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h i g h l i g h t sPilot-scale investigation of harvesting Chlorella minutissima by microfiltration. Modelling and harvesting costs determined as a function of energy consumption. Influence of the operating parameters on harvesting costs was investigated. Feasibility of membrane filtration was discussed in relation to DSP. a b s t r a c tMicroalgae biomass is seen as a sustainable and socially more responsible feedstock for the production of biofuels and other fine chemical products. Dewatering algae using membrane filtration is a leading technology, however the associated costs are typically not determined. This work investigates the filtration of Chlorella minutissima using a pilot-scale cross-flow microfiltration unit. A filtration model was developed and validated based on permeate flux as a function of biomass concentration (0.6-19.0 dry cell weight/L) and transmembrane pressure (DP, 1.80-2.10 bar). Processing times for harvesting C. minutissima were determined by iteration of the model and costs were related to energy consumption. For the experimental conditions of 1.95 bar, 1.0 g DCW/L initial biomass concentration, 0.70 kWh, 25°C and 3.8 m 2 membrane area, harvesting costs were determined as 2.86 kWh/kg biomass. Subsequent investigation of the influence of the operating parameters and scale-up effects demonstrated that significant cost reduction to 1.27 kWh/kg biomass was possible at 1.95 bar, 2.0 g DCW/L initial biomass concentration, 0.46 kWh, 20°C and 7.6 m 2 membrane area. Further, biomass concentration was demonstrated to be one of the major drivers to reduce the cost of harvesting microalgae. Membrane filtration was demonstrated to be a feasible harvesting process allowing biomass concentrations up to 150 g DCW/L without using chemicals which complicate the downstream processing stages.

Abandoned mines cause serious environmental damage to their surroundings with considerable impacts on freshwater ecosystems. These impacts occur mainly due to the uncontrolled discharge of polluted effluents, which may contain high concentrations of heavy metals. Currently, no real solution exists for this important environmental problem, leaving a legacy of global pollution. This study aimed to assess the impact of a metal mining effluent from an abandoned mine on freshwater ecosystems, using aquatic biofilms as an ecological indicator. At the same time, the efficiency of different innovative treatment technologies in reducing the ecological impacts caused by mining effluents was evaluated, consisting of nanofiltration and nanofiltration combined with electrocoagulation. To do that, aquatic biofilms obtained from a pristine stream, were exposed, under microcosms conditions, to a metal mining effluent, untreated or treated by the innovative treatment technologies and responses were compared with unexposed biofilm which served as control. The structural and functional responses of the biofilm were measured with throughout time. Biofilms that were exposed to the untreated mining effluent showed significant differences respect to the rest of treatments and the control, particularly exhibiting inhibitory effects on photosynthetic efficiency just after 24 hours of exposure and a progressive shift of the photosynthetic community composition throughout the exposure period. The treatment technologies significantly reduced the ecological impact caused by the metal mining effluent. However, metal bioaccumulation in biofilm revealed a potential long-term impact. These observations evidenced the biofilm as a useful ecological indicator to assess the ecological impact caused by metal mining effluents on freshwaters and the efficiency of different treatment technologies to reduce it.

Abstract. Removal of silver from wastewater was investigated using continuous cross flow microfiltration (MF) technique hollow fiber membranes with a pore size 0.2µm, with sorbent coated material Al 2 O 3 /SDSH 2 Dz particle size (8 µm). The coating investigated was dithizone (Diphenylthiocarbazone) in 0.005M ammonia solution. In the filtration of silver ion solutions, the effects of the permeate flow rate and cross flow velocity on the absorption of silver ion solutions, and since the pore size of membrane (=0.2 µm) is smaller then that of the (Al 2 O 3 ), no need to consider the variation of (Al 2 O 3 ).rejection as it can be considered to be 100%. The amount of silver absorbed into sorbent material Al 2 O 3 /SDSH 2 Dz was (25.35, 39.68 ppm) for the cross flown velocity of 5, 2.5 L/hr respectively, and were the results as function of permeate flow was (25.35, 39.68 ppm) for the velocity of 5, 2.5 L/hr respectively.