Influences of Fly Ash on Concrete Product's Properties and Environmental Impact Reduction

This research aimed to study effects of incorporating fly ash into concrete products. Scope of this study were (1) hazard identification of fly ash (2) study on standard testing of various concrete products and (3) study on environmental impact assessment of concrete products mixed with fly ash. Various types of fly ash namely A, B, C and D were sampling from different power plants. Hazard identification of fly ash was analyzed in terms of total threshold limit concentration (TTLC) and soluble threshold limit concentration (STLC). It was found that concentrations of chromium, cadmium, lead, mercury, nickel, zinc, copper and arsenic passed the criteria of notification of the ministry of industry regarding disposal of wastes or unusable materials B.E. 2548 (2005) in appendix-2.Three types of concrete products namely brick road, concrete block and ready mixed concrete were studied. Fly ash was used as cementitious materials to replace Portland cement at 10% and 30% mixture. Concrete products with proportion of fly ash showed lower compressive strengths during 28 days of curing times. However, increase of curing times showed higher compressive strengths for all types of concrete products. ANOVA analysis showed that different fly ash proportion and curing times had a significant effect on compressive strength. The method of CML2 baseline 2000, SimaPro 7.3 was used in environmental impact assessment. The functional unit was set up through working area of 1 m3. It was found that concrete products mixed with fly ash showed lower environmental impact compared to concrete products without fly ash. Increasing proportion of fly ash showed decreased environmental impact. From ANOVA analysis, there was no significant effect of fly ash types on environmental impact reduction for all types of concrete products. However, % fly ash mixture showed significant effect on environmental impact reduction especially in terms of global warming. Decrease in global warming (GW) potential for block road, concrete block and ready mixed concrete with 10% fly ash mixture were 6.15% - 6.16%, 8.44% - 8.46% and 9.31% - 9.32% whereas the concrete products with 30% fly ash mixture were 18.41% - 18.46%, 25.35% - 25.41% and 25.22% - 25.26% respectively

Particle and microorganism removal in floating plastic media coupled with microfiltration membrane for surface water treatment

Floating plastic media followed by hollow fiber microfiltration membrane was applied for surface water treatment. The performance of the system in terms of particle and microorganisms was investigated. The floating filter was examined at different filtration rates of 5, 10 and 15 m3/m2 .h. Treated water was then fed into a microfiltration unit where different filtration rates were examined at 0.6, 1.0 and 1.4 m3/m2 .d. It was found that polyaluminum chloride was the best coagulant for the removal of particle, algae and coliform bacteria. Average turbidity in treated water from the floating plastic media filter was 3.3, 12.2 and 15.5 NTU for raw water of 80 NTU and 12.9, 11.7 and 31.2 NTU for raw water of 160 NTU after 6 hours at the filtration rates of 5, 10 and 15 m3/m2 .h, respectively. The microfiltration unit could further reduce the turbidity to 0.2-0.5 NTU with low transmembrane pressure development of 0.3-3.7 kPa. Microfiltration membrane could retain most of algae and coliform bacteria remaining in the effluent from the pretreatment unit. It was found that at higher turbidity, algae and coliform bacteria removal efficiencies were achieved at lower filtration rate of the system of 5 m3/m2.h whereas a higher filtration rate of 15 m3/m2 .h yielded better coliphage removal. © IWA Publishing 2005