Pilot Study on Treatment of Wastewater from an Ethylene Plant with Membrane Bioreactor Technology
Pilot studies were conducted with an anoxic/aerobic concept membrane bioreactor (MBR) technology and a hollow fiber Petro ® MBR system with capacity of 12 m 3 /d was operated continuously (24-hour) during the study. Trials on different membrane fluxes were conducted to obtain the sustainable flux while mixed liquor suspended solid (MLSS) was maintained at 9-11 g/L. The results of the MBR pilot trials showed that no obvious fouling of the membrane was found when the plant was operated at the flux of 12 L /m 2 /h (LMH) over 3 months and 15 LMH over one month during the pilot study. Design guidelines such as hydraulic retention time (HRT), sludge retention time (SRT), anoxic and aera- tion volume ratio, re-circulation flow rate and air scouring were obtained for a full-scale plant. It was concluded that treatment of wastewater from an ethylene plant without addition of any chemicals using MBR technology is feasible. The product quality consistently met the requirement for discharge and was suitable for the feed of further reverse osmosis (RO) post-treatment.
Treatment of urban wastewater in a membrane bioreactor at high organic loading rates.
Membrane bioreactors can replace the activated sludge process and the final clarification step in municipal wastewater treatment. The combination of bioreactor and crossflow microfiltration allows for a high chemical oxygen demand (COD) reduction of synthetic wastewater. From biomass, grown at high production rates in the aerobic bioreactor, energy rich biogas can be obtained in a subsequent anaerobic bioreactor. In this paper, experimental data from a laboratory scale membrane bioreactor are presented. The degradation of synthetic wastewater at short hydraulic retention times down to 1.5 h has been studied. The organic loading rate (OLR) has been varied in the range of 6-13 kg m(-3) per day. At steady state a high quality filtrate could be obtained at different operating conditions. At biomass concentrations of 10-22 g l(-1), COD reduction was above 95%.
The biomass fractions of heterotrophs and phosphate-accumulating organisms in a nitrogen and phosphorus removal system
Abstract In this study, the biomass fractions of heterotrophs ( X H ) and phosphate-accumulating organisms ( X PAO ) were estimated through experimental results and theoretical calculation on the mass balance of organic matter, nitrogen and phosphorus in a pilot scale biological nutrient removal process. The process, comprised of conventional anaerobic–anoxic–aerobic activated sludge and a rotating biological contactor in the aerobic stage, was controlled under steady state under conditions of a solid retention time of 10 days and a dissolved oxygen concentration of 2.0 mg/l in the aerobic stage. For long term operation, the process exhibited high performance in organic matter, nitrogen and phosphorus removal. The removal efficiency was 96.5, 70 and 100% of organic matter, total nitrogen and total phosphorus, respectively. According to the mass balance calculation, approximately 62.0% of organic matter, 48.0% of nitrogen and 47.2% of phosphorus of influent were removed in the form of carbon dioxide, nitrogen gas and polyphosphate, respectively. Regarding X H and X PAO as the major organisms responsible for biomass production, the yield fractions of X H growth in anoxic and aerobic conditions were 48.4 and 39.4%, respectively. Moreover, the yield fraction of X PAO growth in aerobic conditions was 12.2%. These results showed that X H was the major community; moreover, only a minute amount of X PAO was present in this nitrogen and phosphorus removal system for municipal wastewater treatment.