Darren L. Oatley-Radcliffe

Moving towards sustainable resources: Recovery and fractionation of nutrients from dairy manure digestate using membranes

The fractionation of nitrogen (as ammonia/ammonium) and phosphorus (as phosphate ions) present in the dairy manure digestate was investigated using a nanofiltration membrane NF270. The filtration and separation efficiencies were correlated to pH across the range 3 < pH < 11. Filtration at pH 11 enabled higher permeate flux of 125-150 LMH at 20 bar, however rejection of ammonia was high at 30-36% and phosphate was 96.4-97.2%. At pH 3 and pH 7, electrostatic charge effects led to higher permeation of ammonium and thus more efficient separation of nitrogen. The rejection of phosphorus was relatively constant at any given pH and determined as 83% at pH 3, 97% at pH 7 and 95% at pH 11. The fractionation of nitrogen and phosphorus from complex aqueous solutions was demonstrated to be highly dependent on the charge of the membrane and ionic speciation. Solutions rich in nitrogen (as ammonia/ammonium) were obtained with almost no phosphorus present (<1 ppm) whilst the purification of the PO4-P was achieved by series of diafiltration (DF) operations which further separated the nitrogen. The separation of nutrients benefited from an advantageous membrane process with potential added value for a wide range of industries. The analysis of the process economics for a membrane based plant illustrates that the recovery of nutrients, particularly NH3-N, may be commercially feasible when compared to manufactured anhydrous NH3.

Minimizing the Energy Requirement of Dewatering Scenedesmus sp. by Microfiltration: Performance, Costs, and Feasibility

The harvesting of the microalgae Scenedesmus species using a 200 L pilot-scale microfiltration system was investigated and critically assessed. The energy requirement was determined and correlated to the different operating parameters, such as transmembrane pressure (ΔP), membrane area, temperature, and initial biomass concentration. A filtration model was developed and showed a strong correlation with experimental data up to 20.0 g of dry cell weight (DCW)/L. The non-optimized filtration system had an energy requirement of 2.23 kWh/m(3) with an associated cost of

Utilising light-emitting diodes of specific narrow wavelengths for the optimization and co-production of multiple high-value compounds in Porphyridium purpureum

0.282/kg of microalgae. The investigation into the influence of the operating parameters and scale-up effects showed that the energy requirement could be substantially reduced to 0.90 kWh/m(3) and

Superhydrophilic Functionalization of Microfiltration Ceramic Membranes Enables Separation of Hydrocarbons from Frac and Produced Water

0.058/kg of microalgae harvested. Maintenance costs associated with cleaning were estimated to be 0.23 kWh or

Electrokinetic Phenomena for Membrane Charge

0.029/batch of microalgae processed. Dependent upon the operating conditions, harvesting may represent 6-45% of the energy embedded in the microalgae with a carbon footprint of 0.74-1.67 kg of CO2/kg of microalgae. Microfiltration was demonstrated to be a feasible microalgae harvesting technology allowing for more than 99% volume reduction. The energy requirement and associated carbon footprint of microalgae harvesting reported here do not forfeit the need for an industrial-scale study; however, the information provided presents a more realistic approximation than the literature reported to date.

The Use of Modeling for Characterization of Membranes

The effect of specific narrow light-emitting diode (LED) wavelengths (red, green, blue) and a combination of LED wavelengths (red, green and blue - RGB) on biomass composition produced by Porphyridium purpureum is studied. Phycobiliprotein, fatty acids, exopolysaccharides, pigment content, and the main macromolecules composition were analysed to determine the effect of wavelength on multiple compounds of commercial interest. The results demonstrate that green light plays a significant role in the growth of rhodophyta, due to phycobiliproteins being able to harvest green wavelengths where chlorophyll pigments absorb poorly. However, under multi-chromatic LED wavelengths, P. purpureum biomass accumulated the highest yield of valuable products such as eicosapentaenoic acid (∼2.9% DW), zeaxanthin (∼586μgg-1DW), β-carotene (397μgg-1DW), exopolysaccharides (2.05g/L-1), and phycobiliproteins (∼4.8% DW). This increased accumulation is likely to be the combination of both photo-adaption and photo-protection, under the combined specific wavelengths employed.

