New approach for determination of Cd, Cu, Cr, Ni, Pb, and Zn in sewage sludges, fired brick, and sediments using two analytical methods by microwave-induced plasma optical spectrometry and induced coupled plasma optical spectrometry

Efficiency enhancement of electrocoagulation, ion-exchange resin and reverse osmosis (RO) membrane filtration by prior organic precipitation for treatment of anaerobically-treated palm oil mill effluent

Anaerobically-treated palm oil mill effluent (POME) still has unacceptable properties for water recycling and reuse, with an unpleasant appearance due to the brownish color caused by tannins and phenolic compounds. This study proposes an approach for treating anaerobically-treated POME for water recycling by combining organic precipitation, electrocoagulation (EC), and ion-exchange resin, followed by reverse osmosis (RO) membrane filtration in series. The results indicated that the organic precipitation enhanced the efficiency of EC treatment in reducing the concentrations of tannins, color, and chemical oxygen demand (COD) of the anaerobically-treated POME effluent, with reductions of 95.73%, 96.31%, and 93.96% for tannin, color, and COD, respectively. Moreover, organic precipitation affected the effectiveness of Ca2+ and Mg2+ ion removal using ion exchange resin and RO membrane filtration. Without prior organic precipitation, the ion-exchange resin process required a longer contact time, and the RO membrane filtration treatment was hardly effective in removing total dissolved solids (TDS). The combined process gave a water quality that meets the criteria set by the Thailand Ministry of Industry for industrial boiler use (COD 88 mg/L, TDS <0.001 mg/L, water hardness <5 mg-CaCO3/L, and pH 6.9).

Differential Zn and Mn sensitivity of microalgae species from genera Bracteacoccus and Lobosphaera

One of the most common pollutants in natural ecosystems is heavy metals. Algae are sensitive to the action of heavy metals. This allows to use algae to assess the toxicity of heavy metals, bioindication, and during phycoremediation. This study examines the effect of different Zn and Mn concentrations (1.0, 5.0, 25.0, 50.0, 500.0, 1000.0 mg L^-1) on green algae Bracteacoccus minor and Lobosphaera incisa in a chronic bioassay. The results of this study showed that the toxic effect of Zn and Mn on B. minor and L. incisa begins to manifest itself at the lowest of the studied metal concentrations-1 mg L^-1. The critical concentration of Zn, which leads to the complete death of B. minor and L. incisa, is 50.0 and 500.0 mg L^-1, and Mn is 1000.0 mg L^-1 and 500.0 mg L^-1, respectively. It was found that principal component (PC) 1 accounts for 60.47% of the total variance and reflects changes associated with low concentrations of heavy metals (up to 5.0 mg L^-1). PC2 accounts for 27.95% of the total variance. PC2 is mostly associated with high concentrations of ions of heavy metals. Thus, the effect of Zn and Mn concentrations up to 5 mg L^-1and above 50 mg L^-1on B. minor and L. incisa has a different character. At the same time, the response of the studied algae species to the action of Zn and Mn has individual differences. In general, B. minor is more resistant to Mn, while L. incisa is more resistant to Zn.