2.1 Wastewater Treatment with Microalgae
Microalgae have a great potential to solve energy and environmental challenges around the world. Wastewater treatment with microalgae is a more environmental sound approach to reduce nitrogen and phosphorus and to remove heavy metals from wastewater. Microalgae can absorb significant amount of nutrients because they need large amounts of nitrogen and phosphorus for proteins (45-60% microalgae dry weight) and metals as micronutrients for their growth. William Oswald first developed the idea of treating wastewater using microalgae and performed photosynthesis in sewage treatment [29]. Figure 2.1 briefly depicts the process involved in high rate algal pond in which algae plays a dual role by assimilating nutrients from wastewater and supplying oxygen to bacteria. The bacteria take up the oxygen and degrade organic material in the wastewater, the same process which is used in activated sludge treatment [29].
Figure 2.1. Process involved in a high rate algal pond [29].
The selection of algae strain to be used in wastewater treatment is determined by their robustness against wastewater and by their ability to grow in and to assimilate nutrients from wastewater [30]. Chlorella, Scenedesmus, Neochloris and Spirulina are the widely used algae species in experimental studies of wastewater treatment. The major advantages of using microalgae over conventional methods as summarized by De la Noüe (1992) [31] are: (a) nutrients can be removed more efficiently; (b) no generation of toxic by-product (sludge) (c) biofuels can be produced from biomass harvested (energy efficient); (d) cost–effective.
2.2 Mechanisms of nutrient and heavy metal removal
Nutrient removal by algae involve...
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...l density. The major advantage of autotrophic growth condition is that it can reduce carbon dioxide to make useful organic compounds. However, the limitation is that light penetration is inversely proportional to the algal density. As the density of algae increases, the light exposure to algae cell decreases resulting in limitation of nutrient removal from wastewater.
During heterotrophic growth, no light is required and organic carbon source such as glucose or glycerol acts as source of carbon. Algae uses this organic carbon for growth.
High algal densities can be obtained in heterotrophic growth as the growth is not limited by the light. Mixotrophic growth is a combination of heterotrophic and autotrophic growth, where carbon dioxide and organic carbon are simultaneously assimilated and both respiratory and photosynthetic metabolism operates concurrently [49, 50].
An abiotic factor affecting growth of T. californicus is the concentration of salinity of the seawater. It can range from 35ppt too much higher salinity concentrations. The concentration of UV radiation also affects t. californicus. They tend to stay in places of low concentration of UV rays when the sun is the strongest.
The Effect of Light on the Organic Plant Elodea Aim: To calculate the rate of photosynthesis from the number of oxygen bubbles produced by the plant. Photosynthesis: The process by which green plants use the sun's energy to build up carbohydrate reserves. Plants make their own organic food such as starch. Plants need Carbon dioxide, water, light and chlorophyll in order to make food; and starch and oxygen are produced. Carbon dioxide and water are the raw materials of photosynthesis.
The Chesapeake Bay is the nation’s largest estuary with six major tributaries, the James, the Potomac, the Susquehanna, the Patuxent, the York, and the Rappahannock Rivers, feeding into the bay from various locations in Maryland, Virginia, Pennsylvania, and the District of Columbia (Chemical Contaminants in the Chesapeake Bay – Workshop Discussion 1). These areas depend on the Bay as both an environmental and an economic resource. Throughout the last 15 years the Chesapeake Bay has suffered from elevated levels of pollution. Nitrogen and phosphorous from wastewater treatment plants, farmland, air pollution, and development all lead to reduced water clarity and lowered oxygen levels, which harm fish, crabs, oysters and underwater grasses (Key Commission Issues 1). There are other types of pollution in the bay such as toxic chemicals, but because nutrient pollution is the most significant and most widespread in the Bay its effects are the most harmful to fisheries. Nitrogen and phosphorous fuel algal blooms which cloud the water and block sunlight from reaching underwater grass beds that provide food and habitat for waterfowl, juvenile fish, blue crabs, and other species (Blankenship 11-12). Algae plays a vital role in the food chain by providing food for small fish and oysters. However, when there is an overabundance of algae it dies, sinks to the bottom of the Bay, and decomposes in such a manner that depletes the oxygen levels of the Bay (11). The reduced oxygen levels in the Bay reduce the carrying capacity of the environment and these “dead areas” sometimes kill off species that can not migrate to other areas of the Bay, such as oysters (11). Increased abundance of algal blooms also led to the overabundance of harmful and toxic algae species and microbes such as the microbe Pfiesteria, which was responsible in 1997 for eating fish alive and making dozens of people sick (12). The heightened awareness of diseases that can be contracted through consumption of contaminated fish also has an economic impact. Therefore, the excess levels of nitrogen and phosphorous have fueled an overabundance of algal blooms, which has reduced water clarity and lowered oxygen levels, affecting many species within the bay and ultimately the industries that rely on these species.
Eutrophication is a concern in the Chesapeake Bay. Eutrophication is caused by excessive amounts of nutrients. Excessive nutrients in the bay have negative affects on the bay's ecosystem. The extra nutrients make the environment unbalanced. The extra nutrients cause a chain reaction that depletes oxygen and kills most of the organisms in that area. This is what is known as a dead zone.
Autotrophs, can build organic compounds from simple molecules such as water and carbon dioxide and their type of feeding is called autotrophic nutrition. While they are building complex molecules, they need large amounts of energy. They are divided into two groups according to their source of energy: chemoautotrophs and photoautotrophs. Chemoautotrophs can synthesize organic compounds from CO₂ AND H₂O by using inorganic oxidation energy and they do not require sunlight. However, photoautotrophs, including green plants, produce sugar and O₂ from CO₂ and H₂O by using sunlight. The green pigment which absorbs the light is called chlorophyll and this process is called photosynthesis.
