(752e) Nutrient Capture By a Sustainable Symbiotic Biofilm: Simultaneous Phosphorous and Nitrogen Recovery By Attached Fungi and Microalgae Biofilm

Nutrient pollution, a condition of excess phosphate (P) and nitrate (N) from point and non-point sources, is a major water quality concern worldwide due to the tremendous volume of urban, agricultural and industrial wastewater production [1]. The elimination of phosphorus from effluents before discharging is made mandatory as even traces of P (above 0.02 mg/L) can cause eutrophication, also P level is regulated to be lower than 0.05 mg/L, if streams discharge into lakes or reservoirs. On the other hand, the P reserves are being depleted swiftly which apparently is linked to global food security, with more than 90% of phosphorus used for agricultural purpose [2]. Currently a curative solution to combat water pollution by recuperating N and P, recycling the P for food production by closing the nutrient loop to effectively manage dwindling rock P reserve are the major challenges. The most common phosphorus removal techniques for municipal and industrial wastewater are biological treatment and chemical precipitation. Bio-valorization offers an excellent alternative to chemical treatment technologies as the biomass produced can be a source of protein and other valuable bio-chemicals also it is an eco-friendly and low cost technology.

In this present work, a novel composite biofilm called mycoalgae biofilm [3] was developed using the isolated strains of polyphosphate accumulating fungi and microalgae and we want to apply this platform for the efficient recovery and recycling of nutrients in waste stream. The effect of various process conditions (fungal strain, carbon levels, temperature, P/N ratio) on the nutrient recovery efficiency and the changes in the biofilm biomass composition was studied. Since the biofilm will be used for nutrient recovery from an array of samples a synthetic medium for the cell growth with the initial P (40 mg/L), N (200 mg/L) and other nutrients were used as the medium for the biofilm development. Depending on the nature of the waste water and its composition, and the fungi-microalgae combination intended to use for bio-remediation, the developed mycoalgae biofilm can be a sustainable microbial process for food, feed or energy source.

Methods: Water and soil samples were collected from Sarita wetland near UMN to isolate the native fungi for the biofilm formation. Fungal isolates were identified by genetic identification of fungal internal transcribed spacer (ITS) regions. Maximum Phosphorous and Nitrogen removal was observed in strain Sa7 (Mucor sp.) and Chlorella sp, combination which was considered for the biofilm formation and Nutrient recuperation. The morphology of the biofilm was also studied using CLSM and SEM at the optimized conditions to study the interaction between the cells. The nutrient removal efficiencies were calculated using the equation: RE_i = (S_i0 â?? S_it)/S_i0; where RE_i is the removal efficiency of the nutrients i (TN, TP, PO₄-P) or the pollutants (i) using the mycoalgae lichen type biofilm; S_i0 and S_it are the initial and final concentration of component i after t days. The rate of nutrient and pollutant removal by mycoalgae biofilm is an important factor which will be calculated by; dS/dt = r_i = (S_i0 â?? S_it)/ (t_i â?? t₀); Where: r_i (g/L/d) is the removal rate of substrate i (TN, TP, PO₄-P).

Conclusion: The composite biofilm shows promising results in waste water treatment especially in removing the N, P, suspended solids and other organics from nutrient polluted water in a single-step reactor with easy biomass recovery and high efficiency, when compared to the individual pure cell cultures. The biofilm attaches to the polymer matrix completely leaving behind the clean water for recirculation, and the composite biomass for nutrient recycle. The biofilm composition can also be tailored based on the influent stream components, feasibility of the strains to grow together and its nutrition value for further use. The commercial expansion of this biofilm system could be a step ahead in having an integrated and sustainable water treatment systems. References

1. E.K. Wilson, Danger from microcystins in Toledo water unclear, Chem. Eng. News, 92 (32) (2014), p. 9
2. Ye, Y., Gan, J., & Hu, B. (2015). Screening of Phosphorus-Accumulating Fungi and Their Potential for Phosphorus Removal from Waste Streams. Applied biochemistry and biotechnology, 177(5), 1127-1136.
3. Bo Hu, Aravindan Rajendran, A Novel Microalgae Cultivation Technology Using Fungi and Lichen Biofilm, UMN invention disclosure case # 20140274