Nutrients in dairy wastewaters can be remediated through assimilation into algal biomass. Anaerobically digested manure creates an effluent (ADE) that is useful for algal cultivation while alternate processing of manure through a polyhydroxyalkanoate reactor generates a distinct effluent (PHAE), not previously characterized for algal cultivation. Each effluent was evaluated for growth rate, biomass production, and nutrient recovery using type algae species Chlorella vulgaris. Growth rates were elevated in 5, 10, and 20 % dilutions of PHAE (0.59, 0.53, 0.42 days−1) compared to equal concentrations of ADE (0.40, 0.36, 0.37 days−1). In addition, the growth phase lasted up to twice as long for PHAE, resulting in a fourfold higher stationary phase algal concentration (cells∙mL−1) compared to ADE. Growth in ADE was limited by specific inhibitory properties: high concentrations of dissolved organic matter, ammonia, and elevated bacterial load. Maximum nutrient removal rates for ADE and PHAE were 0.95 and 3.46 mg·L−1·day−1 for nitrogen and 0.67 and 0.04 mg·L−1·day−1 for phosphorus, respectively. Finally, biomass derived from PHAE was higher in lipids (11.3 % versus 7.2 %) and thus has a greater potential as a feedstock for biofuel compared to ADE

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Cost-effective methods for protecting crops from grazing organisms like rotifers are needed to reduce the risk of pond crashes in mass algal cultures. We present a novel strategy to optimize the exposure time to free ammonia, via control of media pH, in both defined media and dairy anaerobic digester effluent to suppress rotifers and maintain algal productivity. We tested five different free ammonia exposure times (0, 1, 2, 6, and 12h) and found a significant nonlinear effect of exposure time (p<0.0001) but not pH (p>0.9) on rotifer survival. In both media types, 6-12h of elevated free ammonia significantly reduced Brachionus plicatilis rotifer survival with no negative effects on Nannochloropsis oculata, while shorter exposure times were insufficient to inhibit rotifers, leading to severe algal culture crashes. These results suggest that algal crops can be protected from rotifers, without productivity loss, by elevating free ammonia for 6 or more hours.

This study investigated the production of crude bio‐oils from three laboratory cultivated and two commercial grade algal biomass sources via hydrothermal liquefaction (HTL) process. Results demonstrated the crude bio‐oils generated from laboratory cultivated algae fed 5% anaerobic digestion effluent as sole nutrient source have similar thermochemical characteristics as comparison with that of derived from commercial algae. The HTL conditions were optimized (300°C for 20 min) and the generated bio‐oils were characterized by gas chromatography mass spectrometry, Fourier transform infrared spectroscopy, and electrospray ionization‐mass spectrometry analyses and simulated distillation by thermogravimetric analysis. The bio‐oil yields were between 28 and 41%. The bio‐oils were mainly comprised of fatty acids and alkanes. These bio‐oils can be further upgraded and refined into value added transportation fuels and chemicals. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 781–787, 2017