Hydrothermal processes for simultaneous bioenergy recovery and destruction of bioactive microconstituents from biosolids

Biosolids from animal manure contain bioactive microconstituents that potentially contribute to ecological or health effects. For instance, estrone (E1), 17β-estradiol (E2), and estriol (E3) can have adverse effects on the reproductive biology of vertebrates at very low concentrations (Irwin et al., 2001; Schuh et al., 2011). Antibiotic resistant bacteria that cause life threatening infections can be developed from bacteria exposed to low levels of antibiotics excreted in urine and feces (Wise et al., 1998; Sarmah et al., 2006; Berge et al., 2006; Martinez, 2009). This study investigates the effects of Mixed algal-bacterial bioreactor (MABB) and hydrothermal processes such as hydrothermal liquefaction (HTL) and catalytic hydrothermal gasification (CHG) simultaneously produce biomass for bioenergy production and reduce the discharge of bioactive microconstituents. Thus, the integrated system improves the quality of water resources and increase energy security by removing organics/nutrients and producing bio crude oil/gas, respectively.Fresh swine manure samples were filtered with 0.45 μm membrane to generate the liquid portion of swine manure (LPAM). GC/MS followed by Solid Phase Extraction (SPE) were used to analyze bioactive microconstituents and the concentration of E1, E2, E3, and EE2 in LPAM were ranged from 10,602 to 22,646 ng/L. cytotoxicity of the LPAM was investigated using a previously developed Chinese Hamster Ovary (CHO) cell assay (Hsie AW, 1975; Wagner et al., 1998), and the extracted LPAM organics had a cytotoxicity index of 2.38, which is slightly less than secondary municipal wastewater effluent, 2.64 (Pham et al., 2013). A fluctuation test was developed to measure antibiotic resistance in bacterial populations exposed to antibiotics in manure. E. coli 15597 was exposed to florfenicol (FF) at lethal (17 μg/mL) concentration that provides a selective advantage to individual bacterium that were acclimated to under non-lethal FF selection (2 μg/mL), and this study confirmed that exposure to FF at a non-lethal concentration increased survival during an antibiotic challenge.MABB with adsorbents was operated to extract bioactive microconstituents and other organics from the LPAM under various operating conditions (organic loading: 35.3 to 470 mg sCOD/L/d; light intensity 350 μmol photons/m2/s; temperature: 18 to 25 °C; Hydraulic retention time: 4 days; Solid retention time: 30 days), and biomass was harvested to use as a biofuel feedstock with maximum productivity of 819 mg/L/d.HTL and CHG with 9 different conditions (Temperature: 200 to 550 °C; Time: 60 min; Catalyst: Ruthenium on alumina) were performed to determine the optimal conditions for renewable energy production and to study the effects on the fate of bioactive bioactive microconstituents. E1and E2 in the spiked biomass was removed up to 94.6 and 99.8% with HTL run at 300 °C/60 min which was the most optimal condition to produce bioenergy. The cytotoxicity of the HTL-WW under three conditions (sample I, II, and III: 250°C/60min, 300°C/60min, and 350°C/60min) was investigated CHO cell assay. Mean cytotoxicity index (CTI) values of sample I, II, and III were 3710.2, 2380.8, and 5373.3, respectively, which tells us that the descending cytotoxicity potency was Sample III < Sample I < Sample II and toxicity in HTL-WW is proportional to the temperature of HTL (250° and 300°C < 350°C).In conclusion, the combination of MABB and HTL/CHG can simultaneously remove bioactive microconstituents from swine manure (E2, MABB: 92.3 ± 1.5%; HTL: 99.7 ± 0.1%, CHG: 99.9 ± 0.01%) and convert them into valuable bioenergy products under optimal condition (HTL: 300 °C/60min, CHG: 450 °C/60min/Ru). This will contribute to the development of cost-effective systems to reduce water pollution and increase bioenergy production as well as opportunities for reuse of the aqueous fraction.