated that ATS used for the tertiary treatment of C D secondary treated domestic wastewater would produce 18 MT of dry algal biomass per ha per year by treat- ing 9 million liters per day per ha.
Nutrient runoff A from agriculture fields along with uncaptured N and P from sewage plants reaches major rivers. It was estimated that the yearly algal production in ATS units used to clean rivers in the USA would range from 25 to 45 gm-2d-1 []. The ATS using dairy manure effluents Figure 3. A Aerial view; B wastewater inlet; C algal biofilm growing on 1 g of total N m-2 d-1 []. Global freshwater reserves are rapidly depleting and the and Coelastrum spp.
More research is needed to understand the in the future, through better water management practices. Also, novel energy efficient low-cost harvest- focus of many countries to reduce environmental pollu- ing technologies such as auto-flocculation or bio-floc- tion. Apart from cleaning the algae based wastewater treatment technologies [14,,].
Apart from photoauto- product of a wastewater treatment facility for the pro- trophs, mixotrophic algal strains capable of fixing carbon duction of biofuels is very attractive, because the valu- from CO2 and other organic sources of carbon such as able algal biomass is generated virtually free of cost in f sugars simultaneously in the presence of light have great the wastewater treatment plant.
In addition, algae-based potential in treating the wastewater. Unfortunately, algal wastewater technologies are eligible for carbon credits. Energy requirements for conventional not economically viable and utilization of freshwater for treatment technologies are very high and the treatment cultivation of algae for biofuel applications is not envi- efficiency is totally dependent on availability of power.
In spite of all reduce our dependence on fossil energy. Algae-based the advantages, the major limitation of this technology is wastewater treatment plants have been established and the requirement of a large footprint area, as the treatment are being successfully operated in the USA.
Currently, h is dependent on effective sunlight capture and utiliza- the biomass harvested from algae based wastewater tion. Developing algae-based technologies for treating treatment plants is being used as a fertilizer to improve maximum quantities of wastewater with minimum soil fertility. As this biomass is low in lipids, it can- ut footprint area will be a major challenge for the future. These technologies do not susceptible to grazing by herbivorous protozoa and require dried biomass and pure monoculture of lipid zooplanktons such as rotifers and cladocerans, which rich algal strains, and hence offer great scope for bio- can result in culture crashes.
Similarly, fungal parasit- fuel production.
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