Effects of humic acid on residual AI control in drinking water treatment plants with orthophosphate addition

This study aimed to investigate the effects of humic acid （HA） on residual Al control in drinking water facilities that used orthophosphate addition. The results showed that adding orthophosphate was an effective method for residual Al control for the raw water without HA. When orthophosphate was added at 1.0 min before the addition ofpoly aluminum chloride （PAC1）, the concentrations of soluble aluminum （Sol-AI） and total aluminum （Tot-Al） residue were 0.08 and 0.086 mg. L J, respectively; both were reduced by 46% compared with the control experiment. The presence of HA would notably increase the residual Al concentration. For the raw water with 5 mg-L^-1 of HA, the concentrations of Sol-Al and Tot-Al increased from 0.136 and 0.174mg.L^-1 to 0.172 and 0.272 mg.L 1, respectively. For water with a HA concen- tration above 5 mg. L ^-1, orthophosphate was ineffective in the control of residual Al, though there were still parts of orthophosphate were removed in coagulation. The amounts of Al removal were positively correlated with the solids freshly formed in coagulation. Similar to the raw water without HA, the best AI control was obtained with orthophosphate salt added at 1.0 min before PAC1. HA concentrations in the raw water, solution pH, and the orthophosphate dosage suitable for residual Al control by orthopbosphate precipitation were also investigated.

Use of Fe/Al drinking water treatment residuals as amendments for enhancing the retention capacity of glyphosate in agricultural soils

Fe/Al drinking water treatment residuals（WTRs）, ubiquitous and non-hazardous by-products of drinking water purification, are cost-effective adsorbents for glyphosate. Given that repeated glyphosate applications could significantly decrease glyphosate retention by soils and that the adsorbed glyphosate is potentially mobile, high sorption capacity and stability of glyphosate in agricultural soils are needed to prevent pollution of water by glyphosate.Therefore, we investigated the feasibility of reusing Fe/Al WTR as a soil amendment to enhance the retention capacity of glyphosate in two agricultural soils. The results of batch experiments showed that the Fe/Al WTR amendment significantly enhanced the glyphosate sorption capacity of both soils（p 〈 0.001）. Up to 30% of the previously adsorbed glyphosate desorbed from the non-amended soils, and the Fe/Al WTR amendment effectively decreased the proportion of glyphosate desorbed. Fractionation analyses further demonstrated that glyphosate adsorbed to non-amended soils was primarily retained in the readily labile fraction（Na HCO3-glyphosate）. The WTR amendment significantly increased the relative proportion of the moderately labile fraction（HCl-glyphosate） and concomitantly reduced that of the Na HCO3-glyphosate, hence reducing the potential for the release of soil-adsorbed glyphosate into the aqueous phase. Furthermore, Fe/Al WTR amendment minimized the inhibitory effect of increasing solution p H on glyphosate sorption by soils and mitigated the effects of increasing solution ionic strength. The present results indicate that Fe/Al WTR is suitable for use as a soil amendment to prevent glyphosate pollution of aquatic ecosystems by enhancing the glyphosate retention capacity in soils.

Effect of Surface Polishing Treatment on the Fatigue Performance of Shot-Peened Ti–6Al–4V Alloy

In this study, shot peening is applied to the titanium alloy Ti–6Al–4V, and the surface treatment effect on fatigue life of shot-peened specimens under high cycle loading is investigated. The induced residual stress is measured by using the orbital hole-drilling method. Surface profilometer and optical microscopy are employed to characterize the surface roughness and morphology. The deformed microstructure layers of the shot-peened specimens are investigated by using scanning electron microscopy. Experiments reveal that the fatigue life of Ti–6Al–4V is improved by the shot peening process, and the surface pre-peening polishing. The combination of pre-and post-peening polishing treatments further improves fatigue life of Ti–6Al–4V specimens. The present work provides useful guidelines for developing more efficient shot peening strategies.