ESEL Paper Review_20111111
 
By Hong Guo

1,Title and Author

Title: Domestic Wastewater Treatment as a Net Energy Producer-Can This be Achieved?

Authors:

Perry L.McCarty*1,2, Jaeho Bae2,  and Jeonghwan Kim2

1, Department of Civil and Environmental Engineering, Standford University, 473 Via Ortega MC4020, Stanford, California 94305, United States
2, Department of Environmental Engineering, INHA University , Namgu, Yonghyundong 253, Incheon, Republic of Korea

2. Summary of Paper

In this paper, the author talks about the wastewater treatment as net energy producer. Nowadays, use of the reclaimed wastewater for the crop irrigation and indeed for the domestic consumption is a widely accepted. However when we reuse the water, we also consider the energy consumption for the water treatment and the energy collection from the CH4 using for the varieties of areas like daily life and industrialized place. And the authors show the ideas of using the full scale anaerobic process for converting and producing the CH4 gas and biofuel.

2.1 Energy Potential in Domestic Wastewater

From a board environmental perspective world fossil fuel consumption could be reduce through the direct use of waste water N and P for fertilizer instead of using manufactured fertilizers. And the potential energy to be gaine from the waste water treatment can be used for the heat generating for the low temperature area such as heating the buildings.

2.2 Anaerobic versus Microbial Fuel Cells for treating dissolved organics

There are two methods for treating dissolved organics- one is to replace secondary aerobic treatment with secondary anaerobic treatment and the other is microbial fuel cells to convert the organic energy into electricity. The second method can achieve more efficient conversion than current anaerobic treatment and about 30~40% of the CH4 is converted into the electricity.
Additionally, there is totally about 19%of energy loss in the conversion process. If we consider the combustion, we only expect the 28% of the original energy potential in the biodegradable wastewater organics. 

2.3 Comparisons with conventional activated sludge treatment

Compare to the conventional process, we can find that the anaerobic treatment can give us the results of double production of CH4 than the convention method. However, the CH4 must not be allowed to escape to the atmosphere but be collected and used. 
Moreover, the anaerobic method produce less sludge than conventional method and this will affect the further sludge treatment cost.  

3. Contribution:
Today, we already know the importance of the sustainability in our water system. There are many new advanced treatment systems such as anaerobic membrane bioreactor are developed and applied to real system. Here when we consider the energy reuse and produce from these process, we can achieve goal of sustainability.  And the idea which distributes small wastewater treatment instead of current centralized system to get more efficiency system and easily control the water supply and energy producing is very important key idea for the future water management.