An incredibly scary new type of algae is on the loose on the eastern seaboard of the United States and worst of all not many people know about it. Phiesteria piscicida- Latin for “fish killer” has been living in the mud of rivers for millions of years, but until recently something has jolted its metabolism into overdrive and has caused it to become a fearsome predator. This newly discovered type of dinoflagellate or marine protozoa, which generally has two flagella and cellulose covering, has been living off simple nutrients in the river waters of primarily North Carolina, until now that is. Near the Neuse River in NC, there is a slaughterhouse for pigs and chickens; all of the waste from the pigs is stored in massive lagoons where it is later sprayed onto crops as fertilizer. Unfortunately, a lot of this raw sewage ends up in streams that flow into the Neuse, which in turn enters the Pamlico Sound, a 2,000-mile long estuary in NC. This ultimately brings an immense amount of nutrients to the water thus causing the Phiesteria to shape-shift and enter a state of lethal attack on everything from fish to human. The Center for Disease Control has yet to do anything about this at all, which may be the scariest fact so far.
This is representative of how eutrophication works in an aquatic environment. It shows that the greater the number of blue-green algae then the faster the oxygen depletion
Stephenson, R., & Blackburn, J. J. (1998). The Industrial Wastewater Systems Handbook. New York: Lewis Publishers.
The Chesapeake Bay has faced an excessive amount of pollution over the past century. The water in the bay has become so highly polluted that It is capable of causing harm to humans coming in direct contact with the water. Although algae serves a vital role in the bay’s ecosystem, it also creates a problem that is causing a large amount of the problem.
Algae blooms can develop slowly and their effects can be long lasting. The toxicity continues to take its toll on marine life, long after the bloom has dispersed (Edwards, 2013). Algae blooms in the water can contaminate the food supply of marine life and humans, posing health hazards to both (Phlips et al., 2012). The blooms limit the amount of light that can penetrate down into the water; thus, cutting down oxygen levels needed to sustain plankton and sea grass (Phlips et al., 2015). The toxins released by the blooms pass through the gills of fish and lead to death by respiratory failure (Flaherty & Landsberg, 2011). Plankton, seagrass, and fish are not the only marine life affected by the toxic blooms. Larger animals, such as the Florida manatee, are harmed by these algae blooms. Manatees succumb to toxic poisoning from the algae blooms by ingesting seagrass that has been polluted with neurotoxins (Edwards, 2013). Also, coastal birds that feed on fish in algae bloom infested waters are exposed to deadly bacteria levels. It is evident how climate change issues are causing Florida temperatures and rainfall to rise, while spreading the harmful effects of algae blooms (Phlips et al., 2012). A solution must be found to rid the water of this extremely harmful
There are several types of treatment methods present but biological treatment methods have gained much traction in the recent years due to their low operation costs, comparatively benign effects on the environment and their ease of handling and maintenance. Biological wastewater treatment methods can be subcategorized into dispersed growth systems and attached growth systems. Biofilms fall under the latter category (Sehar & Naz, 2016)
Organisms need their own set of nutrients. These nutrients are what help the cell survive so that the whole organism could survive. Organisms have their own set of nutrients. On earth there are three domains of life. These domains are the bacteria, Archaea, and eukarya (Brooker et al. 2013) most of the cells that are being researched and examined are cells in the domain Eukarya because cells in this domain usually exists in a multicellular complex. In the domain eukarya, the genus that was examined in this lab was Ceratopteris, which is also called c-fern; this plant is used in research to see how plant growth is affected by various changes that affect plant growth. (Lloyd, 1973) The reason that c-fern is used to do research is because of it’s developmental process. The reason why their life cycle is so unique is because it has a biphasic life cycle that has two independent diploid and haploid generations. (Hickok et al., 1995) This is useful because the haploid and the diploid can be isolated which will provide information on how each variable effect each different stage during each life cycle. (Hickok et al., 1995) another advantage of why c-ferns are used in research is because of their short life cycle. After inoculation, germination occurs in the following 3-4 days and full sexual maturity occurs between 6-8 days after germination. After one to two weeks, roots and leaves start to appear on the diploid sporophyte. (Hickok et al., 1995) these are the main reasons why c-ferns were chosen to see the effects of nitrogen on.
In recent years, recirculating aquaculture systems (RAS) have been employed to minimize water usage and environmental nutrient loading due to intensive fish farming. The recirculating of water throughout an RAS relies upon nitrifying microorganisms to transform ammonia and nitrite into nitrate. Nitrate is generally non-toxic to the fish species being raised. Additionally, as recirculating aquaculture systems have evolved, stocking densities have been pushed to their limit. As these RAS are pushed to their limits, problems with...
The main biotic factors are the plants, fish, and microorganisms. The plants are the main component of an aquaponic system, and they play a significant role in forming a symbiotic ecosystem, the plants also provide water full of nutrients for the fish. Additionally, the fish play a role in forming the ecosystem, but they also assist in the growth of the of the plants by allowing for clean water to be produced from their waste. The bacteria allow for the nitrification cycle to take place, in turn, cleaning the water in the
This helps consumers called heterotrophs and autotrophs use organic molecules produced by photosynthesis as a building block for growth and repair and as a source of chemical energy for cellular work. (Mader, 2013) Photosynthesis produces an enormous amount of carbohydrate that humans use to convert it into coal.