1.
Coagulation behavior and floc characteristics of a novel composite poly-ferric aluminum chloride-polydimethyl diallylammonium chloride coagulant with different OH/(Fe3+ + Al3+) molar ratios.
Sun, C, Qiu, J, Zhang, Z, Marhaba, TF, Zhang, Y
Water science and technology : a journal of the International Association on Water Pollution Research. 2016;(7):1636-1643
Abstract
In this paper, flocculating performance and mechanisms of a new composite coagulant, poly-ferric aluminum chloride-polydimethyl diallylammonium chloride (PFAC-PD) with different OH-/(Fe3+ + Al3+) molar ratios, were investigated for humic acid (HA)-kaolin synthetic wastewater treatment. The impact of OH-/(Fe3+ + Al3+) molar ratios on the removal efficiencies of turbidity and dissolved organic carbon, specific UV absorbance, coagulation mechanisms and dynamics was explored during the coagulation process using composite coagulants. The coagulation experimental results revealed that the composite coagulants with lower OH-/(Fe3+ + Al3+) molar ratio exhibited better coagulation efficiency. When OH-/(Fe3+ + Al3+) molar ratio of the composite coagulant was 1.5, adsorption-bridging played a dominant role in coagulating HA-kaolin synthetic wastewater. The floc growth rate and floc size, increased with increasing OH-/(Fe3+ + Al3+) molar ratio and the highest peak height of the size distribution was obtained by PFAC-PD with OH-/(Fe3+ + Al3+) = 1.5. Also, the composite coagulants with higher OH-/(Fe3+ + Al3+) molar ratio formed more compact flocs, as reflected by the higher fractal dimension value. The flocs coagulated by PFAC-PD with basicity value of 1.0 gave strong strength and good recoverability.
2.
Nitrate removal from groundwater by cooperating heterotrophic with autotrophic denitrification in a biofilm-electrode reactor.
Zhao, Y, Feng, C, Wang, Q, Yang, Y, Zhang, Z, Sugiura, N
Journal of hazardous materials. 2011;(3):1033-9
Abstract
An intensified biofilm-electrode reactor (IBER) combining heterotrophic and autotrophic denitrification was developed for treatment of nitrate contaminated groundwater. The reactor was evaluated with synthetic groundwater (NO(3)(-)-N50 mg L(-1)) under different hydraulic retention times (HRTs), carbon to nitrogen ratios (C/N) and electric currents (I). The experimental results demonstrate that high nitrate and nitrite removal efficiency (100%) were achieved at C/N = 1, HRT = 8h, and I = 10 mA. C/N ratios were reduced from 1 to 0.5 and the applied electric current was changed from 10 to 100 mA, showing that the optimum running condition was C/N = 0.75 and I = 40 mA, under which over 97% of NO(3)(-)-N was removed and organic carbon (methanol) was completely consumed in treated water. Simultaneously, the denitrification mechanism in this system was analyzed through pH variation in effluent. The CO(2) produced from the anode acted as a good pH buffer, automatically controlling pH in the reaction zone. The intensified biofilm-electrode reactor developed in the study was effective for the treatment of groundwater polluted by nitrate.