Algal biomass compositional analysis data form the basis of a large number of techno-economic process analysis models that are used to investigate and compare different processes in algal biofuels production. However, the analytical methods used to generate these data are far from standardized. This work investigated the applicability of common methods for rapid chemical analysis of biomass samples with respect to accuracy and precision. This study measured lipids, protein, carbohydrates, ash, and moisture of a single algal biomass sample at 3 institutions by 8 independent researchers over 12 separate workdays. Results show statistically significant differences in the results from a given analytical method among laboratories but not between analysts at individual laboratories, suggesting consistent training is a critical issue for empirical analytical methods. Significantly different results from multiple lipid and protein measurements were found to be due to different measurement chemistries. We identified a set of compositional analysis procedures that are in best agreement with data obtained by more advanced analytical procedures. The methods described here and used for the round robin experiment do not require specialized instrumentation, and with detailed analytical documentation, the differences between laboratories can be markedly reduced.

The effects of algae concentration, ferric chloride dose, and pH on the flocculation efficiency of the freshwater algae Chlorella zofingiensis can be understood by considering the nature of the electrostatic charges on the algae and precipitate surfaces. Two critical conditions are identified which, when met, result in flocculation efficiencies in excess of 90% for freshwater algae. First, a minimum concentration of ferric chloride is required to overcome the electrostatic stabilization of the algae and promote bridging of algae cells by hydroxide precipitates. At low algae concentrations, the minimum amount of ferric chloride required increases linearly with algae concentration, characteristic of flocculation primarily through electrostatic bridging by hydroxide precipitates. At higher algae concentrations, the minimum required concentration of ferric chloride for flocculation is independent of algae concentration, suggesting a change in the primary flocculation mechanism from bridging to sweep flocculation. Second, the algae must have a negative surface charge. Experiments and surface complexation modeling show that the surface charge of C. zofingiensis is negative above a pH of 4.0 ± 0.3 which agrees well with the minimum pH required for effective flocculation. These critical flocculation criteria can be extended to other freshwater algae to design effective flocculation systems.

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Bacteria control has recently become an important topic for discussion among the oil and gas industry, although it can still be misunderstood. A bacteria problem can oftentimes be subtle and difficult to detect. Bacteria detection in the field is difficult because many tests take a long period of time or are simply not accurate. New regulations on flowback and water production have led to the investigation of ways to reduce the amount of residual chemicals in flowbacks. Environmental concerns associated with chemical disinfection have led to the move from traditional chemical disinfection to mechanical procedures (Cho et al. 2002). Water that is used to make fracturing fluids usually requires treatment to reduce aerobic acid-producing bacteria and, more importantly, to eliminate anaerobic sulfate-reducing bacteria that can cause a well to go sour. Typically, this treatment is performed using chemical biocides. Using ultraviolet (UV) light to disinfect water on-the-fly for stimulation treatments will greatly reduce the amount of chemical biocides that are necessary. The effectiveness of UV light in disinfecting water for a fracturing treatment was tested in both a controlled laboratory environment and also on a fracturing location. The equipment used to generate sufficient UV light to disinfect the large volumes of water needed for fracturing was mounted on a trailer for road mobility.