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Domestic Wastewater Treatment as a Net Energy Producer–Can This be Achieved?
McCarty, Perry L.,Bae, Jaeho,Kim, Jeonghwan American Chemical Society 2011 Environmental science & technology Vol.45 No.17
<P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/esthag/2011/esthag.2011.45.issue-17/es2014264/production/images/medium/es-2011-014264_0003.gif'> <P>In seeking greater sustainability in water resources management, wastewater is now being considered more as a resource than as a waste?a resource for water, for plant nutrients, and for energy. Energy, the primary focus of this article, can be obtained from wastewater's organic as well as from its thermal content. Also, using wastewater’s nitrogen and P nutrients for plant fertilization, rather than wasting them, helps offset the high energy cost of producing synthetic fertilizers. Microbial fuel cells offer potential for direct biological conversion of wastewater’s organic materials into electricity, although significant improvements are needed for this process to be competitive with anaerobic biological conversion of wastewater organics into biogas, a renewable fuel used in electricity generation. Newer membrane processes coupled with complete anaerobic treatment of wastewater offer the potential for wastewater treatment to become a net generator of energy, rather than the large energy consumer that it is today.</P></P>
Model to Couple Anaerobic Process Kinetics with Biological Growth Equilibrium Thermodynamics
McCarty, Perry L.,Bae, Jaeho American Chemical Society 2011 Environmental science & technology Vol.45 No.16
<P>Monod kinetics indicates a substrate concentration limit (<I>S</I><SUB>min</SUB>) at biological growth equilibrium where growth is just balanced by decay. A relationship between <I>S</I><SUB>min</SUB> and the Gibbs free energy available at growth equilibrium (Δ<I>G</I><SUB>E</SUB>) was introduced into the Monod model and applied directly to chemostat cultures. Results from four anaerobic mixed-culture chemostat studies yielded Δ<I>G</I><SUB>E</SUB> of −17.7 ± 2.2 kJ/mol acetate converted to methane. Δ<I>G</I><SUB>E</SUB> for propionate syntrophs in propionate-fed cultures was −8.0 ± 3.1 kJ/mol propionate, compared with that of −3.0 ± 0.9 kJ/mol H<SUB>2</SUB> for the hydrogenotrophs present. With ethanol present, however, Δ<I>G</I><SUB>E</SUB> for the hydrogenotrophs became more favorable, −6.1 ± 1.6 kJ/mol H<SUB>2</SUB>, while Δ<I>G</I><SUB>E</SUB> for propionate became positive even though propionate was consumed, suggesting an alternative interspecies electron transport route. The results suggest that <I>S</I><SUB>min</SUB>, normally considered a function of an organism’s intrinsic rate characteristics, is also a function of solution characteristics, and this is likely the case for the substrate affinity coefficient, <I>K</I>, as well. A comparison between Δ<I>G</I><SUB>E</SUB> and <I>S</I><SUB>min</SUB> and reported threshold thermodynamic and concentration limits, leads to the conclusion that Δ<I>G</I><SUB>E</SUB> and <I>S</I><SUB>min</SUB> represent lower and upper bounds, respectively, on such values. This study indicates that knowledge gained from pure-culture studies applies well to more complex natural anaerobic systems.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/esthag/2011/esthag.2011.45.issue-16/es2009055/production/images/medium/es-2011-009055_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/es2009055'>ACS Electronic Supporting Info</A></P>
Lee, Eunseok,McCarty, Perry L.,Kim, Jeonghwan,Bae, Jaeho IWA Publishing 2016 Water Science & Technology Vol.74 No.1
<P>The effects on sulfur removal and membrane fouling resulting from FeCl3 addition to an anaerobic fluidized membrane bioreactor (AFMBR) in a staged AFMBR (SAF-MBR) was investigated. Total sulfur removal in the SAF-MBR was 42-59% without FeCl3 addition, but increased to 87-95% with FeCl3 addition. Sulfide removal in the AFMBR increased to 90% with addition of FeCl3 at a molar Fe3+/S ratio of 0.54 and to 95% when the ratio was increased to 0.95. Effluent sulfide concentration then decreased to 0.3-0.6 mg/L. Phosphate removals were only 19 and 37% with the above added FeCl3 ratios, indicating that iron removed sulfide more readily than phosphate. Neither chemical oxygen demand nor biochemical oxygen demand removal efficiencies were affected by the addition of FeCl3. When the AFMBR permeate became exposed to air, light brown particles were formed from effluent Fe2+| oxidation to Fe3+. FeCl3 addition, while beneficial for sulfide removal, did increase the membrane fouling rate due to the deposition of inorganic precipitates in the membrane pores.</P>
Aslam, Muhammad,McCarty, Perry L.,Shin, Chungheon,Bae, Jaeho,Kim, Jeonghwan Elsevier 2017 Bioresource technology Vol.240 No.-
<P><B>Abstract</B></P> <P>An aluminum dioxide (Al<SUB>2</SUB>O<SUB>3</SUB>) ceramic membrane was used in a single-stage anaerobic fluidized bed ceramic membrane bioreactor (AFCMBR) for low-strength wastewater treatment. The AFCMBR was operated continuously for 395days at 25°C using a synthetic wastewater having a chemical oxygen demand (COD) averaging 260mg/L. A membrane net flux as high as 14.5–17L/m<SUP>2</SUP> h was achieved with only periodic maintenance cleaning, obtained by adding 25mg/L of sodium hypochlorite solution. No adverse effect of the maintenance cleaning on organic removal was observed. An average SCOD in the membrane permeate of 23mg/L was achieved with a 1h hydraulic retention time (HRT). Biosolids production averaged 0.014±0.007gVSS/gCOD removed. The estimated electrical energy required to operate the AFCMBR system was 0.039kWh/m<SUP>3</SUP> <SUB>,</SUB> which is only about 17% of the electrical energy that could be generated with the methane produced.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ceramic membrane was applied in anaerobic fluidized MBR for low-strength wastewater. </LI> <LI> Membrane net flux of 17LMH was achieved with only periodic maintenance cleaning. </LI> <LI> No adverse effect of the maintenance cleaning on organic removal was observed. </LI> <LI> Average SCOD in membrane permeate of 23mg/L was achieved. </LI> <LI> Electrical energy required to operate the AFCMBR was only about 0.038kWh/m<SUP>3</SUP>. </LI> </UL> </P>
Shin, Chungheon,Kim, Kihyun,McCarty, Perry L.,Kim, Jeonghwan,Bae, Jaeho IWA Publishing 2016 Water Science & Technology Vol.74 No.2
<P>A bench-scale short-term test, developed to predict the long-term integrity of membranes with potential for use in anaerobic fluidized-bed membrane bioreactors, was used to evaluate several commercial hollow-fiber membranes. It was found that membrane performance varied widely, some membranes failing much more rapidly than others. Also found was that larger sizes of the fluidized media, in this case granular activated carbon (GAC), severely affected membrane structural integrity more than did smaller sizes, as did the method used for membrane attachment. Within the limits studied, the GAC packing ratio had only a minor impact. A decrease in membrane permeability that sometimes resulted during the testing and was caused by the deposition of fine GAC particles could be eliminated without membrane damage through simultaneous chemical cleaning and sonication. This new testing procedure should be useful for selecting membranes and reactor operating conditions to better ensure long-term operating performance of anaerobic fluidized-bed membrane bioreactors.</P>