Xuejun Bi

Improvement of lime softening treatment of secondary effluent by the addition of fly ash

AbstractThe sludge generated in the lime softening of recirculating cooling water has a large bulk volume and is difficult to dehydrate. The current study tested the effect of fly ash addition on the pollutant removal efficiency and the sludge properties improvement in the softening process. The hardness and alkalinity removal efficiency before and after the addition of fly ash were evaluated. The effects of fly ash addition on chemical sludge properties, such as the sludge water content, particle size, and microstructure, were also investigated. With a fly ash dosage of 270u2009mg/L, the removal rates of calcium hardness, total hardness, and total dissolved solids increased by 20.7, 11.5, and 6.1% compared with those obtained in the absence of fly ash. The addition of fly ash can improve the stability of treated water by reducing the scaling potential. Fly ash can improve the sludge properties. At a fly ash dosage of 200–250u2009mg/L, the median diameter of the flocs is four times bigger than the flocs produced ...

Effect of bio-carrier filling rate on oxygen transfer coefficient of different diffusers in MBBR process

AbstractThis paper mainly discussed the effect of bio-carrier filling rate on the oxygen transfer coefficient of different diffusers in the MBBR process. The results show that bio-carriers could increase the oxygen transfer coefficients of the microporous diffusers both in clean water and in mixed liquor because of the shearing effect that created microbubbles and enhanced microscopic hydrodynamic flow regime of the reactor. Compared to the test without bio-carriers, dosing bio-carriers could increase the oxygen transfer coefficient of microporous membrane diffuser by 10.78% in clean water and 10.17% in mixed liquor. Dosing bio-carriers could increase the oxygen transfer coefficient of the campanulate corundum aerator and perforated pipe more than the microporous membrane diffuser. Compared to the control, dosing bio-carriers could increase the KLa of campanulate corundum aerator and perforated pipe diffuser by almost 13.40 and 17.74% in clean water, and 10.97 and 20.14% in mixed liquor, respectively.