Wastewater & Sewage Treatment
Typically considered a menace targeted for eradication, algae are increasingly recognized as a valuable tool in managing certain phases of wastewater treatment. In the digestion phase, organic solids are broken down into component nutrients by bacteria, which require oxygen to work. Maintaining a high concentration of bacteria speeds the process, but high concentrations can also deplete available oxygen, killing the useful bacteria and throwing off the rest of a carefully balanced cycle. Algae’s powerful oxygen contribution during this step can keep the treatment process going at full speed.
As digestion proceeds, the wastewater is also enriched with nutrients such as potassium, carbon, and nitrogen. An abundance of these nutrients inevitably increases Biochemical Oxygen Demand (BOD) of the wastewater, which must be reduced before the treated water can be released back into circulation. Removal of these nutrients can be difficult, but it’s a task well suited for algae, which quickly takes up phosphates, CO2 and harmful nitrogen compounds like ammonia and nitrates as it produces biomass as well as abundant oxygen.
Some wastewater plants also use maturation or polishing ponds to remove fecal coliform, pathogens, pharmaceuticals and heavy metals. Algae are also a primary driving force in this treatment phase, since they can take up both inorganic and organic toxic substances, pesticides and even radioactive matter in their cells.
Energy production
Microalgae is already well known for its potential as a source for biodiesel production because of its high oil content and rapid growth, which is covered in the next article. However, if the value of algae stopped there, it would not represent such an exciting resource. In addition to biodiesel, microalgae can be used to generate energy in other ways. Some algae can be grown to produce hydrogen gas, and the biomass remaining after oil extraction can be anaerobically digested to produce methane gas, used in the production of heat and electricity. Algal biomass can be treated by pyrolysis to generate crude bio-oil. And once all possibilities for use and re-use have been exhausted, the remaining biomass can be burned, similar to wood.
In fact, algae have a unique property in that, after oil extraction, the remaining algae product (biomass) can be used to create other types of biofuels that, in turn, fuel further power generation sources. This takes pressure off problematic energy sources such as coal, natural gas, and nuclear power. In effect, it’s comparable to hydroelectric and geothermal energy sources.
Agriculture
Algae is extremely valuable as a fertilizer in any production of vegetable crops, whether land or water based.
- As a living organism, algae break down quickly when applied to agricultural land. This rapid breakdown allows nutrients, including critical elements like nitrogen and phosphorus, to become available to growing crops faster than from chemical fertilizers.
- Seaweeds (macroalgae) are particularly valuable as biofertilizers
- Certain algae are widely used to lime soil, decreasing the soil’s acidity and promoting uptake of important plant nutrients.
Soil Remediation
Algae is not only a remarkably promising food crop, but it also offers substantial benefits to land-based agriculture as well, where it can be used to improve physical and chemical soil quality.
- In India, blue-green algae are used to rehabilitate large tracts of land covered with non-cultivable ‘usar’ soil by lowering the soil’s pH, adding organic matter, and increasing its water holding capacity.
- Algae is useful as a stabilizer and binding agent for surfaces where soil has been disturbed, eroded, or burned. Green and blue-green algae can quickly cover soil in these areas, forming mats or crusts which reduce the danger of erosion while still permitting full infiltration of water.
- Similarly, algae have been used in regions where wind erosion is a significant concern. Filamentous algae has been used to stabilize sandy wastes by forming cohesive mats which mitigate both wind and water erosion. Some algae have been discovered growing in desert conditions, where it has vastly increased organic carbon and organic nitrogen, decreased erosion and improved infiltration, making the soil much more suitable for agricultural use.
