Ecotoxicological Evaluation of Ethylammonium Nitrate and Aluminium Salt Mixture

The ecotoxicity of a mixture of the ionic liquid ethylammonium nitrate (EAN) and aluminum nitrate salt (Al(NO3)3), as well as the corresponding pure components, was studied in this work. This mixture is of singular interest as electrolytes in electrochemical applications and data on the effects of mixture and components on the environment can hardly be found in the literature. Changes in the bioluminescence of the Aliivibrio fischeri (Beijerinck) Urbanczyk bacteria, determined through a Microtox® test, and microbial activity, measured by microcalorimetry, of two soils with different organic matter contents when exposed to solutions of different concentrations of these compounds were analyzed.

The Impact of Aluminium Salt Dosing for Chemical Phosphorus Removal on the Settleability of Activated Sludge

The use of metal salts like aluminium in the precipitation of phosphorus in activated sludge plants has increased considerably in recent years due to the need to achieve tighter discharge consents for phosphorus in treated wastewater effluent. The impact of aluminium salt (Al3+) dosing on the settleability of activated sludge as a function of zone settling velocity (ZSV) and stirred specific volume index (SSVI) were investigated in batch settleability tests over a three-year period. The results showed that ZSV increased with increasing dose of aluminium salt as SSVI decreased. This trend was observed for dosing concentrations of less than 100 mg/L. At a dose concentration >100 mg/L, the trend was reversed as ZSV decreased and SSVI increased. At dose concentrations of <100 mg/L, Al3+ helped in the bioaggregation of dispersed activated sludge flocs, thereby improving settleability. The surface morphology from the scanning electron microscope (SEM) images indicated that the initial potential of interfloc bridging, open floc formation, and spindly bulking noticed in the undosed activated sludge flocs were remarkably reduced as the flocs became more compacted after Al3+ treatment. At >100 mg/L of Al3+, the sludge settleability started to disintegrate due mainly to surface charge reversal linked to the formation of aluminium hydroxides and the resultant disintegration of the activated sludge floc structure.