Kitchen garbage generated at a school cafeteria was treated and stabilised in a controlled on-site composting unit for volume reduction and on-site utilisation of processed garbage. The on-site composter was fed with the garbage on a daily basis during the two-months experimental period. Compost was not removed from the unit but was entirely reused as a bulking agent in order to minimise the need for additional bulking agent and compost handling. Performance of the composter tinder this condition was investigated. Most of the easily degradable organic matter (EDM) in the garbage was biodegraded rapidly, and the final product had a low content of EDM. Lipids, total sugar, and hemi-cellulose were degraded 96%, 81%, and 66% respectively. Free air space (FAS) was higher than 0.5 all the time, so accumulation of dry matter in the unit was not significant in reducing reaction efficiency. Other reaction parameters such as pH and MC were kept within a suitable range; however, it was advisable to maintain MC at over 46%. As a result, this method of operation was able to stabilise the garbage with low sawdust demand and little compost production.
Various sludge concentrations and aeration rates were evaluated to find the optimal operation condition of a submerged ceramic membrane filtration system. 5.6 g/L of sludge was diluted with water to concentrations of 2.8 g/L and 1.4 g/L, and the three sludge concentrations were compared in terms of titration characteristics such as pressure and filtrate flux. Flux was at the highest value of about 30 L/m2 x hr at 50 kPa when sludge concentration was 1.4 g/L. In contrast, when sludge concentrations increased to 2.8 g/L and 5.6 g/L, the flux at 50 kPa decreased significantly to 18 L/m2 x hr and 10 L/m2 x hr, respectively. It was concluded that the sludge concentration directly affected the filtration efficiency, and low sludge concentration was suitable for improving filtration efficiency. Adjusting the aeration rate from 2 L/min to 4 L/min at 5.6 g/L of sludge and 50 kPa of pressure increased flux from 10 L/m2 x hr to 13 L/m2 x hr. It was obvious that the vigorous aeration improved the filtration efficiency, but the aeration rate did not seem to be high enough to maintain flux lower than critical flux.
This study focused on the physicochemical and biological characteristics of sludge in submerged membrane bioreactors (MBRs), and their roles in the formation of dynamic membrane and membrane fouling. Three lab-scale submerged MBRs with SRT of 20, 40 and 60 days were performed at a constant permeate flux of 9 L/m 2 /h. Better permeability was achieved at longer SRT (40 and 60 days) with higher sludge concentrations because of the formation of dynamic cake layer. At of SRT 20 days, pore blocking and pore narrowing were more significant having lower sludge concentration. It was found that higher microbial concentration had better permeability, resulting in the formation of dynamic membrane. Size of particulates and colloids, and surface properties of microbial floc appeared the major parameters for the formation of dynamic membrane in the submerged MBRs.
As carbon dioxide (CO 2 ) is believed to be the primary contributor to the greenhouse effect, a lot of effort has been made to decrease it. Among many technologies, the biological carbon dioxide fixation using microalgae has been known as an effective CO 2 reduction technology. With many environmental factors influencing microalgal productivity, the desirable operating factors were investigated using a green alga, Euglena gracilis that has the high protein and vitamin E enough to be used as fodder. In batch culture, the optimum initial pH, temperature, CO 2 and light intensity were found 3.5, 27°C, 5-10% and 520µmol/m 2 /s, respectively. As a medium to cultivate Euglena, tap water without sterilization was effective while freshwater needed pH control. Half-velocity coefficient (K I ) in Monod model under photoautotrophic condition was 86.68 µmol/m 2 /s. In this study, the optimum hydraulic retention time (HRT) for the continuous CO 2 fixation was 3 days at the optimum cultivation conditions obtained at batch experiment.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.