(136c) Use of a Plant-Based Natural Biomaterial in Flocculation-Separation and in Absorption Systems for Removing Organic Contaminants in Water

Recirculating aquaculture systems (RAS) has been successfully used for several decades. The advantages of RAS include reduced use of land and water supplies in places where resources are limited.  However, due to the rigorous reuse of water in RAS, special attention should be provided to RAS’s quality parameters such as dissolved oxygen, suspended solids, alkalinity, ammonia, nitrite and nitrate, and metal content. In particular, RAS are known for generating  high amounts of compounds such as trans-1,10-dimethyl-trans-9-decalol (geosmin) and 2-methylisoborneol (MIB), which provide an earthy-musty  smell in fish (i.e., off-flavor compounds). The purpose of this work is to investigate a new environmental friendly green technology to treat RAS for removing organic compounds such as geosmin and MIB. This technology is inexpensive and uses a plant-based natural biomaterial (cactus mucilage) extracted from a cactus plant (i.e., Opuntia ficus-indica, commonly known as nopal). Previous research in our group has shown that the mucilage is efficient at removing turbidity, bacteria (E. coli, Bacillus sp., and Vibrio furnissii) and arsenic from contaminated water as well as enhancing particle settling rates. This work focusses on investigating the conditions under which cactus mucilage is able to reduce high levels of light and heavy metals, and geosmin and MIB from RAS in two fashions. First, when cactus mucilage is used as a powder in flocculation-separation experiments, and second, when it is embedded in biobeads for absorption systems. The elemental composition (P, Mn, Pb, Cr, Ti, Zn, Ni, Sr, Sb, B, Cu, Co, Mo, U, V, Ba, Fe, Se and As) of RAS samples before and after cactus mucilage  treatment was determined by inductively coupled plasma mass spectrometry (ICP-MS). Off-flavors content (i.e., geosmin and MIB concentrations) was evaluated by solid based micro extraction (SPME), and gas chromatography mass spectrometry (GC-MS). Mucilage concentrations of 100 mg/L were able to reduce metal concentrations using mucilage powder for up to 96% with respect to the controls. In some instances, 10 mg/L of cactus mucilage was enough to remove Mn, Sb, Cu, Ti, V and Se with solution differential concentrations ranging from 30 to 70 %. For off-flavor compounds, it was found that after 24 hours of interaction with biobeds, 10 mg/L of the mucilage removed in average 61% of MIB and 88% of the geosmin. Cactus mucilage can be obtained through sustainable agriculture, it is easy to extract and has a long-shelf life. Therefore, it is expected that this technology can lead to sustainable solutions related to the treatment of RAS.