• PVDF flat-sheet membrane was prepared for boron removal and desalination.• The membrane had a narrow pore size distribution and exhibited good hydrophobicity.• Simultaneous boron removal and desalination from real seawater was carried out.• The influence of antiscalant on boron removal and desalination was investigated.• The prepared membrane was efficient for boron removal and desalination by DCMD. a b s t r a c t a r t i c l e i n f o Boron removal and desalination from seawater by direct contact membrane distillation (DCMD) was studied with self-prepared polyvinylidene fluoride (PVDF) flat-sheet membrane. The membrane had an ultra-thin top skin and a porous network sponge-like layer and its effective pores showed a narrow distribution with a mean pore size of 0.22 μm. The membrane exhibited good hydrophobicity and its contact angle was about 82.6 ± 0.7°. During DCMD test of 35 g/L sodium chloride solution, the maximum permeate flux can achieve 47.6 kg/m 2 h.The natural seawater containing 4.65 mg/L boron was treated by DCMD for simultaneous boron removal and desalination. Although the permeate flux decreased with concentration factor (CF) value increase, the permeate boron kept below 20 μg/L and salt rejection was over 99.9%. When the CF value exceeded 4.0, there would be scale deposits formed, and the permeate quality and flux declined rapidly. The antiscalant polyacrylic acid could delay the deposit formation and the advisable dosage was 10 mg/L. The membrane showed satisfying performance stability in a 300 h continuous DCMD experiment even with the CF value as high as 7.0, indicating that the selfprepared membrane and DCMD process could be efficiently used for boron removal and desalination from seawater.
This study analyzed 15 pharmaceuticals and personal care products (PPCPs) in two rivers with different urbanization levels in the surrounding watershed (urban and suburb) in Beijing, China. Along the rivers, effluent samples from wastewater treatment plants (WWTPs) and wastewater samples from direct discharge outlets were also collected to reveal their possible contribution to the occurrence of PPCPs in these two rivers. Among the 15 PPCPs, 14 compounds were detected with caffeine (maximum 11,900 ng L(-1)) being the dominant compound. The total concentration of the detected PPCPs in direct discharge outlets (median 4706 ng L(-1)) was much higher than that in river waters (2780 ng L(-1)) and WWTP effluents (1971 ng L(-1)). The suburban-influenced Liangshui River had significantly higher PPCP concentrations compared to the urban-influenced Qing River due to more input of untreated wastewater from direct discharge outlets. Source apportionment showed that approximately 55% of the total PPCPs were contributed by untreated wastewater in the suburban-influenced river. Finally, ecological risk assessment has been regarded as a necessary part of general research. According to the environmental risk assessment results, caffeine, trimethoprim and metoprolol were found to be the most critical compounds, due to their high risk quotient values. The results of the present study can provide useful information for future PPCP pollution control and sustainable water management in Beijing, China.
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