The hydrothermal liquefaction (HTL) of algal biomass is a promising route to viable second generation biofuels. In this investigation HTL was assessed for the valorisation of algae used in the remediation of acid mine drainage (AMD). Initially the HTL process was evaluated using Arthrospira platensis (Spirulina) with additional metal sulfates to simulate metal remediation. Optimised conditions were then used to process a natural algal community (predominantly Chlamydomonas sp.) cultivated under two scenarios: high uptake and low uptake of metals from AMD. High metal concentrations appear to catalyse the conversion to bio-oil, and do not significantly affect the heteroatom content or higher heating value of the bio-oil produced. The associated metals were found to partition almost exclusively into the solid residue, favourable for potential metal recovery. High metal loadings also caused partitioning of phosphates from the aqueous phase to the solid phase, potentially compromising attempts to recycle process water as a growth supplement. HTL was therefore found to be a suitable method of processing algae used in AMD remediation, producing a crude oil suitable for upgrading into hydrocarbon fuels, an aqueous and gas stream suitable for supplementing the algal growth and the partitioning of most contaminant metals to the solid residue where they would be readily amenable for recovery and/or disposal.

In this investigation, PHB producing cyanobacteria were converted through hydrothermal liquefaction (HTL) into propylene and a bio--oil suitable for advanced biofuel production. HTL of model compounds demonstrated that in contrast to proteins and carbohydrates, which react to produce a range of alternative intermediates, no synergistic effects were detected when converting PHB in the presence of algal biomass. Subsequently, Synechocystis cf. salina, which had accumulated 7.5 wt% PHB was converted via HTL (15 % dry weight loading at 340 °C). The reaction gave an overall propylene yield of 2.6 %, higher than that obtained from the analogous model compounds, in addition to a bio--oil with a low total nitrogen content of 4.6 %. No propylene was recovered from the alternative non--PHB producing cyanobacterial strains, Anabaena, Spirulina or Synechococcus, suggesting that PHB is the sole source of propylene. PHB producing microorganisms could therefore be used as a feedstock for a biorefinery to produce polypropylene and advanced biofuels, with the level of propylene being directly proportional to the accumulated amount of PHB.

Algae have been proposed as a source of biofuels and high value chemical products, but if this potential is to be fully realised, it is crucial to understand the factors a↵ecting the suspension rheology. Suspensions of three algae species, Tetraselmis chuii, Chlorella sp. and Phaeodactylum tricornutum, were sheared in a rotational rheometer in order to characterise their rheology and examine the e↵ects of cell concentration, motility and morphology. The volume fraction ranged from 0.05 to 0.2, and the shear rate from 20 to 200 s 1. The rheology measurements are fitted to the Herschel-Bulkley model, and the intrinsic viscosity is estimated using both Einstein's equation and the Krieger-Dougherty model, which are found to perform well for low concentrations. The intrinsic viscosity of T. chuii suspensions is shown not to be constant, but decreases with strain rate, indicating that the suspension viscosity is less sensitive to the cell concentration at high strain rates. The rate of decline is constant for strain rates below approximately 100 s 1 , after which it continues to decline linearly but at a slower rate. It is speculated that this transition at

a b s t r a c tDespite the increasing use of Decentralised Waste Water Systems (DEWATS) in the developing world, which effectively dewater sludge, the problem of preventing the pathogen-laden water produced by these systems from re-entering the food chain constitutes a continuing burden on developing countries, which hinders subsequent advancements. We report on a swirl flow reactor generating high mixing areas which in conjunction with Cu/alginate beads effectively reduces Escherichia coli numbers by five orders of magnitude in 10 min. The system is simple, low cost, portable and modular; it can be assembled with simple plastic plumbing parts available in most areas and, once further developed, may represent a useful adjunct for both existing and new DEWATS facilities.