The stability of drinking water treatment residue with ozone treatment

<p>The best management of drinking water treatment residue (DWTR) in environmental remediation should be based on comprehensively understanding the effectiveness and risk of DWTR. In this study, the variation in physicochemical properties, metal lability, and adsorption capability of DWTR under oxidizing condition were investigated. The oxidizing condition was set up using ozone treatment, and the laboratory incubation test were performed within 50 d in association with thermogravimetry, Fourier Transform Infrared Spectrometry, specific surface area and porosity analyzer, fractionation, and P adsorption test. The results showed that ozone treatment had limited effect on the properties of organic matter, the lability of Al, Cu, and Fe, the P adsorption capability, and the distributions of the adsorbed P in DWTR, but the treatment increased N₂ sorption/desorption, specific surface area, total pore volume of DWTR and led to the transformation of Mn from acid-soluble to reducible fractions. These findings demonstrated that DWTR generally kept stable under oxidizing environment; even oxidizing environment may induce a tendency of increasing the adsorption capability and decreasing the environmental risk of DWTR. Accordingly, the effectiveness and safety of DWTR can be maintained under natural aerobic environment, and DWTR is a reliable adsorbent that could be recycled in environmental remediation.</p

Temperature and Cyanobacterial Bloom Biomass Influence Phosphorous Cycling in Eutrophic Lake Sediments

<div><p>Cyanobacterial blooms frequently occur in freshwater lakes, subsequently, substantial amounts of decaying cyanobacterial bloom biomass (CBB) settles onto the lake sediments where anaerobic mineralization reactions prevail. Coupled Fe/S cycling processes can influence the mobilization of phosphorus (P) in sediments, with high releases often resulting in eutrophication. To better understand eutrophication in Lake Taihu (PRC), we investigated the effects of CBB and temperature on phosphorus cycling in lake sediments. Results indicated that added CBB not only enhanced sedimentary iron reduction, but also resulted in a change from net sulfur oxidation to sulfate reduction, which jointly resulted in a spike of soluble Fe(II) and the formation of FeS/FeS₂. Phosphate release was also enhanced with CBB amendment along with increases in reduced sulfur. Further release of phosphate was associated with increases in incubation temperature. In addition, CBB amendment resulted in a shift in P from the Fe-adsorbed P and the relatively unreactive Residual-P pools to the more reactive Al-adsorbed P, Ca-bound P and organic-P pools. Phosphorus cycling rates increased on addition of CBB and were higher at elevated temperatures, resulting in increased phosphorus release from sediments. These findings suggest that settling of CBB into sediments will likely increase the extent of eutrophication in aquatic environments and these processes will be magnified at higher temperatures.</p></div

Temperature effects on calculated Q10 of metabolic processes in freshwater systems.

<p>*Q10 values were calculated from the data in the reference.</p

Iron reduction and sulfate reduction in sediments.

△<p>Data are means ± standard deviation;</p>¶<p>Parentheses indicate the time (day) of the maximum iron reduction rate;</p><p>*ND, not detected;</p>a<p>Significant difference for iron reduction at 25°C and 32°C in unamended sediments (<i>P</i><0.05);</p>b<p>Significant difference for iron reduction at 15°C and 32°C in CBB-amended sediments (<i>P</i><0.05);</p>c<p>Significant difference for iron reduction at 25°C and 32°C in CBB-amended sediments (<i>P</i><0.05);</p>d<p>Sulfate reduction rates in amended sediments at any two respective temperatures show significant difference (<i>P</i><0.05).</p

Acid volatile sulfide (AVS) and chromium reducible sulphur (CRS) content in sediments.

△<p>Data are means ± standard deviation.</p><p>*Significant differences between initial values and final values at the respective temperatures (<i>P</i><°.05).</p>a–e<p>The same letter represents a significant difference for AVS at two different temperatures (<i>P</i><0.05).</p>A–D<p>The same letter represents a significant difference for CRS at two different temperatures (<i>P</i><0.05).</p

Fe(II) concentrations (a), and sulfate concentrations in sediment pore-water (b).

<p>Fe(II) concentrations (a), and sulfate concentrations in sediment pore-water (b).</p