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.

Promoting sustainability in the mussel industry: mussel shell recycling to fight fluoride pollution

Journal of Cleaner Production, 131 (2016) 485–490

http://dx.doi.org/10.1016/j.jclepro.2016.04.154

Taking into account a background situation where some industrial activities greatly influence fluoride pollution, while other industries generate by-products that could be effective as fluoride bio-sorbents, and bearing in mind sustainability and environmental concern, batch-type experiments were performed to study fluoride sorption/desorption on individual (un-amended) and mussel shell-amended soils and materials. Specifically, the research focused on a forest soil, a vineyard soil, pyritic material, granitic material, and ground mussel shell, as well as on both soils and the pyritic and granitic materials amended with mussel shell. The main findings of the research indicate that the shell amendment clearly increased fluoride sorption in the pyritic material (reaching more than 90%), showing no effect as regards fluoride desorption from this material. The amendment caused a slight increase in fluoride sorption on forest soil, as well as a slight decrease in fluoride desorption from it. The un-amended vineyard soil and the un-amended granitic material had lower fluoride-retention capacity than the forest soil and pyritic material, and it did not change after amending with mussel shell. The mussel shell by itself showed the lowest fluoride-retention potential among the tested materials. As a conclusion, and focusing on applicability, these results can be useful to program the correct use of mussel shell amendment on soils and even on degraded environments with the aim of increasing fluoride retention or removal, thus decreasing risk of environmental pollution due to excessive fluoride concentrations in solid and/or liquid media, also facilitating recycling, sustainability and cleaner production in the mussel shell industry.

As (V)/Cr (VI) pollution control in soils, hemp waste, and other by-products: competitive sorption trials

Environmental Science and Pollution Research

DOI: 10.1007/s11356-016-7108-0

We study As(V)/Cr(VI) competitive sorption on a forest soil, a vineyard soil, pyritic material, mussel shell, pine bark, oak ash, and hemp waste, adding variable As(V) and Cr(VI) concentrations or displacing each pollutant with the same concentration of the other. When using variable concentrations, As(V) showed more affinity than Cr(VI) for sorption sites on most materials (sorption up to >84 % on oak ash and pyritic material). The only exception was pine bark, with clearly higher Cr(VI) sorption (>90 %) for any Cr(VI)/As(V) concentration added. Regarding the displacement experiments, when As(V) was added and reached sorption equilibrium, the subsequent addition of equal Cr(VI) concentration did not cause relevant As displacement from oak ash and pyritic material, indicating strong As bindings, and/or low competitive effects. When Cr(VI) was added and reached sorption equilibrium, the subsequent addition of equal As(V) concentration caused Cr(VI) displacement from all materials except pine bark, indicating weak Cr bindings. In view of these results, oak ash and the pyritic material could be used to remove As(V) in concentrations as high as 6 mmol L−1, even in the presence of a wide range of Cr(VI) concentrations, whereas pine bark could be used to remove Cr(VI) concentrations as high as 6 mmol L−1. The other materials assayed (including hemp waste, studied for the first time as As(V) and Cr(VI) bio-sorbent) cannot be considered appropriate to remove As(V) and/or Cr(VI) from polluted media.

Changes in Cd, Cu, Ni, Pb and Zn Fractionation and Liberation Due to Mussel Shell Amendment on a Mine Soil

Land Degradation and Development 27 (2016) 1276–1285

DOI: 10.1002/ldr.2505

Mining activities are related to relevant environmental pollution issues that should be controlled. We used sequential extractions to fractionate Cd, Cu, Ni, Pb and Zn retained on unamended or mussel shell-amended mine soil samples, all of them treated with a mixture of the five heavy metals (total metal concentration of 1·57 mmol L−1), after 1, 7 and 30 days of incubation. In addition, we used the stirred flow chamber technique to study the release of each of the five heavy metals from these different unamended and shell-amended soil samples. The results indicate that the shell amendment caused a decrease in the most soluble fraction, while increasing the most recalcitrant (least mobile) fraction. With equivalent implications, the stirred flow chamber experiments showed that mussel shell amendment was associated to a decrease in heavy metal release and increased retention. The highest mussel shell dose and incubation time caused the most relevant changes in pH values and thus in metal retention, also indicating the importance of pH modifications in the mechanism of retention acting in the amended samples. In view of these results, the use of mussel shell amendment can be encouraged to increase heavy metal retention in acid mine soils, in order to minimise risks of environmental pollution. 

Effect of crushed mussel shell addition on bacterial growth in acid polluted soils

Applied Soil Ecology, 85 (2015) 65-68

doi:10.1016/j.apsoil.2014.09.010

We applied three different doses of crushed mussel shell (CMS) on two Cu-polluted acid soils to study the effect of these amendments on the growth of the bacterial community during 730 days. Soil pH increased in the short and medium term due to CMS addition. In a first stage, bacterial growth was lower in the CMS-amended than in the un-amended samples. Thereafter, bacterial growth increased slowly. The soil having the highest initial pH value (4.5) showed the first significant increase in bacterial growth 95 days after the CMS amendment. However, in the soil with the lowest initial pH value (3.8) bacterial growth increased significantly only after 730 days from the CMS addition. The highest dose of CMS caused that, at the end of the incubation period, pH value have increased 2 units, whereas bacterial growth was 4–10 times higher. In view of these results, CMS amendment could be considered as an agronomic sound practice for strongly acid soils (pH <4.5).