PubMed · 169400
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J A Heidman. 1975. Solid wastes and water quality.. https://pubmed.ncbi.nlm.nih.gov/169400/
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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%.
Household derived biowaste was degraded by biological methods. The system involves the combined method of low-solids (up to 10% w/v of total solids (TS)) anaerobic digestion and aerobic degradation for the recovery of energy (biogas) and the production of fine humus-like material which can be used as a soil amender or a substrate for further thermal treatment (pyrolysis, gasification). The performance of batch and continuous processes carried out in bioreactors (stirred tank reactor, air-lift) of working volume 6 and 18 dm(3), at different temperatures (25-42 degrees C) was monitored by reduction of TS, volatile solids, chemical oxygen demand, total organic carbon, C/N in time. The application of continuous process with recirculation (33%) caused that for residence time of 8-16 h the obtained degree of organic load reduction was similar to that obtained after 72-96 h of the batch process. The experimental data of batch aerobic degradation was also subjected to kinetic analysis. The sequence of the two processes: aerobic and anaerobic or anaerobic and aerobic showed that the degree of organic load reduction was similar in both cases, while the amount of produced biogas was four times higher when the first stage was anaerobic. The final product after dewatering was subjected to pyrolysis and gasification. The gases obtained were characterised by a high heat of combustion of about 11-15 MJ Nm(-3).
The system of producing long chain dicarboxylic acid (DCA) by Candida tropicalis is an aerobic and viscous fermentation system. A method to overcome the gas-liquid transport resistance and to increase oxygen supply is by adding hydrogen peroxide (H(2)O(2)) to the fermentation system. Here we report that the H(2)O(2) not only can enhance the oxygen supply but also change the metabolism by inducing cytochrome P450, the key enzyme of a, o-oxidation. When C. tropicalis was cultivated in a 3-L bioreactor using the combination of aeration and H(2)O(2) feeding, DCA production rates increased by about 10% after a short period of decrease at the beginning. Furthermore, the experiments showed that the maximum activities of P450 could be induced at 2 mM H(2)O(2), and the inducible mechanisms are also discussed. Moreover, we suggest that alkane might be oxidized through the "peroxide shunt pathway" when H(2)O(2) is present. By adding H(2)O(2), the DCA yield in a 22-L bioreactor could increase by 25.3% and reach 153.9 g/L.