Jar tests were conducted to investigate the performance of enhanced primary treatment processes for low-concentra-tion municipal wastewater from South China by using composite flocculant combined with bio-flocculants ...Jar tests were conducted to investigate the performance of enhanced primary treatment processes for low-concentra-tion municipal wastewater from South China by using composite flocculant combined with bio-flocculants Pullulan and poly-aluminum-chloride (PAC). The optimum dosage for composite flocculant and conditions for flocculation were determined. The experimental results indicated that composite flocculant had high efficiency for removing over 95% of turbidity, over 58% of CODCr (chemical oxygen demand determined with potassium dichromate), over 91% of TP (total phosphate), and over 15% of NH3-N. Moreover, it could improve sludge settling and dehydration properties, and decrease the treatment cost.展开更多
The effectiveness of enhancing treatment of water with low turbidity through combined effects of permanganate oxidation, PAM aiding coagulation and sludge recycling was investigated through continuous bench scale stud...The effectiveness of enhancing treatment of water with low turbidity through combined effects of permanganate oxidation, PAM aiding coagulation and sludge recycling was investigated through continuous bench scale studies. In comparing with ferric chloride coagulation, only recycling sedimentation sludge was ineffective in enhancing treatment of water with low turbidity. PAM with recycled sludge showed positive effects, and the additional permanganate dosing exhibited the best potential of favoring coagulation, which leaded to much lower effluent turbidity and CODMa. Additionally, it was observed that the optimal permanganate dosage was 0. 4 mg/ L and the higher permanganate dosage exhibited inhibiting effects for pollutants removal. SEM analysis indicated that the floes were loosely formed and the particle diameter was critically low for ferric chloride coagulation process. Comparatively, the addition of PAM and permanganate with recycled sludge facilitated the aggregation of tinny particles onto compact PAM polymer chains, therefore contributing to the formation of compact floes with high particle diameter. The combined employment of recycled sludge, PAM and permanganate showed the best potential of favoring coagulation, mainly through synergistic effects between seeding, polymer bridging and increasing effective collision in mechanism. Additionally, the variation of Fe and Mn concentration after recycling and sedimentating units was studied for the processes, and the main species was also investigated for elements Fe and Mn. Sludge recycling and permanganate addition did not increase Fe and Mn concentration in the sedimented water.展开更多
The present study describes the experiments on the application of geopolymer paste for groutless in situ casting or flooring. The paste was synthesized from fly ash and sodium silicate solution and cured at room tempe...The present study describes the experiments on the application of geopolymer paste for groutless in situ casting or flooring. The paste was synthesized from fly ash and sodium silicate solution and cured at room temperature, 60 and 80℃ for 24 hours. To simulate flooring application, the geopolymer paste was casted on Portland cement cubes which have been fully hydrated for 28 days. Silica fume was added to reduce cracks but at the same time compressive strength decreased. Averaged compressive strength decreased from 53 MPa to 37 MPa for paste cured at 60℃. Curing at higher temperatures produced stronger geopolymer, with compressive strength of 12 MPa, 53 MPa and 67 MPa for geopolymer cured at room temperature, 60℃ and 80℃ respectively, however, higher curing temperature resulted in more cracking when the geopolymer paste was applied on the Portland cement substrate. Averaged hardness values were 65 and 43 Brinnel scale （BHN）, and wear rate, measured using Ogoshi machine, were 0.66 and 1.80 mm3/min for samples cured at 60 and 80℃ respectively. Unless surface hardening was applied, the material is not suitable for flooring but do so for decorative masonry.展开更多
基金Project (No. 2005AA601010) supported by the Hi-Tech Research and Development Program (863) of China
文摘Jar tests were conducted to investigate the performance of enhanced primary treatment processes for low-concentra-tion municipal wastewater from South China by using composite flocculant combined with bio-flocculants Pullulan and poly-aluminum-chloride (PAC). The optimum dosage for composite flocculant and conditions for flocculation were determined. The experimental results indicated that composite flocculant had high efficiency for removing over 95% of turbidity, over 58% of CODCr (chemical oxygen demand determined with potassium dichromate), over 91% of TP (total phosphate), and over 15% of NH3-N. Moreover, it could improve sludge settling and dehydration properties, and decrease the treatment cost.
基金Sponsored by the National High Technology Research and Development Program of China(Grant No.2004AA601020)
文摘The effectiveness of enhancing treatment of water with low turbidity through combined effects of permanganate oxidation, PAM aiding coagulation and sludge recycling was investigated through continuous bench scale studies. In comparing with ferric chloride coagulation, only recycling sedimentation sludge was ineffective in enhancing treatment of water with low turbidity. PAM with recycled sludge showed positive effects, and the additional permanganate dosing exhibited the best potential of favoring coagulation, which leaded to much lower effluent turbidity and CODMa. Additionally, it was observed that the optimal permanganate dosage was 0. 4 mg/ L and the higher permanganate dosage exhibited inhibiting effects for pollutants removal. SEM analysis indicated that the floes were loosely formed and the particle diameter was critically low for ferric chloride coagulation process. Comparatively, the addition of PAM and permanganate with recycled sludge facilitated the aggregation of tinny particles onto compact PAM polymer chains, therefore contributing to the formation of compact floes with high particle diameter. The combined employment of recycled sludge, PAM and permanganate showed the best potential of favoring coagulation, mainly through synergistic effects between seeding, polymer bridging and increasing effective collision in mechanism. Additionally, the variation of Fe and Mn concentration after recycling and sedimentating units was studied for the processes, and the main species was also investigated for elements Fe and Mn. Sludge recycling and permanganate addition did not increase Fe and Mn concentration in the sedimented water.
文摘The present study describes the experiments on the application of geopolymer paste for groutless in situ casting or flooring. The paste was synthesized from fly ash and sodium silicate solution and cured at room temperature, 60 and 80℃ for 24 hours. To simulate flooring application, the geopolymer paste was casted on Portland cement cubes which have been fully hydrated for 28 days. Silica fume was added to reduce cracks but at the same time compressive strength decreased. Averaged compressive strength decreased from 53 MPa to 37 MPa for paste cured at 60℃. Curing at higher temperatures produced stronger geopolymer, with compressive strength of 12 MPa, 53 MPa and 67 MPa for geopolymer cured at room temperature, 60℃ and 80℃ respectively, however, higher curing temperature resulted in more cracking when the geopolymer paste was applied on the Portland cement substrate. Averaged hardness values were 65 and 43 Brinnel scale （BHN）, and wear rate, measured using Ogoshi machine, were 0.66 and 1.80 mm3/min for samples cured at 60 and 80℃ respectively. Unless surface hardening was applied, the material is not suitable for flooring but do so for decorative masonry.
