Phosphorus removal from wastewater using mussel shell: Investigation on retention mechanisms

Ecological Engineering, 97, 2016, 558–566

http://dx.doi.org/10.1016/j.ecoleng.2016.10.066

Mussel shell is a carbonate-rich by-product that could be recycled in wastewater treatment. In this work, phosphorus removal from aqueous solutions was obtained in a series of batch and column experiments in the laboratory, using a calcined and a finely-ground (non-calcined) mussel shell. Phosphorus removal followed a Freundlich model at high contact times (72 h) and a Langmuir model at lower time (24 h). Phosphorus removal capacity increased with contact time and with P concentration in the solution, while desorption of the retained P was very low (<4%). Calcined mussel shell presented a higher retention capacity than the fine shell, which can be attributed to differences in mineralogy and composition. The process of P removal from aqueous solution showed features that are typical of chemical reactions rather than denoting adsorption; concretely, the percentage of P removed increased with initial P concentration in the solution, thus pointing at a relevant role of precipitation in P removal. The results corresponding to the fractionation of the P retained in the mussel shell after the experiments showed that both mechanisms, adsorption and precipitation, contributed to P removal.

Sepia ink as a surrogate for colloid transport tests in porous media

Journal of Contaminant Hydrology, 191, 2016, 88–98

http://dx.doi.org/10.1016/j.jconhyd.2016.05.005

We examined the suitability of the ink of Sepia officinalis as a surrogate for transport studies of microorganisms and microparticles in porous media. Sepia ink is an organic pigment consisted on a suspension of eumelanin, and that has several advantages for its use as a promising material for introducing the frugal-innovation in the fields of public health and environmental research: very low cost, non-toxic, spherical shape, moderate polydispersivity, size near large viruses, non-anomalous electrokinetic behavior, low retention in the soil, and high stability.

Electrokinetic determinations and transport experiments in quartz sand columns and soil columns were done with purified suspensions of sepia ink. Influence of ionic strength on the electrophoretic mobility of ink particles showed the typical behavior of polystyrene latex spheres. Breakthrough curve (BTC) and retention profile (RP) in quartz sand columns showed a depth dependent and blocking adsorption model with an increase in adsorption rates with the ionic strength. Partially saturated transport through undisturbed soil showed less retention than in quartz sand, and matrix exclusion was also observed. Quantification of ink in leachate fractions by light absorbance is direct, but quantification in the soil profile with moderate to high organic matter content was rather cumbersome.

We concluded that sepia ink is a suitable cheap surrogate for exploring transport of pathogenic viruses, bacteria and particulate contaminants in groundwater, and could be used for developing frugal-innovation related with the assessment of soil and aquifer filtration function, and monitoring of water filtration systems in low-income regions.