Printing Ink Wastewater Treatment Using Hydrodynamic Cavitation and Coagulants/Flocculants.

Raw printing ink wastewater (PIW) was treated with various inorganic coagulants and organic flocculants (anionic and cationic polyacrylamides). These processes were also examined as post treatment step following hydrodynamic cavitation. Treatment effectiveness was assessed through color, chemical oxygen demand (COD) and total suspended solids (TSS) removal. The addition of 4500 mg L-1 polyaluminum chloride coagulant in undiluted PIW (COD: 17000 mg L-1) resulted in 99% color removal, 96% COD and TSS removal, after settling for 2 h. The addition of 10 mg L-1 of anionic polyacrylamides in the sample reduced settling time to only 5 min, with concomitant 96-98% removal efficiency. The addition of a 4 min hydrodynamic cavitation pretreatment step reduced coagulant addition by 33%, for the treatment of undiluted PIW (with 10 mg L-1 anionic polyacrylamide), while removals were ranged between 96 and 98%. Economic analysis for the undiluted PIW showed that costs were reduced by ca. 20% with the hydrodynamic cavitation pretreatment step. Moreover, sludge characterization showed the presence of maghemite, aluminum chloride and potassium aluminum silicate. Finally, toxicity tests revealed a significant attenuation of the toxic potential of undiluted PIW, thus indicating the enhanced efficiency of the proposed combined process (hydrodynamic cavitation and coagulation/flocculation).

Membrane filtration of olive mill wastewater and exploitation of its fractions.

Olive mill wastewater (OMW) produced from small units scattered in rural areas of Southern Europe is a major source of pollution of surface and subsurface water. In the present work, a treatment scheme based on physical separation methods is presented. The investigation was carried out using a pilot-plant unit equipped with ultrafiltration, nanofiltration, and reverse osmosis membranes. Approximately 80% of the total volume of wastewater treated by the membrane units was sufficiently cleaned to meet the standards for irrigation water. The concentrated fractions collected in the treatment concentrates were characterized by high organic load and high content of phenolic compounds. The concentrates were tested in hydroponic systems to examine their toxicity towards undesired herbs. The calculations of the cost of the overall process showed that fixed and operational costs could be recovered from the exploitation of OMW byproducts as water for irrigation and/or as bioherbicides.

Computation of light scattering by axisymmetric nonspherical particles and comparison with experimental results.

A laboratory prototype of a novel experimental apparatus for the analysis of spherical and axisymmetric nonspherical particles in liquid suspensions has been developed. This apparatus determines shape, volume, and refractive index, and this is the main difference of this apparatus from commercially available particle analyzers. Characterization is based on the scattering of a monochromatic laser beam by particles [which can be inorganic, organic, or biological (such as red blood cells and bacteria)] and on the strong relation between the light-scattering pattern and the morphology and the volume, shape, and refractive index of the particles. To keep things relatively simple, first we focus attention on axisymmetrical particles, in which case hydrodynamic alignment can be used to simplify signal gathering and processing. Fast and reliable characterization is achieved by comparison of certain properly selected characteristics of the scattered-light pattern with the corresponding theoretical values, which are readily derived from theoretical data and are stored in a look-up table. The data in this table were generated with a powerful boundary-element method, which can solve the direct scattering problem for virtually arbitrary shapes. A specially developed fast pattern-recognition technique makes possible the on-line characterization of axisymmetric particles. Successful results with red blood cells and bacteria are presented.