Chapter 16 – The Use of Modeling for Characterization of Membranes

The environmental impact of shale oil and gas production by hydraulic fracturing (fracking) is of increasing concern. The biggest potential source of environmental contamination is flowback and produced water, which is highly contaminated with hydrocarbons, bacteria and particulates, meaning that traditional membranes are readily fouled. We show the chemical functionalisation of alumina ceramic microfiltration membranes (0.22 μm pore size) with cysteic acid creates a superhydrophilic surface, allowing for separation of hydrocarbons from frac and produced waters without fouling. The single pass rejection coefficients was >90% for all samples. The separation of hydrocarbons from water when the former have hydrodynamic diameters smaller than the pore size of the membrane is due to the zwitter ionically charged superhydrophilic pore surface. Membrane fouling is essentially eliminated, while a specific flux is obtained at a lower pressure (<2 bar) than that required achieving the same flux for the untreated membrane (4–8 bar).

Mass Transport in Porous Liquid Phase Membranes

Membrane charge is fundamental to the separation of ions from a membrane and is a major factor in the separation efficiency of ultrafiltration, nanofiltration, and reverse osmosis membranes. Characterization of the charge properties of membranes can be performed using a variety of different methods. In this chapter, the electrokinetic phenomena of electrophoresis, electro-osmosis, sedimentation potential, and streaming potential are described. Each of these methods is capable of measuring the zeta potential of the membrane in a given electrolyte solution and has been discussed. The fundamental basis of each of the methods is provided and theoretical descriptions are provided. The streaming potential method is the most commonly employed method for the characterization of membrane charge and this technique is described in detail. Typical commercial equipment is shown and discussed and a set of experimental results is provided to illustrate the methodology.

Feed Solution Characterization

The typical characteristics of membranes can be estimated directly from experimental data. To successfully characterize membranes using such techniques a representative model of the membrane process must be used that is simple enough for solution yet detailed enough to capture the key characteristics required. Two cases have been considered where the membrane process has been characterized. The first case is for large pore membranes where slurry filtration or gel layers form on the membrane surface, which is quite typical for microfiltration and ultrafiltration processes. A simple model was described that considers the membrane resistance and the specific cake resistance. The experimental data required are outlined and worked examples are provided that show how to manipulate the data to capture the membrane characteristics. More intensive models that describe the complex microhydrodynamics and interfacial events occurring at the surface and within the small pore membranes are also described. These models are shown to be far more complex and the solution methodologies are not trivial. However, these methods are capable of providing characterization of the pore radius and electrical properties of the membrane at almost atomic scale dimensions. For the case of pore size characterization a simple analytical equation is available and a worked example is provided along with a narrative on best practice. The characterization of electrical properties is far more complicated and involves the solution of nonlinear differential equations. A solution methodology has been explained and tips on best practices have been provided. Overall, membrane characterization using models and experimental data has been demonstrated and can be used for the evaluation of novel membranes or as a guide for the scientist or engineer in the design, scale-up, and optimization of new membrane processes.

Atomic Force Microscopy (AFM)

The typical characteristics of membranes can be estimated directly from experimental data. To successfully characterize membranes using such techniques a representative model of the membrane process must be used that is simple enough for solution yet detailed enough to capture the key characteristics required. Two cases have been considered where the membrane process has been characterized. The first case is for large pore membranes where slurry filtration or gel layers form on the membrane surface, which is quite typical for microfiltration and ultrafiltration processes. A simple model was described that considers the membrane resistance and the specific cake resistance. The experimental data required are outlined and worked examples are provided that show how to manipulate the data to capture the membrane characteristics. More intensive models that describe the complex microhydrodynamics and interfacial events occurring at the surface and within the small pore membranes are also described. These models are shown to be far more complex and the solution methodologies are not trivial. However, these methods are capable of providing characterization of the pore radius and electrical properties of the membrane at almost atomic scale dimensions. For the case of pore size characterization a simple analytical equation is available and a worked example is provided along with a narrative on best practice. The characterization of electrical properties is far more complicated and involves the solution of nonlinear differential equations. A solution methodology has been explained and tips on best practices have been provided. Overall, membrane characterization using models and experimental data has been demonstrated and can be used for the evaluation of novel membranes or as a guide for the scientist or engineer in the design, scale-up, and optimization of new membrane processes.