There are a total of 9,416 water bodies in the United States classified by the Environmental Protection Agency as ‘impaired’ due to nutrients, ammonia and algae. Near such impaired water bodies, efforts are being made to improve water quality by reducing the nutrients, mainly nitrogen and phosphorus, discharged by publicly owned water treatment works (POTWs).
Landfill leachate is commonly routed to POTWs and can contain high nutrient levels, such as nitrogen concentrations of 50 to upwards of 2500 mg N/L (usually in the form of ammonia), that can be received at a treatment plant. One option to deal with landfill leachate is to treat it on-site rather than sending it to a POTW.
Biological treatment systems can be used to remove nutrients and various types of systems have been explored for treating leachate. One such approach has been the use of algae as the main biological component for such a treatment system since algae naturally consumes nitrogen and phosphorus for growth, both of which are found in abundance in leachate.
In addition to removing nutrients from leachate and reducing overall nutrient content from POTW effluent, algal biomass can be harvested to produce various useful by-products, such as: biofuels, livestock diet supplements, cosmetics and pharmaceuticals, and even electrical components such as supercapacitors. The use of lipids from algal biomass is frequently considered in the search for alternative transport fuel sources. One of the largest hurdles in the use of algae for biodiesel is making it economically affordable. Coupling algae production for biomass production system to a leachate treatment approach could offset some of the treatment costs associated while producing a useful end product.
When considering wastewater sources to be used as nutrients for algal growth, leachate is often overlooked. While domestic wastewater is one of the most commonly investigated, research at Drexel University by the author and faculty, Mira Olson and Christopher Sales, has found that a mixed algae-bacteria culture proliferates in the high ammonia conditions of landfill leachate. These studies show an average of 29 percent nitrogen removal from leachate. The use of a nutrient source high in ammonia, along with a mixed algal-bacterial culture, resulted in a greater overall nitrogen removal.
The challenges of operating this type of algal treatment system include the variability of both environmental factors (temperature, sunlight) as well as the leachate composition, such as fluctuating ammonia concentrations, organic particulates, heavy metals, and any other constituent that may aide or inhibit biological growth. While more research is needed to refine the approach, the data show that the use of algae may prove attractive in the long run as new approaches to utilize waste as a resource are being explored.
Kaitie Sniffen is a Ph.D. candidate at Drexel University and a PTR Baler & Compactor EREF Scholar. Her research interests include sustainable practices, resource reuse, waste to energy technology, water remediation and alternative energies. Kaitie received her bachelor’s degree in chemistry from the University of Massachusetts – Amherst where she also studied the fate of gold nanoparticles in aquatic environments. In her free time she enjoys reading, traveling and any activity that involves being outside or on a body of water.